aiferry.c

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/***********************************************************************
 Freeciv - Copyright (C) 2004 - The Freeciv Project
   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 "log.h"
 
/* common */
#include "game.h"
#include "movement.h"
#include "unit.h"
#include "unitlist.h"
 
/* aicore */
#include "path_finding.h"
#include "pf_tools.h"
 
/* server/advisors */
#include "advgoto.h"
#include "autoexplorer.h"
#include "autosettlers.h"
 
/* server */
#include "hand_gen.h"
#include "srv_log.h"
#include "unithand.h"
#include "unittools.h"
 
/* server/advisors */
#include "advdata.h"
 
/* ai */
#include "handicaps.h"
 
/* ai/default */
#include "aiguard.h"
#include "aitools.h"
#include "daicity.h"
#include "daidata.h"
#include "daiplayer.h"
 
#include "aiferry.h"
 
 
/* =================== constants with special meaning =================== */
 
/* 
 * This one is used only by ferryboats in ai.passenger field 
 */
#define FERRY_AVAILABLE     (-1)  /* Boat is looking for a passenger */
#define FERRY_ABANDON_BOSS  (-2)  /* Passenger is assigned for boat, but boat
                                   * might take another passenger. Probably
                                   * passenger already left the boat*/
 
/* 
 * The below is used only by passengers in ai.ferryboat field 
 */ 
#define FERRY_WANTED       (-1)   /* Needs a boat */
#define FERRY_NONE         0      /* Has no boat and doesn't need one */
 
 
/* =================== group log levels, debug options ================= */
 
/* Logging in ferry management functions */
#define LOGLEVEL_FERRY LOG_DEBUG
/* Logging in go_by_boat functions */
#define LOGLEVEL_GOBYBOAT LOG_DEBUG
/* Logging in find_ferry functions */
#define LOGLEVEL_FINDFERRY LOG_DEBUG
/* Extra consistency checks */
#ifdef FREECIV_DEBUG
#define LOGLEVEL_FERRY_STATS LOG_NORMAL
#endif
 
 
/* ========= managing statistics and boat/passenger assignments ======== */
 
/**********************************************************************/
void aiferry_init_stats(struct ai_type *ait, struct player *pplayer)
{
  /* def_ai_player_data() instead of dai_plr_data_get() is deliberate.
     We are only initializing player data structures and dai_plr_data_get()
     would try to use it uninitialized. We are only setting values to
     data structure, not reading them, so we have no need for extra
     arrangements dai_plr_data_get() would do compared to def_ai_player_data()
  */
  struct ai_plr *ai = def_ai_player_data(pplayer, ait);
 
  ai->stats.passengers = 0;
  ai->stats.boats = 0;
  ai->stats.available_boats = 0;
 
  unit_list_iterate(pplayer->units, punit) {
    struct unit_ai *unit_data = def_ai_unit_data(punit, ait);
 
    if (dai_is_ferry(punit, ait)) {
      ai->stats.boats++;
      if (unit_data->passenger == FERRY_AVAILABLE) {
        ai->stats.available_boats++;
      }
    }
    if (unit_data->ferryboat == FERRY_WANTED) {
      UNIT_LOG(LOG_DEBUG, punit, "wants a boat.");
      ai->stats.passengers++;
    }
  } unit_list_iterate_end;
}
 
/**********************************************************************/
#ifdef LOGLEVEL_FERRY_STATS
static void aiferry_print_stats(struct ai_type *ait, struct player *pplayer)
{
  struct ai_plr *ai = dai_plr_data_get(ait, pplayer, NULL);
  int n = 1;
 
  log_base(LOGLEVEL_FERRY_STATS, "Boat stats for %s[%d]",
           player_name(pplayer), player_number(pplayer));
  log_base(LOGLEVEL_FERRY_STATS, "Registered: %d free out of total %d",
           ai->stats.available_boats, ai->stats.boats);
  unit_list_iterate(pplayer->units, punit) {
    if (dai_is_ferry(punit, ait)) {
      log_base(LOGLEVEL_FERRY_STATS, "#%d. %s[%d], psngr=%d", n,
               unit_rule_name(punit), punit->id,
               def_ai_unit_data(punit, ait)->passenger);
      n++;
    }
  } unit_list_iterate_end;
}
#endif /* LOGLEVEL_FERRY_STATS */
 
