unithand.c

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/***********************************************************************
 Freeciv - Copyright (C) 1996 - A Kjeldberg, L Gregersen, P Unold
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
***********************************************************************/
 
#ifdef HAVE_CONFIG_H
#include <fc_config.h>
#endif
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
/* dependencies/lua */
#include "lua.h" /* lua_Integer */
 
/* utility */
#include "astring.h"
#include "fcintl.h"
#include "mem.h"
#include "rand.h"
#include "shared.h"
 
/* common */
#include "actions.h"
#include "ai.h"
#include "city.h"
#include "combat.h"
#include "events.h"
#include "featured_text.h"
#include "game.h"
#include "log.h"
#include "map.h"
#include "movement.h"
#include "packets.h"
#include "player.h"
#include "research.h"
#include "specialist.h"
#include "traderoutes.h"
#include "unit.h"
#include "unitlist.h"
 
/* common/scriptcore */
#include "luascript_types.h"
 
/* server */
#include "actiontools.h"
#include "barbarian.h"
#include "citizenshand.h"
#include "citytools.h"
#include "cityturn.h"
#include "diplomats.h"
#include "maphand.h"
#include "notify.h"
#include "plrhand.h"
#include "sanitycheck.h"
#include "spacerace.h"
#include "srv_main.h"
#include "techtools.h"
#include "unittools.h"
 
/* server/advisors */
#include "autoexplorer.h"
#include "autoworkers.h"
 
/* server/scripting */
#include "script_server.h"
 
#include "unithand.h"
 
/* An explanation why an action isn't enabled. */
struct ane_expl {
  /* The kind of reason why an action isn't enabled. */
  enum ane_kind kind;
 
  union {
    /* The city without the needed capacity- */
    struct city *capacity_city;
 
    /* The bad terrain in question. */
    struct terrain *no_act_terrain;
 
    /* The player to advice declaring war on. */
    struct player *no_war_with;
 
    /* The player to advice breaking peace with. */
    struct player *peace_with;
 
    /* The nation that can't be involved. */
    struct nation_type *no_act_nation;
 
    /* The unit type that can't be targeted. */
    const struct unit_type *no_tgt_utype;
 
    /* The action that blocks the action. */
    struct action *blocker;
 
    /* The required distance. */
    int distance;
 
    /* The required amount of gold. */
    int gold_needed;
  };
};
 
static bool unit_activity_internal(struct unit *punit,
                                   enum unit_activity new_activity,
                                   enum gen_action trigger_action);
static bool unit_activity_targeted_internal(struct unit *punit,
                                            enum unit_activity new_activity,
                                            struct extra_type **new_target,
                                            enum gen_action trigger_action);
static void illegal_action(struct player *pplayer,
                           struct unit *actor,
                           action_id stopped_action,
                           struct player *tgt_player,
                           struct tile *target_tile,
                           const struct city *target_city,
                           const struct unit *target_unit,
                           int request_kind,
                           const enum action_requester requester);
static bool city_add_unit(struct player *pplayer, struct unit *punit,
                          struct city *pcity, const struct action *paction);
static bool city_build(struct player *pplayer, struct unit *punit,
                       struct tile *ptile, const char *name,
                       const struct action *paction);
static bool do_unit_establish_trade(struct player *pplayer,
                                    struct unit *punit,
                                    struct city *pcity_dest,
                                    const struct action *paction);
 
static bool unit_do_help_build(struct player *pplayer,
                               struct unit *punit,
                               struct city *pcity_dest,
                               const struct action *paction);
static bool unit_do_regular_move(struct player *actor_player,
                                 struct unit *actor_unit,
                                 struct tile *target_tile,
                                 const struct action *paction);
static bool unit_bombard(struct unit *punit, struct tile *ptile,
                         const struct action *paction);
static bool unit_nuke(struct player *pplayer, struct unit *punit,
                      struct tile *def_tile,
                      const struct action *paction);
static bool unit_do_destroy_city(struct player *act_player,
                                 struct unit *act_unit,
                                 struct city *tgt_city,
                                 const struct action *paction);
static bool do_unit_change_homecity(struct unit *punit,
                                    struct city *pcity,
                                    const struct action *paction);
static bool do_attack(struct unit *actor_unit, struct tile *target_tile,
                      const struct action *paction);
static bool do_unit_strike_city_production(struct player *act_player,
                                           struct unit *act_unit,
                                           struct city *tgt_city,
                                           const struct action *paction);
static bool do_unit_strike_city_building(struct player *act_player,
                                         struct unit *act_unit,
                                         struct city *tgt_city,
                                         Impr_type_id tgt_bld_id,
                                         const struct action *paction);
static bool do_unit_conquer_city(struct player *act_player,
                                 struct unit *act_unit,
                                 struct city *tgt_city,
                                 struct action *paction);
static bool do_action_activity(struct unit *punit,
                               const struct action *paction);
static bool do_action_activity_targeted(struct unit *punit,
                                        const struct action *paction,
                                        struct extra_type **new_target);
static inline bool
non_allied_not_listed_at(const struct player *pplayer,
                         const int *list, int n, const struct tile *ptile);
 
/**********************************************************************/
void handle_unit_type_upgrade(struct player *pplayer, Unit_type_id uti)
{
  const struct unit_type *to_unittype;
  struct unit_type *from_unittype = utype_by_number(uti);
  int number_of_upgraded_units = 0;
  struct action *paction = action_by_number(ACTION_UPGRADE_UNIT);
  const struct civ_map *nmap = &(wld.map);
 
  if (NULL == from_unittype) {
    /* Probably died or bribed. */
    log_verbose("handle_unit_type_upgrade() invalid unit type %d", uti);
    return;
  }
 
  to_unittype = can_upgrade_unittype(pplayer, from_unittype);
  if (!to_unittype) {
    notify_player(pplayer, NULL, E_BAD_COMMAND, ftc_server,
                  _("Illegal packet, can't upgrade %s (yet)."),
                  utype_name_translation(from_unittype));
    return;
  }
 
  /* 
   * Try to upgrade units. The order we upgrade in is arbitrary (if
   * the player really cared they should have done it manually). 
   */
  conn_list_do_buffer(pplayer->connections);
  unit_list_iterate(pplayer->units, punit) {
    if (unit_type_get(punit) == from_unittype) {
      struct city *pcity = tile_city(unit_tile(punit));
 
      if (is_action_enabled_unit_on_city(nmap, paction->id, punit, pcity)
          && unit_perform_action(pplayer, punit->id, pcity->id, 0, "",
                                 paction->id, ACT_REQ_SS_AGENT)) {
        number_of_upgraded_units++;
      } else if (UU_NO_MONEY == unit_upgrade_test(nmap, punit, FALSE)) {
        break;
      }
    }
  } unit_list_iterate_end;
  conn_list_do_unbuffer(pplayer->connections);
 
  /* Alert the player about what happened. */
  if (number_of_upgraded_units > 0) {
    const int cost = unit_upgrade_price(pplayer, from_unittype, to_unittype);
    notify_player(pplayer, NULL, E_UNIT_UPGRADED, ftc_server,
                  /* FIXME: plurality of number_of_upgraded_units ignored!
                   * (Plurality of unit names is messed up anyway.) */
                  /* TRANS: "2 Musketeers upgraded to Riflemen for 100 gold."
                   * Plurality is in gold (second %d), not units. */
                  PL_("%d %s upgraded to %s for %d gold.",
                      "%d %s upgraded to %s for %d gold.",
                      cost * number_of_upgraded_units),
                  number_of_upgraded_units,
                  utype_name_translation(from_unittype),
                  utype_name_translation(to_unittype),
                  cost * number_of_upgraded_units);
    send_player_info_c(pplayer, pplayer->connections);
  } else {
    notify_player(pplayer, NULL, E_UNIT_UPGRADED, ftc_server,
                  _("No units could be upgraded."));
  }
}
 
/**********************************************************************/
static bool do_unit_upgrade(struct player *pplayer,
                            struct unit *punit, struct city *pcity,
                            enum action_requester ordered_by,
                            const struct action *paction)
{
  const struct unit_type *from_unit = unit_type_get(punit);
  const struct unit_type *to_unit = can_upgrade_unittype(pplayer, from_unit);
  int cost = unit_upgrade_price(pplayer, from_unit, to_unit);
 
  transform_unit(punit, to_unit, game.server.upgrade_veteran_loss);
  pplayer->economic.gold -= cost;
  send_player_info_c(pplayer, pplayer->connections);
 
  if (ordered_by == ACT_REQ_PLAYER) {
    notify_player(pplayer, unit_tile(punit), E_UNIT_UPGRADED, ftc_server,
                  PL_("%s upgraded to %s for %d gold.",
                      "%s upgraded to %s for %d gold.", cost),
                  utype_name_translation(from_unit),
                  unit_link(punit),
                  cost);
  }
 
  return TRUE;
}
 
/**********************************************************************/
static inline bool
non_allied_not_listed_at(const struct player *pplayer,
                         const int *list, int n, const struct tile *ptile)
{
  unit_list_iterate(ptile->units, punit) {
    if (!pplayers_allied(pplayer, unit_owner(punit))) {
      bool listed = FALSE;
      int id = punit->id;
      int i;
 
      for (i = 0; i < n; i++) {
        if (id == list[i]) {
          listed = TRUE;
          break;
        }
      }
      if (!listed) {
        return TRUE;
      }
    }
  } unit_list_iterate_end;
  return FALSE;
}
 
/**********************************************************************/
static bool do_capture_units(struct player *pplayer,
                             struct unit *punit,
                             struct tile *pdesttile,
                             const struct action *paction)
{
  struct city *pcity;
  char capturer_link[MAX_LEN_LINK];
  char hcity_name[MAX_LEN_NAME] = {'\0'};
  const char *capturer_nation = nation_plural_for_player(pplayer);
  bv_unit_types unique_on_tile;
  const struct unit_type *act_utype;
  int id, hcity;
  int n = 0, capt[unit_list_size(pdesttile->units)];
  bool lost_with_city = FALSE;
  int i;
 
  /* Sanity check: The actor still exists. */
  fc_assert_ret_val(pplayer, FALSE);
  fc_assert_ret_val(punit, FALSE);
  id = punit->id;
 
  act_utype = unit_type_get(punit);
 
  /* Sanity check: make sure that the capture won't result in the actor
   * ending up with more than one unit of each unique unit type. */
  BV_CLR_ALL(unique_on_tile);
  unit_list_iterate(pdesttile->units, to_capture) {
    bool unique_conflict = FALSE;
 
    /* Check what the player already has. */
    if (utype_player_already_has_this_unique(pplayer,
                                             unit_type_get(to_capture))) {
      /* The player already has a unit of this kind. */
      unique_conflict = TRUE;
    }
 
    if (utype_has_flag(unit_type_get(to_capture), UTYF_UNIQUE)) {
      /* The type of the units at the tile must also be checked. Two allied
       * players can both have their unique unit at the same tile.
       * Capturing them both would give the actor two units of a kind that
       * is supposed to be unique. */
 
      if (BV_ISSET(unique_on_tile, utype_index(unit_type_get(to_capture)))) {
        /* There is another unit of the same kind at this tile. */
        unique_conflict = TRUE;
      } else {
        /* Remember the unit type in case another unit of the same kind is
         * encountered later. */
        BV_SET(unique_on_tile, utype_index(unit_type_get(to_capture)));
      }
    }
 
    if (unique_conflict) {
      log_debug("capture units: already got unique unit");
      notify_player(pplayer, pdesttile, E_UNIT_ILLEGAL_ACTION, ftc_server,
                    /* TRANS: You can only have one Leader. */
                    _("You can only have one %s."),
                    unit_link(to_capture));
 
      return FALSE;
    }
    /* Remember the units here
     * for the mess callbacks may do in the process of transferring */
     capt[n++] = to_capture->id;
  } unit_list_iterate_end;
 
  /* N.B: unit_link() always returns the same pointer. */
  sz_strlcpy(capturer_link, unit_link(punit));
 
  pcity = tile_city(pdesttile);
  hcity = game.server.homecaughtunits
    ? punit->homecity : IDENTITY_NUMBER_ZERO;
  if (hcity) {
    /* Rarely, we'll need it... */
    sz_strlcpy(hcity_name, city_name_get(game_city_by_number(hcity)));
  }
 
  for (i = 0; i < n; i++) {
    struct unit *to_capture = game_unit_by_number(capt[i]);
    struct player *uplayer;
    const char *victim_link;
    const struct unit_type *utype;
    struct tile *ptile = NULL;
    bool really_lost = FALSE;
 
    if (!to_capture) {
      continue;
    }
    uplayer = unit_owner(to_capture);
    if (uplayer == pplayer) {
      /* Somehow transferred by scripts (e.g. diplomat incited a city) */
      continue;
    }
    utype = unit_type_get(to_capture);
    really_lost = lost_with_city && !utype_has_flag(utype, UTYF_NOHOME);
    uplayer->score.units_lost++;
    if (!really_lost) {
      /* A hack: if the captured unit is lost with a capturer's city,
       * we link the old unit, otherwise the new one */
      to_capture = unit_change_owner(to_capture, pplayer,
                                     hcity, ULR_CAPTURED);
    }
    if (!to_capture) {
      /* Lost during capturing */
      victim_link = utype_name_translation(utype);
    } else {
      /* As unit_change_owner() currently remove the old unit and
       * replace by a new one (with a new id), we want to make link to
       * the new unit. */
      victim_link = unit_link(to_capture);
      ptile = unit_tile(to_capture);
      /* Notify capturer only if there is a gain */
      notify_player(pplayer, pdesttile, E_MY_DIPLOMAT_BRIBE, ftc_server,
                    /* TRANS: <unit> ... <unit> */
                    _("Your %s succeeded in capturing the %s %s."),
                    capturer_link, nation_adjective_for_player(uplayer),
                    victim_link);
    }
 
    /* Notify loser */
    notify_player(uplayer, pdesttile,
                  E_ENEMY_DIPLOMAT_BRIBE, ftc_server,
                  /* TRANS: <unit> ... <Poles> */
                  _("Your %s was captured by the %s."),
                  victim_link, capturer_nation);
 
    /* May cause an incident */
    action_consequence_success(paction, pplayer, act_utype, uplayer,
                               pdesttile, victim_link);
 
    if (really_lost) {
      /* The city for which the unit was captured has perished! */
      /* Nobody actually gets the unit. */
      pplayer->score.units_lost++;
      notify_player(pplayer, pdesttile,
                    E_UNIT_LOST_MISC, ftc_server,
                    _("%s lost along with control of %s."),
                    victim_link, hcity_name);
      /* As in unit_change_owner(), don't say pplayer is killer */
      wipe_unit(to_capture, ULR_CAPTURED, NULL);
      continue;
    }
 
    if (to_capture != NULL) {
      struct player *new_owner = unit_owner(to_capture);
 
      if (NULL != pcity /* Keep old behavior */
          || is_non_allied_city_tile(ptile, new_owner)
          || (new_owner == pplayer
              ? non_allied_not_listed_at(pplayer, capt + (i + 1),
                                         n - (i + 1), ptile)
              : (bool)
                is_non_allied_unit_tile(ptile, new_owner,
                                        unit_has_type_flag(to_capture,
                                                           UTYF_FLAGLESS)))) {
        /* The captured unit is in a city or with a foreign unit
         * that its owner is not capturing. Bounce it. */
        bounce_unit(to_capture, TRUE);
      }
    }
 
    /* Check if the city we are going to home units in stays. */
    if (hcity && i + 1 < n && !player_city_by_number(pplayer, hcity)) {
      /* Oops, it's lost. Maybe the capturer is rehomed? */
      if (player_unit_by_number(pplayer, id)) {
        /* Well, it's natural to home them here now */
        hcity = punit->homecity;
      } else {
        /* Removing the rest of the stack (except "NoHome" units) */
        lost_with_city = TRUE;
      }
    }
  }
 
  if (!unit_is_alive(id)) {
    /* Callbacks took the capturer, nothing more to do */
    return TRUE;
  }
  unit_did_action(punit);
  unit_forget_last_activity(punit);
 
  send_unit_info(NULL, punit);
 
  return TRUE;
}
 
/**********************************************************************/
static bool occupy_move(struct tile *def_tile, struct unit *punit,
                        const struct action *paction)
{
  if (!is_non_allied_unit_tile(def_tile, unit_owner(punit),
                               unit_has_type_flag(punit, UTYF_FLAGLESS))) {
    /* Hack: make sure the unit has enough moves_left for the move to succeed,
     * and adjust moves_left to afterward (if successful). */
    int old_moves = punit->moves_left;
    int full_moves = unit_move_rate(punit);
    int id = punit->id;
 
    punit->moves_left = full_moves;
    /* Post attack occupy move. */
    if (NULL != action_auto_perf_unit_do(AAPC_POST_ACTION, punit,
                                         NULL, NULL, paction,
                                         def_tile, tile_city(def_tile),
                                         NULL, NULL)) {
      if (unit_is_alive(id)) {
        int mcost = MAX(0, full_moves - punit->moves_left - SINGLE_MOVE);
 
        /* Move cost is bigger of attack (SINGLE_MOVE) and occupying move costs.
         * Attack SINGLE_COST is already calculated in to old_moves. */
        punit->moves_left = old_moves - mcost;
        if (punit->moves_left < 0) {
          punit->moves_left = 0;
        }
      } else {
        return FALSE;
      }
    } else if (unit_is_alive(id)) {
      punit->moves_left = old_moves;
    } else {
      return FALSE;
    }
  }
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_wipe_units(struct unit *punit,
                          struct tile *pdesttile,
                          const struct action *paction)
{
  struct player *wiper = unit_owner(punit);
  int wid = punit->id;
  char wiper_link[MAX_LEN_LINK];
  const char *wiper_nation = nation_plural_for_player(wiper);
  const struct unit_type *act_utype = unit_type_get(punit);
 
  /* N.B: unit_link() always returns the same pointer. */
  sz_strlcpy(wiper_link, unit_link(punit));
 
  unit_list_iterate_safe(pdesttile->units, to_wipe) {
    struct player *owner = unit_owner(to_wipe);
    const char *victim_link = unit_link(to_wipe);
 
    wipe_unit(to_wipe, ULR_KILLED, wiper);
 
    /* Notify players */
    notify_player(wiper, pdesttile, E_UNIT_WIN_ATT, ftc_server,
                  /* TRANS: <unit> ... <unit> */
                  _("Your %s wiped the %s %s."),
                  wiper_link, nation_adjective_for_player(owner),
                  victim_link);
    notify_player(owner, pdesttile,
                  E_UNIT_LOST_DEF, ftc_server,
                  /* TRANS: <unit> ... <Poles> */
                  _("Your %s was wiped by the %s."),
                  victim_link, wiper_nation);
 
    /* May cause an incident */
    action_consequence_success(paction, wiper, act_utype, owner,
                               pdesttile, victim_link);
 
  } unit_list_iterate_safe_end;
 
  if (unit_is_alive(wid) && occupy_move(pdesttile, punit, paction)) {
    unit_did_action(punit);
    unit_forget_last_activity(punit);
 
    send_unit_info(NULL, punit);
  }
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_expel_unit(struct player *pplayer,
                          struct unit *actor,
                          struct unit *target,
                          const struct action *paction)
{
  char target_link[MAX_LEN_LINK];
  struct player *uplayer;
  struct tile *target_tile;
  struct city *pcity;
  const struct unit_type *act_utype;
 
  /* Maybe it didn't survive the Lua call back. Why wasn't this caught by
   * the caller? Check in the code that emits the signal. */
  fc_assert_ret_val(target, FALSE);
 
  uplayer = unit_owner(target);
 
  /* A unit is supposed to have an owner. */
  fc_assert_ret_val(uplayer, FALSE);
 
  /* Maybe it didn't survive the Lua call back. Why wasn't this caught by
   * the caller? Check in the code that emits the signal. */
  fc_assert_ret_val(actor, FALSE);
  act_utype = unit_type_get(actor);
 
  /* Where is the actor player? */
  fc_assert_ret_val(pplayer, FALSE);
 
  target_tile = unit_tile(target);
 
  /* Expel the target unit to its owner's primary capital. */
  /* TODO: Could be also nearest secondary capital */
  pcity = player_primary_capital(uplayer);
 
  /* N.B: unit_link() always returns the same pointer. */
  sz_strlcpy(target_link, unit_link(target));
 
  if (pcity == NULL) {
    /* No where to send the expelled unit. */
 
    /* The price of failing an expulsion is a single move. */
    actor->moves_left = MAX(0, actor->moves_left - SINGLE_MOVE);
    send_unit_info(NULL, actor);
 
    /* Notify the actor player. */
    notify_player(pplayer, target_tile, E_UNIT_ACTION_FAILED, ftc_server,
                  /* TRANS: <Poles> <Spy> */
                  _("The %s don't have a capital to expel their %s to."),
                  nation_plural_for_player(uplayer), target_link);
 
    /* Nothing more could be done. */
    return FALSE;
  }
 
  /* Please review the code below and above (including the strings sent to
   * the players) before allowing expulsion to non capital cities. */
  fc_assert(is_capital(pcity));
 
  /* Notify everybody involved. */
  notify_player(pplayer, target_tile, E_UNIT_DID_EXPEL, ftc_server,
                /* TRANS: <Border Patrol> ... <Spy> */
                _("Your %s succeeded in expelling the %s %s."),
                unit_link(actor), nation_adjective_for_player(uplayer),
                target_link);
  notify_player(uplayer, target_tile, E_UNIT_WAS_EXPELLED, ftc_server,
                /* TRANS: <unit> ... <Poles> */
                _("Your %s was expelled by the %s."),
                target_link, nation_plural_for_player(pplayer));
 
  /* Being expelled destroys all remaining movement. */
  if (!teleport_unit_to_city(target, pcity, 0, FALSE)) {
    log_error("Bug in unit expulsion: unit can't teleport.");
 
    return FALSE;
  }
 
  /* This may cause a diplomatic incident */
  action_consequence_success(paction, pplayer, act_utype, uplayer,
                             target_tile, target_link);
 
  /* Mission accomplished. */
  return TRUE;
}
 
/**********************************************************************/
static bool do_conquer_extras(struct player *act_player,
                              struct unit *act_unit,
                              struct tile *tgt_tile,
                              const struct action *paction)
{
  bool success;
  int move_cost = map_move_cost_unit(&(wld.map), act_unit, tgt_tile);
  struct player *tgt_player = extra_owner(tgt_tile);
 
  /* Sanity check */
  fc_assert_ret_val(act_unit, FALSE);
  fc_assert_ret_val(tgt_tile, FALSE);
 
  unit_move(act_unit, tgt_tile, move_cost,
            NULL, BV_ISSET(paction->sub_results, ACT_SUB_RES_MAY_EMBARK),
            FALSE, TRUE,
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_ENTER),
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_FRIGHTEN));
 
  success = extra_owner(tgt_tile) == act_player;
 
  if (success) {
    const struct unit_type *act_utype = unit_type_get(act_unit);
 
    /* May cause an incident */
    action_consequence_success(paction, act_player, act_utype,
                               tgt_player, tgt_tile,
                               tile_link(tgt_tile));
  }
 
  return success;
}
 
/**********************************************************************/
static bool do_heal_unit(struct player *act_player,
                         struct unit *act_unit,
                         struct unit *tgt_unit,
                         const struct action *paction)
{
  int healing_limit;
  int tgt_hp_max;
  struct player *tgt_player;
  struct tile *tgt_tile;
  char act_unit_link[MAX_LEN_LINK];
  char tgt_unit_link[MAX_LEN_LINK];
  const char *tgt_unit_owner;
  const struct unit_type *act_utype;
 
  /* Sanity checks: got all the needed input. */
  fc_assert_ret_val(act_player, FALSE);
  fc_assert_ret_val(act_unit, FALSE);
  fc_assert_ret_val(tgt_unit, FALSE);
 
  act_utype = unit_type_get(act_unit);
 
  /* The target unit can't have more HP than this. */
  tgt_hp_max = unit_type_get(tgt_unit)->hp;
 
  /* Sanity check: target isn't at full health and can therefore can be
   * healed. */
  fc_assert_ret_val(tgt_unit->hp < tgt_hp_max, FALSE);
 
  /* Fetch the target unit's owner. */
  tgt_player = unit_owner(tgt_unit);
  fc_assert_ret_val(tgt_player, FALSE);
 
  /* Fetch the target unit's tile. */
  tgt_tile = unit_tile(tgt_unit);
  fc_assert_ret_val(tgt_tile, FALSE);
 
  /* The max amount of HP that can be added. */
  healing_limit = ((get_target_bonus_effects(
                      NULL,
                      &(const struct req_context) {
                        .player = unit_owner(act_unit),
                        .city = tile_city(unit_tile(act_unit)),
                        .tile = unit_tile(act_unit),
                        .unit = act_unit,
                        .unittype = unit_type_get(act_unit),
                        .action = paction,
                      },
                      &(const struct req_context) {
                        .player = unit_owner(tgt_unit),
                        .city = tile_city(unit_tile(tgt_unit)),
                        .tile = unit_tile(tgt_unit),
                        .unit = tgt_unit,
                        .unittype = unit_type_get(tgt_unit),
                      },
                      EFT_HEAL_UNIT_PCT
                    ) + 100)
                   * tgt_hp_max) / 100;
 
  /* Heal the target unit. */
  tgt_unit->hp = MIN(tgt_unit->hp + healing_limit, tgt_hp_max);
  send_unit_info(NULL, tgt_unit);
 
  send_unit_info(NULL, act_unit);
 
  /* Every call to unit_link() overwrites the previous. Two units are being
   * linked to. */
  sz_strlcpy(act_unit_link, unit_link(act_unit));
  sz_strlcpy(tgt_unit_link, unit_link(tgt_unit));
 
  /* Notify everybody involved. */
  if (act_player == tgt_player) {
    /* TRANS: used instead of nation adjective when the nation is
     * domestic. */
    tgt_unit_owner = _("your");
  } else {
    tgt_unit_owner = nation_adjective_for_player(unit_nationality(tgt_unit));
  }
 
  notify_player(act_player, tgt_tile, E_MY_UNIT_DID_HEAL, ftc_server,
                /* TRANS: If foreign: Your Leader heals Finnish Warrior.
                 * If domestic: Your Leader heals your Warrior. */
                _("Your %s heals %s %s."),
                act_unit_link, tgt_unit_owner, tgt_unit_link);
 
  if (act_player != tgt_player) {
    notify_player(tgt_player, tgt_tile, E_MY_UNIT_WAS_HEALED, ftc_server,
                  /* TRANS: Norwegian ... Leader ... Warrior */
                  _("%s %s heals your %s."),
                  nation_adjective_for_player(unit_nationality(act_unit)),
                  act_unit_link, tgt_unit_link);
  }
 
  /* This may have diplomatic consequences. */
  action_consequence_success(paction, act_player, act_utype, tgt_player,
                             tgt_tile, unit_link(tgt_unit));
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_deboard(struct player *act_player,
                            struct unit *act_unit,
                            struct unit *tgt_unit,
                            const struct action *paction)
{
  /* Unload the unit and send out info to clients. */
  unit_transport_unload_send(act_unit);
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_board(struct player *act_player,
                          struct unit *act_unit,
                          struct unit *tgt_unit,
                          const struct action *paction)
{
  if (unit_transported(act_unit)) {
    unit_transport_unload(act_unit);
  }
 
  /* Load the unit and send out info to clients. */
  unit_transport_load_send(act_unit, tgt_unit);
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_load(struct player *act_player,
                          struct unit *act_unit,
                          struct unit *tgt_unit,
                          const struct action *paction)
{
  if (unit_transported(tgt_unit)) {
    unit_transport_unload(tgt_unit);
  }
 
  /* Load the unit and send out info to clients. */
  unit_transport_load_send(tgt_unit, act_unit);
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_unload(struct player *act_player,
                           struct unit *act_unit,
                           struct unit *tgt_unit,
                           const struct action *paction)
{
  /* Unload the unit and send out info to clients. */
  unit_transport_unload_send(tgt_unit);
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_disembark(struct player *act_player,
                         struct unit *act_unit,
                         struct tile *tgt_tile,
                         const struct action *paction)
{
  int move_cost = map_move_cost_unit(&(wld.map), act_unit, tgt_tile);
 
