player.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
 
/* utility */
#include "fcintl.h"
#include "log.h"
#include "mem.h"
#include "shared.h"
#include "support.h"
 
/* common */
#include "ai.h"
#include "city.h"
#include "fc_interface.h"
#include "featured_text.h"
#include "game.h"
#include "government.h"
#include "idex.h"
#include "improvement.h"
#include "map.h"
#include "nation.h"
#include "research.h"
#include "rgbcolor.h"
#include "tech.h"
#include "unit.h"
#include "unitlist.h"
#include "vision.h"
 
#include "player.h"
 
 
struct player_slot {
  struct player *player;
};
 
static struct {
  struct player_slot *slots;
  int used_slots; /* number of used/allocated players in the player slots */
} player_slots;
 
static void player_defaults(struct player *pplayer);
 
static void player_diplstate_new(const struct player *plr1,
                                 const struct player *plr2);
static void player_diplstate_defaults(const struct player *plr1,
                                      const struct player *plr2);
static void player_diplstate_destroy(const struct player *plr1,
                                     const struct player *plr2);
 
/*******************************************************************/
enum diplstate_type cancel_pact_result(enum diplstate_type oldstate)
{
  switch (oldstate) {
  case DS_WAR: /* no change */
  case DS_ARMISTICE:
  case DS_CEASEFIRE:
  case DS_PEACE:
    return DS_WAR;
  case DS_ALLIANCE:
    return DS_ARMISTICE;
  case DS_TEAM: /* no change */
    return DS_TEAM;
  case DS_NO_CONTACT:     /* Possible if someone declares war on our ally */
    return DS_NO_CONTACT; /* Can't cancel lack of contact */
  case DS_LAST:
    fc_assert(oldstate != DS_LAST);
    return DS_WAR; /* Arbitrary */
  }
 
  fc_assert(FALSE);
 
  return DS_WAR; /* Arbitrary */
}
 
/*******************************************************************/
enum dipl_reason pplayer_can_cancel_treaty(const struct player *p1,
                                           const struct player *p2)
{
  enum diplstate_type ds = player_diplstate_get(p1, p2)->type;
 
  if (p1 == p2 || ds == DS_WAR || ds == DS_NO_CONTACT) {
    return DIPL_ERROR;
  }
  if (players_on_same_team(p1, p2)) {
    return DIPL_ERROR;
  }
  if (!p1->is_alive || !p2->is_alive) {
    return DIPL_ERROR;
  }
  if (player_diplstate_get(p1, p2)->has_reason_to_cancel == 0
      && get_player_bonus(p1, EFT_HAS_SENATE) > 0
      && get_player_bonus(p1, EFT_NO_ANARCHY) <= 0) {
    return DIPL_SENATE_BLOCKING;
  }
 
  return DIPL_OK;
}
 
/*******************************************************************/
static bool is_valid_alliance(const struct player *p1,
                              const struct player *p2)
{
  players_iterate_alive(pplayer) {
    enum diplstate_type ds = player_diplstate_get(p1, pplayer)->type;
 
    if (pplayer != p1
        && pplayer != p2
        && ds == DS_WAR /* Do not count 'never met' as war here */
        && pplayers_allied(p2, pplayer)) {
      return FALSE;
    }
  } players_iterate_alive_end;
 
  return TRUE;
}
 
/*******************************************************************/
enum dipl_reason pplayer_can_make_treaty(const struct player *p1,
                                         const struct player *p2,
                                         enum diplstate_type treaty)
{
  enum diplstate_type existing = player_diplstate_get(p1, p2)->type;
 
  if (players_on_same_team(p1, p2)) {
    /* This includes the case p1 == p2 */
    return DIPL_ERROR;
  }
  if (get_player_bonus(p1, EFT_NO_DIPLOMACY) > 0
      || get_player_bonus(p2, EFT_NO_DIPLOMACY) > 0) {
    return DIPL_ERROR;
  }
  if (treaty == DS_WAR
      || treaty == DS_NO_CONTACT
      || treaty == DS_ARMISTICE
      || treaty == DS_TEAM
      || treaty == DS_LAST) {
    return DIPL_ERROR; /* These are not negotiable treaties */
  }
  if (treaty == DS_CEASEFIRE && existing != DS_WAR) {
    return DIPL_ERROR; /* Only available from war */
  }
  if (treaty == DS_PEACE
      && (existing != DS_WAR && existing != DS_CEASEFIRE)) {
    return DIPL_ERROR;
  }
  if (treaty == DS_ALLIANCE) {
    if (!is_valid_alliance(p1, p2)) {
      /* Our war with a third party prevents entry to alliance. */
      return DIPL_ALLIANCE_PROBLEM_US;
    } else if (!is_valid_alliance(p2, p1)) {
      /* Their war with a third party prevents entry to alliance. */
      return DIPL_ALLIANCE_PROBLEM_THEM;
    }
  }
  /* This check must be last: */
  if (treaty == existing) {
    return DIPL_ERROR;
  }
 
  return DIPL_OK;
}
 
/*******************************************************************/
bool player_has_embassy(const struct player *pplayer,
                        const struct player *pplayer2)
{
  return (pplayer == pplayer2
          || player_has_real_embassy(pplayer, pplayer2)
          || player_has_embassy_from_effect(pplayer, pplayer2));
}
 
/*******************************************************************/
bool team_has_embassy(const struct team *pteam, const struct player *tgt_player)
{
  if (tgt_player->team == pteam) {
    return TRUE;
  }
 
  player_list_iterate(team_members(pteam), teammate) {
    if (player_has_real_embassy(teammate, tgt_player)
        || player_has_embassy_from_effect(teammate, tgt_player)) {
      return TRUE;
    }
  } player_list_iterate_end;
 
  return FALSE;
}
 
/*******************************************************************/
bool player_has_real_embassy(const struct player *pplayer,
                             const struct player *pplayer2)
{
  return BV_ISSET(pplayer->real_embassy, player_index(pplayer2));
}
 
/*******************************************************************/
bool player_has_embassy_from_effect(const struct player *pplayer,
                                    const struct player *pplayer2)
{
  return (get_player_bonus(pplayer, EFT_HAVE_EMBASSIES) > 0
          && player_diplstate_get(pplayer, pplayer2)->type != DS_NO_CONTACT
          && !is_barbarian(pplayer2));
}
 
/*******************************************************************/
bool player_owns_city(const struct player *pplayer, const struct city *pcity)
{
  return (pcity && pplayer && city_owner(pcity) == pplayer);
}
 