/**********************************************************************/
bool dai_is_ferry_type(const struct unit_type *pferry, struct ai_type *ait)
{
  struct unit_type_ai *utai = utype_ai_data(pferry, ait);
 
  return utai->ferry;
}
 
/**********************************************************************/
bool dai_is_ferry(struct unit *pferry, struct ai_type *ait)
{
  return dai_is_ferry_type(unit_type_get(pferry), ait);
}
 
/**********************************************************************/
void dai_ferry_init_ferry(struct ai_type *ait, struct unit *ferry)
{
  if (dai_is_ferry(ferry, ait)) {
    bool caller_closes;
    struct player *pplayer = unit_owner(ferry);
    struct unit_ai *unit_data = def_ai_unit_data(ferry, ait);
    struct ai_plr *ai = dai_plr_data_get(ait, pplayer,
                                         &caller_closes);
 
    unit_data->passenger = FERRY_AVAILABLE;
    ai->stats.boats++;
    ai->stats.available_boats++;
 
    if (caller_closes) {
      dai_data_phase_finished(ait, pplayer);
    }
  }
}
 
/**********************************************************************/
void dai_ferry_transformed(struct ai_type *ait, struct unit *ferry,
                           const struct unit_type *old)
{
  bool old_f = dai_is_ferry_type(old, ait);
  bool new_f = dai_is_ferry(ferry, ait);
 
  if (old_f && !new_f) {
    struct ai_plr *ai = dai_plr_data_get(ait, unit_owner(ferry), NULL);
    struct unit_ai *unit_data = def_ai_unit_data(ferry, ait);
 
    ai->stats.boats--;
 
    if (unit_data->passenger == FERRY_AVAILABLE) {
      ai->stats.available_boats--;
    } else if (unit_data->passenger > 0) {
      struct unit *passenger = game_unit_by_number(unit_data->passenger);
 
      if (passenger != NULL) {
        aiferry_clear_boat(ait, passenger);
      }
    }
  } else if (!old_f && new_f) {
    struct ai_plr *ai = dai_plr_data_get(ait, unit_owner(ferry), NULL);
 
    ai->stats.boats++;
    ai->stats.available_boats++;
  }
}
 
/**********************************************************************/
void dai_ferry_lost(struct ai_type *ait, struct unit *punit)
{
  /* Ignore virtual units. */
  if (punit->id != 0 && is_ai_data_phase_open(ait, unit_owner(punit))) {
    bool close_here;
    struct unit_ai *unit_data = def_ai_unit_data(punit, ait);
    struct player *pplayer = unit_owner(punit);
    struct ai_plr *ai = dai_plr_data_get(ait, pplayer, &close_here);
 
    if (dai_is_ferry(punit, ait)) {
      ai->stats.boats--;
      if (unit_data->passenger == FERRY_AVAILABLE) {
        ai->stats.available_boats--;
      }
    } else {
      /* Not a ferry */
      if (unit_data->ferryboat > 0) {
        aiferry_clear_boat(ait, punit);
      }
    }
 
    if (close_here) {
      dai_data_phase_finished(ait, pplayer);
    }
  }
}
 
/**********************************************************************/
void aiferry_clear_boat(struct ai_type *ait, struct unit *punit)
{
  struct unit_ai *unit_data = def_ai_unit_data(punit, ait);
 
  if (unit_data->ferryboat == FERRY_WANTED) {
    struct player *pplayer = unit_owner(punit);
 
    if (is_ai_data_phase_open(ait, pplayer)) {
      struct ai_plr *ai = dai_plr_data_get(ait, pplayer, NULL);
 
      ai->stats.passengers--;
    }
  } else {
    struct unit *ferry = game_unit_by_number(unit_data->ferryboat);
 
    if (ferry) {
      struct unit_ai *ferry_data = def_ai_unit_data(ferry, ait);
 
      if (ferry_data->passenger == punit->id) {
        /* punit doesn't want us anymore */
        struct player *pplayer = unit_owner(ferry);
 
        if (is_ai_data_phase_open(ait, pplayer)) {
          dai_plr_data_get(ait, pplayer, NULL)->stats.available_boats++;
        }
        ferry_data->passenger = FERRY_AVAILABLE;
      }
    }
  }
 
  unit_data->ferryboat = FERRY_NONE;
}
 
/**********************************************************************/
static void aiferry_request_boat(struct ai_type *ait, struct unit *punit)
{
  struct ai_plr *ai = dai_plr_data_get(ait, unit_owner(punit), NULL);
  struct unit_ai *unit_data = def_ai_unit_data(punit, ait);
 