  /* Sanity checks */
  fc_assert_ret_val(act_player, FALSE);
  fc_assert_ret_val(act_unit, FALSE);
  fc_assert_ret_val(tgt_tile, FALSE);
  fc_assert_ret_val(paction, FALSE);
 
  unit_move(act_unit, tgt_tile, move_cost,
            NULL, BV_ISSET(paction->sub_results, ACT_SUB_RES_MAY_EMBARK),
            FALSE, FALSE,
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_ENTER),
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_FRIGHTEN));
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_hut(struct player *act_player,
                        struct unit *act_unit,
                        struct tile *tgt_tile,
                        const struct action *paction)
{
  int move_cost = map_move_cost_unit(&(wld.map), act_unit, tgt_tile);
 
  /* Sanity checks */
  fc_assert_ret_val(act_player, FALSE);
  fc_assert_ret_val(act_unit, FALSE);
  fc_assert_ret_val(tgt_tile, FALSE);
  fc_assert_ret_val(paction, FALSE);
 
  unit_move(act_unit, tgt_tile, move_cost,
            NULL, BV_ISSET(paction->sub_results, ACT_SUB_RES_MAY_EMBARK),
            FALSE, FALSE,
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_ENTER),
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_FRIGHTEN));
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_embark(struct player *act_player,
                           struct unit *act_unit,
                           struct unit *tgt_unit,
                           const struct action *paction)
{
  struct tile *tgt_tile;
  int move_cost;
 
  /* Sanity checks */
  fc_assert_ret_val(act_player, FALSE);
  fc_assert_ret_val(act_unit, FALSE);
  fc_assert_ret_val(tgt_unit, FALSE);
  fc_assert_ret_val(paction, FALSE);
 
  if (unit_transported(act_unit)) {
    /* Assumed to be legal. */
    unit_transport_unload(act_unit);
  }
 
  /* Do it. */
  tgt_tile = unit_tile(tgt_unit);
  move_cost = map_move_cost_unit(&(wld.map), act_unit, tgt_tile);
  unit_move(act_unit, tgt_tile, move_cost,
            tgt_unit, BV_ISSET(paction->sub_results,
                               ACT_SUB_RES_MAY_EMBARK),
            FALSE, FALSE,
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_ENTER),
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_FRIGHTEN));
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_make_homeless(struct unit *punit,
                                  const struct action *paction)
{
  unit_change_homecity_handling(punit, NULL, TRUE);
 
  return punit->homecity == IDENTITY_NUMBER_ZERO;
}
 
/**********************************************************************/
static bool rel_may_become_war(const struct player *pplayer,
                               const struct player *oplayer)
{
  enum diplstate_type ds;
 
  fc_assert_ret_val(pplayer, FALSE);
  fc_assert_ret_val(oplayer, FALSE);
 
  ds = player_diplstate_get(pplayer, oplayer)->type;
 
  /* The player can't declare war on
   * someone they already are at war with. */
  return ds != DS_WAR
      /* The player can't declare war on a teammate or on themself. */
      && ds != DS_TEAM && pplayer != oplayer;
}
 
/**********************************************************************/
static bool
need_war_enabler(const struct unit_type *actor_utype,
                 const struct action *paction,
                 struct player *player1,
                 struct player *player2,
                 bool act_if_diplrel_kind(const struct unit_type *,
                                          const action_id,
                                          const int,
                                          const bool))
{
  if (player2 == NULL) {
    /* No one to declare war on */
    return FALSE;
  }
 
  if (!rel_may_become_war(player1, player2)) {
    /* Can't declare war. */
    return FALSE;
  }
 
  if (act_if_diplrel_kind(actor_utype, paction->id,
                          player_diplstate_get(player1,
                                               player2)->type,
                          TRUE)) {
    /* The current diplrel isn't the problem. */
    return FALSE;
  }
 
  if (!act_if_diplrel_kind(actor_utype, paction->id, DS_WAR, TRUE)) {
    /* War won't make this action legal. */
    return FALSE;
  }
 
  return TRUE;
}
 
/**********************************************************************/
static struct player *need_war_player_hlp(const struct unit *actor,
                                          const action_id act,
                                          const struct tile *target_tile,
                                          const struct city *target_city,
                                          const struct unit *target_unit)
{
  struct player *target_player = NULL;
  struct player *actor_player = unit_owner(actor);
  struct action *paction = action_by_number(act);
 
  fc_assert_ret_val(paction != NULL, NULL);
 
  if (action_id_get_actor_kind(act) != AAK_UNIT) {
    /* No unit can ever do this action so it isn't relevant. */
    return NULL;
  }
 
  if (!unit_can_do_action(actor, act)) {
    /* The unit can't do the action no matter if there is war or not. */
    return NULL;
  }
 
  /* Look for hard coded war requirements without support for looking up in
   * an action enabler requirement. */
  switch (paction->result) {
  case ACTRES_ATTACK:
  case ACTRES_WIPE_UNITS:
  case ACTRES_SPY_BRIBE_STACK:
  case ACTRES_COLLECT_RANSOM:
    /* Target is a unit stack but a city can block it. */
    fc_assert_action(action_get_target_kind(paction) == ATK_STACK, break);
 
    if (!unit_has_type_flag(actor, UTYF_FLAGLESS)) {
      if (target_tile != NULL) {
        struct city *tcity;
 
        if ((tcity = tile_city(target_tile))
            && rel_may_become_war(unit_owner(actor), city_owner(tcity))) {
          return city_owner(tcity);
        }
      }
    }
    break;
 
  case ACTRES_PARADROP:
  case ACTRES_PARADROP_CONQUER:
    /* Target is a tile but a city can block it. */
    fc_assert_action(action_get_target_kind(paction) == ATK_TILE, break);
    if (target_tile != NULL
        && map_is_known_and_seen(target_tile, actor_player, V_MAIN)) {
      /* Seen tile unit savers */
 
      struct city *tcity;
 
      if ((tcity = tile_non_attack_city(target_tile, actor_player))) {
        return city_owner(tcity);
      }
    }
    break;
  case ACTRES_CONQUER_EXTRAS:
  case ACTRES_ESTABLISH_EMBASSY:
  case ACTRES_SPY_INVESTIGATE_CITY:
  case ACTRES_SPY_POISON:
  case ACTRES_SPY_SPREAD_PLAGUE:
  case ACTRES_SPY_STEAL_GOLD:
  case ACTRES_SPY_SABOTAGE_CITY:
  case ACTRES_SPY_TARGETED_SABOTAGE_CITY:
  case ACTRES_SPY_SABOTAGE_CITY_PRODUCTION:
  case ACTRES_SPY_STEAL_TECH:
  case ACTRES_SPY_TARGETED_STEAL_TECH:
  case ACTRES_SPY_INCITE_CITY:
  case ACTRES_TRADE_ROUTE:
  case ACTRES_MARKETPLACE:
  case ACTRES_HELP_WONDER:
  case ACTRES_SPY_BRIBE_UNIT:
  case ACTRES_SPY_SABOTAGE_UNIT:
  case ACTRES_CAPTURE_UNITS: /* Only foreign is a hard req. */
  case ACTRES_FOUND_CITY:
  case ACTRES_JOIN_CITY:
  case ACTRES_STEAL_MAPS:
  case ACTRES_SPY_NUKE:
  case ACTRES_NUKE:
  case ACTRES_NUKE_UNITS:
  case ACTRES_DESTROY_CITY:
  case ACTRES_EXPEL_UNIT:
  case ACTRES_DISBAND_UNIT_RECOVER:
  case ACTRES_DISBAND_UNIT:
  case ACTRES_HOME_CITY:
  case ACTRES_HOMELESS:
  case ACTRES_UPGRADE_UNIT:
  case ACTRES_AIRLIFT:
  case ACTRES_HEAL_UNIT:
  case ACTRES_STRIKE_BUILDING:
  case ACTRES_STRIKE_PRODUCTION:
  case ACTRES_BOMBARD:
  case ACTRES_CONQUER_CITY:
  case ACTRES_TRANSFORM_TERRAIN:
  case ACTRES_CULTIVATE:
  case ACTRES_PLANT:
  case ACTRES_PILLAGE:
  case ACTRES_CLEAN:
  case ACTRES_FORTIFY:
  case ACTRES_CONVERT:
  case ACTRES_ROAD:
  case ACTRES_BASE:
  case ACTRES_MINE:
  case ACTRES_IRRIGATE:
  case ACTRES_TRANSPORT_DEBOARD:
  case ACTRES_TRANSPORT_UNLOAD:
  case ACTRES_TRANSPORT_DISEMBARK:
  case ACTRES_TRANSPORT_BOARD:
  case ACTRES_TRANSPORT_LOAD:
  case ACTRES_TRANSPORT_EMBARK:
  case ACTRES_SPY_ATTACK:
  case ACTRES_HUT_ENTER:
  case ACTRES_HUT_FRIGHTEN:
  case ACTRES_UNIT_MOVE:
  case ACTRES_TELEPORT:
  case ACTRES_TELEPORT_CONQUER:
  case ACTRES_ENABLER_CHECK:
  case ACTRES_SPY_ESCAPE:
  case ACTRES_NONE:
    /* No special help. */
    break;
 
  ASSERT_UNUSED_ACTRES_CASES;
  }
 
  /* Look for war requirements from the action enablers. */
  switch (action_get_target_kind(paction)) {
  case ATK_CITY:
    if (target_city == NULL) {
      /* No target city. */
      return NULL;
    }
 
    target_player = city_owner(target_city);
    break;
  case ATK_UNIT:
    if (target_unit == NULL) {
      /* No target unit. */
      return NULL;
    }
    if (unit_has_type_flag(target_unit, UTYF_FLAGLESS)) {
      /* Target unit is flagless anyway - no war needed */
      return NULL;
    }
 
    target_player = unit_owner(target_unit);
    break;
  case ATK_STACK:
    if (target_tile == NULL) {
      /* No target units since no target tile. */
      return NULL;
    }
 
    unit_list_iterate(target_tile->units, tunit) {
      if (!unit_has_type_flag(tunit, UTYF_FLAGLESS)
          && rel_may_become_war(actor_player, unit_owner(tunit))) {
        target_player = unit_owner(tunit);
        break;
      }
    } unit_list_iterate_end;
    break;
  case ATK_TILE:
    if (target_tile == NULL) {
      /* No target tile. */
      return NULL;
    }
    target_player = tile_owner(target_tile);
    break;
  case ATK_EXTRAS:
    if (target_tile == NULL) {
      /* No target tile. */
      return NULL;
    }
    target_player = target_tile->owner;
    break;
  case ATK_SELF:
    /* Can't declare war on itself. */
    return NULL;
    break;
  case ATK_COUNT:
    /* Nothing to check. */
    fc_assert(action_id_get_target_kind(act) != ATK_COUNT);
    return NULL;
  }
 
  if (target_player == NULL) {
    /* Declaring war won't enable the specified action. */
    return NULL;
  }
 
  /* Look for DiplRelTileOther war requirements from the action enablers. */
  if (target_tile != NULL
      && need_war_enabler(unit_type_get(actor), paction,
                          actor_player, tile_owner(target_tile),
                          utype_can_act_if_tgt_diplrel_tile_other)) {
    return tile_owner(target_tile);
  }
 
  /* Look for DiplRel war requirements from the action enablers. */
  if (need_war_enabler(unit_type_get(actor), paction,
                       actor_player, target_player,
                       can_utype_do_act_if_tgt_diplrel)) {
    return target_player;
  }
 
  /* No check if other, non war, diplomatic states also could make the
   * action legal. This is need_war_player() so war is always the answer.
   * If you disagree and decide to add support please check that
   * webperimental's "can't found a city on a tile belonging to a non enemy"
   * rule still is detected. */
 
  return NULL;
}
 
/**********************************************************************/
static struct player *need_war_player(const struct unit *actor,
                                      const action_id act_id,
                                      const struct tile *target_tile,
                                      const struct city *target_city,
                                      const struct unit *target_unit)
{
  if (act_id == ACTION_ANY) {
    /* Any action at all will do. */
    action_iterate(act) {
      struct player *war_player;
 
      war_player = need_war_player_hlp(actor, act,
                                       target_tile, target_city,
                                       target_unit);
 
      if (war_player != NULL) {
        /* Declaring war on this player may enable this action. */
        return war_player;
      }
    } action_iterate_end;
 
    /* No action at all may be enabled by declaring war. */
    return NULL;
  } else {
    /* Look for the specified action. */
    return need_war_player_hlp(actor, act_id,
                               target_tile, target_city,
                               target_unit);
  }
}
 
/**********************************************************************/
static bool
tile_has_units_not_allied_to_but_seen_by(const struct tile *ptile,
                                         const struct player *pplayer)
{
  unit_list_iterate(ptile->units, pother) {
    if (can_player_see_unit(pplayer, pother)
        && !pplayers_allied(pplayer, unit_owner(pother))) {
      return TRUE;
    }
  } unit_list_iterate_end;
 
  return FALSE;
}
 
/**********************************************************************/
static bool does_terrain_block_action(const action_id act_id,
                                      bool is_target,
                                      struct unit *actor_unit,
                                      struct terrain *pterrain)
{
  if (act_id == ACTION_ANY) {
    /* Any action is OK. */
    action_iterate(alt_act) {
      if (utype_can_do_action(unit_type_get(actor_unit), alt_act)
          && !does_terrain_block_action(alt_act, is_target,
                                        actor_unit, pterrain)) {
        /* Only one action has to be possible. */
        return FALSE;
      }
    } action_iterate_end;
 
    /* No action enabled. */
    return TRUE;
  }
 
  /* ACTION_ANY is handled above. */
  fc_assert_ret_val(action_id_exists(act_id), FALSE);
 
  action_enabler_list_iterate(action_enablers_for_action(act_id),
                              enabler) {
    if (requirement_fulfilled_by_terrain(pterrain,
            (is_target ? &enabler->target_reqs : &enabler->actor_reqs))
        && requirement_fulfilled_by_unit_type(unit_type_get(actor_unit),
                                              &enabler->actor_reqs)) {
      /* This terrain kind doesn't block this action enabler. */
      return FALSE;
    }
  } action_enabler_list_iterate_end;
 
  return TRUE;
}
 
/**********************************************************************/
static bool does_nation_block_action(const action_id act_id,
                                     bool is_target,
                                     struct unit *actor_unit,
                                     struct nation_type *pnation)
{
  if (act_id == ACTION_ANY) {
    /* Any action is OK. */
    action_iterate(alt_act) {
      if (utype_can_do_action(unit_type_get(actor_unit), alt_act)
          && !does_nation_block_action(alt_act, is_target,
                                       actor_unit, pnation)) {
        /* Only one action has to be possible. */
        return FALSE;
      }
    } action_iterate_end;
 
    /* No action enabled. */
    return TRUE;
  }
 
  /* ACTION_ANY is handled above. */
  fc_assert_ret_val(action_id_exists(act_id), FALSE);
 
  action_enabler_list_iterate(action_enablers_for_action(act_id),
                              enabler) {
    if (requirement_fulfilled_by_nation(pnation,
                                       (is_target ? &enabler->target_reqs
                                                  : &enabler->actor_reqs))
        && requirement_fulfilled_by_unit_type(unit_type_get(actor_unit),
                                              &enabler->actor_reqs)) {
      /* This nation doesn't block this action enabler. */
      return FALSE;
    }
  } action_enabler_list_iterate_end;
 
  return TRUE;
}
 
/**********************************************************************/
static struct ane_expl *expl_act_not_enabl(struct unit *punit,
                                           const action_id act_id,
                                           const struct tile *target_tile,
                                           const struct city *target_city,
                                           const struct unit *target_unit)
{
  struct player *must_war_player;
  const struct action *paction;
  struct action *blocker;
  struct player *act_player = unit_owner(punit);
  struct player *tgt_player = NULL;
  struct ane_expl *explnat = fc_malloc(sizeof(struct ane_expl));
  struct civ_map *nmap = &(wld.map);
  bool can_exist = can_unit_exist_at_tile(nmap, punit, unit_tile(punit));
  bool on_native = is_native_tile(unit_type_get(punit), unit_tile(punit));
  int action_custom;
 
  /* Not know yet. (Initialize before the below check.) */
  explnat->kind = ANEK_UNKNOWN;
 
  paction = action_by_number(act_id);
 
  if (act_id != ACTION_ANY) {
    /* A specific action should have a suitable target. */
    switch (action_get_target_kind(paction)) {
    case ATK_CITY:
      if (target_city == NULL) {
        explnat->kind = ANEK_MISSING_TARGET;
      }
      break;
    case ATK_UNIT:
      if (target_unit == NULL) {
        explnat->kind = ANEK_MISSING_TARGET;
      }
      break;
    case ATK_STACK:
    case ATK_TILE:
    case ATK_EXTRAS:
      if (target_tile == NULL) {
        explnat->kind = ANEK_MISSING_TARGET;
      }
      break;
    case ATK_SELF:
      /* No other target. */
      break;
    case ATK_COUNT:
      fc_assert(action_get_target_kind(paction) != ATK_COUNT);
      break;
    }
  }
 
  if (explnat->kind == ANEK_MISSING_TARGET) {
    /* No point continuing. */
    return explnat;
  }
 
  if (act_id == ACTION_ANY) {
    /* Find the target player of some actions. */
    if (target_city) {
      /* Individual city targets have the highest priority. */
      tgt_player = city_owner(target_city);
    } else if (target_unit) {
      /* Individual unit targets have the next priority. */
      tgt_player = unit_owner(target_unit);
    } else if (target_tile) {
      /* Tile targets have the lowest priority. */
      tgt_player = tile_owner(target_tile);
    }
  } else {
    /* Find the target player of this action. */
    switch (action_get_target_kind(paction)) {
    case ATK_CITY:
      tgt_player = city_owner(target_city);
      break;
    case ATK_UNIT:
      tgt_player = unit_owner(target_unit);
      break;
    case ATK_TILE:
      tgt_player = tile_owner(target_tile);
      break;
    case ATK_EXTRAS:
      tgt_player = target_tile->extras_owner;
      break;
    case ATK_STACK:
      /* A unit stack may contain units with multiple owners. Pick the
       * first one. */
      if (target_tile
          && unit_list_size(target_tile->units) > 0) {
        tgt_player = unit_owner(unit_list_get(target_tile->units, 0));
      }
      break;
    case ATK_SELF:
      /* A unit acting against itself. */
      tgt_player = act_player;
      break;
    case ATK_COUNT:
      fc_assert(action_get_target_kind(paction) != ATK_COUNT);
      break;
    }
  }
 
  if (act_id == ACTION_ANY) {
    action_custom = 0;
  } else {
    switch (paction->result) {
    case ACTRES_UPGRADE_UNIT:
      action_custom = unit_upgrade_test(nmap, punit, FALSE);
      break;
    case ACTRES_AIRLIFT:
      action_custom = test_unit_can_airlift_to(nmap, NULL, punit, target_city);
      break;
    case ACTRES_NUKE_UNITS:
      action_custom = unit_attack_units_at_tile_result(punit, paction,
                                                       target_tile);
      break;
    case ACTRES_ATTACK:
      action_custom = unit_attack_units_at_tile_result(punit, paction,
                                                       target_tile);
      break;
    case ACTRES_WIPE_UNITS:
      action_custom = unit_wipe_units_at_tile_result(punit, target_tile);
      break;
    case ACTRES_CONQUER_CITY:
      if (target_city) {
        action_custom = unit_move_to_tile_test(nmap, punit,
                                               punit->activity,
                                               unit_tile(punit),
                                               city_tile(target_city),
                                               FALSE, FALSE, NULL, TRUE);
      } else {
        action_custom = MR_OK;
      }
      break;
    case ACTRES_TRANSPORT_EMBARK:
      if (target_unit) {
        action_custom = unit_move_to_tile_test(nmap, punit,
                                               punit->activity,
                                               unit_tile(punit),
                                               unit_tile(target_unit),
                                               FALSE, TRUE, NULL, FALSE);
      } else {
        action_custom = MR_OK;
      }
      break;
    case ACTRES_TRANSPORT_DISEMBARK:
    case ACTRES_HUT_ENTER:
    case ACTRES_HUT_FRIGHTEN:
    case ACTRES_CONQUER_EXTRAS:
    case ACTRES_UNIT_MOVE:
      if (target_tile) {
        action_custom = unit_move_to_tile_test(nmap, punit,
                                               punit->activity,
                                               unit_tile(punit),
                                               target_tile,
                                               FALSE, FALSE, NULL, FALSE);
      } else {
        action_custom = MR_OK;
      }
      break;
    case ACTRES_TELEPORT:
      if (target_tile != NULL) {
        action_custom = unit_teleport_to_tile_test(nmap, punit,
                                                   punit->activity,
                                                   unit_tile(punit),
                                                   target_tile,
                                                   FALSE, NULL, FALSE);
      } else {
        action_custom = MR_OK;
      }
      break;
    default:
      action_custom = 0;
      break;
    }
  }
 
  if (!unit_can_do_action(punit, act_id)) {
    explnat->kind = ANEK_ACTOR_UNIT;
  } else if (action_has_result_safe(paction, ACTRES_FOUND_CITY)
             && tile_city(target_tile)) {
    explnat->kind = ANEK_BAD_TARGET;
  } else if ((action_has_result_safe(paction, ACTRES_PARADROP_CONQUER)
              || action_has_result_safe(paction, ACTRES_PARADROP))
             && tile_has_units_not_allied_to_but_seen_by(target_tile,
                                                         act_player)) {
    explnat->kind = ANEK_TGT_NON_ALLIED_UNITS_ON_TILE;
  } else if ((!can_exist
       && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                        USP_LIVABLE_TILE, FALSE))
      || (can_exist
          && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                           USP_LIVABLE_TILE, TRUE))) {
    explnat->kind = ANEK_BAD_TERRAIN_ACT;
    explnat->no_act_terrain = tile_terrain(unit_tile(punit));
  } else if ((!on_native
       && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                        USP_NATIVE_TILE, FALSE))
      || (on_native
          && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                           USP_NATIVE_TILE, TRUE))) {
    explnat->kind = ANEK_BAD_TERRAIN_ACT;
    explnat->no_act_terrain = tile_terrain(unit_tile(punit));
  } else if (punit
             && does_terrain_block_action(act_id, FALSE,
                 punit, tile_terrain(unit_tile(punit)))) {
    /* No action enabler allows acting against this terrain kind. */
    explnat->kind = ANEK_BAD_TERRAIN_ACT;
    explnat->no_act_terrain = tile_terrain(unit_tile(punit));
  } else if (action_has_result_safe(paction, ACTRES_FOUND_CITY)
             && target_tile
             && terrain_has_flag(tile_terrain(target_tile),
                                 TER_NO_CITIES)) {
    explnat->kind = ANEK_BAD_TERRAIN_TGT;
    explnat->no_act_terrain = tile_terrain(target_tile);
  } else if ((action_has_result_safe(paction, ACTRES_PARADROP)
              || action_has_result_safe(paction, ACTRES_PARADROP_CONQUER))
             && target_tile != NULL
             && map_is_known_and_seen(target_tile, act_player,
                                      V_MAIN)
             && (!can_unit_exist_at_tile(nmap, punit, target_tile)
                 && (!BV_ISSET(paction->sub_results, ACT_SUB_RES_MAY_EMBARK)
                     || !unit_could_load_at(punit, target_tile)))) {
    explnat->kind = ANEK_BAD_TERRAIN_TGT;
    explnat->no_act_terrain = tile_terrain(target_tile);
  } else if (target_tile
             && does_terrain_block_action(act_id, TRUE,
                 punit, tile_terrain(target_tile))) {
    /* No action enabler allows acting against this terrain kind. */
    explnat->kind = ANEK_BAD_TERRAIN_TGT;
    explnat->no_act_terrain = tile_terrain(target_tile);
  } else if (unit_transported(punit)
             && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                              USP_TRANSPORTED, TRUE)) {
    explnat->kind = ANEK_IS_TRANSPORTED;
  } else if (!unit_transported(punit)
             && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                              USP_TRANSPORTED, FALSE)) {
    explnat->kind = ANEK_IS_NOT_TRANSPORTED;
  } else if (0 < get_transporter_occupancy(punit)
             && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                              USP_TRANSPORTING, TRUE)) {
    explnat->kind = ANEK_IS_TRANSPORTING;
  } else if (!(0 < get_transporter_occupancy(punit))
             && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                              USP_TRANSPORTING, FALSE)) {
    explnat->kind = ANEK_IS_NOT_TRANSPORTING;
  } else if ((punit->homecity > 0)
             && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                              USP_HAS_HOME_CITY, TRUE)) {
    explnat->kind = ANEK_ACTOR_HAS_HOME_CITY;
  } else if ((punit->homecity <= 0)
             && !utype_can_do_act_when_ustate(unit_type_get(punit), act_id,
                                              USP_HAS_HOME_CITY, FALSE)) {
    explnat->kind = ANEK_ACTOR_HAS_NO_HOME_CITY;
  } else if ((punit->homecity <= 0)
             && (action_has_result_safe(paction, ACTRES_TRADE_ROUTE)
                 || action_has_result_safe(paction, ACTRES_MARKETPLACE))) {
    explnat->kind = ANEK_ACTOR_HAS_NO_HOME_CITY;
  } else if (act_player && tgt_player
             && (player_diplstate_get(act_player, tgt_player)->type
                 == DS_PEACE)
             && can_utype_do_act_if_tgt_diplrel(unit_type_get(punit),
                                                act_id,
                                                DS_PEACE,
                                                FALSE)
             && !can_utype_do_act_if_tgt_diplrel(unit_type_get(punit),
                                                 act_id,
                                                 DS_PEACE,
                                                 TRUE)) {
    explnat->kind = ANEK_PEACE;
    explnat->peace_with = tgt_player;
  } else if ((must_war_player = need_war_player(punit,
                                                act_id,
                                                target_tile,
                                                target_city,
                                                target_unit)) != NULL) {
    explnat->kind = ANEK_NO_WAR;
    explnat->no_war_with = must_war_player;
  } else if (action_mp_full_makes_legal(punit, act_id)) {
    explnat->kind = ANEK_LOW_MP;
  } else if (tgt_player != NULL
             && act_player != tgt_player
             && !can_utype_do_act_if_tgt_diplrel(unit_type_get(punit),
                                                 act_id,
                                                 DRO_FOREIGN,
                                                 TRUE)) {
    explnat->kind = ANEK_FOREIGN;
  } else if (tgt_player != NULL
             && act_player == tgt_player
             && !can_utype_do_act_if_tgt_diplrel(unit_type_get(punit),
                                                 act_id,
                                                 DRO_FOREIGN,
                                                 FALSE)) {
    explnat->kind = ANEK_DOMESTIC;
  } else if (punit != NULL
             && does_nation_block_action(act_id, FALSE,
                                         punit, act_player->nation)) {
    explnat->kind = ANEK_NATION_ACT;
    explnat->no_act_nation = act_player->nation;
  } else if (tgt_player
             && does_nation_block_action(act_id, TRUE,
                                         punit, tgt_player->nation)) {
    explnat->kind = ANEK_NATION_TGT;
    explnat->no_act_nation = tgt_player->nation;
  } else if ((target_tile && tile_city(target_tile))
             && !utype_may_act_tgt_city_tile(unit_type_get(punit),
                                             act_id,
                                             CITYT_CENTER,
                                             TRUE)) {
    explnat->kind = ANEK_IS_CITY_CENTER;
  } else if ((target_tile && !tile_city(target_tile))
             && !utype_may_act_tgt_city_tile(unit_type_get(punit),
                                             act_id,
                                             CITYT_CENTER,
                                             FALSE)) {
    explnat->kind = ANEK_IS_NOT_CITY_CENTER;
  } else if ((target_tile && tile_owner(target_tile) != NULL)
             && !utype_may_act_tgt_city_tile(unit_type_get(punit),
                                             act_id,
                                             CITYT_CLAIMED,
                                             TRUE)) {
    explnat->kind = ANEK_TGT_IS_CLAIMED;
  } else if ((target_tile && tile_owner(target_tile) == NULL)
             && !utype_may_act_tgt_city_tile(unit_type_get(punit),
                                             act_id,
                                             CITYT_CLAIMED,
                                             FALSE)) {
    explnat->kind = ANEK_TGT_IS_UNCLAIMED;
  } else if (paction && punit
             && ((target_tile
                  && !action_distance_inside_max(paction,
                      real_map_distance(unit_tile(punit), target_tile)))
                 || (target_city
                     && !action_distance_inside_max(paction,
                         real_map_distance(unit_tile(punit),
                                           city_tile(target_city))))
                 || (target_unit
                     && !action_distance_inside_max(paction,
                         real_map_distance(unit_tile(punit),
                                           unit_tile(target_unit)))))) {
    explnat->kind = ANEK_DISTANCE_FAR;
    explnat->distance = paction->max_distance;
  } else if ((action_has_result_safe(paction, ACTRES_PARADROP_CONQUER)
              || action_has_result_safe(paction, ACTRES_PARADROP))
             && punit && target_tile
             && real_map_distance(unit_tile(punit), target_tile)
                > unit_type_get(punit)->paratroopers_range) {
    explnat->kind = ANEK_DISTANCE_FAR;
    explnat->distance = unit_type_get(punit)->paratroopers_range;
  } else if (paction && punit
             && ((target_tile
                  && real_map_distance(unit_tile(punit), target_tile)
                      < paction->min_distance)
                 || (target_city
                     && real_map_distance(unit_tile(punit),
                                          city_tile(target_city))
                        < paction->min_distance)
                 || (target_unit
                     && real_map_distance(unit_tile(punit),
                                          unit_tile(target_unit))
                        < paction->min_distance))) {
    explnat->kind = ANEK_DISTANCE_NEAR;
    explnat->distance = paction->min_distance;
  } else if (target_city
             && (action_has_result_safe(paction, ACTRES_JOIN_CITY)
                 && action_actor_utype_hard_reqs_ok(paction,
                                                    unit_type_get(punit))
                 && (city_size_get(target_city) + unit_pop_value(punit)
                     > game.info.add_to_size_limit))) {
    /* TODO: Check max city size requirements from action enabler target
     * vectors. */
    explnat->kind = ANEK_CITY_TOO_BIG;
  } else if (target_city
             && (action_has_result_safe(paction, ACTRES_JOIN_CITY)
                 && action_actor_utype_hard_reqs_ok(paction,
                                                    unit_type_get(punit))
                 && (!city_can_grow_to(target_city,
                                       city_size_get(target_city)
                                       + unit_pop_value(punit))))) {
    explnat->kind = ANEK_CITY_POP_LIMIT;
  } else if ((action_has_result_safe(paction, ACTRES_NUKE_UNITS)
              || action_has_result_safe(paction, ACTRES_ATTACK)
              || action_has_result_safe(paction, ACTRES_WIPE_UNITS))
             && action_custom != ATT_OK) {
    switch (action_custom) {
    case ATT_NON_ATTACK:
      explnat->kind = ANEK_ACTOR_UNIT;
      break;
    case ATT_UNREACHABLE:
      explnat->kind = ANEK_TGT_UNREACHABLE;
      break;
    case ATT_NONNATIVE_SRC:
      explnat->kind = ANEK_BAD_TERRAIN_ACT;
      explnat->no_act_terrain = tile_terrain(unit_tile(punit));
      break;
    case ATT_NONNATIVE_DST:
      explnat->kind = ANEK_BAD_TERRAIN_TGT;
      explnat->no_act_terrain = tile_terrain(target_tile);
      break;
    case ATT_NOT_WIPABLE:
      explnat->kind = ANEK_NOT_WIPABLE;
      break;
    default:
      fc_assert(action_custom != ATT_OK);
      explnat->kind = ANEK_UNKNOWN;
      break;
    }
  } else if (action_has_result_safe(paction, ACTRES_AIRLIFT)
             && action_custom == AR_SRC_NO_FLIGHTS) {
    explnat->kind = ANEK_CITY_NO_CAPACITY;
    explnat->capacity_city = tile_city(unit_tile(punit));
  } else if (action_has_result_safe(paction, ACTRES_AIRLIFT)
             && action_custom == AR_DST_NO_FLIGHTS) {
    explnat->kind = ANEK_CITY_NO_CAPACITY;
    explnat->capacity_city = game_city_by_number(target_city->id);
  } else if (action_has_result_safe(paction, ACTRES_FOUND_CITY)
             && citymindist_prevents_city_on_tile(nmap, target_tile)) {
    explnat->kind = ANEK_CITY_TOO_CLOSE_TGT;
  } else if ((action_has_result_safe(paction, ACTRES_PARADROP_CONQUER)
              || action_has_result_safe(paction, ACTRES_PARADROP))
             && target_tile != NULL
             && !map_is_known(target_tile, act_player)) {
    explnat->kind = ANEK_TGT_TILE_UNKNOWN;
  } else if ((action_has_result_safe(paction, ACTRES_CONQUER_CITY)
              || action_id_has_result_safe(act_id, ACTRES_CONQUER_EXTRAS)
              || action_id_has_result_safe(act_id, ACTRES_HUT_ENTER)
              || action_id_has_result_safe(act_id, ACTRES_HUT_FRIGHTEN)
              || action_id_has_result_safe(act_id, ACTRES_UNIT_MOVE)
              || action_has_result_safe(paction,
                                        ACTRES_TRANSPORT_EMBARK)
              || action_has_result_safe(paction,
                                        ACTRES_TRANSPORT_DISEMBARK))
             && action_custom != MR_OK) {
    switch (action_custom) {
    case MR_CANNOT_DISEMBARK:
      explnat->kind = ANEK_DISEMBARK_ACT;
      break;
    case MR_TRIREME:
      explnat->kind = ANEK_TRIREME_MOVE;
      break;
    case MR_DESTINATION_OCCUPIED_BY_NON_ALLIED_UNIT:
      explnat->kind = ANEK_TGT_NON_ALLIED_UNITS_ON_TILE;
      break;
    default:
      fc_assert(action_custom != MR_OK);
      explnat->kind = ANEK_UNKNOWN;
      break;
    }
  } else if (action_has_result_safe(paction, ACTRES_SPY_BRIBE_UNIT)
             && utype_player_already_has_this_unique(act_player,
                 unit_type_get(target_unit))) {
    explnat->kind = ANEK_TGT_IS_UNIQUE_ACT_HAS;
    explnat->no_tgt_utype = unit_type_get(target_unit);
  } else if ((game.scenario.prevent_new_cities
              && utype_can_do_action(unit_type_get(punit), ACTION_FOUND_CITY))
             && (action_has_result_safe(paction, ACTRES_FOUND_CITY)
                 || act_id == ACTION_ANY)) {
    /* Please add a check for any new action forbidding scenario setting
     * above this comment. */
    explnat->kind = ANEK_SCENARIO_DISABLED;
  } else if (action_has_result_safe(paction, ACTRES_UPGRADE_UNIT)
             && action_custom == UU_NO_MONEY) {
    const struct unit_type *act_utype = unit_type_get(punit);
 