/*******************************************************************/
bool player_can_invade_tile(const struct player *pplayer,
                            const struct tile *ptile)
{
  const struct player *ptile_owner = tile_owner(ptile);
 
  return (!ptile_owner
          || ptile_owner == pplayer
          || terrain_has_flag(tile_terrain(ptile), TER_ENTER_BORDERS)
          || !players_non_invade(pplayer, ptile_owner));
}
 
/*******************************************************************/
static void player_diplstate_new(const struct player *plr1,
                                 const struct player *plr2)
{
  struct player_diplstate *diplstate;
 
  fc_assert_ret(plr1 != nullptr);
  fc_assert_ret(plr2 != nullptr);
 
  const struct player_diplstate **diplstate_slot
    = plr1->diplstates + player_index(plr2);
 
  fc_assert_ret(*diplstate_slot == nullptr);
 
  diplstate = fc_calloc(1, sizeof(*diplstate));
  *diplstate_slot = diplstate;
}
 
/*******************************************************************/
static void player_diplstate_defaults(const struct player *plr1,
                                      const struct player *plr2)
{
  struct player_diplstate *diplstate = player_diplstate_get(plr1, plr2);
 
  fc_assert_ret(diplstate != nullptr);
 
  diplstate->type                 = DS_NO_CONTACT;
  diplstate->max_state            = DS_NO_CONTACT;
  diplstate->first_contact_turn   = 0;
  diplstate->turns_left           = 0;
  diplstate->has_reason_to_cancel = 0;
  diplstate->contact_turns_left   = 0;
  diplstate->auto_cancel_turn     = -1;
}
 
/*******************************************************************/
struct player_diplstate *player_diplstate_get(const struct player *plr1,
                                              const struct player *plr2)
{
  fc_assert_ret_val(plr1 != nullptr, nullptr);
  fc_assert_ret_val(plr2 != nullptr, nullptr);
 
  const struct player_diplstate **diplstate_slot
    = plr1->diplstates + player_index(plr2);
 
  fc_assert_ret_val(*diplstate_slot != nullptr, nullptr);
 
  return (struct player_diplstate *) *diplstate_slot;
}
 
/*******************************************************************/
static void player_diplstate_destroy(const struct player *plr1,
                                     const struct player *plr2)
{
  fc_assert_ret(plr1 != nullptr);
  fc_assert_ret(plr2 != nullptr);
 
  const struct player_diplstate **diplstate_slot
    = plr1->diplstates + player_index(plr2);
 
  if (*diplstate_slot != nullptr) {
    free(player_diplstate_get(plr1, plr2));
  }
 
  *diplstate_slot = nullptr;
}
 
/*******************************************************************/
void player_slots_init(void)
{
  int i;
 
  /* Init player slots. */
  player_slots.slots = fc_calloc(player_slot_count(),
                                 sizeof(*player_slots.slots));
  /* Can't use the defined functions as the needed data will be
   * defined here. */
  for (i = 0; i < player_slot_count(); i++) {
    player_slots.slots[i].player = nullptr;
  }
  player_slots.used_slots = 0;
}
 
/*******************************************************************/
bool player_slots_initialised(void)
{
  return (player_slots.slots != nullptr);
}
 
/*******************************************************************/
void player_slots_free(void)
{
  players_iterate(pplayer) {
    player_destroy(pplayer);
  } players_iterate_end;
  free(player_slots.slots);
  player_slots.slots = nullptr;
  player_slots.used_slots = 0;
}
 
/*******************************************************************/
struct player_slot *player_slot_first(void)
{
  return player_slots.slots;
}
 
/*******************************************************************/
struct player_slot *player_slot_next(struct player_slot *pslot)
{
  pslot++;
 
  return (pslot < player_slots.slots + player_slot_count()
          ? pslot : nullptr);
}
 
/*******************************************************************/
int player_slot_count(void)
{
  return (MAX_NUM_PLAYER_SLOTS);
}
 
/*******************************************************************/
int player_slot_index(const struct player_slot *pslot)
{
  fc_assert_ret_val(pslot != nullptr, -1);
 
  return pslot - player_slots.slots;
}
 
/*******************************************************************/
struct player *player_slot_get_player(const struct player_slot *pslot)
{
  fc_assert_ret_val(pslot != nullptr, nullptr);
 
  return pslot->player;
}
 
/*******************************************************************/
bool player_slot_is_used(const struct player_slot *pslot)
{
  fc_assert_ret_val(pslot != nullptr, FALSE);
 
  /* No player slot available, if the game is not initialised. */
  if (!player_slots_initialised()) {
    return FALSE;
  }
 
  return pslot->player != nullptr;
}
 
/*******************************************************************/
struct player_slot *player_slot_by_number(int player_id)
{
  if (!player_slots_initialised()
      || !(0 <= player_id && player_id < player_slot_count())) {
    return nullptr;
  }
 
  return player_slots.slots + player_id;
}
 
/*******************************************************************/
int player_slot_max_used_number(void)
{
  int max_pslot = 0;
 
  player_slots_iterate(pslot) {
    if (player_slot_is_used(pslot)) {
      max_pslot = player_slot_index(pslot);
    }
  } player_slots_iterate_end;
 
  return max_pslot;
}
 
/*******************************************************************/
struct player *player_new(struct player_slot *pslot)
{
  struct player *pplayer;
 
  fc_assert_ret_val(player_slots_initialised(), nullptr);
 
  if (pslot == nullptr) {
    player_slots_iterate(aslot) {
      if (!player_slot_is_used(aslot)) {
        pslot = aslot;
        break;
      }
    } player_slots_iterate_end;
 
    if (pslot == nullptr) {
      return nullptr;
    }
  } else if (pslot->player != nullptr) {
    return pslot->player;
  }
 
  /* Now create the player. */
  log_debug("Create player for slot %d.", player_slot_index(pslot));
  pplayer = fc_calloc(1, sizeof(*pplayer));
  pplayer->slot = pslot;
  pslot->player = pplayer;
 
  pplayer->diplstates = fc_calloc(player_slot_count(),
                                  sizeof(*pplayer->diplstates));
  player_slots_iterate(dslot) {
    const struct player_diplstate **diplstate_slot
      = pplayer->diplstates + player_slot_index(dslot);
 
    *diplstate_slot = nullptr;
  } player_slots_iterate_end;
 
  players_iterate(aplayer) {
    /* Create diplomatic states for all other players. */
    player_diplstate_new(pplayer, aplayer);
    /* Create diplomatic state of this player. */
    if (aplayer != pplayer) {
      player_diplstate_new(aplayer, pplayer);
    }
  } players_iterate_end;
 
  /* Set default values. */
  player_defaults(pplayer);
 