  /* First clear the previous assignments (just in case there are). 
   * Subtract virtual units or already counted */
  if ((punit->id == 0) || 
      ((ai->stats.passengers > 0) && 
       (unit_data->ferryboat == FERRY_WANTED))) {
    aiferry_clear_boat(ait, punit);
  }
 
  /* Now add ourselves to the list of potential passengers */
  ai->stats.passengers++;
  UNIT_LOG(LOG_DEBUG, punit, "requests a boat (total passengers=%d).",
           ai->stats.passengers);
  unit_data->ferryboat = FERRY_WANTED;
 
  /* Lastly, wait for ferry. */
  unit_data->done = TRUE;
}
 
/**********************************************************************/
static void aiferry_psngr_meet_boat(struct ai_type *ait,
                                    struct unit *punit, struct unit *pferry)
{
  struct unit_ai *ferry_data = def_ai_unit_data(pferry, ait);
  struct player *ferry_owner = unit_owner(pferry);
 
  fc_assert_ret(unit_owner(punit) == ferry_owner);
 
  /* First delete the unit from the list of passengers and 
   * release its previous ferry */
  aiferry_clear_boat(ait, punit);
 
  /* If ferry was available, update the stats */
  if (ferry_data->passenger == FERRY_AVAILABLE) {
    dai_plr_data_get(ait, ferry_owner, NULL)->stats.available_boats--;
  }
 
  /* Exchange the phone numbers */
  def_ai_unit_data(punit, ait)->ferryboat = pferry->id;
  ferry_data->passenger = punit->id;
}
 
/**********************************************************************/
static void aiferry_make_available(struct ai_type *ait, struct unit *pferry)
{
  struct unit_ai *ferry_data = def_ai_unit_data(pferry, ait);
 
  if (ferry_data->passenger != FERRY_AVAILABLE) {
    dai_plr_data_get(ait, unit_owner(pferry), NULL)->stats.available_boats++;
    ferry_data->passenger = FERRY_AVAILABLE;
  }
}
 
/**********************************************************************/
int aiferry_avail_boats(struct ai_type *ait, struct player *pplayer)
{
  struct ai_plr *ai = dai_plr_data_get(ait, pplayer, NULL);
 
  /* To developer: Switch this checking on when testing some new 
   * ferry code. */
#ifdef LOGLEVEL_FERRY_STATS
  int boats = 0;
 
  unit_list_iterate(pplayer->units, punit) {
    if (dai_is_ferry(punit, ait)
        && def_ai_unit_data(punit, ait)->passenger == FERRY_AVAILABLE) {
      boats++;
    }
  } unit_list_iterate_end;
 
  if (boats != ai->stats.available_boats) {
    log_error("Player[%d] in turn %d: boats miscounted.",
              player_number(pplayer), game.info.turn);
    aiferry_print_stats(ait, pplayer);
  }
#endif /* LOGLEVEL_FERRY_STATS */
 
  return ai->stats.available_boats;
}
 
/* ================== functions to find a boat ========================= */
 
/**********************************************************************/
static unsigned combined_land_sea_move(const struct tile *src_tile,
                                       enum pf_move_scope src_scope,
                                       const struct tile *tgt_tile,
                                       enum pf_move_scope dst_scope,
                                       const struct pf_parameter *param)
{
  unsigned move_cost;
 
  if (!((PF_MS_NATIVE | PF_MS_CITY) & dst_scope)) {
    /* Any-to-Sea */
    move_cost = 0;
  } else if (!((PF_MS_NATIVE | PF_MS_CITY) & src_scope)) {
    /* Sea-to-Land */
    move_cost = PF_IMPOSSIBLE_MC;
  } else {
    /* Land-to-Land */
    move_cost = map_move_cost(&(wld.map), param->owner, param->utype,
                              src_tile, tgt_tile);
  }
 
  return move_cost;
}
 
/**********************************************************************/
static unsigned sea_move(const struct tile *ptile, enum known_type known,
                         const struct pf_parameter *param)
{
  if (is_ocean_tile(ptile)) {
    /* Approximately TURN_FACTOR / average ferry move rate 
     * we can pass a better guess of the move rate through param->data
     * but we don't know which boat we will find out there */
    return SINGLE_MOVE * PF_TURN_FACTOR / 12;
  } else {
    return 0;
  }
}
 