    explnat->kind = ANEK_ACT_NOT_ENOUGH_MONEY;
    explnat->gold_needed = unit_upgrade_price(act_player, act_utype,
                                              can_upgrade_unittype(
                                                  act_player, act_utype));
  } else if (paction
             && (blocker = action_is_blocked_by(nmap, paction, punit,
                                                target_tile, target_city,
                                                target_unit))) {
    explnat->kind = ANEK_ACTION_BLOCKS;
    explnat->blocker = blocker;
  } else {
    explnat->kind = ANEK_UNKNOWN;
  }
 
  return explnat;
}
 
/**********************************************************************/
enum ane_kind action_not_enabled_reason(struct unit *punit,
                                        action_id act_id,
                                        const struct tile *target_tile,
                                        const struct city *target_city,
                                        const struct unit *target_unit)
{
  struct ane_expl *explnat = expl_act_not_enabl(punit, act_id,
                                                target_tile,
                                                target_city, target_unit);
  enum ane_kind out = explnat->kind;
 
  free(explnat);
 
  return out;
}
 
/**********************************************************************/
static void explain_why_no_action_enabled(struct unit *punit,
                                          const struct tile *target_tile,
                                          const struct city *target_city,
                                          const struct unit *target_unit)
{
  struct player *pplayer = unit_owner(punit);
  struct ane_expl *explnat = expl_act_not_enabl(punit, ACTION_ANY,
                                                target_tile,
                                                target_city, target_unit);
  const struct civ_map *nmap = &(wld.map);
 
  switch (explnat->kind) {
  case ANEK_ACTOR_UNIT:
    /* This shouldn't happen unless the client is buggy given the current
     * users. */
    fc_assert_msg(explnat->kind != ANEK_ACTOR_UNIT,
                  "Asked to explain why a non actor can't act.");
 
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("Unit cannot do anything."));
    break;
  case ANEK_MISSING_TARGET:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("Your %s found no suitable target."),
                  unit_name_translation(punit));
    break;
  case ANEK_BAD_TARGET:
    /* This shouldn't happen at the moment. Only specific action checks
     * will trigger bad target checks. This is a reply to a question about
     * any action. */
    fc_assert(explnat->kind != ANEK_BAD_TARGET);
 
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("Your %s found no suitable target."),
                  unit_name_translation(punit));
    break;
  case ANEK_BAD_TERRAIN_ACT:
    {
      const char *types[utype_count()];
      int i = 0;
 
      if (!utype_can_do_act_when_ustate(unit_type_get(punit),
                                        ACTION_ANY, USP_LIVABLE_TILE,
                                        FALSE)
          && !can_unit_exist_at_tile(nmap, punit, unit_tile(punit))) {
        unit_type_iterate(utype) {
          if (utype_can_do_act_when_ustate(utype, ACTION_ANY,
                                           USP_LIVABLE_TILE, FALSE)) {
            types[i++] = utype_name_translation(utype);
          }
        } unit_type_iterate_end;
      }
 
      if (0 < i) {
        struct astring astr = ASTRING_INIT;
 
        notify_player(pplayer, unit_tile(punit),
                      E_BAD_COMMAND, ftc_server,
                      /* TRANS: terrain name
                       * "Your Diplomat cannot act from Ocean. Only
                       * Spy or Partisan ... */
                      _("Your %s cannot act from %s. "
                        "Only %s can act from a non livable tile."),
                      unit_name_translation(punit),
                      terrain_name_translation(explnat->no_act_terrain),
                      astr_build_or_list(&astr, types, i));
 
        astr_free(&astr);
      } else {
        notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                      /* TRANS: terrain name */
                      _("Unit cannot act from %s."),
                      terrain_name_translation(explnat->no_act_terrain));
      }
    }
    break;
  case ANEK_BAD_TERRAIN_TGT:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  /* TRANS: terrain name */
                  _("Unit cannot act against %s."),
                  terrain_name_translation(explnat->no_act_terrain));
    break;
  case ANEK_IS_TRANSPORTED:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit is being transported, and"
                    " so cannot act."));
    break;
  case ANEK_IS_NOT_TRANSPORTED:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act when it isn't being "
                    "transported."));
    break;
  case ANEK_IS_TRANSPORTING:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit is transporting, and"
                    " so cannot act."));
    break;
  case ANEK_IS_NOT_TRANSPORTING:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act when it isn't transporting."));
    break;
  case ANEK_ACTOR_HAS_HOME_CITY:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit has a home city, and so cannot act."));
    break;
  case ANEK_ACTOR_HAS_NO_HOME_CITY:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act unless it has a home city."));
    break;
  case ANEK_NO_WAR:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("You must declare war on %s first. Try using "
                    "the Nations report"
#ifndef FREECIV_WEB
                    " (F3)"
#endif /* FREECIV_WEB */
                    "."),
                  player_name(explnat->no_war_with));
    break;
  case ANEK_PEACE:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("You must break peace with %s first. Try using "
                    "the Nations report to declare war"
#ifndef FREECIV_WEB
                    " (F3)"
#endif /* FREECIV_WEB */
                    "."),
                  player_name(explnat->peace_with));
    break;
  case ANEK_DOMESTIC:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act against domestic targets."));
    break;
  case ANEK_FOREIGN:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act against foreign targets."));
    break;
  case ANEK_TGT_NON_ALLIED_UNITS_ON_TILE:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  /* TRANS: Riflemen */
                  _("%s cannot act against tiles with non allied units."),
                  unit_name_translation(punit));
    break;
  case ANEK_NATION_ACT:
     notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                   /* TRANS: Swedish ... Riflemen */
                   _("%s %s cannot act."),
                   nation_adjective_translation(explnat->no_act_nation),
                   unit_name_translation(punit));
     break;
  case ANEK_NATION_TGT:
     notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                   /* TRANS: ... Pirate ... */
                   _("This unit cannot act against %s targets."),
                   nation_adjective_translation(explnat->no_act_nation));
     break;
  case ANEK_LOW_MP:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit has too few moves left to act."));
    break;
  case ANEK_IS_CITY_CENTER:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act against city centers."));
    break;
  case ANEK_IS_NOT_CITY_CENTER:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act against non city centers."));
    break;
  case ANEK_TGT_IS_CLAIMED:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act against claimed tiles."));
    break;
  case ANEK_TGT_IS_UNCLAIMED:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit cannot act against unclaimed tiles."));
    break;
  case ANEK_DISTANCE_NEAR:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit is too near its target to act."));
    break;
  case ANEK_DISTANCE_FAR:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("This unit is too far away from its target to act."));
    break;
  case ANEK_SCENARIO_DISABLED:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("Can't perform any action this scenario permits."));
    break;
  case ANEK_CITY_TOO_CLOSE_TGT:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("Can't perform any action this close to a city."));
    break;
  case ANEK_CITY_TOO_BIG:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  /* TRANS: Settler ... Berlin */
                  _("%s can't do anything to %s. It is too big."),
                  unit_name_translation(punit),
                  city_name_get(target_city));
    break;
  case ANEK_CITY_POP_LIMIT:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  /* TRANS: London ... Settlers */
                  _("%s needs an improvement to grow, so "
                    "%s cannot do anything to it."),
                  city_name_get(target_city),
                  unit_name_translation(punit));
    break;
  case ANEK_CITY_NO_CAPACITY:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  /* TRANS: Paris ... Warriors (think: airlift) */
                  _("%s don't have enough capacity, so "
                    "%s cannot do anything."),
                  city_name_get(explnat->capacity_city),
                  unit_name_translation(punit));
    break;
  case ANEK_TGT_TILE_UNKNOWN:
    notify_player(pplayer, target_tile, E_BAD_COMMAND, ftc_server,
                  /* TRANS: Paratroopers ... */
                  _("%s can't do anything to an unknown target tile."),
                  unit_name_translation(punit));
    break;
  case ANEK_ACT_NOT_ENOUGH_MONEY:
    {
      char tbuf[MAX_LEN_MSG];
 
      /* TRANS: Used below. Separate so treasury content too can determine
       * if this is plural. */
      fc_snprintf(tbuf, ARRAY_SIZE(tbuf), PL_("Treasury contains %d gold.",
                                              "Treasury contains %d gold.",
                                              pplayer->economic.gold),
                  pplayer->economic.gold);
 
      notify_player(pplayer, target_tile, E_BAD_COMMAND, ftc_server,
                    /* TRANS: "Spy can't do anything. 154 gold may help.
                     * Treasury contains 100 gold." */
                    PL_("%s can't do anything. %d gold may help. %s",
                        "%s can't do anything. %d gold may help. %s",
                        explnat->gold_needed),
                    unit_name_translation(punit),
                    explnat->gold_needed, tbuf);
    }
    break;
  case ANEK_TRIREME_MOVE:
    notify_player(pplayer, target_tile, E_BAD_COMMAND, ftc_server,
                  _("%s cannot move that far from the coast line."),
                  unit_link(punit));
    break;
  case ANEK_DISEMBARK_ACT:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("%s cannot disembark outside of a city or a native base "
                    "for %s."),
                  unit_link(punit),
                  utype_name_translation(
                      unit_type_get(unit_transport_get(punit))));
    break;
  case ANEK_TGT_UNREACHABLE:
    notify_player(pplayer, target_tile, E_BAD_COMMAND, ftc_server,
                  _("%s can't do anything since there is an unreachable "
                    "unit."),
                  unit_name_translation(punit));
    break;
  case ANEK_NOT_WIPABLE:
    notify_player(pplayer, target_tile, E_BAD_COMMAND, ftc_server,
                  _("%s can't do anything since there is unit with a positive "
                    "defense value."),
                  unit_name_translation(punit));
    break;
  case ANEK_TGT_IS_UNIQUE_ACT_HAS:
    notify_player(pplayer, target_tile, E_BAD_COMMAND, ftc_server,
                  _("%s can't do anything since you already have a %s."),
                  unit_name_translation(punit),
                  utype_name_translation(explnat->no_tgt_utype));
    break;
  case ANEK_ACTION_BLOCKS:
    /* If an action blocked another action the blocking action must be
     * possible. */
    fc_assert(explnat->kind != ANEK_ACTION_BLOCKS);
    fc__fallthrough; /* Fall through to unknown cause. */
  case ANEK_UNKNOWN:
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("No action possible."));
    break;
  }
 
  free(explnat);
}
 
/**********************************************************************/
void handle_unit_get_actions(struct connection *pc,
                             const int actor_unit_id,
                             const int target_unit_id_client,
                             const int target_tile_id,
                             const int target_extra_id_client,
                             const int request_kind)
{
  struct player *actor_player;
  struct unit *actor_unit;
  struct tile *target_tile;
  struct act_prob probabilities[MAX_NUM_ACTIONS];
  struct unit *target_unit;
  struct city *target_city;
  struct extra_type *target_extra;
  int actor_target_distance;
  const struct player_tile *plrtile;
  int target_extra_id = target_extra_id_client;
  const struct civ_map *nmap = &(wld.map);
 
  /* No potentially legal action is known yet. If none is found the player
   * should get an explanation. */
  bool at_least_one_action = FALSE;
 
  /* A target should only be sent if it is possible to act against it */
  int target_city_id = IDENTITY_NUMBER_ZERO;
  int target_unit_id = IDENTITY_NUMBER_ZERO;
 
  actor_player = pc->playing;
  actor_unit = game_unit_by_number(actor_unit_id);
  target_tile = index_to_tile(nmap, target_tile_id);
 
  /* Initialize the action probabilities. */
  action_iterate(act) {
    probabilities[act] = ACTPROB_NA;
  } action_iterate_end;
 
  /* Check if the request is valid. */
  if (!target_tile || !actor_unit || !actor_player
      || actor_unit->owner != actor_player) {
    dsend_packet_unit_actions(pc, actor_unit_id,
                              IDENTITY_NUMBER_ZERO, IDENTITY_NUMBER_ZERO,
                              target_tile_id, target_extra_id,
                              request_kind,
                              probabilities);
    return;
  }
 
  /* Select the targets. */
 
  if (target_unit_id_client == IDENTITY_NUMBER_ZERO) {
    /* Find a new target unit. */
    target_unit = action_tgt_unit(actor_unit, target_tile, TRUE);
  } else {
    /* Prepare the client selected target unit. */
    target_unit = game_unit_by_number(target_unit_id_client);
  }
 
  /* Find the target city. */
  target_city = action_tgt_city(actor_unit, target_tile, TRUE);
 
  /* The specified target unit must be located at the target tile. */
  if (target_unit && unit_tile(target_unit) != target_tile) {
    notify_player(actor_player, unit_tile(actor_unit),
                  E_BAD_COMMAND, ftc_server,
                  _("Target not at target tile."));
    dsend_packet_unit_actions(pc, actor_unit_id,
                              IDENTITY_NUMBER_ZERO, IDENTITY_NUMBER_ZERO,
                              target_tile_id, target_extra_id,
                              request_kind,
                              probabilities);
    return;
  }
 
  if (target_extra_id_client == EXTRA_NONE) {
    /* See if a target extra can be found. */
    target_extra = action_tgt_tile_extra(actor_unit, target_tile, TRUE);
  } else {
    /* Use the client selected target extra. */
    target_extra = extra_by_number(target_extra_id_client);
  }
 
  /* The player may have outdated information about the target tile.
   * Limiting the player knowledge look up to the target tile is OK since
   * all targets must be located at it. */
  plrtile = map_get_player_tile(target_tile, actor_player);
 
  /* Distance between actor and target tile. */
  actor_target_distance = real_map_distance(unit_tile(actor_unit),
                                            target_tile);
 
  /* Find out what can be done to the targets. */
 
  /* Set the probability for the actions. */
  action_noninternal_iterate(act) {
    if (action_id_get_actor_kind(act) != AAK_UNIT) {
      /* Not relevant. */
      continue;
    }
 
    switch (action_id_get_target_kind(act)) {
    case ATK_CITY:
      if (plrtile && plrtile->site) {
        /* Only a known city may be targeted. */
        if (target_city) {
          /* Calculate the probabilities. */
          probabilities[act] = action_prob_vs_city(nmap, actor_unit, act,
                                                   target_city);
        } else if (!tile_is_seen(target_tile, actor_player)
                   && action_maybe_possible_actor_unit(nmap, act, actor_unit)
                   && action_id_distance_accepted(act,
                                                  actor_target_distance)) {
          /* The target city is non existing. The player isn't aware of this
           * fact because they can't see the tile it was located on. The
           * actor unit it self doesn't contradict the requirements to
           * perform the action. The (no longer existing) target city was
           * known to be close enough. */
          probabilities[act] = ACTPROB_NOT_KNOWN;
        } else {
          /* The actor unit is known to be unable to act or the target city
           * is known to be too far away. */
          probabilities[act] = ACTPROB_IMPOSSIBLE;
        }
      } else {
        /* No target to act against. */
        probabilities[act] = ACTPROB_IMPOSSIBLE;
      }
      break;
    case ATK_UNIT:
      if (target_unit) {
        /* Calculate the probabilities. */
        probabilities[act] = action_prob_vs_unit(nmap, actor_unit, act,
                                                 target_unit);
      } else {
        /* No target to act against. */
        probabilities[act] = ACTPROB_IMPOSSIBLE;
      }
      break;
    case ATK_STACK:
      if (target_tile) {
        /* Calculate the probabilities. */
        probabilities[act] = action_prob_vs_stack(nmap, actor_unit, act,
                                                  target_tile);
      } else {
        /* No target to act against. */
        probabilities[act] = ACTPROB_IMPOSSIBLE;
      }
      break;
    case ATK_TILE:
      if (target_tile) {
        /* Calculate the probabilities. */
        probabilities[act] = action_prob_vs_tile(nmap, actor_unit, act,
                                                 target_tile, target_extra);
      } else {
        /* No target to act against. */
        probabilities[act] = ACTPROB_IMPOSSIBLE;
      }
      break;
    case ATK_EXTRAS:
      if (target_tile) {
        /* Calculate the probabilities. */
        probabilities[act] = action_prob_vs_extras(nmap, actor_unit, act,
                                                   target_tile,
                                                   target_extra);
      } else {
        /* No target to act against. */
        probabilities[act] = ACTPROB_IMPOSSIBLE;
      }
      break;
    case ATK_SELF:
      if (actor_target_distance == 0) {
        /* Calculate the probabilities. */
        probabilities[act] = action_prob_self(nmap, actor_unit, act);
      } else {
        /* Don't bother with self targeted actions unless the actor is
         * asking about what can be done to its own tile. */
        probabilities[act] = ACTPROB_IMPOSSIBLE;
      }
      break;
    case ATK_COUNT:
      fc_assert_action(action_id_get_target_kind(act) != ATK_COUNT,
                       probabilities[act] = ACTPROB_IMPOSSIBLE);
      break;
    }
  } action_noninternal_iterate_end;
 
  /* Analyze the probabilities. Decide what targets to send and if an
   * explanation is needed. */
  action_noninternal_iterate(act) {
    if (action_prob_possible(probabilities[act])) {
      /* An action can be done. No need to explain why no action can be
       * done. */
      at_least_one_action = TRUE;
 
      switch (action_id_get_target_kind(act)) {
      case ATK_CITY:
        /* The city should be sent as a target since it is possible to act
         * against it. */
 
        /* All city targeted actions requires that the player is aware of
         * the target city. It is therefore in the player's map. */
        fc_assert_action(plrtile, continue);
        fc_assert_action(plrtile->site, continue);
 
        target_city_id = plrtile->site->identity;
        break;
      case ATK_UNIT:
        /* The unit should be sent as a target since it is possible to act
         * against it. */
        fc_assert(target_unit != NULL);
        target_unit_id = target_unit->id;
        break;
      case ATK_TILE:
      case ATK_EXTRAS:
        /* The target tile isn't selected here so it hasn't changed. */
        fc_assert(target_tile != NULL);
 
        if (target_extra && action_id_has_complex_target(act)) {
          /* The target extra may have been set here. */
          target_extra_id = target_extra->id;
        }
        break;
      case ATK_STACK:
        /* The target tile isn't selected here so it hasn't changed. */
        fc_assert(target_tile != NULL);
        break;
      case ATK_SELF:
        /* The target unit is the actor unit. It is already sent. */
        fc_assert(actor_unit != NULL);
        break;
      case ATK_COUNT:
        fc_assert_msg(action_id_get_target_kind(act) != ATK_COUNT,
                      "Invalid action target kind.");
        break;
      }
 
      if (target_city_id != IDENTITY_NUMBER_ZERO
          && target_unit_id != IDENTITY_NUMBER_ZERO) {
        /* No need to find out more. */
        break;
      }
    }
  } action_noninternal_iterate_end;
 
  /* Send possible actions and targets. */
  dsend_packet_unit_actions(pc,
                            actor_unit_id, target_unit_id, target_city_id,
                            target_tile_id, target_extra_id,
                            request_kind,
                            probabilities);
 
  if (request_kind == REQEST_PLAYER_INITIATED && !at_least_one_action) {
    /* The user should get an explanation why no action is possible. */
    explain_why_no_action_enabled(actor_unit,
                                  target_tile, target_city, target_unit);
  }
}
 
/**********************************************************************/
void illegal_action_msg(struct player *pplayer,
                        const enum event_type event,
                        struct unit *actor,
                        const action_id stopped_action,
                        const struct tile *target_tile,
                        const struct city *target_city,
                        const struct unit *target_unit)
{
  struct ane_expl *explnat;
  const struct civ_map *nmap = &(wld.map);
 