  /* Increase number of players. */
  player_slots.used_slots++;
 
  return pplayer;
}
 
/*******************************************************************/
static void player_defaults(struct player *pplayer)
{
  int i;
 
  sz_strlcpy(pplayer->name, ANON_PLAYER_NAME);
  sz_strlcpy(pplayer->username, _(ANON_USER_NAME));
  pplayer->unassigned_user = TRUE;
  sz_strlcpy(pplayer->ranked_username, _(ANON_USER_NAME));
  pplayer->unassigned_ranked = TRUE;
  pplayer->user_turns = 0;
  pplayer->is_male = TRUE;
  pplayer->government = nullptr;
  pplayer->target_government = nullptr;
  pplayer->nation = NO_NATION_SELECTED;
  pplayer->team = nullptr;
  pplayer->is_ready = FALSE;
  pplayer->nturns_idle = 0;
  pplayer->is_alive = TRUE;
  pplayer->turns_alive = 0;
  pplayer->is_winner = FALSE;
  pplayer->last_war_action = -1;
  pplayer->phase_done = FALSE;
 
  pplayer->revolution_finishes = -1;
  pplayer->primary_capital_id = 0;
 
  BV_CLR_ALL(pplayer->real_embassy);
  players_iterate(aplayer) {
    /* create diplomatic states for all other players */
    player_diplstate_defaults(pplayer, aplayer);
    /* create diplomatic state of this player */
    if (aplayer != pplayer) {
      player_diplstate_defaults(aplayer, pplayer);
    }
  } players_iterate_end;
 
  pplayer->style      = 0;
  pplayer->music_style = -1;          /* even getting value 0 triggers change */
  pplayer->cities = city_list_new();
  pplayer->units = unit_list_new();
 
  pplayer->economic.gold    = 0;
  pplayer->economic.tax     = PLAYER_DEFAULT_TAX_RATE;
  pplayer->economic.science = PLAYER_DEFAULT_SCIENCE_RATE;
  pplayer->economic.luxury  = PLAYER_DEFAULT_LUXURY_RATE;
  pplayer->economic.infra_points = 0;
 
  spaceship_init(&pplayer->spaceship);
 
  BV_CLR_ALL(pplayer->flags);
 
  set_as_human(pplayer);
  pplayer->ai_common.skill_level = ai_level_invalid();
  pplayer->ai_common.fuzzy = 0;
  pplayer->ai_common.expand = 100;
  pplayer->ai_common.barbarian_type = NOT_A_BARBARIAN;
  player_slots_iterate(pslot) {
    pplayer->ai_common.love[player_slot_index(pslot)] = 1;
  } player_slots_iterate_end;
  pplayer->ai_common.traits = nullptr;
 
  pplayer->ai = nullptr;
  pplayer->was_created = FALSE;
  pplayer->savegame_ai_type_name = nullptr;
  pplayer->random_name = TRUE;
  pplayer->is_connected = FALSE;
  pplayer->current_conn = nullptr;
  pplayer->connections = conn_list_new();
  pplayer->autoselect_weight = -1;
  BV_CLR_ALL(pplayer->gives_shared_vision);
  BV_CLR_ALL(pplayer->gives_shared_tiles);
  for (i = 0; i < B_LAST; i++) {
    pplayer->wonders[i] = WONDER_NOT_BUILT;
  }
 
  pplayer->attribute_block.data = nullptr;
  pplayer->attribute_block.length = 0;
  pplayer->attribute_block_buffer.data = nullptr;
  pplayer->attribute_block_buffer.length = 0;
 
  pplayer->tile_known.vec = nullptr;
  pplayer->tile_known.bits = 0;
 
  pplayer->rgb = nullptr;
 
  memset(pplayer->multipliers, 0, sizeof(pplayer->multipliers));
 
  /* pplayer->server is initialised in
      ./server/plrhand.c:server_player_init()
     and pplayer->client in
      ./client/climisc.c:client_player_init() */
}
 
/*******************************************************************/
void player_set_color(struct player *pplayer,
                      const struct rgbcolor *prgbcolor)
{
  if (pplayer->rgb != nullptr) {
    rgbcolor_destroy(pplayer->rgb);
    pplayer->rgb = nullptr;
  }
 
  if (prgbcolor) {
    pplayer->rgb = rgbcolor_copy(prgbcolor);
  }
}
 
/*******************************************************************/
void player_clear(struct player *pplayer, bool full)
{
  bool client = !is_server();
 
  if (pplayer == nullptr) {
    return;
  }
 
  if (pplayer->savegame_ai_type_name != nullptr) {
    free(pplayer->savegame_ai_type_name);
    pplayer->savegame_ai_type_name = nullptr;
  }
 
  /* Clears the attribute blocks. */
  if (pplayer->attribute_block.data) {
    free(pplayer->attribute_block.data);
    pplayer->attribute_block.data = nullptr;
  }
  pplayer->attribute_block.length = 0;
 
  if (pplayer->attribute_block_buffer.data) {
    free(pplayer->attribute_block_buffer.data);
    pplayer->attribute_block_buffer.data = nullptr;
  }
  pplayer->attribute_block_buffer.length = 0;
 
  /* Clears units and cities. */
  unit_list_iterate(pplayer->units, punit) {
    /* Unload all cargos. */
    unit_list_iterate(unit_transport_cargo(punit), pcargo) {
      unit_transport_unload(pcargo);
      if (client) {
        pcargo->client.transported_by = -1;
      }
    } unit_list_iterate_end;
    /* Unload the unit. */
    unit_transport_unload(punit);
    if (client) {
      punit->client.transported_by = -1;
    }
 
    game_remove_unit(&wld, punit);
  } unit_list_iterate_end;
 
  city_list_iterate(pplayer->cities, pcity) {
    if (fc_funcs->destroy_city != nullptr) {
      fc_funcs->destroy_city(pcity);
    } else {
      game_remove_city(&wld, pcity);
    }
  } city_list_iterate_end;
 
  if (full) {
    team_remove_player(pplayer);
 
    players_iterate_alive(owner) {
      unit_list_iterate(owner->units, owned) {
        if (unit_nationality(owned) == pplayer) {
          /* Switch nationality to that of current owner. */
          owned->nationality = owner;
        }
      } unit_list_iterate_end;
    } players_iterate_alive_end;
 
    /* This comes last because log calls in the above functions
     * may use it. */
    if (pplayer->nation != nullptr) {
      player_set_nation(pplayer, nullptr);
    }
  }
}
 
/*******************************************************************/
void player_ruleset_close(struct player *pplayer)
{
  pplayer->government = nullptr;
  pplayer->target_government = nullptr;
  player_set_nation(pplayer, nullptr);
  pplayer->style = nullptr;
}
 