/**********************************************************************/
bool is_boat_free(struct ai_type *ait, struct unit *boat,
                  struct unit *punit, int cap)
{
  /* - Only transporters capable of transporting this unit are eligible.
   * - Units with orders are skipped (the AI doesn't control units with
   *   orders).
   * - Only boats that we own are eligible.
   * - Only available boats or boats that are already dedicated to this unit
   *   are eligible.
   * - Only boats with enough remaining capacity are eligible.
   * - Only units that can travel at sea are eligible.
   * - Units that require fuel, except "Coast" ones, or lose hitpoints are
   *   not eligible.
   */
  struct unit_class *ferry_class = unit_class_get(boat);
  const struct unit_type *ferry_type = unit_type_get(boat);
  struct unit_ai *boat_data = def_ai_unit_data(boat, ait);
 
  return (can_unit_transport(boat, punit)
          && !unit_has_orders(boat)
          && unit_owner(boat) == unit_owner(punit)
          && (boat_data->passenger == FERRY_AVAILABLE
              || boat_data->passenger == punit->id)
          && (get_transporter_capacity(boat)
              - get_transporter_occupancy(boat) >= cap)
          && ferry_class->adv.sea_move != MOVE_NONE
          && !is_losing_hp(boat)
          && (ferry_type->fuel == 0 || utype_has_flag(ferry_type, UTYF_COAST)));
}
 
/**********************************************************************/
bool is_boss_of_boat(struct ai_type *ait, struct unit *punit)
{
  if (!unit_transported(punit)) {
    /* Not even in boat */
    return FALSE;
  }
 
  if (unit_transported(punit)
      && def_ai_unit_data(unit_transport_get(punit), ait)->passenger
         == punit->id) {
    return TRUE;
  }
 
  return FALSE;
}
 
/**********************************************************************/
int aiferry_find_boat(struct ai_type *ait, struct unit *punit,
                      int cap, struct pf_path **path)
{
  int best_turns = FC_INFINITY;
  int best_id = 0;
  struct pf_parameter param;
  struct pf_map *search_map;
  struct player *pplayer = unit_owner(punit);
  const struct civ_map *nmap = &(wld.map);
 
  /* currently assigned ferry */
  int ferryboat = def_ai_unit_data(punit, ait)->ferryboat;
 
  /* We may end calling pf_destroy_path for *path if it's not NULL.
   * Most likely you are passing garbage or path you don't want
   * destroyed if this assertion fails.
   * Don't try to be clever and pass 'fallback' path that will be returned
   * if no path is found. Instead check for NULL return value and then
   * use fallback path in calling function. */
  fc_assert_ret_val(path == NULL || *path == NULL, 0);
 
  fc_assert_ret_val(0 < ferryboat
                    || FERRY_NONE == ferryboat
                    || FERRY_WANTED == ferryboat, 0);
  UNIT_LOG(LOGLEVEL_FINDFERRY, punit, "asked aiferry_find_boat for a boat");
 
  if (aiferry_avail_boats(ait, pplayer) <= 0 
      && ferryboat <= 0) {
    /* No boats to be found (the second check is to ensure that we are not 
     * the ones keeping the last boat busy) */
    return 0;
  }
 
  pft_fill_unit_parameter(&param, nmap, punit);
  param.omniscience = !has_handicap(pplayer, H_MAP);
  param.get_TB = no_fights_or_unknown;
  param.get_EC = sea_move;
  param.get_MC = combined_land_sea_move;
  param.ignore_none_scopes = FALSE;
 
  search_map = pf_map_new(&param);
 
  pf_map_positions_iterate(search_map, pos, TRUE) {
   /* Should this be !can_unit_exist_at_tile() instead of is_ocean() some day?
    * That would allow special units to wade in shallow coast waters to meet
    * ferry where deep sea starts. */
    int radius = (is_ocean_tile(pos.tile) ? 1 : 0);
 