  /* Explain why the action was illegal. */
  explnat = expl_act_not_enabl(actor, stopped_action,
                               target_tile, target_city, target_unit);
  switch (explnat->kind) {
  case ANEK_ACTOR_UNIT:
    {
      struct astring astr = ASTRING_INIT;
 
      if (role_units_translations(&astr,
                                  action_id_get_role(stopped_action),
                                  TRUE)) {
        notify_player(pplayer, unit_tile(actor),
                      event, ftc_server,
                      /* TRANS: Only Diplomat or Spy can do Steal Gold. */
                      _("Only %s can do %s."),
                      astr_str(&astr),
                      action_id_name_translation(stopped_action));
        astr_free(&astr);
      } else {
        notify_player(pplayer, unit_tile(actor),
                      event, ftc_server,
                      /* TRANS: Spy can't do Capture Units. */
                      _("%s can't do %s."),
                      unit_name_translation(actor),
                      action_id_name_translation(stopped_action));
      }
    }
    break;
  case ANEK_MISSING_TARGET:
    notify_player(pplayer, unit_tile(actor), event, ftc_server,
                  /* TRANS: "Your Spy found ... suitable for
                   * Bribe Enemy Unit." */
                  _("Your %s found no target suitable for %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_BAD_TARGET:
    notify_player(pplayer, unit_tile(actor), event, ftc_server,
                  /* TRANS: "Having your Spy do Bribe Enemy Unit to
                   * this target ..." */
                  _("Having your %s do %s to this target is redundant."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_BAD_TERRAIN_ACT:
    {
      const char *types[utype_count()];
      int i = 0;
 
      if (!utype_can_do_act_when_ustate(unit_type_get(actor),
                                        stopped_action, USP_LIVABLE_TILE,
                                        FALSE)
          && !can_unit_exist_at_tile(nmap, actor, unit_tile(actor))) {
        unit_type_iterate(utype) {
          if (utype_can_do_act_when_ustate(utype, stopped_action,
                                           USP_LIVABLE_TILE, FALSE)) {
            types[i++] = utype_name_translation(utype);
          }
        } unit_type_iterate_end;
      }
 
      if (0 < i) {
        struct astring astr = ASTRING_INIT;
 
        notify_player(pplayer, unit_tile(actor),
                      event, ftc_server,
                      /* TRANS: action name.
                       * "Your Spy can't do Steal Gold from Ocean.
                       * Only Explorer or Partisan can do Steal Gold ..." */
                      _("Your %s can't do %s from %s. "
                        "Only %s can do %s from a non livable tile."),
                      unit_name_translation(actor),
                      action_id_name_translation(stopped_action),
                      terrain_name_translation(explnat->no_act_terrain),
                      astr_build_or_list(&astr, types, i),
                      action_id_name_translation(stopped_action));
 
        astr_free(&astr);
      } else {
        notify_player(pplayer, unit_tile(actor),
                      event, ftc_server,
                      /* TRANS: action name.
                       * "Your Spy can't do Steal Gold from Ocean." */
                      _("Your %s can't do %s from %s."),
                      unit_name_translation(actor),
                      action_id_name_translation(stopped_action),
                      terrain_name_translation(explnat->no_act_terrain));
      }
    }
    break;
  case ANEK_BAD_TERRAIN_TGT:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage to Mountains." */
                  _("Your %s can't do %s to %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action),
                  terrain_name_translation(explnat->no_act_terrain));
    break;
  case ANEK_IS_TRANSPORTED:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage while ..." */
                  _("Your %s can't do %s while being transported."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_IS_NOT_TRANSPORTED:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage while ..." */
                  _("Your %s can't do %s while not being transported."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_IS_TRANSPORTING:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage while ..." */
                  _("Your %s can't do %s while transporting."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_IS_NOT_TRANSPORTING:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage while ..." */
                  _("Your %s can't do %s while not transporting."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_ACTOR_HAS_HOME_CITY:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage because ..." */
                  _("Your %s can't do %s because it has a home city."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_ACTOR_HAS_NO_HOME_CITY:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage because ..." */
                  _("Your %s can't do %s because it is homeless."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_NO_WAR:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage while you
                   * aren't at war with Prester John." */
                  _("Your %s can't do %s while you"
                    " aren't at war with %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action),
                  player_name(explnat->no_war_with));
    break;
  case ANEK_PEACE:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Industrial Sabotage while you
                   * are at peace with Prester John. Try using the
                   * Nations report (F3)." */
                  _("Your %s can't do %s while you "
                    "are at peace with %s. Try using "
                    "the Nations report to declare war"
#ifndef FREECIV_WEB
                    " (F3)"
#endif /* FREECIV_WEB */
                    "."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action),
                  player_name(explnat->peace_with));
    break;
  case ANEK_DOMESTIC:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Riflemen can't do Expel Unit to domestic 
                   * unit stacks." */
                  _("Your %s can't do %s to domestic %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action),
                  action_target_kind_translated_name(
                    action_id_get_target_kind(stopped_action)));
    break;
  case ANEK_FOREIGN:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Leader can't do Use Court Physician to foreign
                   * unit stacks." */
                  _("Your %s can't do %s to foreign %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action),
                  action_target_kind_translated_name(
                    action_id_get_target_kind(stopped_action)));
    break;
  case ANEK_TGT_NON_ALLIED_UNITS_ON_TILE:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: Paratroopers ... Drop Paratrooper */
                  _("Your %s can't do %s to tiles with non allied units."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_NATION_ACT:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Swedish Riflemen can't do Expel Unit." */
                  _("%s %s can't do %s."),
                  nation_adjective_translation(explnat->no_act_nation),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_NATION_TGT:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Riflemen... Expel Unit... Pirate Migrants." */
                  _("Your %s can't do %s to %s %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action),
                  nation_adjective_translation(explnat->no_act_nation),
                  action_target_kind_translated_name(
                    action_id_get_target_kind(stopped_action)));
    break;
  case ANEK_LOW_MP:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy has ... to do Bribe Enemy Unit." */
                  _("Your %s has too few moves left to do %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_IS_CITY_CENTER:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Bribe Enemy Unit to city centers." */
                  _("Your %s can't do %s to city centers."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_IS_NOT_CITY_CENTER:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can only do Investigate City to
                   * city centers." */
                  _("Your %s can only do %s to city centers."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_TGT_IS_CLAIMED:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Settlers can't do Build City to claimed tiles." */
                  _("Your %s can't do %s to claimed tiles."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_TGT_IS_UNCLAIMED:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy can't do Bribe Enemy Unit to
                   * unclaimed tiles." */
                  _("Your %s can't do %s to unclaimed tiles."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_DISTANCE_NEAR:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy must be at least 2 tiles away to do
                   * Incite a Revolt and Escape." */
                  PL_("Your %s must be at least %d tile away to do %s.",
                      "Your %s must be at least %d tiles away to do %s.",
                      explnat->distance),
                  unit_name_translation(actor),
                  explnat->distance,
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_DISTANCE_FAR:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Diplomat can't be more than 1 tile away to do
                   * Establish Embassy." */
                  PL_("Your %s can't be more than %d tile away to do %s.",
                      "Your %s can't be more than %d tiles away to do %s.",
                      explnat->distance),
                  unit_name_translation(actor),
                  explnat->distance,
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_SCENARIO_DISABLED:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: Can't do Build City in this scenario. */
                  _("Can't do %s in this scenario."),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_CITY_TOO_CLOSE_TGT:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: Can't do Build City this close to a city. */
                  _("Can't do %s this close to a city."),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_CITY_TOO_BIG:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: Settlers ... Join City ... London */
                  _("%s can't do %s to %s. It is too big."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action),
                  city_name_get(target_city));
    break;
  case ANEK_CITY_POP_LIMIT:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: London ... Settlers ... Join City */
                  _("%s needs an improvement to grow, so "
                    "%s cannot do %s."),
                  city_name_get(target_city),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_CITY_NO_CAPACITY:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: Paris ... Airlift to City ... Warriors */
                  _("%s has no capacity to %s %s."),
                  city_name_get(explnat->capacity_city),
                  action_id_name_translation(stopped_action),
                  unit_name_translation(actor));
    break;
  case ANEK_TGT_TILE_UNKNOWN:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: Paratroopers ... Drop Paratrooper */
                  _("%s can't do %s to an unknown tile."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_ACT_NOT_ENOUGH_MONEY:
    {
      char tbuf[MAX_LEN_MSG];
 
      /* TRANS: Used below. Separate so treasury content too can determine
       * if this is plural. */
      fc_snprintf(tbuf, ARRAY_SIZE(tbuf), PL_("Treasury contains %d gold.",
                                              "Treasury contains %d gold.",
                                              pplayer->economic.gold),
                  pplayer->economic.gold);
 
      notify_player(pplayer, unit_tile(actor),
                    event, ftc_server,
                    /* TRANS: "Spy can't do Bribe Unit for 154 gold.
                     * Treasury contains 100 gold." */
                    PL_("%s can't do %s for %d gold. %s",
                        "%s can't do %s for %d gold. %s",
                        explnat->gold_needed),
                    unit_name_translation(actor),
                    action_id_name_translation(stopped_action),
                    explnat->gold_needed, tbuf);
    }
    break;
  case ANEK_TRIREME_MOVE:
    notify_player(pplayer, target_tile, event, ftc_server,
                  /* TRANS: "Trireme cannot move ..." */
                  _("%s cannot move that far from the coast line."),
                  unit_link(actor));
    break;
  case ANEK_DISEMBARK_ACT:
    notify_player(pplayer, unit_tile(actor), event, ftc_server,
                  /* TRANS: "Riflemen cannot disembark ... native base
                   * for Helicopter." */
                  _("%s cannot disembark outside of a city or a native base "
                    "for %s."),
                  unit_link(actor),
                  utype_name_translation(
                      unit_type_get(unit_transport_get(actor))));
    break;
  case ANEK_TGT_UNREACHABLE:
    notify_player(pplayer, target_tile,
                  event, ftc_server,
                  /* TRANS: "Your Spy can't do Bribe Enemy Unit there ..." */
                  _("Your %s can't do %s there since there's an "
                    "unreachable unit."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_NOT_WIPABLE:
    notify_player(pplayer, target_tile,
                  event, ftc_server,
                  /* TRANS: "Your Legion can't do Wipe Units there ..." */
                  _("Your %s can't do %s there since there's an "
                    "unit with positive defense value."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  case ANEK_TGT_IS_UNIQUE_ACT_HAS:
    notify_player(pplayer, target_tile, event, ftc_server,
                  /* TRANS: "You already have a Leader." */
                  _("You already have a %s."),
                  utype_name_translation(explnat->no_tgt_utype));
    break;
  case ANEK_ACTION_BLOCKS:
    {
      char *stop_act_name = fc_strdup(action_id_name_translation(stopped_action));
 
      notify_player(pplayer, unit_tile(actor),
                    event, ftc_server,
                    /* TRANS: Freight ... Disband Unit Recover ... Help Wonder ... */
                    _("Your %s can't do %s when %s is legal."),
                    unit_name_translation(actor),
                    stop_act_name,
                    action_id_name_translation(explnat->blocker->id));
      free(stop_act_name);
    }
    break;
  case ANEK_UNKNOWN:
    notify_player(pplayer, unit_tile(actor),
                  event, ftc_server,
                  /* TRANS: action name.
                   * "Your Spy was unable to do Bribe Enemy Unit." */
                  _("Your %s was unable to do %s."),
                  unit_name_translation(actor),
                  action_id_name_translation(stopped_action));
    break;
  }
 
  free(explnat);
}
 
/**********************************************************************/
static bool illegal_action_pay_price(struct player *pplayer,
                                     bool information_revealed,
                                     struct unit *act_unit,
                                     struct action *stopped_action,
                                     struct player *tgt_player,
                                     struct tile *tgt_tile,
                                     const enum action_requester requester)
{
  int punishment_mp;
  int punishment_hp;
 
  const struct req_context actor_ctxt = {
    .player = unit_owner(act_unit),
    .unit = act_unit,
    .unittype = unit_type_get(act_unit),
    .action = stopped_action,
  };
  const struct req_context tgt_ctxt = {
    .player = tgt_player,
  };
 
  /* Don't punish the player for something the game did. Don't tell the
   * player that the rules required the game to try to do something
   * illegal. */
  fc_assert_ret_val_msg((requester == ACT_REQ_PLAYER
                         || requester == ACT_REQ_SS_AGENT),
                        FALSE,
                        "The player wasn't responsible for this.");
 
  if (!information_revealed) {
    /* The player already had enough information to determine that this
     * action is illegal. Don't punish a client error or an accident. */
    return FALSE;
  }
 
  /* The mistake may have a cost. */
 
  /* HP cost */
  punishment_hp = get_target_bonus_effects(NULL, &actor_ctxt, &tgt_ctxt,
                                           EFT_ILLEGAL_ACTION_HP_COST);
 
  /* Stay in range */
  punishment_hp = MAX(0, punishment_hp);
 
  /* Punish the unit's hit points. */
  act_unit->hp = MAX(0, act_unit->hp - punishment_hp);
 
  if (punishment_hp != 0) {
    if (utype_is_moved_to_tgt_by_action(stopped_action,
                                        unit_type_get(act_unit))) {
      /* The consolation prize is some information about the potentially
       * distant target tile and maybe some contacts. */
      map_show_circle(pplayer, tgt_tile,
                      unit_type_get(act_unit)->vision_radius_sq);
      unit_make_contact(act_unit, tgt_tile, pplayer);
    }
 
    if (act_unit->hp > 0) {
      /* The actor unit survived */
 
      /* The player probably wants to be disturbed if their unit was punished
       * with the loss of hit points. */
      notify_player(pplayer, unit_tile(act_unit),
                    E_UNIT_ILLEGAL_ACTION, ftc_server,
                    /* TRANS: Spy ... 5 ... Drop Paratrooper */
                    _("Your %s lost %d hit points while attempting to"
                      " do %s."),
                    unit_name_translation(act_unit), punishment_hp,
                    action_name_translation(stopped_action));
      send_unit_info(NULL, act_unit);
    } else {
      /* The unit didn't survive */
 
      /* The player probably wants to be disturbed if their unit was punished
       * with death. */
      notify_player(pplayer, unit_tile(act_unit),
                    E_UNIT_ILLEGAL_ACTION, ftc_server,
                    /* TRANS: Spy ... Drop Paratrooper */
                    _("Your %s was killed while attempting to do %s."),
                    unit_name_translation(act_unit),
                    action_name_translation(stopped_action));
 
      wipe_unit(act_unit, ULR_KILLED, NULL);
      act_unit = NULL;
 
      return TRUE;
    }
  }
 
  /* MP cost */
  punishment_mp = get_target_bonus_effects(NULL, &actor_ctxt, &tgt_ctxt,
                                           EFT_ILLEGAL_ACTION_MOVE_COST);
 
  /* Stay in range */
  punishment_mp = MAX(0, punishment_mp);
 
  /* Punish the unit's move fragments. */
  act_unit->moves_left = MAX(0, act_unit->moves_left - punishment_mp);
  send_unit_info(NULL, act_unit);
 
  if (punishment_mp != 0) {
    /* The player probably wants to be disturbed if their unit was punished
     * with the loss of movement points. */
    notify_player(pplayer, unit_tile(act_unit),
                  E_UNIT_ILLEGAL_ACTION, ftc_server,
                  /* TRANS: Spy ... movement point text that may include
                   * fractions. */
                  _("Your %s lost %s MP for attempting an illegal action."),
                  unit_name_translation(act_unit),
                  move_points_text(punishment_mp, TRUE));
  }
 
  return punishment_mp != 0 || punishment_hp != 0;
}
 
/**********************************************************************/
static void illegal_action(struct player *pplayer,
                           struct unit *actor,
                           action_id stopped_action_id,
                           struct player *tgt_player,
                           struct tile *target_tile,
                           const struct city *target_city,
                           const struct unit *target_unit,
                           int request_kind,
                           const enum action_requester requester)
{
  bool information_revealed;
  bool was_punished;
  const struct civ_map *nmap = &(wld.map);
 
  struct action *stopped_action = action_by_number(stopped_action_id);
 
  /* Why didn't the game check before trying something illegal? Did a good
   * reason to not call is_action_enabled_unit_on...() appear? The game is
   * omniscient... */
  fc_assert(requester != ACT_REQ_RULES);
 
 
  information_revealed = action_prob_possible(action_prob_unit_vs_tgt(
                                                 nmap,
                                                 stopped_action,
                                                 actor,
                                                 target_city, target_unit,
                                                 target_tile, NULL));
 
  if (request_kind == REQEST_PLAYER_INITIATED) {
    /* This is a foreground request. */
    illegal_action_msg(pplayer, (information_revealed
                                 ? E_UNIT_ILLEGAL_ACTION : E_BAD_COMMAND),
                       actor, stopped_action_id,
                       target_tile, target_city, target_unit);
  }
 
  was_punished = illegal_action_pay_price(pplayer, information_revealed,
                                          actor, stopped_action,
                                          tgt_player, target_tile,
                                          requester);
 
  if (request_kind != REQEST_PLAYER_INITIATED && was_punished) {
    /* FIXME: Temporary work around to prevent wrong information and/or
     * crashes. See hrm Bug #879880 */
    /* TODO: Get the explanation before the punishment and show it here.
     * See hrm Bug #879881 */
    notify_player(pplayer, unit_tile(actor),
                  (information_revealed
                   ? E_UNIT_ILLEGAL_ACTION : E_BAD_COMMAND), ftc_server,
                  _("No explanation why you couldn't do %s. This is a bug."
                    " Sorry about that. -- Sveinung"),
                  action_id_name_translation(stopped_action_id));
  }
}
 
/**********************************************************************/
static void unit_query_impossible(struct connection *pc,
                                  const int actor_id,
                                  const int target_id,
                                  int request_kind)
{
  dsend_packet_unit_action_answer(pc,
                                  actor_id, target_id,
                                  0,
                                  ACTION_NONE,
                                  request_kind);
}
 
/**********************************************************************/
void handle_unit_action_query(struct connection *pc,
                              const int actor_id,
                              const int target_id,
                              const action_id action_type,
                              int request_kind)
{
  struct player *pplayer = pc->playing;
  struct unit *pactor = player_unit_by_number(pplayer, actor_id);
  struct action *paction = action_by_number(action_type);
  struct unit *punit = game_unit_by_number(target_id);
  struct city *pcity = game_city_by_number(target_id);
  struct tile *ptile = index_to_tile(&(wld.map), target_id);
  const struct civ_map *nmap = &(wld.map);
 
  if (NULL == paction) {
    /* Non existing action */
    log_error("handle_unit_action_query() the action %d doesn't exist.",
              action_type);
 
    unit_query_impossible(pc, actor_id, target_id, request_kind);
    return;
  }
 
  if (NULL == pactor) {
    /* Probably died or bribed. */
    log_verbose("handle_unit_action_query() invalid actor %d",
                actor_id);
    unit_query_impossible(pc, actor_id, target_id, request_kind);
    return;
  }
 
  switch (paction->result) {
  case ACTRES_SPY_BRIBE_UNIT:
    if (punit != nullptr
        && is_action_enabled_unit_on_unit(nmap, action_type,
                                          pactor, punit)) {
      dsend_packet_unit_action_answer(pc,
                                      actor_id, target_id,
                                      unit_bribe_cost(punit, pplayer,
                                                      pactor),
                                      action_type, request_kind);
    } else {
      illegal_action(pplayer, pactor, action_type,
                     punit ? unit_owner(punit) : nullptr,
                     nullptr, nullptr, punit, request_kind, ACT_REQ_PLAYER);
      unit_query_impossible(pc, actor_id, target_id, request_kind);
      return;
    }
    break;
  case ACTRES_SPY_BRIBE_STACK:
    if (ptile != nullptr
        && is_action_enabled_unit_on_stack(nmap, action_type,
                                           pactor, ptile)) {
      dsend_packet_unit_action_answer(pc,
                                      actor_id, target_id,
                                      stack_bribe_cost(ptile, pplayer,
                                                       pactor),
                                      action_type, request_kind);
    } else {
      illegal_action(pplayer, pactor, action_type,
                     punit ? unit_owner(punit) : nullptr,
                     nullptr, nullptr, punit, request_kind, ACT_REQ_PLAYER);
      unit_query_impossible(pc, actor_id, target_id, request_kind);
      return;
    }
    break;
  case ACTRES_SPY_INCITE_CITY:
    if (pcity
        && is_action_enabled_unit_on_city(nmap, action_type,
                                          pactor, pcity)) {
      dsend_packet_unit_action_answer(pc,
                                      actor_id, target_id,
                                      city_incite_cost(pplayer, pcity),
                                      action_type, request_kind);
    } else {
      illegal_action(pplayer, pactor, action_type,
                     pcity ? city_owner(pcity) : NULL,
                     NULL, pcity, NULL, request_kind, ACT_REQ_PLAYER);
      unit_query_impossible(pc, actor_id, target_id, request_kind);
      return;
    }
    break;
  case ACTRES_UPGRADE_UNIT:
    if (pcity
        && is_action_enabled_unit_on_city(nmap, action_type,
                                          pactor, pcity)) {
      const struct unit_type *tgt_utype;
      int upgr_cost;
 
      tgt_utype = can_upgrade_unittype(pplayer, unit_type_get(pactor));
      /* Already checked via is_action_enabled_unit_on_city() */
      fc_assert_ret(tgt_utype);
      upgr_cost = unit_upgrade_price(pplayer,
                                      unit_type_get(pactor), tgt_utype);
 
      dsend_packet_unit_action_answer(pc,
                                      actor_id, target_id,
                                      upgr_cost, action_type,
                                      request_kind);
    } else {
      illegal_action(pplayer, pactor, action_type,
                     pcity ? city_owner(pcity) : NULL,
                     NULL, pcity, NULL, request_kind, ACT_REQ_PLAYER);
      unit_query_impossible(pc, actor_id, target_id, request_kind);
      return;
    }
    break;
  case ACTRES_SPY_TARGETED_SABOTAGE_CITY:
  case ACTRES_STRIKE_BUILDING:
    if (pcity
        && is_action_enabled_unit_on_city(nmap, action_type,
                                          pactor, pcity)) {
      spy_send_sabotage_list(pc, pactor, pcity,
                             action_by_number(action_type), request_kind);
    } else {
      illegal_action(pplayer, pactor, action_type,
                     pcity ? city_owner(pcity) : NULL,
                     NULL, pcity, NULL, request_kind, ACT_REQ_PLAYER);
      unit_query_impossible(pc, actor_id, target_id, request_kind);
      return;
    }
    break;
  default:
    unit_query_impossible(pc, actor_id, target_id, request_kind);
    return;
  };
}
 
/**********************************************************************/
void handle_unit_do_action(struct player *pplayer,
                           const int actor_id,
                           const int target_id,
                           const int sub_tgt_id,
                           const char *name,
                           const action_id action_type)
{
  (void) unit_perform_action(pplayer, actor_id, target_id, sub_tgt_id, name,
                             action_type, ACT_REQ_PLAYER);
}
 
/**********************************************************************/
void unit_do_action(struct player *pplayer,
                    const int actor_id,
                    const int target_id,
                    const int sub_tgt_id,
                    const char *name,
                    const action_id action_type)
{
  unit_perform_action(pplayer, actor_id, target_id,
                      sub_tgt_id, name, action_type, ACT_REQ_PLAYER);
}
 
/**********************************************************************/
bool unit_perform_action(struct player *pplayer,
                         const int actor_id,
                         const int target_id,
                         const int sub_tgt_id_incoming,
                         const char *name,
                         const action_id action_type,
                         const enum action_requester requester)
{
  struct action *paction;
  int sub_tgt_id;
  struct unit *actor_unit = player_unit_by_number(pplayer, actor_id);
  struct tile *target_tile = NULL;
  struct extra_type *target_extra;
  struct impr_type *sub_tgt_impr;
  struct unit *punit = NULL;
  struct city *pcity = NULL;
  const struct civ_map *nmap = &(wld.map);
 
  if (!action_id_exists(action_type)) {
    /* Non existing action */
    log_error("unit_perform_action() the action %d doesn't exist.",
              action_type);
 
    return FALSE;
  }
 
  paction = action_by_number(action_type);
 
  if (NULL == actor_unit) {
    /* Probably died or bribed. */
    log_verbose("unit_perform_action() invalid actor %d",
                actor_id);
    return FALSE;
  }
 
  switch (action_get_target_kind(paction)) {
  case ATK_CITY:
    pcity = game_city_by_number(target_id);
    if (pcity == NULL) {
      log_verbose("unit_perform_action() invalid target city %d",
                  target_id);
      return FALSE;
    }
    target_tile = city_tile(pcity);
    fc_assert_ret_val(target_tile != NULL, FALSE);
    break;
  case ATK_UNIT:
    punit = game_unit_by_number(target_id);
    if (punit == NULL) {
      log_verbose("unit_perform_action() invalid target unit %d",
                  target_id);
      return FALSE;
    }
    target_tile = unit_tile(punit);
    fc_assert_ret_val(target_tile != NULL, FALSE);
    pcity = tile_city(target_tile);
    break;
  case ATK_STACK:
  case ATK_TILE:
  case ATK_EXTRAS:
    target_tile = index_to_tile(nmap, target_id);
    if (target_tile == NULL) {
      log_verbose("unit_perform_action() invalid target tile %d",
                  target_id);
      return FALSE;
    }
    pcity = tile_city(target_tile);
    break;
  case ATK_SELF:
    target_tile = unit_tile(actor_unit);
    fc_assert_ret_val(target_tile != NULL, FALSE);
    pcity = tile_city(target_tile);
    break;
  case ATK_COUNT:
    fc_assert_ret_val(action_get_target_kind(paction) != ATK_COUNT, FALSE);
    break;
  }
 
  /* Server side sub target assignment */
  if (paction->target_complexity == ACT_TGT_COMPL_FLEXIBLE
      && sub_tgt_id_incoming == NO_TARGET) {
    sub_tgt_id = action_sub_target_id_for_action(paction, actor_unit);
  } else {
    sub_tgt_id = sub_tgt_id_incoming;
  }
 
  if (sub_tgt_id >= 0 && sub_tgt_id < MAX_EXTRA_TYPES
      && sub_tgt_id != NO_TARGET) {
    target_extra = extra_by_number(sub_tgt_id);
    fc_assert(!(target_extra->ruledit_disabled));
  } else {
    target_extra = NULL;
  }
 
  sub_tgt_impr = improvement_by_number(sub_tgt_id);
 
  /* Sub targets should now be assigned */
  switch (paction->sub_target_kind) {
  case ASTK_NONE:
    /* No sub target. */
    break;
  case ASTK_BUILDING:
    if (sub_tgt_impr == NULL) {
      /* Missing sub target */
      return FALSE;
    }
    break;
  case ASTK_TECH:
    /* Not handled here yet */
    break;
  case ASTK_EXTRA:
  case ASTK_EXTRA_NOT_THERE:
    if (target_extra == NULL) {
      /* Missing sub target */
      return FALSE;
    }
    break;
  case ASTK_COUNT:
    break;
  }
 
  if (action_get_activity(paction) != ACTIVITY_LAST
      && unit_activity_needs_target_from_client(
           action_get_activity(paction))
      && target_extra == NULL) {
    /* Missing required action extra target. */
    log_verbose("unit_perform_action() action %d requires action "
                "but extra id %d is invalid.",
                action_type, sub_tgt_id);
    return FALSE;
  }
 
  if (paction->actor.is_unit.unitwaittime_controlled
      && !unit_can_do_action_now(actor_unit)) {
    /* Action not possible due to unitwaittime setting. */
    return FALSE;
  }
 
#define ACTION_PERFORM_UNIT_CITY(action, actor, target, action_performer) \
  if (pcity                                                               \
      && is_action_enabled_unit_on_city(nmap, action_type,                \
                                        actor_unit, pcity)) {             \
    bool success;                                                         \
    script_server_signal_emit("action_started_unit_city",                 \
                              action_by_number(action), actor, target);   \
    if (!actor || !unit_is_alive(actor_id)) {                             \
      /* Actor unit was destroyed during pre action Lua. */               \
      return FALSE;                                                       \
    }                                                                     \
    if (!target || !city_exist(target_id)) {                              \
      /* Target city was destroyed during pre action Lua. */              \
      return FALSE;                                                       \
    }                                                                     \
    success = action_performer;                                           \
    if (success) {                                                        \
      action_success_actor_price(paction, actor_id, actor);               \
    }                                                                     \
    script_server_signal_emit("action_finished_unit_city",                \
                              action_by_number(action), success,          \
                              unit_is_alive(actor_id) ? actor : NULL,     \
                              city_exist(target_id) ? target : NULL);     \
    return success;                                                       \
  } else {                                                                \
    illegal_action(pplayer, actor_unit, action_type,                      \
                   pcity ? city_owner(pcity) : NULL, NULL, pcity, NULL,   \
                   TRUE, requester);                                      \
  }
 
#define ACTION_PERFORM_UNIT_SELF(action, actor, action_performer)         \
  if (actor_unit                                                          \
      && is_action_enabled_unit_on_self(nmap, action_type, actor_unit)) { \
    bool success;                                                         \
    script_server_signal_emit("action_started_unit_self",                 \
                              action_by_number(action), actor);           \
    if (!actor || !unit_is_alive(actor_id)) {                             \
      /* Actor unit was destroyed during pre action Lua. */               \
      return FALSE;                                                       \
    }                                                                     \
    success = action_performer;                                           \
    if (success) {                                                        \
      action_success_actor_price(paction, actor_id, actor);               \
    }                                                                     \
    script_server_signal_emit("action_finished_unit_self",                \
                              action_by_number(action), success,          \
                              unit_is_alive(actor_id) ? actor : NULL);    \
    return success;                                                       \
  } else {                                                                \
    illegal_action(pplayer, actor_unit, action_type,                      \
                   unit_owner(actor_unit), NULL, NULL, actor_unit,        \
                   TRUE, requester);                                      \
  }
 