/*******************************************************************/
void player_destroy(struct player *pplayer)
{
  struct player_slot *pslot;
 
  fc_assert_ret(pplayer != nullptr);
 
  pslot = pplayer->slot;
  fc_assert(pslot->player == pplayer);
 
  /* Remove all that is game-dependent in the player structure. */
  player_clear(pplayer, TRUE);
 
  fc_assert(0 == unit_list_size(pplayer->units));
  unit_list_destroy(pplayer->units);
  fc_assert(0 == city_list_size(pplayer->cities));
  city_list_destroy(pplayer->cities);
 
  fc_assert(conn_list_size(pplayer->connections) == 0);
  conn_list_destroy(pplayer->connections);
 
  players_iterate(aplayer) {
    /* Destroy the diplomatic states of this player with others ... */
    player_diplstate_destroy(pplayer, aplayer);
    /* ...and of others with this player. */
    if (aplayer != pplayer) {
      player_diplstate_destroy(aplayer, pplayer);
 
      /* Check if any cities of the other player have been founded
       * by the removed player. */
      city_list_iterate(aplayer->cities, pcity) {
        if (pcity->original == pplayer) {
          /* Unknown origin is better than giving baseless
           * benefits to current owner */
          pcity->original = nullptr;
        }
      } city_list_iterate_end;
    }
  } players_iterate_end;
  free(pplayer->diplstates);
 
  /* Clear player color. */
  if (pplayer->rgb) {
    rgbcolor_destroy(pplayer->rgb);
  }
 
  dbv_free(&pplayer->tile_known);
 
  if (!is_server()) {
    vision_layer_iterate(v) {
      dbv_free(&pplayer->client.tile_vision[v]);
    } vision_layer_iterate_end;
  }
 
  free(pplayer);
  pslot->player = nullptr;
  player_slots.used_slots--;
}
 
/*******************************************************************/
int player_count(void)
{
  return player_slots.used_slots;
}
 
/*******************************************************************/
int player_index(const struct player *pplayer)
{
  return player_number(pplayer);
}
 
/*******************************************************************/
int player_number(const struct player *pplayer)
{
  fc_assert_ret_val(pplayer != nullptr, -1);
 
  return player_slot_index(pplayer->slot);
}
 
/*******************************************************************/
struct player *player_by_number(const int player_id)
{
  struct player_slot *pslot = player_slot_by_number(player_id);
 
  return (pslot != nullptr ? player_slot_get_player(pslot) : nullptr);
}
 
/*******************************************************************/
bool player_set_nation(struct player *pplayer, struct nation_type *pnation)
{
  if (pplayer->nation != pnation) {
    if (pplayer->nation) {
      fc_assert(pplayer->nation->player == pplayer);
      pplayer->nation->player = nullptr;
    }
    if (pnation) {
      fc_assert(pnation->player == nullptr);
      pnation->player = pplayer;
    }
    pplayer->nation = pnation;
 
    return TRUE;
  }
 
  return FALSE;
}
 
/*******************************************************************/
struct player *player_by_name(const char *name)
{
  players_iterate(pplayer) {
    if (fc_strcasecmp(name, pplayer->name) == 0) {
      return pplayer;
    }
  } players_iterate_end;
 
  return nullptr;
}
 
/*******************************************************************/
const char *player_name(const struct player *pplayer)
{
  if (!pplayer) {
    return nullptr;
  }
 
  return pplayer->name;
}
 
/*******************************************************************/
static const char *player_name_by_number(int i)
{
  struct player *pplayer;
 
  pplayer = player_by_number(i);
 
  return player_name(pplayer);
}
 
/*******************************************************************/
struct player *player_by_name_prefix(const char *name,
                                     enum m_pre_result *result)
{
  int ind;
 
  *result = match_prefix(player_name_by_number,
                         player_slot_count(), MAX_LEN_NAME - 1,
                         fc_strncasequotecmp, effectivestrlenquote,
                         name, &ind);
 
  if (*result < M_PRE_AMBIGUOUS) {
    return player_by_number(ind);
  } else {
    return nullptr;
  }
}
 
/*******************************************************************/
struct player *player_by_user(const char *name)
{
  players_iterate(pplayer) {
    if (fc_strcasecmp(name, pplayer->username) == 0) {
      return pplayer;
    }
  } players_iterate_end;
 
  return nullptr;
}
 
/*******************************************************************/
int player_age(const struct player *pplayer)
{
  fc_assert_ret_val(pplayer != nullptr, 0);
 
  return pplayer->turns_alive;
}
 
/*******************************************************************/
bool player_can_trust_tile_has_no_units(const struct player *pplayer,
                                        const struct tile *ptile)
{
  /* Can't see invisible units. */
  if (!fc_funcs->player_tile_vision_get(ptile, pplayer, V_INVIS)
      || !fc_funcs->player_tile_vision_get(ptile, pplayer, V_SUBSURFACE)) {
    return FALSE;
  }
 
  /* Units within some extras may be hidden. */
  if (!pplayers_allied(pplayer, ptile->extras_owner)) {
    extra_type_list_iterate(extra_type_list_of_unit_hiders(), pextra) {
      if (tile_has_extra(ptile, pextra)) {
        return FALSE;
      }
    } extra_type_list_iterate_end;
  }
 
  return TRUE;
}
 
/*******************************************************************/
bool can_player_see_hypotetic_units_at(const struct player *pplayer,
                                       const struct tile *ptile)
{
  struct city *pcity;
 
  if (!player_can_trust_tile_has_no_units(pplayer, ptile)) {
    /* The existence of any units at all is hidden from the player. */
    return FALSE;
  }
 
  /* Can't see city units. */
  pcity = tile_city(ptile);
  if (pcity && !can_player_see_units_in_city(pplayer, pcity)
      && unit_list_size(ptile->units) > 0) {
    return FALSE;
  }
 
  /* Can't see non-allied units in transports. */
  unit_list_iterate(ptile->units, punit) {
    if (unit_type_get(punit)->transport_capacity > 0
        && unit_owner(punit) != pplayer) {
 
      /* An ally could transport a non ally */
      if (unit_list_size(punit->transporting) > 0) {
        return FALSE;
      }
    }
  } unit_list_iterate_end;
 
  return TRUE;
}
 
/*******************************************************************/
bool can_player_see_unit_at(const struct player *pplayer,
                            const struct unit *punit,
                            const struct tile *ptile,
                            bool is_transported)
{
  struct city *pcity;
  bool allied;
  struct unit_class *pclass;
 
  /* If the player can't even see the tile... */
  if (TILE_KNOWN_SEEN != tile_get_known(ptile, pplayer)) {
    return FALSE;
  }
 
  /* Don't show non-allied units that are in transports. This is logical
   * because allied transports can also contain our units. Shared vision
   * isn't taken into account. */
  allied = pplayers_allied(pplayer, unit_owner(punit));
  if (is_transported && !allied) {
    return FALSE;
  }
 