#define ACTION_PERFORM_UNIT_UNIT(action, actor, target, action_performer) \
  if (punit                                                               \
      && is_action_enabled_unit_on_unit(nmap, action_type, actor_unit, punit)) { \
    bool success;                                                         \
    script_server_signal_emit("action_started_unit_unit",                 \
                              action_by_number(action), actor, target);   \
    if (!actor || !unit_is_alive(actor_id)) {                             \
      /* Actor unit was destroyed during pre action Lua. */               \
      return FALSE;                                                       \
    }                                                                     \
    if (!target || !unit_is_alive(target_id)) {                           \
      /* Target unit was destroyed during pre action Lua. */              \
      return FALSE;                                                       \
    }                                                                     \
    success = action_performer;                                           \
    if (success) {                                                        \
      action_success_actor_price(paction, actor_id, actor);               \
      action_success_target_pay_mp(paction, target_id, punit);            \
    }                                                                     \
    script_server_signal_emit("action_finished_unit_unit",                \
                              action_by_number(action), success,          \
                              unit_is_alive(actor_id) ? actor : NULL,     \
                              unit_is_alive(target_id) ? target : NULL);  \
    return success;                                                       \
  } else {                                                                \
    illegal_action(pplayer, actor_unit, action_type,                      \
                   punit ? unit_owner(punit) : NULL, NULL, NULL, punit,   \
                   TRUE, requester);                                      \
  }
 
#define ACTION_PERFORM_UNIT_STACK(action, actor, target, action_performer)\
  if (target_tile                                                         \
      && is_action_enabled_unit_on_stack(nmap, action_type,               \
                                         actor_unit, target_tile)) {      \
    bool success;                                                         \
    script_server_signal_emit("action_started_unit_stack",                \
                              action_by_number(action), actor, target);   \
    script_server_signal_emit("action_started_unit_units",                \
                              action_by_number(action), actor, target);   \
    if (!actor || !unit_is_alive(actor_id)) {                             \
      /* Actor unit was destroyed during pre action Lua. */               \
      return FALSE;                                                       \
    }                                                                     \
    success = action_performer;                                           \
    if (success) {                                                        \
      action_success_actor_price(paction, actor_id, actor);               \
    }                                                                     \
    script_server_signal_emit("action_finished_unit_stack",               \
                              action_by_number(action), success,          \
                              unit_is_alive(actor_id) ? actor : NULL,     \
                              target);                                    \
    script_server_signal_emit("action_finished_unit_units",               \
                              action_by_number(action), success,          \
                              unit_is_alive(actor_id) ? actor : NULL,     \
                              target);                                    \
    return success;                                                       \
  } else {                                                                \
    illegal_action(pplayer, actor_unit, action_type,                      \
                   NULL, target_tile, NULL, NULL,                         \
                   TRUE, requester);                                      \
  }
 
#define ACTION_PERFORM_UNIT_TILE(action, actor, target, action_performer) \
  if (target_tile                                                         \
      && is_action_enabled_unit_on_tile(nmap, action_type,                \
                                        actor_unit, target_tile,          \
                                        target_extra)) {                  \
    bool success;                                                         \
    script_server_signal_emit("action_started_unit_tile",                 \
                              action_by_number(action), actor, target);   \
    if (!actor || !unit_is_alive(actor_id)) {                             \
      /* Actor unit was destroyed during pre action Lua. */               \
      return FALSE;                                                       \
    }                                                                     \
    success = action_performer;                                           \
    if (success) {                                                        \
      action_success_actor_price(paction, actor_id, actor);               \
    }                                                                     \
    script_server_signal_emit("action_finished_unit_tile",                \
                              action_by_number(action), success,          \
                              unit_is_alive(actor_id) ? actor : NULL,     \
                              target);                                    \
    return success;                                                       \
  } else {                                                                \
    illegal_action(pplayer, actor_unit, action_type,                      \
                   target_tile ? tile_owner(target_tile) : NULL,          \
                   target_tile, NULL, NULL,                               \
                   TRUE, requester);                                      \
  }
 
#define ACTION_PERFORM_UNIT_EXTRAS(action, actor, target, action_performer)\
  if (target_tile                                                         \
      && is_action_enabled_unit_on_extras(nmap, action_type,              \
                                          actor_unit, target_tile,        \
                                          target_extra)) {                \
    bool success;                                                         \
    script_server_signal_emit("action_started_unit_extras",               \
                              action_by_number(action), actor, target);   \
    if (!actor || !unit_is_alive(actor_id)) {                             \
      /* Actor unit was destroyed during pre action Lua. */               \
      return FALSE;                                                       \
    }                                                                     \
    success = action_performer;                                           \
    if (success) {                                                        \
      action_success_actor_price(paction, actor_id, actor);               \
    }                                                                     \
    script_server_signal_emit("action_finished_unit_extras",              \
                              action_by_number(action), success,          \
                              unit_is_alive(actor_id) ? actor : NULL,     \
                              target);                                    \
    return success;                                                       \
  } else {                                                                \
    illegal_action(pplayer, actor_unit, action_type,                      \
                   target_tile ? target_tile->extras_owner : NULL,        \
                   target_tile, NULL, NULL,                               \
                   TRUE, requester);                                      \
  }
 
#define ACTION_PERFORM_UNIT_ANY(paction, actor,                           \
                                target_city, target_unit, target_tile,    \
                                action_performer)                         \
  switch (action_get_target_kind(paction)) {                              \
  case ATK_CITY:                                                          \
    ACTION_PERFORM_UNIT_CITY(paction->id, actor, target_city,             \
                             action_performer);                           \
    break;                                                                \
  case ATK_UNIT:                                                          \
    ACTION_PERFORM_UNIT_UNIT(paction->id, actor, target_unit,             \
                             action_performer);                           \
    break;                                                                \
  case ATK_STACK:                                                         \
    ACTION_PERFORM_UNIT_STACK(paction->id, actor, target_tile,            \
                              action_performer);                          \
    break;                                                                \
  case ATK_TILE:                                                          \
    ACTION_PERFORM_UNIT_TILE(paction->id, actor, target_tile,             \
                             action_performer);                           \
    break;                                                                \
  case ATK_EXTRAS:                                                        \
    ACTION_PERFORM_UNIT_EXTRAS(paction->id, actor, target_tile,           \
                               action_performer);                         \
    break;                                                                \
  case ATK_SELF:                                                          \
    ACTION_PERFORM_UNIT_SELF(paction->id, actor, TRUE);                   \
    break;                                                                \
  case ATK_COUNT:                                                         \
    fc_assert(action_get_target_kind(paction) != ATK_COUNT);              \
    break;                                                                \
  }
 
  switch (paction->result) {
  case ACTRES_SPY_BRIBE_UNIT:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             diplomat_bribe_unit(pplayer, actor_unit, punit,
                                                 paction));
    break;
  case ACTRES_SPY_SABOTAGE_UNIT:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             spy_sabotage_unit(pplayer, actor_unit,
                                               punit, paction));
    break;
  case ACTRES_EXPEL_UNIT:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             do_expel_unit(pplayer, actor_unit, punit,
                                           paction));
    break;
  case ACTRES_HEAL_UNIT:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             do_heal_unit(pplayer, actor_unit, punit,
                                          paction));
    break;
  case ACTRES_TRANSPORT_DEBOARD:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             do_unit_deboard(pplayer, actor_unit, punit,
                                             paction));
    break;
  case ACTRES_TRANSPORT_UNLOAD:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             do_unit_unload(pplayer, actor_unit, punit,
                                            paction));
    break;
  case ACTRES_TRANSPORT_BOARD:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             do_unit_board(pplayer, actor_unit, punit,
                                           paction));
    break;
  case ACTRES_TRANSPORT_LOAD:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             do_unit_load(pplayer, actor_unit, punit,
                                          paction));
    break;
  case ACTRES_TRANSPORT_EMBARK:
    ACTION_PERFORM_UNIT_UNIT(action_type, actor_unit, punit,
                             do_unit_embark(pplayer, actor_unit, punit,
                                            paction));
    break;
  case ACTRES_DISBAND_UNIT:
    /* All consequences are handled by the action system. */
    ACTION_PERFORM_UNIT_SELF(action_type, actor_unit, TRUE);
    break;
  case ACTRES_FORTIFY:
    ACTION_PERFORM_UNIT_SELF(action_type, actor_unit,
                             do_action_activity(actor_unit, paction));
    break;
  case ACTRES_CONVERT:
    ACTION_PERFORM_UNIT_SELF(action_type, actor_unit,
                             do_action_activity(actor_unit, paction));
    break;
  case ACTRES_HOMELESS:
    ACTION_PERFORM_UNIT_SELF(action_type, actor_unit,
                             do_unit_make_homeless(actor_unit, paction));
    break;
  case ACTRES_SPY_ESCAPE:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             spy_escape(pplayer, actor_unit,
                                        pcity, target_tile, paction));
    break;
  case ACTRES_SPY_SABOTAGE_CITY:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_sabotage(pplayer, actor_unit, pcity,
                                               B_LAST, paction));
    break;
  case ACTRES_SPY_TARGETED_SABOTAGE_CITY:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_sabotage(pplayer, actor_unit, pcity,
                                               sub_tgt_impr->item_number,
                                               paction));
    break;
  case ACTRES_SPY_SABOTAGE_CITY_PRODUCTION:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_sabotage(pplayer, actor_unit, pcity,
                                               -1, paction));
    break;
  case ACTRES_SPY_POISON:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             spy_poison(pplayer, actor_unit, pcity,
                                        paction));
    break;
  case ACTRES_SPY_SPREAD_PLAGUE:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             spy_spread_plague(pplayer, actor_unit, pcity,
                                               paction));
    break;
  case ACTRES_SPY_INVESTIGATE_CITY:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_investigate(pplayer,
                                                  actor_unit, pcity,
                                                  paction));
    break;
  case ACTRES_ESTABLISH_EMBASSY:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_embassy(pplayer, actor_unit, pcity,
                                              paction));
    break;
  case ACTRES_SPY_INCITE_CITY:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_incite(pplayer, actor_unit, pcity,
                                             paction));
    break;
  case ACTRES_SPY_STEAL_TECH:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_get_tech(pplayer, actor_unit, pcity,
                                               A_UNSET, paction));
    break;
  case ACTRES_SPY_TARGETED_STEAL_TECH:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             diplomat_get_tech(pplayer, actor_unit, pcity,
                                               sub_tgt_id, paction));
    break;
  case ACTRES_SPY_STEAL_GOLD:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             spy_steal_gold(pplayer, actor_unit, pcity,
                                            paction));
    break;
  case ACTRES_STEAL_MAPS:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             spy_steal_some_maps(pplayer, actor_unit,
                                                 pcity, paction));
    break;
  case ACTRES_TRADE_ROUTE:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_unit_establish_trade(pplayer, actor_unit,
                                                     pcity, paction));
    break;
  case ACTRES_MARKETPLACE:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_unit_establish_trade(pplayer, actor_unit,
                                                     pcity, paction));
    break;
  case ACTRES_HELP_WONDER:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             unit_do_help_build(pplayer,
                                                actor_unit, pcity,
                                                paction));
    break;
  case ACTRES_SPY_NUKE:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             spy_nuke_city(pplayer, actor_unit, pcity,
                                           paction));
    break;
  case ACTRES_JOIN_CITY:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             city_add_unit(pplayer, actor_unit, pcity,
                                           paction));
    break;
  case ACTRES_DESTROY_CITY:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             unit_do_destroy_city(pplayer,
                                                  actor_unit, pcity,
                                                  paction));
    break;
  case ACTRES_DISBAND_UNIT_RECOVER:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             unit_do_help_build(pplayer, actor_unit, pcity,
                                                paction));
    break;
  case ACTRES_HOME_CITY:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_unit_change_homecity(actor_unit, pcity,
                                                     paction));
    break;
  case ACTRES_UPGRADE_UNIT:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_unit_upgrade(pplayer, actor_unit,
                                             pcity, requester, paction));
    break;
  case ACTRES_CONQUER_CITY:
    /* Difference is caused by the ruleset. ("Fake generalized" actions) */
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_unit_conquer_city(pplayer, actor_unit,
                                                  pcity, paction));
    break;
  case ACTRES_STRIKE_BUILDING:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_unit_strike_city_building(pplayer,
                                                          actor_unit,
                                                          pcity,
                                                          sub_tgt_impr->item_number,
                                                          paction));
    break;
  case ACTRES_STRIKE_PRODUCTION:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_unit_strike_city_production(pplayer,
                                                            actor_unit,
                                                            pcity,
                                                            paction));
    break;
  case ACTRES_CONQUER_EXTRAS:
    ACTION_PERFORM_UNIT_EXTRAS(action_type, actor_unit, target_tile,
                               do_conquer_extras(pplayer, actor_unit,
                                                 target_tile, paction));
    break;
  case ACTRES_AIRLIFT:
    ACTION_PERFORM_UNIT_CITY(action_type, actor_unit, pcity,
                             do_airline(actor_unit, pcity, paction));
    break;
  case ACTRES_CAPTURE_UNITS:
    ACTION_PERFORM_UNIT_STACK(action_type, actor_unit, target_tile,
                              do_capture_units(pplayer, actor_unit,
                                               target_tile, paction));
    break;
  case ACTRES_BOMBARD:
    /* Difference is caused by the ruleset. ("Fake generalized" actions) */
    ACTION_PERFORM_UNIT_STACK(action_type, actor_unit, target_tile,
                              unit_bombard(actor_unit, target_tile,
                                           paction));
    break;
  case ACTRES_ATTACK:
  case ACTRES_COLLECT_RANSOM:
    /* Difference is caused by data in the action structure. */
    ACTION_PERFORM_UNIT_STACK(action_type, actor_unit, target_tile,
                              do_attack(actor_unit, target_tile, paction));
    break;
  case ACTRES_WIPE_UNITS:
    ACTION_PERFORM_UNIT_STACK(action_type, actor_unit, target_tile,
                              do_wipe_units(actor_unit, target_tile, paction));
    break;
  case ACTRES_SPY_BRIBE_STACK:
    ACTION_PERFORM_UNIT_STACK(action_type, actor_unit, target_tile,
                              diplomat_bribe_stack(pplayer, actor_unit,
                                                   target_tile, paction));
    break;
  case ACTRES_NUKE_UNITS:
    ACTION_PERFORM_UNIT_STACK(action_type, actor_unit, target_tile,
                              unit_nuke(pplayer, actor_unit, target_tile,
                                        paction));
    break;
  case ACTRES_SPY_ATTACK:
    ACTION_PERFORM_UNIT_STACK(action_type, actor_unit, target_tile,
                              spy_attack(pplayer, actor_unit, target_tile,
                                         paction));
    break;
  case ACTRES_FOUND_CITY:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             city_build(pplayer, actor_unit,
                                        target_tile, name, paction));
    break;
  case ACTRES_NUKE:
    ACTION_PERFORM_UNIT_ANY(paction, actor_unit,
                            pcity, punit, target_tile,
                            unit_nuke(pplayer, actor_unit, target_tile,
                                      paction));
    break;
  case ACTRES_PARADROP:
  case ACTRES_PARADROP_CONQUER:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_paradrop(actor_unit, target_tile, paction));
    break;
  case ACTRES_TRANSPORT_DISEMBARK:
    /* Difference is caused by the ruleset. ("Fake generalized" actions) */
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_disembark(pplayer, actor_unit,
                                          target_tile, paction));
    break;
  case ACTRES_HUT_ENTER:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_unit_hut(pplayer, actor_unit,
                                         target_tile, paction));
    break;
  case ACTRES_HUT_FRIGHTEN:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_unit_hut(pplayer, actor_unit,
                                         target_tile, paction));
    break;
  case ACTRES_UNIT_MOVE:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             unit_do_regular_move(pplayer, actor_unit,
                                                  target_tile, paction));
    break;
  case ACTRES_TELEPORT:
  case ACTRES_TELEPORT_CONQUER:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             unit_move(actor_unit, target_tile, 0,
                                       NULL, FALSE,
                                       paction->result == ACTRES_TELEPORT_CONQUER,
                                       paction->result == ACTRES_TELEPORT_CONQUER,
                                       FALSE, FALSE));
    break;
  case ACTRES_TRANSFORM_TERRAIN:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity(actor_unit, paction));
    break;
  case ACTRES_CULTIVATE:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity(actor_unit, paction));
    break;
  case ACTRES_PLANT:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity(actor_unit, paction));
    break;
  case ACTRES_PILLAGE:
    ACTION_PERFORM_UNIT_ANY(paction, actor_unit, pcity, punit, target_tile,
                            do_action_activity_targeted(actor_unit,
                                                        paction,
                                                        &target_extra));
    break;
  case ACTRES_CLEAN:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity_targeted(actor_unit,
                                                         paction,
                                                         &target_extra));
    break;
  case ACTRES_ROAD:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity_targeted(actor_unit,
                                                         paction,
                                                         &target_extra));
    break;
  case ACTRES_BASE:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity_targeted(actor_unit,
                                                         paction,
                                                         &target_extra));
    break;
  case ACTRES_MINE:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity_targeted(actor_unit,
                                                         paction,
                                                         &target_extra));
    break;
  case ACTRES_IRRIGATE:
    ACTION_PERFORM_UNIT_TILE(action_type, actor_unit, target_tile,
                             do_action_activity_targeted(actor_unit,
                                                         paction,
                                                         &target_extra));
    break;
  case ACTRES_NONE:
    /* 100% ruleset defined. */
    ACTION_PERFORM_UNIT_ANY(paction, actor_unit, pcity, punit, target_tile,
                            TRUE);
    break;
  case ACTRES_ENABLER_CHECK:
    fc_assert(paction->result != ACTRES_ENABLER_CHECK);
    return FALSE;
 
  ASSERT_UNUSED_ACTRES_CASES;
  }
 
  /* Something must have gone wrong. */
  return FALSE;
}
 
/**********************************************************************/
void unit_change_homecity_handling(struct unit *punit, struct city *new_pcity,
                                   bool rehome)
{
  struct city *old_pcity = game_city_by_number(punit->homecity);
  struct player *old_owner = unit_owner(punit);
  struct player *new_owner = (new_pcity == NULL ? old_owner
                                                : city_owner(new_pcity));
  const struct civ_map *nmap = &(wld.map);
 
  /* Calling this function when new_pcity is same as old_pcity should
   * be safe with current implementation, but it is not meant to
   * be used that way. */
  fc_assert_ret(new_pcity != old_pcity);
 
  /* If 'rehome' is not set, this function should only be used to change
   * which player owns the unit */
  fc_assert_ret(rehome || new_owner != old_owner);
 
  if (old_owner != new_owner) {
    struct city *pcity = tile_city(punit->tile);
 
    fc_assert(!utype_player_already_has_this_unique(new_owner,
                                                    unit_type_get(punit)));
 
    vision_clear_sight(punit->server.vision);
    vision_free(punit->server.vision);
 
    if (pcity != NULL
        && !can_player_see_units_in_city(old_owner, pcity)) {
      /* Special case when city is being transferred. At this point city
       * itself has changed owner, so it's enemy city now that old owner
       * cannot see inside. All the normal methods of removing transferred
       * unit from previous owner's client think that there's no need to
       * remove unit as client shouldn't have it in first place. */
      unit_goes_out_of_sight(old_owner, punit);
    }
 
    /* Remove AI control of the old owner. */
    CALL_PLR_AI_FUNC(unit_lost, old_owner, punit);
 
    unit_list_remove(old_owner->units, punit);
    unit_list_prepend(new_owner->units, punit);
    punit->owner = new_owner;
 
    /* Activate AI control of the new owner. */
    CALL_PLR_AI_FUNC(unit_got, new_owner, punit);
 
    punit->server.vision = vision_new(new_owner, unit_tile(punit));
    unit_refresh_vision(punit);
  }
 
  if (rehome) {
    /* Remove from old city first and add to new city only after that. */
    if (old_pcity) {
      /* Even if unit is dead, we have to unlink unit pointer (punit). */
      unit_list_remove(old_pcity->units_supported, punit);
      /* update unit upkeep */
      city_units_upkeep(old_pcity);
    }
 
    if (new_pcity != NULL) {
      unit_list_prepend(new_pcity->units_supported, punit);
 
      /* update unit upkeep */
      city_units_upkeep(new_pcity);
 
      punit->homecity = new_pcity->id;
    } else {
      punit->homecity = IDENTITY_NUMBER_ZERO;
    }
  }
 
  if (!can_unit_continue_current_activity(nmap, punit)) {
    /* This is mainly for cases where unit owner changes to one not knowing
     * Railroad tech when unit is already building railroad.
     * Does also send_unit_info() */
    unit_activities_cancel(punit);
  } else {
    /* Send info to players and observers. */
    send_unit_info(NULL, punit);
  }
 
  if (new_pcity != NULL) {
    city_refresh(new_pcity);
    send_city_info(new_owner, new_pcity);
    fc_assert(unit_owner(punit) == city_owner(new_pcity));
  }
 
  if (old_pcity) {
    fc_assert(city_owner(old_pcity) == old_owner);
    city_refresh(old_pcity);
    send_city_info(old_owner, old_pcity);
  }
 
  unit_get_goods(punit);
 
  if (old_owner != new_owner) {
    script_server_signal_emit("unit_transferred", punit, old_owner);
  }
}
 
/**********************************************************************/
static bool do_unit_change_homecity(struct unit *punit,
                                    struct city *pcity,
                                    const struct action *paction)
{
  const char *giver = NULL;
 
  if (unit_owner(punit) != city_owner(pcity)) {
    /* This is a gift. Tell the receiver. */
    giver = player_name(unit_owner(punit));
  }
 
  unit_change_homecity_handling(punit, pcity, TRUE);
 
  if (punit->homecity == pcity->id && giver) {
    /* Notify the city owner about the gift they received. */
    notify_player(city_owner(pcity), city_tile(pcity), E_UNIT_BUILT,
                  ftc_server,
                  /* TRANS: other player ... unit type ... city name. */
                  _("%s transferred control over a %s to you in %s."),
                  giver,
                  unit_tile_link(punit),
                  city_link(pcity));
  }
 
  return punit->homecity == pcity->id;
}
 
/**********************************************************************/
static bool city_add_unit(struct player *pplayer, struct unit *punit,
                          struct city *pcity, const struct action *paction)
{
  int amount = unit_pop_value(punit);
  const struct unit_type *act_utype;
 
  /* Sanity check: The actor is still alive. */
  fc_assert_ret_val(punit, FALSE);
 
  act_utype = unit_type_get(punit);
 
  /* Sanity check: The target city still exists. */
  fc_assert_ret_val(pcity, FALSE);
 
  fc_assert_ret_val(amount > 0, FALSE);
 
  city_size_add(pcity, amount);
  /* Make the new people something, otherwise city fails the checks */
  pcity->specialists[DEFAULT_SPECIALIST] += amount;
  citizens_update(pcity, unit_nationality(punit));
  /* Refresh the city data. */
  city_refresh(pcity);
 
  /* Notify the unit owner that the unit successfully joined the city. */
  notify_player(pplayer, city_tile(pcity), E_CITY_BUILD, ftc_server,
                _("%s added to aid %s in growing."),
                unit_tile_link(punit),
                city_link(pcity));
  if (pplayer != city_owner(pcity)) {
    /* Notify the city owner when a foreign unit joins a city. */
    notify_player(city_owner(pcity), city_tile(pcity), E_CITY_BUILD,
                  ftc_server,
                  /* TRANS: another player had their unit join your city. */
                  _("%s adds %s to your city %s."),
                  player_name(unit_owner(punit)),
                  unit_tile_link(punit),
                  city_link(pcity));
  }
 
  action_consequence_success(paction, pplayer, act_utype,
                             city_owner(pcity), city_tile(pcity),
                             city_link(pcity));
 
  sanity_check_city(pcity);
 
  send_city_info(NULL, pcity);
 
  script_server_signal_emit("city_size_change", pcity,
                            (lua_Integer)amount, "unit_added");
 
  return TRUE;
}
 
/**********************************************************************/
static bool city_build(struct player *pplayer, struct unit *punit,
                       struct tile *ptile, const char *name,
                       const struct action *paction)
{
  char message[1024];
  int size;
  struct player *nationality;
  struct player *towner;
  const struct unit_type *act_utype;
 
  /* Sanity check: The actor still exists. */
  fc_assert_ret_val(pplayer, FALSE);
  fc_assert_ret_val(punit, FALSE);
 
  towner = tile_owner(ptile);
 
  if (!is_allowed_city_name(pplayer, name, message, sizeof(message))) {
    notify_player(pplayer, ptile, E_BAD_COMMAND, ftc_server,
                  "%s", message);
    return FALSE;
  }
 
  act_utype = unit_type_get(punit);
 
  nationality = unit_nationality(punit);
 
  create_city(pplayer, ptile, name, nationality);
  size = unit_type_get(punit)->city_size;
  if (size > 1) {
    struct city *pcity = tile_city(ptile);
 
    fc_assert_ret_val(pcity != NULL, FALSE);
 
    city_change_size(pcity, size, nationality, NULL);
  }
 
  /* May cause an incident even if the target tile is unclaimed. A ruleset
   * could give everyone a casus belli against the city founder. A rule
   * like that would make sense in a story where deep ecology is on the
   * table. (See also Voluntary Human Extinction Movement) */
  action_consequence_success(paction, pplayer, act_utype, towner,
                             ptile, tile_link(ptile));
 
  return TRUE;
}
 
/**********************************************************************/
static void handle_unit_change_activity_real(struct player *pplayer,
                                             int unit_id,
                                             enum unit_activity activity,
                                             struct extra_type *activity_target,
                                             enum gen_action trigger_action)
{
  struct unit *punit = player_unit_by_number(pplayer, unit_id);
 
  if (NULL == punit) {
    /* Probably died or bribed. */
    log_verbose("handle_unit_change_activity() invalid unit %d", unit_id);
    return;
  }
 
  if (punit->activity == activity
      && punit->activity_target == activity_target) {
    return;
  }
 
  /* Remove city spot reservations for AI settlers on city founding
   * mission, before goto_tile reset. */
  if (punit->server.adv->task != AUT_NONE) {
    adv_unit_new_task(punit, AUT_NONE, NULL);
  }
 
  punit->goto_tile = NULL;
 
  if (activity == ACTIVITY_GOTO) {
    /* Don't permit a client to set a unit's activity to ACTIVITY_GOTO.
     * Setting ACTIVITY_GOTO from the client results in a unit indicating
     * it is going somewhere while it is standing still. The appearance of
     * the unit doing something can trick the user to not make use of it.
     *
     * Handled here because adv_follow_path() uses unit_activity_handling()
     * to set a unit's activity to ACTIVITY_GOTO. */
    return;
  }
 
  if (activity == ACTIVITY_EXPLORE) {
    /* Please use unit_server_side_agent_set(). */
    return;
  }
 
  /* The activity can now be set. */
  unit_activity_handling_targeted(punit, activity, &activity_target,
                                  trigger_action);
}
 
/**********************************************************************/
void handle_unit_change_activity(struct player *pplayer, int unit_id,
                                 enum unit_activity activity,
                                 int target_id)
{
  struct extra_type *activity_target;
 
  if (target_id < 0 || target_id >= game.control.num_extra_types) {
    activity_target = NULL;
  } else {
    activity_target = extra_by_number(target_id);
  }
 
#ifdef FREECIV_WEB
  /* Web-client is not capable of selecting target, so we do it server side */
  if (activity_target == NULL) {
    struct unit *punit = player_unit_by_number(pplayer, unit_id);
    bool required = TRUE;
 
    if (punit == NULL) {
      return;
    }
 
    if (activity == ACTIVITY_IRRIGATE) {
      struct tile *ptile = unit_tile(punit);
 
      activity_target = next_extra_for_tile(ptile, EC_IRRIGATION,
                                            pplayer, punit);
    } else if (activity == ACTIVITY_MINE) {
      struct tile *ptile = unit_tile(punit);
 
      activity_target = next_extra_for_tile(ptile, EC_MINE,
                                            pplayer, punit);
    } else if (activity == ACTIVITY_BASE) {
      struct tile *ptile = unit_tile(punit);
      struct base_type *pbase =
        get_base_by_gui_type(BASE_GUI_FORTRESS, punit, ptile);
 
      if (pbase != NULL) {
        activity_target = base_extra_get(pbase);
      }
 
    } else if (activity == ACTIVITY_CLEAN) {
      activity_target = prev_extra_in_tile(unit_tile(punit), ERM_CLEAN,
                                           pplayer, punit);
    } else {
      required = FALSE;
    }
 
    if (activity_target == NULL && required) {
      /* Nothing more we can do */
      return;
    }
  }
#endif /* FREECIV_WEB */
 
  handle_unit_change_activity_real(pplayer, unit_id, activity, activity_target,
                                   activity_default_action(activity));
}
 
/**********************************************************************/
static void see_combat(struct unit *pattacker, struct unit *pdefender)
{
  struct packet_unit_short_info unit_att_short_packet, unit_def_short_packet;
  struct packet_unit_info unit_att_packet, unit_def_packet;
 
  /* 
   * Special case for attacking/defending:
   * 
   * Normally the player doesn't get the information about the units inside a
   * city. However for attacking/defending the player has to know the unit of
   * the other side.  After the combat a remove_unit packet will be sent
   * to the client to tidy up.
   *
   * Note these packets must be sent out before unit_versus_unit() is called,
   * so that the original unit stats (HP) will be sent.
   */
  package_short_unit(pattacker, &unit_att_short_packet,
                     UNIT_INFO_IDENTITY, 0);
  package_short_unit(pdefender, &unit_def_short_packet,
                     UNIT_INFO_IDENTITY, 0);
  package_unit(pattacker, &unit_att_packet);
  package_unit(pdefender, &unit_def_packet);
 
  conn_list_iterate(game.est_connections, pconn) {
    struct player *pplayer = pconn->playing;
 
    if (pplayer != NULL) {
 
      /* NOTE: this means the player can see combat between submarines even
       * if neither sub is visible.  See similar comment in send_combat. */
      if (map_is_known_and_seen(unit_tile(pattacker), pplayer, V_MAIN)
          || map_is_known_and_seen(unit_tile(pdefender), pplayer,
                                   V_MAIN)) {
 
        /* Units are sent even if they were visible already. They may
         * have changed orientation for combat. */
        if (pplayer == unit_owner(pattacker)) {
          send_packet_unit_info(pconn, &unit_att_packet);
        } else {
          send_packet_unit_short_info(pconn, &unit_att_short_packet, FALSE);
        }
        
        if (pplayer == unit_owner(pdefender)) {
          send_packet_unit_info(pconn, &unit_def_packet);
        } else {
          send_packet_unit_short_info(pconn, &unit_def_short_packet, FALSE);
        }
      }
    } else if (pconn->observer) {
      /* Global observer sees everything... */
      send_packet_unit_info(pconn, &unit_att_packet);
      send_packet_unit_info(pconn, &unit_def_packet);
    }
  } conn_list_iterate_end;
}
 
/**********************************************************************/
static void send_combat(struct unit *pattacker, struct unit *pdefender, 
                        int att_veteran, int def_veteran, int bombard)
{
  struct packet_unit_combat_info combat;
 
  combat.attacker_unit_id = pattacker->id;
  combat.defender_unit_id = pdefender->id;
  combat.attacker_hp = pattacker->hp;
  combat.defender_hp = pdefender->hp;
  combat.make_att_veteran = att_veteran;
  combat.make_def_veteran = def_veteran;
 
  players_iterate(other_player) {
    /* NOTE: this means the player can see combat between submarines even
     * if neither sub is visible.  See similar comment in see_combat. */
    if (map_is_known_and_seen(unit_tile(pattacker), other_player, V_MAIN)
        || map_is_known_and_seen(unit_tile(pdefender), other_player,
                                 V_MAIN)) {
      lsend_packet_unit_combat_info(other_player->connections, &combat);
 
      /* 
       * Remove the client knowledge of the units.  This corresponds to the
       * send_packet_unit_short_info calls up above.
       */
      if (!can_player_see_unit(other_player, pattacker)) {
        unit_goes_out_of_sight(other_player, pattacker);
      }
      if (!can_player_see_unit(other_player, pdefender)) {
        unit_goes_out_of_sight(other_player, pdefender);
      }
    }
  } players_iterate_end;
 
  /* Send combat info to non-player observers as well.  They already know
   * about the unit so no unit_info is needed. */
  conn_list_iterate(game.est_connections, pconn) {
    if (NULL == pconn->playing && pconn->observer) {
      send_packet_unit_combat_info(pconn, &combat);
    }
  } conn_list_iterate_end;
}
 
/**********************************************************************/
static void unit_attack_civilian_casualties(const struct unit *punit,
                                            struct city *pcity,
                                            const struct action *paction,
                                            const char *reason)
{
  struct player *pplayer = unit_owner(punit);
 
  if (pcity
      && get_target_bonus_effects(NULL,
                                  &(const struct req_context) {
                                    .player = city_owner(pcity),
                                    .city = pcity,
                                    .tile = city_tile(pcity),
                                    .unit = punit,
                                    .unittype = unit_type_get(punit),
                                    .action = paction,
                                  },
                                  NULL, EFT_UNIT_NO_LOSE_POP) <= 0
      && (game.info.killcitizen
          && uclass_has_flag(unit_class_get(punit), UCF_KILLCITIZEN))) {
    struct player *cplayer = city_owner(pcity);
    struct tile *ctile = city_tile(pcity);
    const char *clink = city_link(pcity);
 
    if (city_reduce_size(pcity, 1, pplayer, reason)) {
      city_refresh(pcity);
      send_city_info(NULL, pcity);
    } else {
      notify_player(pplayer, ctile, E_UNIT_ACTION_ACTOR_SUCCESS, ftc_server,
                    /* TRANS: Battleship ... Los Angeles ... Bombard */
                    _("Your %s destroyed %s by doing %s."),
                    unit_link(punit), clink,
                    action_name_translation(paction));
      notify_player(cplayer, ctile,
                    E_UNIT_ACTION_TARGET_HOSTILE, ftc_server,
                    /* TRANS: Sigurd I Magnusson ... Alkasse ... Attack */
                    _("%s destroyed %s by doing %s."),
                    player_name(pplayer), clink,
                    action_name_translation(paction));
    }
  }
}
 
/**********************************************************************/
static bool unit_bombard(struct unit *punit, struct tile *ptile,
                         const struct action *paction)
{
  struct player *pplayer = unit_owner(punit);
  struct city *pcity = tile_city(ptile);
  const struct unit_type *act_utype;
  const struct civ_map *nmap = &(wld.map);
 
  /* Sanity check: The actor still exists. */
  fc_assert_ret_val(pplayer, FALSE);
  fc_assert_ret_val(punit, FALSE);
 
  act_utype = unit_type_get(punit);
 
  log_debug("Start bombard: %s %s to %d, %d.",
            nation_rule_name(nation_of_player(pplayer)),
            unit_rule_name(punit), TILE_XY(ptile));
 
  unit_list_iterate_safe(ptile->units, pdefender) {
    if (is_unit_reachable_at(pdefender, punit, ptile)) {
      bool adj;
      enum direction8 facing;
      int att_hp, def_hp;
 
      adj = base_get_direction_for_step(nmap,
                                        punit->tile, pdefender->tile, &facing);
 
      if (adj) {
        punit->facing = facing;
 
        /* Unlike with normal attack, we don't change orientation of
         * defenders when bombarding */
      }
 
      unit_bombs_unit(punit, pdefender, &att_hp, &def_hp, paction);
 
      if (def_hp <= 0) {
        notify_player(pplayer, ptile,
                      E_UNIT_WIN_ATT, ftc_server,
                      /* TRANS: Your Bomber killed the English Rifleman by
                       * doing Bombard. */
                      _("Your %s killed the %s %s by doing %s."),
                      unit_name_translation(punit),
                      nation_adjective_for_player(unit_owner(pdefender)),
                      unit_name_translation(pdefender),
                      action_name_translation(paction));
        notify_player(unit_owner(pdefender), ptile,
                      E_UNIT_WIN_DEF, ftc_server,
                      /* TRANS: Your Rifleman was killed by the French
                       * Bomber doing Bombard. */
                      _("Your %s was killed by the %s %s doing %s."),
                      unit_name_translation(pdefender),
                      nation_adjective_for_player(pplayer),
                      unit_name_translation(punit),
                      action_name_translation(paction));
      } else {
        notify_player(pplayer, ptile,
                      E_UNIT_WIN_ATT, ftc_server,
                      /* TRANS: Your Bomber bombards the English Rifleman. */
                      _("Your %s bombards the %s %s."),
                      unit_name_translation(punit),
                      nation_adjective_for_player(unit_owner(pdefender)),
                      unit_name_translation(pdefender));
        notify_player(unit_owner(pdefender), ptile,
                      E_UNIT_WIN_DEF, ftc_server,
                      /* TRANS: Your Rifleman is bombarded by the French
                       * Bomber. */
                      _("Your %s is bombarded by the %s %s."),
                      unit_name_translation(pdefender),
                      nation_adjective_for_player(pplayer),
                      unit_name_translation(punit));
      }
 
      see_combat(punit, pdefender);
 
      punit->hp = att_hp;
      pdefender->hp = def_hp;
 
      send_combat(punit, pdefender, 0, 0, 1);
 
      /* May cause an incident */
      action_consequence_success(paction,
                                 unit_owner(punit), act_utype,
                                 unit_owner(pdefender),
                                 unit_tile(pdefender),
                                 unit_link(pdefender));
 
      if (def_hp <= 0) {
        wipe_unit(pdefender, ULR_KILLED, unit_owner(pdefender));
      } else {
        send_unit_info(NULL, pdefender);
      }
    }
 
  } unit_list_iterate_safe_end;
 
  unit_did_action(punit);
  unit_forget_last_activity(punit);
  
  unit_attack_civilian_casualties(punit, pcity, paction, "bombard");
 
  send_unit_info(NULL, punit);
 
  return TRUE;
}
 
/**********************************************************************/
static bool unit_nuke(struct player *pplayer, struct unit *punit,
                      struct tile *def_tile, const struct action *paction)
{
  struct city *pcity;
  const struct unit_type *act_utype;
  struct civ_map *nmap = &(wld.map);
 
  /* Sanity check: The actor still exists. */
  fc_assert_ret_val(pplayer, FALSE);
  fc_assert_ret_val(punit, FALSE);
 
  act_utype = unit_type_get(punit);
 
  log_debug("Start nuclear attack: %s %s against (%d, %d).",
            nation_rule_name(nation_of_player(pplayer)),
            unit_rule_name(punit),
            TILE_XY(def_tile));
 
  if ((pcity = sdi_try_defend(nmap, pplayer, def_tile))) {
    /* FIXME: Remove the hard coded reference to SDI defense. */
    notify_player(pplayer, unit_tile(punit), E_UNIT_LOST_ATT, ftc_server,
                  _("Your %s was shot down by "
                    "SDI defenses, what a waste."), unit_tile_link(punit));
    notify_player(city_owner(pcity), def_tile, E_UNIT_WIN_DEF, ftc_server,
                  _("The nuclear attack on %s was avoided by"
                    " your SDI defense."), city_link(pcity));
 
    /* Trying to nuke something this close can be... unpopular. */
    action_consequence_caught(paction, pplayer, act_utype,
                              city_owner(pcity),
                              def_tile, unit_tile_link(punit));
 
    /* Remove the destroyed nuke. */
    wipe_unit(punit, ULR_SDI, city_owner(pcity));
 
    return FALSE;
  }
 
  dlsend_packet_nuke_tile_info(game.est_connections, tile_index(def_tile));
 
 
  /* The nuke must be wiped here so it won't be seen as a victim of its own
   * detonation. */
  if (paction->actor_consuming_always) {
    wipe_unit(punit, ULR_DETONATED, NULL);
  }
 
  do_nuclear_explosion(paction, act_utype, pplayer, def_tile);
 
  /* May cause an incident even if the target tile is unclaimed. A ruleset
   * could give everyone a casus belli against the tile nuker. A rule
   * like that would make sense in a story where detonating any nuke at all
   * could be forbidden. */
  action_consequence_success(paction, pplayer, act_utype,
                             tile_owner(def_tile),
                             def_tile,
                             tile_link(def_tile));
 
  return TRUE;
}
 
/**********************************************************************/
static bool unit_do_destroy_city(struct player *act_player,
                                 struct unit *act_unit,
                                 struct city *tgt_city,
                                 const struct action *paction)
{
  int tgt_city_id;
  struct player *tgt_player;
  bool capital;
  bool try_civil_war = FALSE;
  const struct unit_type *act_utype;
 
  /* Sanity check: The actor still exists. */
  fc_assert_ret_val(act_player, FALSE);
  fc_assert_ret_val(act_unit, FALSE);
 
  act_utype = unit_type_get(act_unit);
 
  /* Sanity check: The target city still exists. */
  fc_assert_ret_val(tgt_city, FALSE);
 
  tgt_player = city_owner(tgt_city);
 
  /* How can a city be ownerless? */
  fc_assert_ret_val(tgt_player, FALSE);
 
  /* Save city ID. */
  tgt_city_id = tgt_city->id;
 
  capital = (player_primary_capital(tgt_player) == tgt_city);
 
  if (capital
      && (tgt_player->spaceship.state == SSHIP_STARTED
          || tgt_player->spaceship.state == SSHIP_LAUNCHED)) {
    /* Destroying this city destroys the victim's space ship. */
    spaceship_lost(tgt_player);
  }
 
  if (capital
      && civil_war_possible(tgt_player, TRUE, TRUE)
      && normal_player_count() < MAX_NUM_PLAYERS
      && civil_war_triggered(tgt_player)) {
    /* Destroying this city can trigger a civil war. */
    try_civil_war = TRUE;
  }
 
  /* Let the actor know. */
  notify_player(act_player, city_tile(tgt_city),
                E_CITY_CONQUERED, ftc_server,
                _("You destroy %s completely."),
                city_tile_link(tgt_city));
 
  if (tgt_player != act_player) {
    /* This was done to a foreign city. Inform the victim player. */
    notify_player(tgt_player, city_tile(tgt_city),
                  E_CITY_LOST, ftc_server,
                  _("%s has been destroyed by %s."),
                  city_tile_link(tgt_city),
                  player_name(act_player));
  }
 
  /* May cause an incident */
  action_consequence_success(paction, act_player, act_utype,
                             tgt_player, city_tile(tgt_city),
                             city_link(tgt_city));
 
  /* Run post city destruction Lua script. */
  script_server_signal_emit("city_destroyed", tgt_city, tgt_player,
                            act_player);
 
  /* Can't be sure of city existence after running script. */
  if (city_exist(tgt_city_id)) {
    remove_city(tgt_city);
  }
 
  if (try_civil_war) {
    /* Try to start the civil war. */
    (void) civil_war(tgt_player);
  }
 
  /* The city is no more. */
  return TRUE;
}
 
/**********************************************************************/
static const char *unit_veteran_level_string(const struct unit *punit)
{
  static char buf[MAX_LEN_LINK];
  const struct veteran_level *vlevel;
 
  if (!punit) {
    buf[0] = '\0'; /* If no unit, return empty string */
    return buf;
  }
 
  vlevel = utype_veteran_level(unit_type_get(punit), punit->veteran);
  fc_snprintf(buf, sizeof(buf), "%s", name_translation_get(&vlevel->name));
 
  return buf;
}
 
/**********************************************************************/
static const char *unit_achieved_rank_string(const struct unit *punit)
{
  static char buf[MAX_LEN_LINK];
 
  fc_snprintf(buf, sizeof(buf),
              /* TRANS: " and achieved the rank of <veteran level>";
               * preserve leading space */
              _(" and achieved the rank of %s"),
              unit_veteran_level_string(punit));
  return buf;
}
 
/**********************************************************************/
static const char *unit_tired_attack_string(const struct unit *punit)
{
  static char buf[MAX_LEN_LINK];
 
  if (is_tired_attack(punit->moves_left)) {
    fc_snprintf(buf, sizeof(buf),
                /* TRANS: tired; note trailing space */
                _("tired "));
  } else {
    buf[0] = '\0';
  }
 
  return buf;
}
 
/**********************************************************************/
static const char *unit_firepower_if_not_one(int firepower)
{
  static char buf[MAX_LEN_LINK];
 
  if (firepower == 1) {
    buf[0] = '\0';
  } else {
    fc_snprintf(buf, sizeof(buf),
                /* TRANS: FP = Firepower of a unit; note trailing space */
                _("FP:%d "),
                firepower);
  }
 
  return buf;
}
 
/**********************************************************************/
static bool do_attack(struct unit *punit, struct tile *def_tile,
                      const struct action *paction)
{
  char loser_link[MAX_LEN_LINK], winner_link[MAX_LEN_LINK];
  char attacker_vet[MAX_LEN_LINK], defender_vet[MAX_LEN_LINK];
  char attacker_fp[MAX_LEN_LINK], defender_fp[MAX_LEN_LINK];
  char attacker_tired[MAX_LEN_LINK];
  struct unit *ploser, *pwinner;
  int moves_used, def_moves_used; 
  int old_unit_vet, old_defender_vet, vet;
  int winner_id;
  struct player *pplayer = unit_owner(punit);
  bool adj;
  enum direction8 facing;
  int att_hp, def_hp, att_fp, def_fp;
  int att_hp_start, def_hp_start;
  int def_power, att_power;
  int att_vet, def_vet;
  struct unit *pdefender;
  const struct unit_type *act_utype = unit_type_get(punit);
  struct civ_map *nmap = &(wld.map);
  bool powerless;
 
  if (!(pdefender = get_defender(nmap, punit, def_tile, paction))) {
    /* Can't fight air... */
    return FALSE;
  }
 
  att_hp_start = punit->hp;
  def_hp_start = pdefender->hp;
  def_power = get_total_defense_power(punit, pdefender);
  att_power = get_total_attack_power(punit, pdefender, paction);
  get_modified_firepower(nmap, punit, pdefender, &att_fp, &def_fp);
 
  log_debug("Start attack: %s %s against %s %s.",
            nation_rule_name(nation_of_player(pplayer)),
            unit_rule_name(punit), 
            nation_rule_name(nation_of_unit(pdefender)),
            unit_rule_name(pdefender));
 
  /* Sanity checks */
  fc_assert_ret_val_msg(!pplayers_non_attack(pplayer,
                                             unit_owner(pdefender))
                        || unit_has_type_flag(punit, UTYF_FLAGLESS)
                        || unit_has_type_flag(pdefender, UTYF_FLAGLESS),
                        FALSE,
                        "Trying to attack a unit with which you have peace "
                        "or cease-fire at (%d, %d).", TILE_XY(def_tile));
  fc_assert_ret_val_msg(!pplayers_allied(pplayer, unit_owner(pdefender))
                        || unit_has_type_flag(punit, UTYF_FLAGLESS)
                        || unit_has_type_flag(pdefender, UTYF_FLAGLESS),
                        FALSE,
                        "Trying to attack a unit with which you have "
                        "alliance at (%d, %d).", TILE_XY(def_tile));
 
  moves_used = unit_move_rate(punit) - punit->moves_left;
  def_moves_used = unit_move_rate(pdefender) - pdefender->moves_left;
 
  adj = base_get_direction_for_step(nmap,
                                    punit->tile, pdefender->tile, &facing);
 
  fc_assert(adj);
  if (adj) {
    punit->facing = facing;
    pdefender->facing = opposite_direction(facing);
  }
 
  old_unit_vet = punit->veteran;
  old_defender_vet = pdefender->veteran;
 
  /* N.B.: unit_veteran_level_string always returns the same pointer. */
  sz_strlcpy(attacker_vet, unit_veteran_level_string(punit));
  sz_strlcpy(defender_vet, unit_veteran_level_string(pdefender));
 
  /* N.B.: unit_firepower_if_not_one always returns the same pointer. */
  sz_strlcpy(attacker_fp, unit_firepower_if_not_one(att_fp));
  sz_strlcpy(defender_fp, unit_firepower_if_not_one(def_fp));
 
  /* Record tired attack string before attack */
  sz_strlcpy(attacker_tired, unit_tired_attack_string(punit));
 
  powerless = unit_versus_unit(punit, pdefender, &att_hp, &def_hp,
                               &att_vet, &def_vet, paction);
 
  if ((att_hp <= 0 || utype_is_consumed_by_action(paction, punit->utype))
      && unit_transported(punit)) {
    /* Dying attacker must be first unloaded so it doesn't die inside transport */
    unit_transport_unload_send(punit);
  }
 
  see_combat(punit, pdefender);
 
  punit->hp = att_hp;
  pdefender->hp = def_hp;
 
  combat_veterans(punit, pdefender, powerless, att_vet, def_vet);
 
  /* Adjust attackers moves_left _after_ unit_versus_unit() so that
   * the movement attack modifier is correct! --dwp
   *
   * For greater Civ2 compatibility (and game balance issues), we recompute 
   * the new total MP based on the HP the unit has left after being damaged, 
   * and subtract the MPs that had been used before the combat (plus the 
   * points used in the attack itself, for the attacker). -GJW, Glip
   */
  punit->moves_left = unit_move_rate(punit) - moves_used;
  pdefender->moves_left = unit_move_rate(pdefender) - def_moves_used;
 
  if (punit->moves_left < 0) {
    punit->moves_left = 0;
  }
  if (pdefender->moves_left < 0) {
    pdefender->moves_left = 0;
  }
  unit_did_action(punit);
  unit_forget_last_activity(punit);
 
  /* This may cause a diplomatic incident. */
  action_consequence_success(paction, pplayer, act_utype,
                             unit_owner(pdefender),
                             def_tile, unit_link(pdefender));
 
  if (punit->hp > 0 && pdefender->hp > 0) {
    /* Neither died */
    send_combat(punit, pdefender, punit->veteran - old_unit_vet,
                pdefender->veteran - old_defender_vet, 0);
    return TRUE;
  }
  pwinner = (punit->hp > 0) ? punit : pdefender;
  winner_id = pwinner->id;
  ploser = (pdefender->hp > 0) ? punit : pdefender;
 
  vet = (pwinner->veteran == ((punit->hp > 0) ? old_unit_vet :
        old_defender_vet)) ? 0 : 1;
 
  send_combat(punit, pdefender, punit->veteran - old_unit_vet,
              pdefender->veteran - old_defender_vet, 0);
 
  /* N.B.: unit_link always returns the same pointer. */
  sz_strlcpy(loser_link, unit_tile_link(ploser));
  sz_strlcpy(winner_link,
             utype_is_consumed_by_action(paction, pwinner->utype)
             ? unit_tile_link(pwinner) : unit_link(pwinner));
 
  if (punit == ploser) {
    /* The attacker lost */
    log_debug("Attacker lost: %s %s against %s %s.",
              nation_rule_name(nation_of_player(pplayer)),
              unit_rule_name(punit),
              nation_rule_name(nation_of_unit(pdefender)),
              unit_rule_name(pdefender));
 
    if (is_flagless_to_player(ploser, unit_owner(pwinner))) {
      notify_player(unit_owner(pwinner), unit_tile(pwinner),
                    E_UNIT_WIN_DEF, ftc_server,
                    /* TRANS: "Your green Legion [id:100 ...D:4.0 lost 1 HP,
                     * 9 HP remaining] survived the pathetic ...attack from
                     * green Warriors [id:90 ...A:1.0 HP:10]. */
                    _("Your %s %s [id:%d %sD:%.1f lost %d HP, %d HP remaining]"
                      " survived the pathetic %sattack from %s %s "
                      "[id:%d %sA:%.1f HP:%d]."),
                    defender_vet,
                    winner_link,
                    pdefender->id,
                    defender_fp,
                    (float)def_power/POWER_FACTOR,
                    def_hp_start - pdefender->hp,
                    pdefender->hp,
                    attacker_tired,
                    attacker_vet,
                    loser_link,
                    punit->id,
                    attacker_fp,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start);
    } else {
      notify_player(unit_owner(pwinner), unit_tile(pwinner),
                    E_UNIT_WIN_DEF, ftc_server,
                    /* TRANS: "Your green Legion [id:100 ...D:4.0 lost 1 HP,
                     * 9 HP remaining] survived the pathetic ...attack from the
                     * Greek green Warriors [id:90 ...A:1.0 HP:10]. */
                    _("Your %s %s [id:%d %sD:%.1f lost %d HP, %d HP remaining]"
                      " survived the pathetic %sattack from the %s %s %s "
                      "[id:%d %sA:%.1f HP:%d]."),
                    defender_vet,
                    winner_link,
                    pdefender->id,
                    defender_fp,
                    (float)def_power/POWER_FACTOR,
                    def_hp_start - pdefender->hp,
                    pdefender->hp,
                    attacker_tired,
                    nation_adjective_for_player(unit_owner(ploser)),
                    attacker_vet,
                    loser_link,
                    punit->id,
                    attacker_fp,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start);
    }
 
    if (vet) {
      notify_unit_experience(pwinner);
    }
 
    if (is_flagless_to_player(pdefender, unit_owner(ploser))) {
      notify_player(unit_owner(ploser), def_tile,
                    E_UNIT_LOST_ATT, ftc_server,
                    /* TRANS: "Your attacking green Cannon [id:100 ...A:8.0
                     * failed against green Destroyer [id:200 lost
                     * 27 HP, 3 HP remaining%s]!";
                     * last %s is either "and ..." or empty string */
                    _("Your attacking %s %s [id:%d %sA:%.1f HP:%d] failed "
                      "against %s %s [id:%d lost %d HP, %d HP "
                      "remaining%s]!"),
                    attacker_vet,
                    loser_link,
                    punit->id,
                    attacker_fp,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start,
                    defender_vet,
                    winner_link,
                    pdefender->id,
                    def_hp_start - pdefender->hp,
                    pdefender->hp,
                    vet ? unit_achieved_rank_string(pdefender) : "");
    } else {
      notify_player(unit_owner(ploser), def_tile,
                    E_UNIT_LOST_ATT, ftc_server,
                    /* TRANS: "Your attacking green Cannon [id:100 ...A:8.0
                     * failed against the Polish green Destroyer [id:200 lost
                     * 27 HP, 3 HP remaining%s]!";
                     * last %s is either "and ..." or empty string */
                    _("Your attacking %s %s [id:%d %sA:%.1f HP:%d] failed "
                      "against the %s %s %s [id:%d lost %d HP, %d HP "
                      "remaining%s]!"),
                    attacker_vet,
                    loser_link,
                    punit->id,
                    attacker_fp,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start,
                    nation_adjective_for_player(unit_owner(pdefender)),
                    defender_vet,
                    winner_link,
                    pdefender->id,
                    def_hp_start - pdefender->hp,
                    pdefender->hp,
                    vet ? unit_achieved_rank_string(pdefender) : "");
    }
 
    wipe_unit(ploser, ULR_KILLED, unit_owner(pwinner));
  } else {
    /* The defender lost, the attacker punit lives! */
    struct city *pcity;
 
    log_debug("Defender lost: %s %s against %s %s.",
              nation_rule_name(nation_of_player(pplayer)),
              unit_rule_name(punit),
              nation_rule_name(nation_of_unit(pdefender)),
              unit_rule_name(pdefender));
 
    if (is_flagless_to_player(punit, unit_owner(pdefender))) {
      notify_player(unit_owner(pdefender), unit_tile(pdefender),
                    E_UNIT_LOST_DEF, ftc_server,
                    /* TRANS: "Your green Warriors [id:100 ...D:1.0 HP:10]
                     * lost to an attack by green Legion
                     * [id:200 ...A:4.0 lost 1 HP, has 9 HP remaining%s]."
                     * last %s is either "and ..." or empty string */
                    _("Your %s %s [id:%d %sD:%.1f HP:%d] lost to an attack by "
                      "%s %s [id:%d %sA:%.1f lost %d HP, has %d HP "
                      "remaining%s]."),
                    defender_vet,
                    loser_link,
                    pdefender->id,
                    defender_fp,
                    (float)def_power/POWER_FACTOR,
                    def_hp_start,
                    attacker_vet,
                    winner_link,
                    punit->id,
                    attacker_fp,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start - pwinner->hp,
                    pwinner->hp,
                    vet ? unit_achieved_rank_string(punit) : "");
    } else {
      notify_player(unit_owner(pdefender), unit_tile(pdefender),
                    E_UNIT_LOST_DEF, ftc_server,
                    /* TRANS: "Your green Warriors [id:100 ...D:1.0 HP:10]
                     * lost to an attack by the Greek green Legion
                     * [id:200 ...A:4.0 lost 1 HP, has 9 HP remaining%s]."
                     * last %s is either "and ..." or empty string */
                    _("Your %s %s [id:%d %sD:%.1f HP:%d] lost to an attack by "
                      "the %s %s %s [id:%d %sA:%.1f lost %d HP, has %d HP "
                      "remaining%s]."),
                    defender_vet,
                    loser_link,
                    pdefender->id,
                    defender_fp,
                    (float)def_power/POWER_FACTOR,
                    def_hp_start,
                    nation_adjective_for_player(unit_owner(punit)),
                    attacker_vet,
                    winner_link,
                    punit->id,
                    attacker_fp,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start - pwinner->hp,
                    pwinner->hp,
                    vet ? unit_achieved_rank_string(punit) : "");
    }
 
    if (is_flagless_to_player(pdefender, unit_owner(punit))) {
      notify_player(unit_owner(punit), unit_tile(punit),
                    E_UNIT_WIN_ATT, ftc_server,
                    /* TRANS: "Your attacking green Legion [id:200 ...A:4.0
                     * lost 1 HP, has 9 HP remaining] succeeded against
                     * green Warriors [id:100 HP:10]." */
                    _("Your attacking %s %s [id:%d %s%sA:%.1f lost %d HP, "
                      "has %d remaining] succeeded against %s %s "
                      "[id:%d HP:%d]."),
                    attacker_vet,
                    winner_link,
                    punit->id,
                    attacker_fp,
                    attacker_tired,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start - pwinner->hp,
                    pwinner->hp,
                    defender_vet,
                    loser_link,
                    pdefender->id,
                    def_hp_start);
    } else {
      notify_player(unit_owner(punit), unit_tile(punit),
                    E_UNIT_WIN_ATT, ftc_server,
                    /* TRANS: "Your attacking green Legion [id:200 ...A:4.0
                     * lost 1 HP, has 9 HP remaining] succeeded against the
                     * Greek green Warriors [id:100 HP:10]." */
                    _("Your attacking %s %s [id:%d %s%sA:%.1f lost %d HP, "
                      "has %d remaining] succeeded against the %s %s %s "
                      "[id:%d HP:%d]."),
                    attacker_vet,
                    winner_link,
                    punit->id,
                    attacker_fp,
                    attacker_tired,
                    (float)att_power/POWER_FACTOR,
                    att_hp_start - pwinner->hp,
                    pwinner->hp,
                    nation_adjective_for_player(unit_owner(pdefender)),
                    defender_vet,
                    loser_link,
                    pdefender->id,
                    def_hp_start);
    }
 
    punit->moved = TRUE;        /* We moved */
 
    if (paction->result == ACTRES_COLLECT_RANSOM) {
      collect_ransom(pwinner, ploser,
                     vet && !utype_is_consumed_by_action(paction, punit->utype));
    } else {
      kill_unit(pwinner, ploser,
                vet && !utype_is_consumed_by_action(paction, punit->utype));
    }
 