  /* Units in cities may be hidden. */
  pcity = tile_city(ptile);
  if (pcity && !can_player_see_units_in_city(pplayer, pcity)) {
    return FALSE;
  }
 
  /* Allied units are always seen.
   * See also stealth unit hiding part in map_change_seen() */
  if (allied) {
    return TRUE;
  }
 
  /* Units within some extras may be hidden. */
  pclass = unit_class_get(punit);
 
  extra_type_list_iterate(pclass->cache.hiding_extras, pextra) {
    if (tile_has_extra(ptile, pextra)) {
      return FALSE;
    }
  } extra_type_list_iterate_end;
 
  /* Non-hiding units are always seen.
   * See also stealth unit hiding part in map_change_seen() */
  if (!is_hiding_unit(punit)) {
    return TRUE;
  }
 
  /* Hiding units are only seen by the V_INVIS fog layer. */
  return fc_funcs->player_tile_vision_get(ptile, pplayer,
                                          unit_type_get(punit)->vlayer);
}
 
/**********************************************************************/
bool can_player_see_tile(const struct player *plr,
                         const struct tile *ptile)
{
  return plr != nullptr
    && ptile != nullptr
    && (tile_get_known(ptile, plr) == TILE_KNOWN_SEEN);
}
 
/*******************************************************************/
bool can_player_see_unit(const struct player *pplayer,
                         const struct unit *punit)
{
  return can_player_see_unit_at(pplayer, punit, unit_tile(punit),
                                unit_transported(punit));
}
 
/*******************************************************************/
bool can_player_see_units_in_city(const struct player *pplayer,
                                  const struct city *pcity)
{
  return (!pplayer
          || can_player_see_city_internals(pplayer, pcity)
          || pplayers_allied(pplayer, city_owner(pcity)));
}
 
/*******************************************************************/
bool can_player_see_city_internals(const struct player *pplayer,
                                   const struct city *pcity)
{
  return (!pplayer || pplayer == city_owner(pcity));
}
 
/*******************************************************************/
bool player_can_see_city_externals(const struct player *pow_player,
                                   const struct city *target_city)
{
  fc_assert_ret_val(target_city, FALSE);
  fc_assert_ret_val(pow_player, FALSE);
 
  if (can_player_see_city_internals(pow_player, target_city)) {
    /* City internals includes city externals. */
    return TRUE;
  }
 
  if (tile_is_seen(city_tile(target_city), pow_player)) {
    /* The tile is being observed. */
    return TRUE;
  }
 
  fc_assert_ret_val(target_city->routes, FALSE);
 
  if (game.info.reveal_trade_partner) {
    trade_partners_iterate(target_city, trade_city) {
      if (city_owner(trade_city) == pow_player) {
        /* Revealed because of the trade route. */
        return TRUE;
      }
    } trade_partners_iterate_end;
  }
 
  return FALSE;
}
 
/*******************************************************************/
struct city *player_city_by_number(const struct player *pplayer, int city_id)
{
  /* We call idex directly. Should use game_city_by_number() instead? */
  struct city *pcity = idex_lookup_city(&wld, city_id);
 
  if (!pcity) {
    return nullptr;
  }
 
  if (!pplayer || (city_owner(pcity) == pplayer)) {
    /* Correct owner */
    return pcity;
  }
 
  return nullptr;
}
 
/*******************************************************************/
struct unit *player_unit_by_number(const struct player *pplayer, int unit_id)
{
  /* We call idex directly. Should use game_unit_by_number() instead? */
  struct unit *punit = idex_lookup_unit(&wld, unit_id);
 
  if (!punit) {
    return nullptr;
  }
 
  if (!pplayer || (unit_owner(punit) == pplayer)) {
    /* Correct owner */
    return punit;
  }
 
  return nullptr;
}
 
/*******************************************************************/
bool player_in_city_map(const struct player *pplayer,
                        const struct tile *ptile)
{
  const struct civ_map *nmap = &(wld.map);
 
  city_tile_iterate(nmap, CITY_MAP_MAX_RADIUS_SQ, ptile, ptile1) {
    struct city *pcity = tile_city(ptile1);
 
    if (pcity
        && (pplayer == nullptr || city_owner(pcity) == pplayer)
        && city_map_radius_sq_get(pcity) >= sq_map_distance(ptile,
                                                            ptile1)) {
      return TRUE;
    }
  } city_tile_iterate_end;
 
  return FALSE;
}
 
/*******************************************************************/
int num_known_tech_with_flag(const struct player *pplayer,
                             enum tech_flag_id flag)
{
  return research_get(pplayer)->num_known_tech_with_flag[flag];
}
 
/*******************************************************************/
int player_get_expected_income(const struct player *pplayer)
{
  int income = 0;
 
  /* City income/expenses. */
  city_list_iterate(pplayer->cities, pcity) {
    /* Gold suplus accounts for imcome plus building and unit upkeep. */
    income += pcity->surplus[O_GOLD];
 
    /* Gold upkeep for buildings and units is defined by the setting
     * 'game.info.gold_upkeep_style':
     * GOLD_UPKEEP_CITY: Cities pay for buildings and units (this is
     *                   included in pcity->surplus[O_GOLD]).
     * GOLD_UPKEEP_MIXED: Cities pay only for buildings; the nation pays
     *                    for units.
     * GOLD_UPKEEP_NATION: The nation pays for buildings and units. */
    switch (game.info.gold_upkeep_style) {
    case GOLD_UPKEEP_CITY:
      break;
    case GOLD_UPKEEP_NATION:
      /* Nation pays for buildings (and units). */
      income -= city_total_impr_gold_upkeep(pcity);
      fc__fallthrough; /* No break. */
    case GOLD_UPKEEP_MIXED:
      /* Nation pays for units. */
      income -= city_total_unit_gold_upkeep(pcity);
      break;
    }
 
    /* Capitalization income. */
    if (city_production_has_flag(pcity, IF_GOLD)) {
      income += pcity->shield_stock + pcity->surplus[O_SHIELD];
    }
  } city_list_iterate_end;
 
  return income;
}
 
/*******************************************************************/
bool player_knows_techs_with_flag(const struct player *pplayer,
                                  enum tech_flag_id flag)
{
  return num_known_tech_with_flag(pplayer, flag) > 0;
}
 
/*******************************************************************/
struct city *player_primary_capital(const struct player *pplayer)
{
  struct city *capital;
 
  if (!pplayer) {
    /* The client depends on this behavior in some places. */
    return nullptr;
  }
 
  capital = player_city_by_number(pplayer, pplayer->primary_capital_id);
 
  return capital;
}
 
/*******************************************************************/
const char *love_text(const int love)
{
  if (love <= - MAX_AI_LOVE * 90 / 100) {
    /* TRANS: These words should be adjectives which can fit in the sentence
       "The x are y towards us"
       "The Babylonians are respectful towards us" */
    return Q_("?attitude:Genocidal");
  } else if (love <= - MAX_AI_LOVE * 70 / 100) {
    return Q_("?attitude:Belligerent");
  } else if (love <= - MAX_AI_LOVE * 50 / 100) {
    return Q_("?attitude:Hostile");
  } else if (love <= - MAX_AI_LOVE * 25 / 100) {
    return Q_("?attitude:Uncooperative");
  } else if (love <= - MAX_AI_LOVE * 10 / 100) {
    return Q_("?attitude:Uneasy");
  } else if (love <= MAX_AI_LOVE * 10 / 100) {
    return Q_("?attitude:Neutral");
  } else if (love <= MAX_AI_LOVE * 25 / 100) {
    return Q_("?attitude:Respectful");
  } else if (love <= MAX_AI_LOVE * 50 / 100) {
    return Q_("?attitude:Helpful");
  } else if (love <= MAX_AI_LOVE * 70 / 100) {
    return Q_("?attitude:Enthusiastic");
  } else if (love <= MAX_AI_LOVE * 90 / 100) {
    return Q_("?attitude:Admiring");
  } else {
    fc_assert(love > MAX_AI_LOVE * 90 / 100);
    return Q_("?attitude:Worshipful");
  }
}
 
/*******************************************************************/
bool pplayers_at_war(const struct player *pplayer,
                     const struct player *pplayer2)
{
  enum diplstate_type ds;
 
  if (pplayer == nullptr || pplayer2 == nullptr) {
    return TRUE;
  }
 
  if (pplayer == pplayer2) {
    return FALSE;
  }
 
  ds = player_diplstate_get(pplayer, pplayer2)->type;
 
  return ds == DS_WAR || ds == DS_NO_CONTACT;
}
 
/*******************************************************************/
bool pplayers_allied(const struct player *pplayer,
                     const struct player *pplayer2)
{
  enum diplstate_type ds;
 
  if (!pplayer || !pplayer2) {
    return FALSE;
  }
 
  if (pplayer == pplayer2) {
    return TRUE;
  }
 
  ds = player_diplstate_get(pplayer, pplayer2)->type;
 
  return (ds == DS_ALLIANCE || ds == DS_TEAM);
}
 
/*******************************************************************/
bool pplayers_in_peace(const struct player *pplayer,
                       const struct player *pplayer2)
{
  enum diplstate_type ds = player_diplstate_get(pplayer, pplayer2)->type;
 
  if (pplayer == pplayer2) {
    return TRUE;
  }
 
  return (ds == DS_PEACE || ds == DS_ALLIANCE
          || ds == DS_ARMISTICE || ds == DS_TEAM);
}
 
/*******************************************************************/
bool players_non_invade(const struct player *pplayer1,
                        const struct player *pplayer2)
{
  if (pplayer1 == pplayer2 || !pplayer1 || !pplayer2) {
    return FALSE;
  }
 
  /* Movement during armistice is allowed so that player can withdraw
     units deeper inside opponent territory. */
 
  return player_diplstate_get(pplayer1, pplayer2)->type == DS_PEACE;
}
 
/*******************************************************************/
bool pplayers_non_attack(const struct player *pplayer,
                         const struct player *pplayer2)
{
  enum diplstate_type ds;
 
  if (pplayer == pplayer2) {
    return FALSE;
  }
 
  ds = player_diplstate_get(pplayer, pplayer2)->type;
 
  return (ds == DS_PEACE || ds == DS_CEASEFIRE || ds == DS_ARMISTICE);
}
 
/*******************************************************************/
bool players_on_same_team(const struct player *pplayer1,
                          const struct player *pplayer2)
{
  return pplayer1->team == pplayer2->team;
}
 
/*******************************************************************/
bool gives_shared_vision(const struct player *me, const struct player *them)
{
  return BV_ISSET(me->gives_shared_vision, player_index(them));
}
 
/*******************************************************************/
bool gives_shared_tiles(const struct player *me, const struct player *them)
{
  return BV_ISSET(me->gives_shared_tiles, player_index(them));
}
 
/*******************************************************************/
bool are_diplstates_equal(const struct player_diplstate *pds1,
                          const struct player_diplstate *pds2)
{
  return (pds1->type == pds2->type && pds1->turns_left == pds2->turns_left
          && pds1->has_reason_to_cancel == pds2->has_reason_to_cancel
          && pds1->contact_turns_left == pds2->contact_turns_left);
}
 
/*******************************************************************/
bool is_diplrel_between(const struct player *player1,
                        const struct player *player2,
                        int diplrel)
{
  fc_assert(player1 != nullptr);
  fc_assert(player2 != nullptr);
 
  /* No relationship to it self. */
  if (player1 == player2 && diplrel != DRO_FOREIGN) {
    return FALSE;
  }
 
  if (diplrel < DS_LAST) {
    return player_diplstate_get(player1, player2)->type == diplrel;
  }
 
  switch (diplrel) {
  case DRO_GIVES_SHARED_VISION:
    return gives_shared_vision(player1, player2);
  case DRO_RECEIVES_SHARED_VISION:
    return gives_shared_vision(player2, player1);
  case DRO_HOSTS_EMBASSY:
    return player_has_embassy(player2, player1);
  case DRO_HOSTS_TEAM_EMBASSY:
    return team_has_embassy(player2->team, player1);
  case DRO_HAS_EMBASSY:
    return player_has_embassy(player1, player2);
  case DRO_HAS_TEAM_EMBASSY:
    return team_has_embassy(player1->team, player2);
  case DRO_HOSTS_REAL_EMBASSY:
    return player_has_real_embassy(player2, player1);
  case DRO_HAS_REAL_EMBASSY:
    return player_has_real_embassy(player1, player2);
  case DRO_HAS_CASUS_BELLI:
    return 0 < player_diplstate_get(player1, player2)->has_reason_to_cancel;
  case DRO_PROVIDED_CASUS_BELLI:
    return 0 < player_diplstate_get(player2, player1)->has_reason_to_cancel;
  case DRO_FOREIGN:
    return player1 != player2;
  }
 
  fc_assert_msg(FALSE, "diplrel_between(): invalid diplrel number %d.",
                diplrel);
 
  return FALSE;
}
 
/*******************************************************************/
bool is_diplrel_to_other(const struct player *pplayer, int diplrel)
{
  fc_assert(pplayer != nullptr);
 
  players_iterate_alive(oplayer) {
    if (oplayer == pplayer) {
      continue;
    }
    if (is_diplrel_between(pplayer, oplayer, diplrel)) {
      return TRUE;
    }
  } players_iterate_alive_end;
  return FALSE;
}
 