    /* Now that dead defender is certainly no longer listed as unit
     * supported by the city, we may even remove the city
     * (if it shrinks from size 1) */
    pcity = tile_city(def_tile);
    if (pcity != NULL) {
      unit_attack_civilian_casualties(punit, pcity, paction, "attack");
    }
    if (unit_is_alive(winner_id)) {
      if (utype_is_consumed_by_action(paction, pwinner->utype)) {
        return TRUE;
      }
    } else {
      return TRUE;
    }
  }
 
  /* If attacker wins, and occupychance > 0, it might move in. Don't move in
   * if there are enemy units in the tile (a fortress, city or air base with
   * multiple defenders and unstacked combat). Note that this could mean
   * capturing (or destroying) a city. */
 
  if (pwinner == punit && fc_rand(100) < game.server.occupychance) {
    occupy_move(def_tile, punit, paction);
  }
 
  /* The attacker may have died for many reasons */
  if (game_unit_by_number(winner_id) != NULL) {
    send_unit_info(NULL, pwinner);
  }
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_strike_city_production(struct player *act_player,
                                           struct unit *act_unit,
                                           struct city *tgt_city,
                                           const struct action *paction)
{
  struct player *tgt_player;
  char prod[256];
  const struct unit_type *act_utype;
  const struct tile *tgt_tile;
  const char *clink;
 
  /* Sanity checks */
  fc_assert_ret_val(act_player, FALSE);
  fc_assert_ret_val(act_unit, FALSE);
  fc_assert_ret_val(tgt_city, FALSE);
  fc_assert_ret_val(paction, FALSE);
 
  tgt_player = city_owner(tgt_city);
  fc_assert_ret_val(tgt_player, FALSE);
 
  tgt_tile = city_tile(tgt_city);
 
  /* The surgical strike may miss. */
  {
    /* Roll the dice. */
    if (action_failed_dice_roll(act_player, act_unit,
                                tgt_city, tgt_player,
                                paction)) {
      /* Notify the player. */
      notify_player(act_player, tgt_tile,
                    E_UNIT_ACTION_ACTOR_FAILURE, ftc_server,
                    /* TRANS: unit, action, city */
                    _("Your %s failed to do %s in %s."),
                    unit_link(act_unit),
                    action_name_translation(paction),
                    city_link(tgt_city));
 
      /* Make the failed attempt cost a single move. */
      act_unit->moves_left = MAX(0, act_unit->moves_left - SINGLE_MOVE);
 
      return FALSE;
    }
  }
 
  /* Get name of the production */
  universal_name_translation(&tgt_city->production, prod, sizeof(prod));
 
  /* Destroy the production */
  tgt_city->shield_stock = 0;
  nullify_prechange_production(tgt_city);
 
  /* Let the players know. */
  clink = city_link(tgt_city); /* Be careful not to call city_link()
                                * again as long as we need clink */
  notify_player(act_player, tgt_tile,
                E_UNIT_ACTION_ACTOR_SUCCESS, ftc_server,
                _("Your %s succeeded in destroying"
                  " the production of %s in %s."),
                unit_link(act_unit),
                prod, clink);
  notify_player(tgt_player, tgt_tile,
                E_UNIT_ACTION_TARGET_HOSTILE, ftc_server,
                _("The production of %s was destroyed in %s,"
                  " %s are suspected."),
                prod, clink,
                nation_plural_for_player(act_player));
 
  act_utype = unit_type_get(act_unit);
 
  /* May cause an incident */
  action_consequence_success(paction, act_player, act_utype,
                             tgt_player, tgt_tile,
                             clink);
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_strike_city_building(struct player *act_player,
                                         struct unit *act_unit,
                                         struct city *tgt_city,
                                         Impr_type_id tgt_bld_id,
                                         const struct action *paction)
{
  struct player *tgt_player;
  struct impr_type *tgt_bld = improvement_by_number(tgt_bld_id);
  const struct tile *tgt_tile;
  const struct unit_type *act_utype;
  const char *clink;
 
  /* Sanity checks */
  fc_assert_ret_val(act_player, FALSE);
  fc_assert_ret_val(act_unit, FALSE);
  fc_assert_ret_val(tgt_city, FALSE);
  fc_assert_ret_val(paction, FALSE);
 
  tgt_tile = city_tile(tgt_city);
 
  tgt_player = city_owner(tgt_city);
  fc_assert_ret_val(tgt_player, FALSE);
 
  /* The surgical strike may miss. */
  {
    /* Roll the dice. */
    if (action_failed_dice_roll(act_player, act_unit,
                                tgt_city, tgt_player,
                                paction)) {
      /* Notify the player. */
      notify_player(act_player, tgt_tile,
                    E_UNIT_ACTION_ACTOR_FAILURE, ftc_server,
                    /* TRANS: unit, action, city */
                    _("Your %s failed to do %s in %s."),
                    unit_link(act_unit),
                    action_name_translation(paction),
                    city_link(tgt_city));
 
      /* Make the failed attempt cost a single move. */
      act_unit->moves_left = MAX(0, act_unit->moves_left - SINGLE_MOVE);
 
      return FALSE;
    }
  }
 
  if (!city_has_building(tgt_city, tgt_bld)) {
    /* Nothing to destroy here. */
 
    /* Notify the player. */
    notify_player(act_player, tgt_tile,
                  E_UNIT_ACTION_ACTOR_FAILURE, ftc_server,
                  _("Your %s didn't find a %s to %s in %s."),
                  unit_link(act_unit),
                  improvement_name_translation(tgt_bld),
                  action_name_translation(paction),
                  city_link(tgt_city));
 
    /* Punish the player for blindly attacking a building. */
    act_unit->moves_left = MAX(0, act_unit->moves_left - SINGLE_MOVE);
 
    return FALSE;
  }
 
  if (improvement_has_flag(tgt_bld, IF_INDESTRUCTIBLE)) {
    /* Notify the player. */
    notify_player(act_player, tgt_tile,
                  E_UNIT_ACTION_ACTOR_FAILURE, ftc_server,
                  _("Your %s cannot do %s to %s in %s."),
                  unit_link(act_unit),
                  action_name_translation(paction),
                  improvement_name_translation(tgt_bld),
                  city_link(tgt_city));
 
    /* Punish the player for blindly attacking a building. */
    act_unit->moves_left = MAX(0, act_unit->moves_left - SINGLE_MOVE);
 
    return FALSE;
  }
 
  act_utype = unit_type_get(act_unit);
 
  /* Destroy the building. */
  building_lost(tgt_city, tgt_bld, "attacked", act_unit);
 
  /* Update the player's view of the city. */
  send_city_info(NULL, tgt_city);
 
  /* Let the players know. */
  clink = city_link(tgt_city); /* Be careful not to call city_link()
                                * again as long as we need clink */
  notify_player(act_player, tgt_tile,
                E_UNIT_ACTION_ACTOR_SUCCESS, ftc_server,
                _("Your %s destroyed the %s in %s."),
                unit_link(act_unit),
                improvement_name_translation(tgt_bld),
                clink);
  notify_player(tgt_player, tgt_tile,
                E_UNIT_ACTION_TARGET_HOSTILE, ftc_server,
                _("The %s destroyed the %s in %s."),
                nation_plural_for_player(act_player),
                improvement_name_translation(tgt_bld),
                clink);
 
  /* May cause an incident */
  action_consequence_success(paction, act_player, act_utype,
                             tgt_player, tgt_tile, clink);
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_conquer_city(struct player *act_player,
                                 struct unit *act_unit,
                                 struct city *tgt_city,
                                 struct action *paction)
{
  bool success;
  struct tile *tgt_tile = city_tile(tgt_city);
  int move_cost = map_move_cost_unit(&(wld.map), act_unit, tgt_tile);
  int tgt_city_id = tgt_city->id;
  struct player *tgt_player = city_owner(tgt_city);
  const char *victim_link = city_link(tgt_city);
 
  /* Sanity check */
  fc_assert_ret_val(tgt_tile, FALSE);
 
  unit_move(act_unit, tgt_tile, move_cost, NULL, FALSE, TRUE, TRUE,
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_ENTER),
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_FRIGHTEN));
 
  /* The city may have been destroyed during the conquest. */
  success = (!city_exist(tgt_city_id)
             || city_owner(tgt_city) == act_player);
 
  if (success) {
    const struct unit_type *act_utype = unit_type_get(act_unit);
 
    /* May cause an incident */
    action_consequence_success(paction, act_player, act_utype,
                               tgt_player, tgt_tile,
                               victim_link);
  }
 
  return success;
}
 
/**********************************************************************/
static bool can_unit_move_to_tile_with_notify(struct unit *punit,
                                              struct tile *dest_tile,
                                              bool igzoc,
                                              struct unit *embark_to,
                                              bool enter_enemy_city)
{
  struct tile *src_tile = unit_tile(punit);
  enum unit_move_result reason =
    unit_move_to_tile_test(&(wld.map), punit, punit->activity,
                           src_tile, dest_tile, igzoc, TRUE, embark_to,
                           enter_enemy_city);
 
  switch (reason) {
  case MR_OK:
    return TRUE;
 
  case MR_NO_WAR:
    notify_player(unit_owner(punit), src_tile, E_BAD_COMMAND, ftc_server,
                  _("Cannot attack unless you declare war first."));
    break;
 
  case MR_ZOC:
    notify_player(unit_owner(punit), src_tile, E_BAD_COMMAND, ftc_server,
                  _("%s can only move into your own zone of control."),
                  unit_link(punit));
    break;
 
  case MR_TRIREME:
    notify_player(unit_owner(punit), src_tile, E_BAD_COMMAND, ftc_server,
                  _("%s cannot move that far from the coast line."),
                  unit_link(punit));
    break;
 
  case MR_PEACE:
    if (tile_owner(dest_tile)) {
      notify_player(unit_owner(punit), src_tile, E_BAD_COMMAND, ftc_server,
                    _("Cannot invade unless you break peace with "
                      "%s first."),
                    player_name(tile_owner(dest_tile)));
    }
    break;
 
  case MR_CANNOT_DISEMBARK:
    notify_player(unit_owner(punit), src_tile, E_BAD_COMMAND, ftc_server,
                  _("%s cannot disembark outside of a city or a native base "
                    "for %s."),
                  unit_link(punit),
                  utype_name_translation(
                      unit_type_get(unit_transport_get(punit))));
    break;
 
  case MR_NON_NATIVE_MOVE:
    notify_player(unit_owner(punit), src_tile, E_BAD_COMMAND, ftc_server,
                  _("Terrain is unsuitable for %s units."),
                  uclass_name_translation(unit_class_get(punit)));
    break;
 
  default:
    /* FIXME: need more explanations someday! */
    break;
  };
 
  return FALSE;
}
 
/**********************************************************************/
static bool unit_do_regular_move(struct player *actor_player,
                                 struct unit *actor_unit,
                                 struct tile *target_tile,
                                 const struct action *paction)
{
  const struct unit_type *act_utype = unit_type_get(actor_unit);
  int move_cost = map_move_cost_unit(&(wld.map), actor_unit, target_tile);
 
  unit_move(actor_unit, target_tile, move_cost,
            NULL, BV_ISSET(paction->sub_results, ACT_SUB_RES_MAY_EMBARK),
            /* Don't override "Conquer City" */
            FALSE,
            /* Don't override "Conquer Extras" */
            FALSE,
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_ENTER),
            BV_ISSET(paction->sub_results, ACT_SUB_RES_HUT_FRIGHTEN));
 
  /* May cause an incident */
  action_consequence_success(paction, actor_player, act_utype,
                             tile_owner(target_tile),
                             target_tile, tile_link(target_tile));
 
  return TRUE;
}
 
/**********************************************************************/
bool unit_move_handling(struct unit *punit, struct tile *pdesttile,
                        bool move_do_not_act)
{
  struct player *pplayer = unit_owner(punit);
  struct unit *ptrans;
  const struct civ_map *nmap = &(wld.map);
 
  /*** Phase 1: Attempted action interpretation checks ***/
 
  /* Check if the move should be interpreted as an attempt to perform an
   * enabler controlled action to the target tile. When the move may be an
   * action attempt the server stops moving the unit, marks it as wanting a
   * decision based on its own movement to the tile it attempted to move to
   * and notifies the client.
   *
   * In response to the unit being marked as wanting a decision the client
   * can query the server for what actions the unit, given the player's
   * knowledge, may be able to perform against a target at the tile it tried
   * to move to. The server will respond to the query with the actions that
   * may be enabled and, when all actions are known to be illegal given the
   * player's knowledge, an explanation why no action could be done. The
   * client will probably use the list of potentially legal actions, if any,
   * to pop up an action selection dialog. See handle_unit_action_query()
   *
   * If move_do_not_act is TRUE the move is never interpreted as an attempt
   * to perform an enabler controlled action.
   * Examples of where this is useful is for AI moves, goto, when the player
   * attempts to move to a tile occupied by potential targets like allied
   * cities or units and during rule forced moves.
   *
   * A move is not interpreted as an attempted action because the unit is
   * able to do a self targeted action.
   *
   * A move is not interpreted as an attempted action because an action
   * with rare_pop_up set to TRUE is legal unless the unit is unable to
   * perform a regular move to the tile.
   *
   * An attempted move to a tile a unit can't move to is always interpreted
   * as trying to perform an action (unless move_do_not_act is TRUE) */
  if (!move_do_not_act) {
    const bool can_not_move = !unit_can_move_to_tile(nmap,
                                                     punit, pdesttile,
                                                     FALSE, FALSE, FALSE);
    bool one_action_may_be_legal
        =  action_tgt_unit(punit, pdesttile, can_not_move)
        || action_tgt_city(punit, pdesttile, can_not_move)
        /* A legal action with an extra sub target is a legal action */
        || action_tgt_tile_extra(punit, pdesttile, can_not_move)
        /* Tile target actions with extra sub targets are handled above */
        || action_tgt_tile(punit, pdesttile, NULL, can_not_move);
 
    if (one_action_may_be_legal || can_not_move) {
      /* There is a target punit, from the player's point of view, may be
       * able to act against OR punit can't do any non action move. The
       * client should therefore ask what action(s) the unit can perform
       * to any targets at pdesttile.
       *
       * In the first case the unit needs a decision about what action, if
       * any at all, to take. Asking what actions the unit can perform
       * will return a list of actions that may, from the players point of
       * view, be possible. The client can then show this list to the
       * player or, if configured to do so, make the choice it self.
       *
       * In the last case the player may need an explanation about why no
       * action could be taken. Asking what actions the unit can perform
       * will provide this explanation. */
      punit->action_decision_want = ACT_DEC_ACTIVE;
      punit->action_decision_tile = pdesttile;
      send_unit_info(player_reply_dest(pplayer), punit);
 
      /* The move wasn't done because the unit wanted the player to
       * decide what to do or because the unit couldn't move to the
       * target tile. */
      return FALSE;
    }
  }
 
  /*** Phase 2: OK now move the unit ***/
  /* This is a regular move, subject to the rules. */
  if (is_action_enabled_unit_on_tile(nmap, ACTION_UNIT_MOVE,
                                     punit, pdesttile, NULL)) {
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_UNIT_MOVE,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_UNIT_MOVE2,
                                            punit, pdesttile, NULL)) {
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_UNIT_MOVE2,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_UNIT_MOVE3,
                                            punit, pdesttile, NULL)) {
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_UNIT_MOVE3,
                               ACT_REQ_PLAYER);
  } else if (!can_unit_survive_at_tile(nmap, punit, pdesttile)
             && ((ptrans = transporter_for_unit_at(punit, pdesttile)))
             && is_action_enabled_unit_on_unit(nmap, ACTION_TRANSPORT_EMBARK,
                                               punit, ptrans)) {
    /* "Transport Embark". */
    return unit_perform_action(pplayer, punit->id, ptrans->id,
                               NO_TARGET, "", ACTION_TRANSPORT_EMBARK,
                               ACT_REQ_PLAYER);
  } else if (!can_unit_survive_at_tile(nmap, punit, pdesttile)
             && ((ptrans = transporter_for_unit_at(punit, pdesttile)))
             && is_action_enabled_unit_on_unit(nmap, ACTION_TRANSPORT_EMBARK2,
                                               punit, ptrans)) {
    /* "Transport Embark 2". */
    return unit_perform_action(pplayer, punit->id, ptrans->id,
                               NO_TARGET, "", ACTION_TRANSPORT_EMBARK2,
                               ACT_REQ_PLAYER);
  } else if (!can_unit_survive_at_tile(nmap, punit, pdesttile)
             && ((ptrans = transporter_for_unit_at(punit, pdesttile)))
             && is_action_enabled_unit_on_unit(nmap, ACTION_TRANSPORT_EMBARK3,
                                               punit, ptrans)) {
    /* "Transport Embark 3". */
    return unit_perform_action(pplayer, punit->id, ptrans->id,
                               NO_TARGET, "", ACTION_TRANSPORT_EMBARK3,
                               ACT_REQ_PLAYER);
  } else if (!can_unit_survive_at_tile(nmap, punit, pdesttile)
             && ((ptrans = transporter_for_unit_at(punit, pdesttile)))
             && is_action_enabled_unit_on_unit(nmap, ACTION_TRANSPORT_EMBARK4,
                                               punit, ptrans)) {
    /* "Transport Embark 4". */
    return unit_perform_action(pplayer, punit->id, ptrans->id,
                               NO_TARGET, "", ACTION_TRANSPORT_EMBARK4,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_TRANSPORT_DISEMBARK1,
                                            punit, pdesttile, NULL)) {
    /* "Transport Disembark". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_TRANSPORT_DISEMBARK1,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_TRANSPORT_DISEMBARK2,
                                            punit, pdesttile, NULL)) {
    /* "Transport Disembark 2". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_TRANSPORT_DISEMBARK2,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_TRANSPORT_DISEMBARK3,
                                            punit, pdesttile, NULL)) {
    /* "Transport Disembark 3". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_TRANSPORT_DISEMBARK3,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_TRANSPORT_DISEMBARK4,
                                            punit, pdesttile, NULL)) {
    /* "Transport Disembark 4". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_TRANSPORT_DISEMBARK4,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_HUT_ENTER,
                                            punit, pdesttile, NULL)) {
    /* "Enter Hut". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_HUT_ENTER,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_HUT_ENTER2,
                                            punit, pdesttile, NULL)) {
    /* "Enter Hut 2". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_HUT_ENTER2,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_HUT_FRIGHTEN,
                                            punit, pdesttile, NULL)) {
    /* "Frighten Hut". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_HUT_FRIGHTEN,
                               ACT_REQ_PLAYER);
  } else if (is_action_enabled_unit_on_tile(nmap, ACTION_HUT_FRIGHTEN2,
                                            punit, pdesttile, NULL)) {
    /* "Frighten Hut 2". */
    return unit_perform_action(pplayer, punit->id, tile_index(pdesttile),
                               NO_TARGET, "", ACTION_HUT_FRIGHTEN2,
                               ACT_REQ_PLAYER);
  } else {
    /* TODO: Extend the action not enabled explanation system to cover all
     * existing reasons and switch to using it. See hrm Feature #920229 */
    can_unit_move_to_tile_with_notify(punit, pdesttile, FALSE,
                                      NULL, FALSE);
    return FALSE;
  }
}
 
/**********************************************************************/
static bool unit_do_help_build(struct player *pplayer,
                               struct unit *punit,
                               struct city *pcity_dest,
                               const struct action *paction)
{
  const char *work;
  const char *prod;
  int shields;
  const struct unit_type *act_utype;
  struct player *cowner;
 
  /* Sanity check: The actor still exists. */
  fc_assert_ret_val(pplayer, FALSE);
  fc_assert_ret_val(punit, FALSE);
 
  /* Sanity check: The target city still exists. */
  fc_assert_ret_val(pcity_dest, FALSE);
 
  act_utype = unit_type_get(punit);
  shields = unit_shield_value(punit, unit_type_get(punit), paction);
 
  if (action_has_result(paction, ACTRES_HELP_WONDER)) {
    /* Add the caravan shields */
    pcity_dest->shield_stock += shields;
 
    /* Will be punished for changing production to something that can't
     * receive "Help Wonder" help. */
    fc_assert(city_production_gets_caravan_shields(
                  &pcity_dest->production));
    pcity_dest->caravan_shields += shields;
  } else {
    fc_assert(action_has_result(paction, ACTRES_DISBAND_UNIT_RECOVER));
    /* Add the shields from recycling the unit to the city's current
     * production. */
    pcity_dest->shield_stock += shields;
 
    /* If we change production later at this turn. No penalty is added. */
    pcity_dest->disbanded_shields += shields;
  }
 
  cowner = city_owner(pcity_dest);
 
  conn_list_do_buffer(cowner->connections);
 
  if (action_has_result(paction, ACTRES_HELP_WONDER)) {
    /* Let the player that just donated shields with "Help Wonder" know
     * the result of their donation. */
    prod = city_production_name_translation(pcity_dest);
  } else {
    fc_assert(action_has_result(paction, ACTRES_DISBAND_UNIT_RECOVER));
    /* TRANS: Your Caravan does "Disband Unit Recover" to help build the
     * current production in Bergen (4 surplus).
     * "Disband Unit Recover" says "current production" rather than its name. */
    prod = _("current production");
  }
 
  if (build_points_left(pcity_dest) >= 0) {
    /* TRANS: Your Caravan does "Help Wonder" to help build the
     * Pyramids in Bergen (4 remaining).
     * You can reorder '4' and 'remaining' in the actual format string. */
    work = _("remaining");
  } else {
    /* TRANS: Your Caravan does "Help Wonder" to help build the
     * Pyramids in Bergen (4 surplus).
     * You can reorder '4' and 'surplus' in the actual format string. */
    work = _("surplus");
  }
 
  notify_player(pplayer, city_tile(pcity_dest), E_CARAVAN_ACTION,
                ftc_server,
                /* TRANS: Your Caravan does "Help Wonder" to help build the
                 * Pyramids in Bergen (4 surplus). */
                _("Your %s does %s to help build the %s in %s (%d %s)."),
                unit_link(punit),
                action_name_translation(paction),
                prod,
                city_link(pcity_dest), 
                abs(build_points_left(pcity_dest)),
                work);
 
  /* May cause an incident */
  action_consequence_success(paction, pplayer, act_utype, cowner,
                             city_tile(pcity_dest), city_link(pcity_dest));
 
  if (cowner != unit_owner(punit)) {
    /* Tell the city owner about the gift they just received. */
 
    notify_player(cowner, city_tile(pcity_dest),
                  E_CARAVAN_ACTION, ftc_server,
                  /* TRANS: Help building the Pyramids in Bergen received
                   * from Persian Caravan (4 surplus). */
                  _("Help building the %s in %s received from %s %s "
                    "(%d %s)."),
                  city_production_name_translation(pcity_dest),
                  city_link(pcity_dest),
                  nation_adjective_for_player(pplayer),
                  unit_link(punit),
                  abs(build_points_left(pcity_dest)),
                  work);
  }
 
  send_player_info_c(cowner, pplayer->connections);
  send_city_info(cowner, pcity_dest);
  conn_list_do_unbuffer(cowner->connections);
 
  return TRUE;
}
 
/**********************************************************************/
static bool do_unit_establish_trade(struct player *pplayer,
                                    struct unit *punit,
                                    struct city *pcity_dest,
                                    const struct action *paction)
{
  char homecity_link[MAX_LEN_LINK], destcity_link[MAX_LEN_LINK];
  char punit_link[MAX_LEN_LINK];
  int revenue;
  bool can_establish;
  int home_overbooked = 0;
  int dest_overbooked = 0;
  int home_max;
  int dest_max;
  struct city *pcity_homecity;
  struct trade_route_list *routes_out_of_dest;
  struct trade_route_list *routes_out_of_home;
  enum trade_route_bonus_type bonus_type;
  struct goods_type *goods;
  const char *goods_str;
  const struct unit_type *act_utype;
 
  /* Sanity check: The actor still exists. */
  fc_assert_ret_val(pplayer, FALSE);
  fc_assert_ret_val(punit, FALSE);
 
  /* Sanity check: The target city still exists. */
  fc_assert_ret_val(pcity_dest, FALSE);
 
  pcity_homecity = player_city_by_number(pplayer, punit->homecity);
 
  if (!pcity_homecity) {
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("Sorry, your %s cannot establish"
                    " a trade route because it has no home city."),
                  unit_link(punit));
    return FALSE;
  }
 
  goods = unit_current_goods(punit, pcity_homecity);
 
  if (goods == NULL) {
    notify_player(pplayer, unit_tile(punit), E_BAD_COMMAND, ftc_server,
                  _("Sorry, your %s cannot establish"
                    " a trade route because it's not carrying any goods."),
                  unit_link(punit));
    return FALSE;
  }
 
  sz_strlcpy(homecity_link, city_link(pcity_homecity));
  sz_strlcpy(destcity_link, city_link(pcity_dest));
 
  if (!can_cities_trade(pcity_homecity, pcity_dest)) {
    notify_player(pplayer, city_tile(pcity_dest), E_BAD_COMMAND, ftc_server,
                  _("Sorry, your %s cannot establish"
                    " a trade route between %s and %s."),
                  unit_link(punit),
                  homecity_link,
                  destcity_link);
    return FALSE;
  }
 
  act_utype = unit_type_get(punit);
 
  sz_strlcpy(punit_link, unit_tile_link(punit));
  routes_out_of_home = trade_route_list_new();
  routes_out_of_dest = trade_route_list_new();
 
  /* This part of code works like can_establish_trade_route(), except
   * that we actually do the action of making the trade route. */
 