/*******************************************************************/
int diplrel_by_rule_name(const char *value)
{
  /* Look for asymmetric diplomatic relations */
  int diplrel = diplrel_other_by_name(value, fc_strcasecmp);
 
  if (diplrel != diplrel_other_invalid()) {
    return diplrel;
  }
 
  /* Look for symmetric diplomatic relations */
  diplrel = diplstate_type_by_name(value, fc_strcasecmp);
 
  /*
   * Make sure DS_LAST isn't returned as DS_LAST is the first diplrel_other.
   *
   * Can't happend now. This is in case that changes in the future. */
  fc_assert_ret_val(diplrel != DS_LAST, diplrel_other_invalid());
 
  /*
   * Make sure that diplrel_other_invalid() is returned.
   *
   * Can't happen now. At the moment dpilrel_asym_invalid() is the same as
   * diplstate_type_invalid(). This is in case that changes in the future.
   */
  if (diplrel != diplstate_type_invalid()) {
    return diplrel;
  }
 
  return diplrel_other_invalid();
}
 
/*******************************************************************/
const char *diplrel_rule_name(int value)
{
  if (value < DS_LAST) {
    return diplstate_type_name(value);
  } else {
    return diplrel_other_name(value);
  }
}
 
/*******************************************************************/
const char *diplrel_name_translation(int value)
{
  if (value < DS_LAST) {
    return diplstate_type_translated_name(value);
  } else {
    return _(diplrel_other_name(value));
  }
}
 
/**************************************************************************
  Return the Casus Belli range when offender performs paction to tgt_plr
  at tgt_tile and the outcome is outcome.
**************************************************************************/
enum casus_belli_range casus_belli_range_for(const struct player *offender,
                                             const struct unit_type *off_ut,
                                             const struct player *tgt_plr,
                                             const enum effect_type outcome,
                                             const struct action *paction,
                                             const struct tile *tgt_tile)
{
  int casus_belli_amount;
 
  /* The victim gets a casus belli if CASUS_BELLI_VICTIM or above. Everyone
   * gets a casus belli if CASUS_BELLI_OUTRAGE or above. */
  casus_belli_amount =
      get_target_bonus_effects(nullptr,
                               &(const struct req_context) {
                                 .player = offender,
                                 .city = tile_city(tgt_tile),
                                 .tile = tgt_tile,
                                 .unittype = off_ut,
                                 .action = paction,
                               },
                               &(const struct req_context) {
                                 .player = tgt_plr,
                               },
                               outcome);
 
  if (casus_belli_amount >= CASUS_BELLI_OUTRAGE) {
    /* International outrage: This isn't just between the offender and the
     * victim. */
    return CBR_INTERNATIONAL_OUTRAGE;
  }
 
  if (casus_belli_amount >= CASUS_BELLI_VICTIM) {
    /* In this situation the specified action provides a casus belli
     * against the actor. */
    return CBR_VICTIM_ONLY;
  }
 
  return CBR_NONE;
}
 
/* The number of mutually exclusive requirement sets that
 * diplrel_mess_gen() creates for the DiplRel requirement type. */
#define DIPLREL_MESS_SIZE (3 + (DRO_LAST * (5 + 4 + 3 + 2 + 1)))
 
/*******************************************************************/
static bv_diplrel_all_reqs *diplrel_mess_gen(void)
{
  /* The ranges supported by the DiplRel requiremnt type. */
  const enum req_range legal_ranges[] = {
    REQ_RANGE_LOCAL,
    REQ_RANGE_PLAYER,
    REQ_RANGE_ALLIANCE,
    REQ_RANGE_TEAM,
    REQ_RANGE_WORLD
  };
 
  /* Iterators. */
  int rel;
  int i;
  int j;
 
  /* Storage for the mutually exclusive requirement sets. */
  bv_diplrel_all_reqs *mess = fc_malloc(DIPLREL_MESS_SIZE
                                        * sizeof(bv_diplrel_all_reqs));
 
  /* Position in mess. */
  int mess_pos = 0;
 
  /* The first mutually exclusive set is about local diplstate. */
  BV_CLR_ALL(mess[mess_pos]);
 
  /* It is not possible to have more than one diplstate to a nation. */
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DS_ARMISTICE, REQ_RANGE_LOCAL, TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DS_WAR, REQ_RANGE_LOCAL, TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DS_CEASEFIRE, REQ_RANGE_LOCAL, TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DS_PEACE, REQ_RANGE_LOCAL, TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DS_ALLIANCE, REQ_RANGE_LOCAL, TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DS_NO_CONTACT, REQ_RANGE_LOCAL, TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DS_TEAM, REQ_RANGE_LOCAL, TRUE));
 
  /* It is not possible to have a diplstate to your self. */
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DRO_FOREIGN, REQ_RANGE_LOCAL, FALSE));
 
  mess_pos++;
 
  /* Having a real embassy excludes not having an embassy. */
  BV_CLR_ALL(mess[mess_pos]);
 
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DRO_HAS_REAL_EMBASSY, REQ_RANGE_LOCAL,
                                  TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DRO_HAS_EMBASSY, REQ_RANGE_LOCAL,
                                  FALSE));
 
  mess_pos++;
 
  /* Hosting a real embassy excludes not hosting an embassy. */
  BV_CLR_ALL(mess[mess_pos]);
 
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DRO_HOSTS_REAL_EMBASSY, REQ_RANGE_LOCAL,
                                  TRUE));
  BV_SET(mess[mess_pos],
         requirement_diplrel_ereq(DRO_HOSTS_EMBASSY, REQ_RANGE_LOCAL,
                                  FALSE));
 
  mess_pos++;
 
  /* Loop over diplstate_type and diplrel_other. */
  for (rel = 0; rel < DRO_LAST; rel++) {
    /* The presence of a DiplRel at a more local range proves that it can't
     * be absent in a more global range. (The alliance range includes the
     * Team range) */
    for (i = 0; i < 5; i++) {
      for (j = i; j < 5; j++) {
        BV_CLR_ALL(mess[mess_pos]);
 
        BV_SET(mess[mess_pos],
               requirement_diplrel_ereq(rel, legal_ranges[i], TRUE));
        BV_SET(mess[mess_pos],
               requirement_diplrel_ereq(rel, legal_ranges[j], FALSE));
 
        mess_pos++;
      }
    }
  }
 
  /* No uninitialized element exists. */
  fc_assert(mess_pos == DIPLREL_MESS_SIZE);
 
  return mess;
}
 
/* An array of mutually exclusive requirement sets for the DiplRel
 * requirement type. Is initialized the first time diplrel_mess_get() is
 * called. */
static bv_diplrel_all_reqs *diplrel_mess = nullptr;
 