  /* If we can't make a new trade route we can still get the trade bonus. */
  can_establish = action_has_result(paction, ACTRES_TRADE_ROUTE)
                  && !have_cities_trade_route(pcity_homecity, pcity_dest);
 
  if (can_establish) {
    home_max = max_trade_routes(pcity_homecity);
    dest_max = max_trade_routes(pcity_dest);
    home_overbooked = city_num_trade_routes(pcity_homecity) - home_max;
    dest_overbooked = city_num_trade_routes(pcity_dest) - dest_max;
  }
 
  if (can_establish && (home_overbooked >= 0 || dest_overbooked >= 0)) {
    int trade = trade_base_between_cities(pcity_homecity, pcity_dest);
 
    /* See if there's a trade route we can cancel at the home city. */
    if (home_overbooked >= 0) {
      if (home_max <= 0
          || (city_trade_removable(pcity_homecity, goods->replace_priority,
                                   routes_out_of_home)
              >= trade)) {
        notify_player(pplayer, city_tile(pcity_dest),
                      E_BAD_COMMAND, ftc_server,
                     _("Sorry, your %s cannot establish"
                       " a trade route here!"),
                       punit_link);
        if (home_max > 0) {
          notify_player(pplayer, city_tile(pcity_dest),
                        E_BAD_COMMAND, ftc_server,
                        PL_("      The city of %s already has %d "
                            "better trade route!",
                            "      The city of %s already has %d "
                            "better trade routes!", home_max),
                        homecity_link,
                        home_max);
        }
        can_establish = FALSE;
      }
    }
 
    /* See if there's a trade route we can cancel at the dest city. */
    if (can_establish && dest_overbooked >= 0) {
      if (dest_max <= 0
          || (city_trade_removable(pcity_dest, goods->replace_priority,
                                   routes_out_of_dest)
              >= trade)) {
        notify_player(pplayer, city_tile(pcity_dest),
                      E_BAD_COMMAND, ftc_server,
                      _("Sorry, your %s cannot establish"
                        " a trade route here!"),
                      punit_link);
        if (dest_max > 0) {
          notify_player(pplayer, city_tile(pcity_dest),
                        E_BAD_COMMAND, ftc_server,
                        PL_("      The city of %s already has %d "
                            "better trade route!",
                            "      The city of %s already has %d "
                            "better trade routes!", dest_max),
                        destcity_link,
                        dest_max);
        }
        can_establish = FALSE;
      }
    }
  }
 
  /* We now know for sure whether we can establish a trade route. */
 
  /* Calculate and announce initial revenue. */
  revenue
    = get_caravan_enter_city_trade_bonus(pcity_homecity, pcity_dest, act_utype,
                                         goods, can_establish);
 
  bonus_type = trade_route_settings_by_type
      (cities_trade_route_type(pcity_homecity, pcity_dest))->bonus_type;
 
  conn_list_do_buffer(pplayer->connections);
 
  goods_str = goods_name_translation(goods);
 
  /* We want to keep the bonus type string as the part of the format of the PL_() strings
   * for supporting proper pluralization for it. */
  switch (bonus_type) {
  case TBONUS_NONE:
    notify_player(pplayer, city_tile(pcity_dest),
                  E_CARAVAN_ACTION, ftc_server,
                  /* TRANS: ... Caravan ... Paris ... Stockholm ... Goods */
                  _("Your %s from %s has arrived in %s carrying %s."),
                  punit_link,
                  homecity_link,
                  destcity_link,
                  goods_str);
    break;
  case TBONUS_GOLD:
    notify_player(pplayer, city_tile(pcity_dest),
                  E_CARAVAN_ACTION, ftc_server,
                  /* TRANS: ... Caravan ... Paris ... Stockholm, ... Goods... */
                  PL_("Your %s from %s has arrived in %s carrying %s,"
                      " and revenues amount to %d in gold.",
                      "Your %s from %s has arrived in %s carrying %s,"
                      " and revenues amount to %d in gold.",
                      revenue),
                  punit_link,
                  homecity_link,
                  destcity_link,
                  goods_str,
                  revenue);
    break;
  case TBONUS_SCIENCE:
    notify_player(pplayer, city_tile(pcity_dest),
                  E_CARAVAN_ACTION, ftc_server,
                  /* TRANS: ... Caravan ... Paris ... Stockholm, ... Goods... */
                  PL_("Your %s from %s has arrived in %s carrying %s,"
                      " and revenues amount to %d in research.",
                      "Your %s from %s has arrived in %s carrying %s,"
                      " and revenues amount to %d in research.",
                      revenue),
                  punit_link,
                  homecity_link,
                  destcity_link,
                  goods_str,
                  revenue);
    break;
  case TBONUS_BOTH:
    notify_player(pplayer, city_tile(pcity_dest),
                  E_CARAVAN_ACTION, ftc_server,
                  /* TRANS: ... Caravan ... Paris ... Stockholm, ... Goods... */
                  PL_("Your %s from %s has arrived in %s carrying %s,"
                      " and revenues amount to %d in gold and research.",
                      "Your %s from %s has arrived in %s carrying %s,"
                      " and revenues amount to %d in gold and research.",
                      revenue),
                  punit_link,
                  homecity_link,
                  destcity_link,
                  goods_str,
                  revenue);
    break;
  }
 
  if (bonus_type == TBONUS_GOLD || bonus_type == TBONUS_BOTH) {
    pplayer->economic.gold += revenue;
 
    send_player_info_c(pplayer, pplayer->connections);
  }
 
  if (bonus_type == TBONUS_SCIENCE || bonus_type == TBONUS_BOTH) {
    /* add bulbs and check for finished research */
    update_bulbs(pplayer, revenue, TRUE, TRUE);
 
    /* Inform everyone about tech changes */
    send_research_info(research_get(pplayer), NULL);
  }
 
  if (can_establish) {
    struct city_list *cities_out_of_home;
    struct city_list *cities_out_of_dest;
    struct player *partner_player;
 
    /* Announce creation of trade route (it's not actually created until
     * later in this function, as we have to cancel existing routes, but
     * it makes more sense to announce in this order) */
 
    partner_player = city_owner(pcity_dest);
 
    /* Always tell the unit owner */
    notify_player(pplayer, NULL,
                  E_CARAVAN_ACTION, ftc_server,
                  _("New trade route established from %s to %s."),
                  homecity_link,
                  destcity_link);
    if (pplayer != partner_player) {
      notify_player(partner_player, city_tile(pcity_dest),
                    E_CARAVAN_ACTION, ftc_server,
                    _("The %s established a trade route between their "
                      "city %s and %s."),
                    nation_plural_for_player(pplayer),
                    homecity_link,
                    destcity_link);
    }
 
    cities_out_of_home = city_list_new();
    cities_out_of_dest = city_list_new();
 
    /* Now cancel any less profitable trade route from the home city. */
    trade_route_list_iterate(routes_out_of_home, premove) {
      struct trade_route *pback;
 
      city_list_append(cities_out_of_home, game_city_by_number(premove->partner));
 
      pback = remove_trade_route(pcity_homecity, premove, TRUE, FALSE);
      free(premove);
      free(pback);
    } trade_route_list_iterate_end;
 
    /* And the same for the dest city. */
    trade_route_list_iterate(routes_out_of_dest, premove) {
      struct trade_route *pback;
 
      city_list_append(cities_out_of_dest, game_city_by_number(premove->partner));
 
      pback = remove_trade_route(pcity_dest, premove, TRUE, FALSE);
      free(premove);
      free(pback);
    } trade_route_list_iterate_end;
 
    create_trade_route(pcity_homecity, pcity_dest, goods);
 
    /* Refresh the cities. */
    city_refresh(pcity_homecity);
    city_refresh(pcity_dest);
    city_list_iterate(cities_out_of_home, pcity) {
      city_refresh(pcity);
    } city_list_iterate_end;
    city_list_iterate(cities_out_of_dest, pcity) {
      city_refresh(pcity);
    } city_list_iterate_end;
 
    /* Notify the owners of the cities. */
    send_city_info(pplayer, pcity_homecity);
    send_city_info(partner_player, pcity_dest);
    city_list_iterate(cities_out_of_home, pcity) {
      send_city_info(city_owner(pcity), pcity);
    } city_list_iterate_end;
    city_list_iterate(cities_out_of_dest, pcity) {
      send_city_info(city_owner(pcity), pcity);
    } city_list_iterate_end;
 
    /* Notify each player about the other's cities. */
    if (pplayer != partner_player && game.info.reveal_trade_partner) {
      map_show_tile(partner_player, city_tile(pcity_homecity));
      send_city_info(partner_player, pcity_homecity);
      map_show_tile(pplayer, city_tile(pcity_dest));
      send_city_info(pplayer, pcity_dest);
    }
 
    city_list_iterate(cities_out_of_home, pcity) {
      if (partner_player != city_owner(pcity)) {
        send_city_info(partner_player, pcity);
        send_city_info(city_owner(pcity), pcity_dest);
      }
      if (pplayer != city_owner(pcity)) {
        send_city_info(pplayer, pcity);
        send_city_info(city_owner(pcity), pcity_homecity);
      }
    } city_list_iterate_end;
 
    city_list_iterate(cities_out_of_dest, pcity) {
      if (partner_player != city_owner(pcity)) {
        send_city_info(partner_player, pcity);
        send_city_info(city_owner(pcity), pcity_dest);
      }
      if (pplayer != city_owner(pcity)) {
        send_city_info(pplayer, pcity);
        send_city_info(city_owner(pcity), pcity_homecity);
      }
    } city_list_iterate_end;
 
    city_list_destroy(cities_out_of_home);
    city_list_destroy(cities_out_of_dest);
  }
 
  /* May cause an incident */
  action_consequence_success(paction,
                             pplayer, act_utype, city_owner(pcity_dest),
                             city_tile(pcity_dest),
                             city_link(pcity_dest));
 
  conn_list_do_unbuffer(pplayer->connections);
 
  /* Free data. */
  trade_route_list_destroy(routes_out_of_home);
  trade_route_list_destroy(routes_out_of_dest);
 
  return TRUE;
}
 
/**********************************************************************/
void create_trade_route(struct city *from, struct city *to,
                        struct goods_type *goods)
{
  struct trade_route *proute_from, *proute_to;
 
  /* Actually create the new trade route */
  proute_from = fc_malloc(sizeof(struct trade_route));
  proute_from->partner = to->id;
  proute_from->goods = goods;
 
  proute_to = fc_malloc(sizeof(struct trade_route));
  proute_to->partner = from->id;
  proute_to->goods = goods;
 
  if (goods_has_flag(goods, GF_BIDIRECTIONAL)) {
    proute_from->dir = RDIR_BIDIRECTIONAL;
    proute_to->dir = RDIR_BIDIRECTIONAL;
  } else {
    proute_from->dir = RDIR_FROM;
    proute_to->dir = RDIR_TO;
  }
  trade_route_list_append(from->routes, proute_from);
  trade_route_list_append(to->routes, proute_to);
}
 
/**********************************************************************/
void handle_unit_sscs_set(struct player *pplayer,
                          int unit_id,
                          enum unit_ss_data_type type,
                          int value)
{
  struct unit *punit = player_unit_by_number(pplayer, unit_id);
  const struct civ_map *nmap = &(wld.map);
 
  if (NULL == punit) {
    /* Being asked to unqueue a "spent" unit because the client haven't
     * been told that it's gone is expected. */
    if (type != USSDT_UNQUEUE) {
      /* Probably died or bribed. */
      log_verbose("handle_unit_sscs_set() invalid unit %d", unit_id);
    }
 
    return;
  }
 
  switch (type) {
  case USSDT_QUEUE:
    /* Reminds the client to ask the server about what actions the unit can
     * perform against the target tile. Action decision state can be set by
     * the server it self too. */
 
    if (index_to_tile(nmap, value) == NULL) {
      /* Asked to be reminded to ask what actions the unit can do to a non
       * existing target tile. */
      log_verbose("unit_sscs_set() invalid target tile %d for unit %d",
                  value, unit_id);
      break;
    }
 
    punit->action_decision_want = ACT_DEC_ACTIVE;
    punit->action_decision_tile = index_to_tile(nmap, value);
 
    /* Let the client know that this unit needs the player to decide
     * what to do. */
    send_unit_info(player_reply_dest(pplayer), punit);
 
    break;
  case USSDT_UNQUEUE:
    /* Delete the reminder for the client to ask the server about what
     * actions the unit can perform against a certain target tile.
     * Action decision state can be set by the server it self too. */
 
    punit->action_decision_want = ACT_DEC_NOTHING;
    punit->action_decision_tile = NULL;
 
    /* Let the client know that this unit no longer needs the player to
     * decide what to do. */
    send_unit_info(pplayer->connections, punit);
 
    break;
  case USSDT_BATTLE_GROUP:
    /* Battlegroups are handled entirely by the client, so all we have to
       do here is save the battlegroup ID so that it'll be persistent. */
 
    punit->battlegroup = CLIP(-1, value, MAX_NUM_BATTLEGROUPS);
 
    break;
  case USSDT_SENTRY:
    if (value == 0) {
      if (punit->activity != ACTIVITY_SENTRY) {
        return;
      }
 
      if (!unit_activity_internal(punit, ACTIVITY_IDLE, ACTION_NONE)) {
        /* Impossible to set to Idle? */
        fc_assert(FALSE);
      }
    } else if (value == 1) {
      if (!can_unit_do_activity(nmap, punit, ACTIVITY_SENTRY)) {
        return;
      }
 
      if (!unit_activity_internal(punit, ACTIVITY_SENTRY, ACTION_NONE)) {
        /* Should have been caught above */
        fc_assert(FALSE);
      }
    } else {
      log_verbose("handle_unit_sscs_set(): illegal sentry state for %s %d",
                  unit_rule_name(punit), punit->id);
    }
    break;
  }
}
 
/**********************************************************************/
static void unit_plans_clear(struct unit *punit)
{
  /* Remove city spot reservations for AI settlers on city founding
   * mission. */
  adv_unit_new_task(punit, AUT_NONE, NULL);
 
  /* Get rid of old orders. */
  free_unit_orders(punit);
 
  /* Make sure that no old goto_tile remains. */
  punit->goto_tile = NULL;
}
 
/**********************************************************************/
void handle_unit_server_side_agent_set(struct player *pplayer,
                                       int unit_id,
                                       enum server_side_agent agent)
{
  struct unit *punit = player_unit_by_number(pplayer, unit_id);
 
  if (NULL == punit) {
    /* Probably died or bribed. */
    log_verbose("handle_unit_server_side_agent_set() invalid unit %d",
                unit_id);
    return;
  }
 
  if (!server_side_agent_is_valid(agent)) {
    /* Client error. */
    log_verbose("handle_unit_server_side_agent_set() invalid agent %d",
                agent);
    return;
  }
 
  /* Set the state or exit */
  if (!unit_server_side_agent_set(pplayer, punit, agent)) {
    return;
  }
 
  /* Give the new agent a blank slate */
  unit_plans_clear(punit);
 
  if (agent == SSA_AUTOEXPLORE) {
    if (!unit_activity_internal(punit, ACTIVITY_EXPLORE, ACTION_NONE)) {
      /* Should have been caught above */
      fc_assert(FALSE);
      punit->ssa_controller = SSA_NONE;
    }
 
    /* Exploring is handled here explicitly, since the player expects to
     * see an immediate response from setting a unit to auto-explore.
     * Handling it deeper in the code leads to some tricky recursive loops -
     * see PR#2631. */
    if (punit->moves_left > 0) {
      do_explore(punit);
    }
  }
}
 
/**********************************************************************/
bool unit_server_side_agent_set(struct player *pplayer,
                                struct unit *punit,
                                enum server_side_agent agent)
{
  const struct civ_map *nmap = &(wld.map);
 
  /* Check that the agent can be activated for this unit. */
  switch (agent) {
  case SSA_AUTOWORKER:
    if (!can_unit_do_autoworker(punit)) {
      return FALSE;
    }
    break;
  case SSA_AUTOEXPLORE:
    if (!can_unit_do_activity(nmap, punit, ACTIVITY_EXPLORE)) {
      return FALSE;
    }
    break;
  case SSA_NONE:
    /* Always possible. */
    break;
  case SSA_COUNT:
    fc_assert_ret_val(agent != SSA_COUNT, FALSE);
    break;
  }
 
  if (punit->ssa_controller != agent) {
    punit->ssa_controller = agent;
    send_unit_info(NULL, punit);
  }
 
  return TRUE;
}
 
/**********************************************************************/
static void unit_activity_dependencies(struct unit *punit,
                                       enum unit_activity old_activity,
                                       struct extra_type *old_target)
{
  switch (punit->activity) {
  case ACTIVITY_IDLE:
    switch (old_activity) {
    case ACTIVITY_PILLAGE: 
      {
        if (old_target != NULL) {
          unit_list_iterate_safe(unit_tile(punit)->units, punit2) {
            if (punit2->activity == ACTIVITY_PILLAGE) {
              extra_deps_iterate(&(punit2->activity_target->reqs), pdep) {
                if (pdep == old_target) {
                  set_unit_activity(punit2, ACTIVITY_IDLE, ACTION_NONE);
                  send_unit_info(NULL, punit2);
                  break;
                }
              } extra_deps_iterate_end;
            }
          } unit_list_iterate_safe_end;
        }
        break;
      }
    case ACTIVITY_EXPLORE:
      /* Restore unit's control status */
      punit->ssa_controller = SSA_NONE;
      break;
    default: 
      ; /* Do nothing */
    }
    break;
  case ACTIVITY_EXPLORE:
    punit->ssa_controller = SSA_AUTOEXPLORE;
    set_unit_activity(punit, ACTIVITY_EXPLORE, ACTION_NONE);
    send_unit_info(NULL, punit);
    break;
  default:
    /* Do nothing */
    break;
  }
}
 
/**********************************************************************/
static bool do_action_activity(struct unit *punit,
                               const struct action *paction)
{
  enum unit_activity new_activity = action_get_activity(paction);
 
  fc_assert_ret_val(new_activity != ACTIVITY_LAST, FALSE);
  fc_assert_ret_val(!activity_requires_target(new_activity), FALSE);
 
  return unit_activity_internal(punit, new_activity, action_id(paction));
}
 
/**********************************************************************/
bool unit_activity_handling(struct unit *punit,
                            enum unit_activity new_activity,
                            enum gen_action trigger_action)
{
  const struct civ_map *nmap = &(wld.map);
 
  /* Must specify target for ACTIVITY_BASE */
  fc_assert_ret_val(new_activity != ACTIVITY_BASE
                    && new_activity != ACTIVITY_GEN_ROAD, FALSE);
 
  if (new_activity == ACTIVITY_PILLAGE) {
    struct extra_type *target = NULL;
 
    /* Assume untargeted pillaging if no target specified */
    unit_activity_handling_targeted(punit, new_activity, &target,
                                    trigger_action);
  } else if (can_unit_do_activity(nmap, punit, new_activity)) {
    free_unit_orders(punit);
    unit_activity_internal(punit, new_activity, trigger_action);
  }
 
  return TRUE;
}
 
/**********************************************************************/
static bool unit_activity_internal(struct unit *punit,
                                   enum unit_activity new_activity,
                                   enum gen_action trigger_action)
{
  if (!can_unit_do_activity(&(wld.map), punit, new_activity)) {
    return FALSE;
  } else {
    enum unit_activity old_activity = punit->activity;
    struct extra_type *old_target = punit->activity_target;
 
    set_unit_activity(punit, new_activity, trigger_action);
    send_unit_info(NULL, punit);
    unit_activity_dependencies(punit, old_activity, old_target);
 
    return TRUE;
  }
}
 
/**********************************************************************/
static bool do_action_activity_targeted(struct unit *punit,
                                        const struct action *paction,
                                        struct extra_type **new_target)
{
  enum unit_activity new_activity = action_get_activity(paction);
 
  fc_assert_ret_val(new_activity != ACTIVITY_LAST, FALSE);
  fc_assert_ret_val(activity_requires_target(new_activity),
                    unit_activity_internal(punit, new_activity,
                                           action_id(paction)));
 
  return unit_activity_targeted_internal(punit, new_activity, new_target,
                                         action_id(paction));
}
 
/**********************************************************************/
bool unit_activity_handling_targeted(struct unit *punit,
                                     enum unit_activity new_activity,
                                     struct extra_type **new_target,
                                     enum gen_action trigger_action)
{
  if (!activity_requires_target(new_activity)) {
    unit_activity_handling(punit, new_activity, trigger_action);
  } else if (can_unit_do_activity_targeted(&(wld.map), punit,
                                           new_activity, *new_target)) {
    struct action_list *list = action_list_by_activity(new_activity);
 
    free_unit_orders(punit);
 
    if (list != NULL && action_list_size(list) > 0) {
      /* Trigger action system */
      unit_do_action(unit_owner(punit), punit->id, punit->tile->index,
                     (*new_target) != NULL ? (*new_target)->id : NO_TARGET,
                     "", action_number(action_list_get(list, 0)));
    } else {
      unit_activity_targeted_internal(punit, new_activity, new_target,
                                      trigger_action);
    }
  }
 
  return TRUE;
}
 
/**********************************************************************/
static bool unit_activity_targeted_internal(struct unit *punit,
                                            enum unit_activity new_activity,
                                            struct extra_type **new_target,
                                            enum gen_action trigger_action)
{
  if (!can_unit_do_activity_targeted(&(wld.map), punit,
                                     new_activity, *new_target)) {
    return FALSE;
  } else {
    enum unit_activity old_activity = punit->activity;
    struct extra_type *old_target = punit->activity_target;
    enum unit_activity stored_activity = new_activity;
 
    unit_assign_specific_activity_target(punit,
                                         &new_activity, new_target);
    if (new_activity != stored_activity
        && !activity_requires_target(new_activity)) {
      /* unit_assign_specific_activity_target() changed our target activity
       * (to ACTIVITY_IDLE in practice) */
      unit_activity_handling(punit, new_activity, trigger_action);
    } else {
      set_unit_activity_targeted(punit, new_activity, *new_target,
                                 trigger_action);
      send_unit_info(NULL, punit);
      unit_activity_dependencies(punit, old_activity, old_target);
 
      if (new_activity == ACTIVITY_PILLAGE) {
        /* Casus Belli for when the activity successfully begins. */
        /* TODO: is it more logical to change Casus_Belli_Complete to
         * Casus_Belli_Successful_Beginning and trigger it here? */
        action_consequence_success(action_by_number(trigger_action),
                                   unit_owner(punit), unit_type_get(punit),
                                   tile_owner(unit_tile(punit)),
                                   unit_tile(punit),
                                   tile_link(unit_tile(punit)));
      }
    }
 
    return TRUE;
  }
}
 
/**********************************************************************/
void handle_unit_orders(struct player *pplayer,
                        const struct packet_unit_orders *packet)
{
  int length = packet->length;
  struct unit *punit = player_unit_by_number(pplayer, packet->unit_id);
  const struct civ_map *nmap = &(wld.map);
  struct tile *src_tile = index_to_tile(nmap, packet->src_tile);
  struct unit_order *order_list;
#ifdef FREECIV_DEBUG
  int i;
#endif
 
  if (NULL == punit) {
    /* Probably died or bribed. */
    log_verbose("handle_unit_orders() invalid unit %d", packet->unit_id);
    return;
  }
 
  if (0 > length || MAX_LEN_ROUTE < length) {
    /* Shouldn't happen */
    log_error("handle_unit_orders() invalid %s (%d) "
              "packet length %d (max %d)", unit_rule_name(punit),
              packet->unit_id, length, MAX_LEN_ROUTE);
    return;
  }
 
  if (src_tile != unit_tile(punit)) {
    /* Failed sanity check.  Usually this happens if the orders were sent
     * in the previous turn, and the client thought the unit was in a
     * different position than it's actually in.  The easy solution is to
     * discard the packet.  We don't send an error message to the client
     * here (though maybe we should?). */
    log_verbose("handle_unit_orders() invalid %s (%d) tile (%d, %d) "
                "!= (%d, %d)", unit_rule_name(punit), punit->id,
                TILE_XY(src_tile), TILE_XY(unit_tile(punit)));
    return;
  }
 
  if (ACTIVITY_IDLE != punit->activity) {
    /* New orders implicitly abandon current activity */
    unit_activity_handling(punit, ACTIVITY_IDLE, ACTION_NONE);
  }
 
  if (length) {
    order_list = create_unit_orders(nmap, length, packet->orders);
    if (!order_list) {
      log_error("received invalid orders from %s for %s (%d).",
                player_name(pplayer), unit_rule_name(punit), packet->unit_id);
      return;
    }
  }
 
  /* This must be before old orders are freed. If this is
   * settlers on city founding mission, city spot reservation
   * from goto_tile must be freed, and free_unit_orders() loses
   * goto_tile information */
  adv_unit_new_task(punit, AUT_NONE, NULL);
 
  free_unit_orders(punit);
  /* If we waited on a tile, reset punit->done_moving */
  punit->done_moving = (punit->moves_left <= 0);
 
  if (length == 0) {
    fc_assert(!unit_has_orders(punit));
    send_unit_info(NULL, punit);
    return;
  }
 
  punit->has_orders = TRUE;
  punit->orders.length = length;
  punit->orders.index = 0;
  punit->orders.repeat = packet->repeat;
  punit->orders.vigilant = packet->vigilant;
  if (length) {
    punit->orders.list = order_list;
  }
 
  if (!packet->repeat) {
    punit->goto_tile = index_to_tile(nmap, packet->dest_tile);
  } else {
    /* Make sure that no old goto_tile remains. */
    punit->goto_tile = NULL;
  }
 
#ifdef FREECIV_DEBUG
  log_debug("Orders for unit %d: length:%d", packet->unit_id, length);
  for (i = 0; i < length; i++) {
    log_debug("  %d,%s,%s,%d,%d",
              packet->orders[i].order, dir_get_name(packet->orders[i].dir),
              packet->orders[i].order == ORDER_PERFORM_ACTION ?
                action_id_rule_name(packet->orders[i].action) :
                packet->orders[i].order == ORDER_ACTIVITY ?
                  unit_activity_name(packet->orders[i].activity) :
                  "no action/activity required",
              packet->orders[i].target,
              packet->orders[i].sub_target);
  }
#endif /* FREECIV_DEBUG */
 
  if (!is_player_phase(unit_owner(punit), game.info.phase)
      || execute_orders(punit, TRUE)) {
    /* Looks like the unit survived. */
    send_unit_info(NULL, punit);
  }
}
 
/**********************************************************************/
void handle_worker_task(struct player *pplayer,
                        const struct packet_worker_task *packet)
{
  struct city *pcity = game_city_by_number(packet->city_id);
  struct worker_task *ptask = NULL;
  struct tile *ptile = index_to_tile(&(wld.map), packet->tile_id);
 
  if (pcity == NULL || pcity->owner != pplayer || ptile == NULL) {
    return;
  }
 
  worker_task_list_iterate(pcity->task_reqs, ptask_old) {
    if (tile_index(ptask_old->ptile) == packet->tile_id) {
      ptask = ptask_old;
    }
  } worker_task_list_iterate_end;
 
  if (ptask == NULL) {
    if (packet->activity == ACTIVITY_LAST) {
      return;
    }
 
    ptask = fc_malloc(sizeof(struct worker_task));
    worker_task_init(ptask);
    worker_task_list_append(pcity->task_reqs, ptask);
  } else {
    if (packet->activity == ACTIVITY_LAST) {
      worker_task_list_remove(pcity->task_reqs, ptask);
      free(ptask);
      ptask = NULL;
    }
  }
 
  if (ptask != NULL) {
    ptask->ptile = ptile;
    ptask->act = packet->activity;
    if (packet->tgt >= 0) {
      if (packet->tgt < MAX_EXTRA_TYPES) {
        ptask->tgt = extra_by_number(packet->tgt);
      } else {
        log_debug("Illegal worker task target %d", packet->tgt);
        ptask->tgt = NULL;
      }
    } else {
      ptask->tgt = NULL;
    }
    ptask->want = packet->want;
  }
 
  if (ptask && !worker_task_is_sane(ptask)) {
    log_debug("Bad worker task");
    worker_task_list_remove(pcity->task_reqs, ptask);
    free(ptask);
    ptask = NULL;
    return;
  }
 
  lsend_packet_worker_task(pplayer->connections, packet);
}