/*******************************************************************/
static bv_diplrel_all_reqs *diplrel_mess_get(void)
{
  if (diplrel_mess == nullptr) {
    /* This is the first call. Initialize diplrel_mess. */
    diplrel_mess = diplrel_mess_gen();
  }
 
  return diplrel_mess;
}
 
/*******************************************************************/
void diplrel_mess_close(void)
{
  if (diplrel_mess != nullptr) {
    free(diplrel_mess);
    diplrel_mess = nullptr;
  }
}
 
/*******************************************************************/
bv_diplrel_all_reqs diplrel_req_contradicts(const struct requirement *req)
{
  int diplrel_req_num;
  bv_diplrel_all_reqs *mess;
  bv_diplrel_all_reqs known;
  int set;
 
  /* Nothing is known to contradict the requirement yet. */
  BV_CLR_ALL(known);
 
  if (!(req->source.kind == VUT_DIPLREL
        || req->source.kind == VUT_DIPLREL_TILE
        || req->source.kind == VUT_DIPLREL_TILE_O
        || req->source.kind == VUT_DIPLREL_UNITANY
        || req->source.kind == VUT_DIPLREL_UNITANY_O)) {
    /* No known contradiction of a requirement of any other kind. */
    fc_assert(req->source.kind == VUT_DIPLREL
              || req->source.kind == VUT_DIPLREL_TILE
              || req->source.kind == VUT_DIPLREL_TILE_O
              || req->source.kind == VUT_DIPLREL_UNITANY
              || req->source.kind == VUT_DIPLREL_UNITANY_O);
 
    return known;
  }
 
  /* Convert the requirement to its position in the enumeration of all
   * DiplRel requirements. */
  diplrel_req_num = requirement_diplrel_ereq(req->source.value.diplrel,
                                             req->range, req->present);
 
  /* Get the mutually exclusive requirement sets for DiplRel. */
  mess = diplrel_mess_get();
 
  /* Add all known contradictions. */
  for (set = 0; set < DIPLREL_MESS_SIZE; set++) {
    if (BV_ISSET(mess[set], diplrel_req_num)) {
      /* The requirement req is mentioned in the set. It is therefore known
       * that all other requirements in the set contradicts it. They should
       * therefore be added to the known contradictions. */
      BV_SET_ALL_FROM(known, mess[set]);
    }
  }
 
  /* The requirement isn't self contradicting. It was set by the mutually
   * exclusive requirement sets that mentioned it. Remove it. */
  BV_CLR(known, diplrel_req_num);
 
  return known;
}
 
/*******************************************************************/
int player_in_territory(const struct player *pplayer,
                        const struct player *pplayer2)
{
  int in_territory = 0;
 
  /* This algorithm should work at server or client. It only returns the
   * number of visible units (a unit can potentially hide inside the
   * transport of a different player).
   *
   * Note this may be quite slow. An even slower alternative is to iterate
   * over the entire map, checking all units inside the player's territory
   * to see if they're owned by the enemy. */
  unit_list_iterate(pplayer2->units, punit) {
    /* Get the owner of the tile/territory. */
    struct player *owner = tile_owner(unit_tile(punit));
 
    if (owner == pplayer && can_player_see_unit(pplayer, punit)) {
      /* Found one! */
      in_territory++;
    }
  } unit_list_iterate_end;
 
  return in_territory;
}
 
/*******************************************************************/
bool is_valid_username(const char *name)
{
  return (strlen(name) > 0
          && !fc_isdigit(name[0])
          && is_ascii_name(name)
          && fc_strcasecmp(name, ANON_USER_NAME) != 0);
}
 
/*******************************************************************/
bool is_settable_ai_level(enum ai_level level)
{
  if (level == AI_LEVEL_AWAY) {
    /* Cannot set away level for AI */
    return FALSE;
  }
 
  return TRUE;
}
 
/*******************************************************************/
int number_of_ai_levels(void)
{
  return AI_LEVEL_COUNT - 1; /* AI_LEVEL_AWAY is not real AI */
}
 
/*******************************************************************/
void *player_ai_data(const struct player *pplayer, const struct ai_type *ai)
{
  return pplayer->server.ais[ai_type_number(ai)];
}
 
/*******************************************************************/
void player_set_ai_data(struct player *pplayer, const struct ai_type *ai,
                        void *data)
{
  pplayer->server.ais[ai_type_number(ai)] = data;
}
 
/*******************************************************************/
int player_multiplier_value(const struct player *pplayer,
                            const struct multiplier *pmul)
{
  return pplayer->multipliers[multiplier_index(pmul)].value;
}
 
/*******************************************************************/
int player_multiplier_effect_value(const struct player *pplayer,
                                   const struct multiplier *pmul)
{
  return (player_multiplier_value(pplayer, pmul) + pmul->offset)
    * pmul->factor;
}
 
/*******************************************************************/
int player_multiplier_target_value(const struct player *pplayer,
                                   const struct multiplier *pmul)
{
  return pplayer->multipliers[multiplier_index(pmul)].target;
}
 
/*******************************************************************/
bool player_has_flag(const struct player *pplayer, enum plr_flag_id flag)
{
  return BV_ISSET(pplayer->flags, flag);
}
 
/*******************************************************************/
bool player_has_state(const struct player *pplayer,
                      enum plrstate_type state)
{
  switch (state) {
  case PLRS_BARBARIAN:
    return is_barbarian(pplayer);
  case PLRS_HAS_CAPITAL:
    return player_primary_capital(pplayer) != nullptr;
  case PLRS_LAST:
    fc_assert(state != PLRS_LAST);
    break;
  }
 
  fc_assert(plrstate_type_is_valid(state));
  return FALSE;
}
 
/*******************************************************************/
bool player_can_do_action_result(struct player *pplayer,
                                 enum action_result result)
{
  action_by_result_iterate(paction, result) {
    action_enabler_list_iterate(action_enablers_for_action(action_id(paction)),
                                penabler) {
      struct universal u[2] = {
        {.kind = VUT_GOVERNMENT, .value = {.govern = (pplayer->government)}},
        {.kind = VUT_MINCITIES,  .value = {.min_cities = (city_list_size(pplayer->cities))}},
      };
 
      if (!universals_mean_unfulfilled(&(penabler->actor_reqs), u, 2)) {
        return TRUE;
      }
    } action_enabler_list_iterate_end;
  } action_by_result_iterate_end;
 
  return FALSE;
}