    if (pos.turn + pos.total_EC/PF_TURN_FACTOR > best_turns) {
      /* Won't find anything better */
      /* FIXME: This condition is somewhat dodgy */
      break;
    }
    
    square_iterate(&(wld.map), pos.tile, radius, ptile) {
      unit_list_iterate(ptile->units, aunit) {
        if (is_boat_free(ait, aunit, punit, cap)) {
          /* Turns for the unit to get to rendezvous pnt */
          int u_turns = pos.turn;
          /* Turns for the boat to get to the rendezvous pnt */
          int f_turns = ((pos.total_EC / PF_TURN_FACTOR * 16 
                          - aunit->moves_left) 
                         / unit_type_get(aunit)->move_rate);
          int turns = MAX(u_turns, f_turns);
 
          if (turns < best_turns) {
            UNIT_LOG(LOGLEVEL_FINDFERRY, punit, 
                     "Found a potential boat %s[%d](%d,%d)(moves left: %d)",
                     unit_rule_name(aunit), aunit->id,
                     TILE_XY(unit_tile(aunit)), aunit->moves_left);
            if (path) {
             if (*path) {
                pf_path_destroy(*path);
              }
              *path = pf_map_iter_path(search_map);
            }
            best_turns = turns;
            best_id = aunit->id;
          }
        }
      } unit_list_iterate_end;
    } square_iterate_end;
  } pf_map_positions_iterate_end;
  pf_map_destroy(search_map);
 
  return best_id;
}
 
/**********************************************************************/
static int aiferry_find_boat_nearby(struct ai_type *ait, struct unit *punit,
                                    int cap)
{
  UNIT_LOG(LOGLEVEL_FINDFERRY, punit, "asked find_ferry_nearby for a boat");
 
  square_iterate(&(wld.map), unit_tile(punit), 1, ptile) {
    unit_list_iterate(ptile->units, aunit) {
      if (is_boat_free(ait, aunit, punit, cap)) {
        return aunit->id;
      }
    } unit_list_iterate_end;
  } square_iterate_end;
 
  return 0;
}
 
 
/* ============================= go by boat ============================== */
 
/**********************************************************************/
static void dai_activate_passengers(struct ai_type *ait, struct unit *ferry)
{
  struct player *ferry_owner = unit_owner(ferry);
  
  unit_list_iterate_safe(unit_tile(ferry)->units, aunit) {
    if (unit_transport_get(aunit) == ferry) {
      unit_activity_handling(aunit, ACTIVITY_IDLE);
      def_ai_unit_data(aunit, ait)->done = FALSE;
 
      if (unit_owner(aunit) == ferry_owner) {
        /* Move it only if it's our own. */
        dai_manage_unit(ait, ferry_owner, aunit);
      }
    }
  } unit_list_iterate_safe_end;
}
 
/**********************************************************************/
bool dai_amphibious_goto_constrained(struct ai_type *ait,
                                     struct unit *ferry,
                                     struct unit *passenger,
                                     struct tile *ptile,
                                     struct pft_amphibious *parameter)
{
  bool alive = TRUE;
  struct pf_map *pfm;
  struct pf_path *path;
  int pass_id = passenger->id;
 
  fc_assert_ret_val(is_ai(unit_owner(passenger)), TRUE);
  fc_assert_ret_val(!unit_has_orders(passenger), TRUE);
  fc_assert_ret_val(unit_tile(ferry) == unit_tile(passenger), TRUE);
 
  ptile = immediate_destination(passenger, ptile);
 
  if (same_pos(unit_tile(passenger), ptile)) {
    /* Not an error; sometimes immediate_destination instructs the unit
     * to stay here. For example, to refuel.*/
    send_unit_info(NULL, passenger);
    return TRUE;
  } else if (passenger->moves_left == 0 && ferry->moves_left == 0) {
    send_unit_info(NULL, passenger);
    return TRUE;
  }
 
  pfm = pf_map_new(&parameter->combined);
  path = pf_map_path(pfm, ptile);
 
  if (path) {
    dai_log_path(passenger, path, &parameter->combined);
    /* Sea leg */
    alive = adv_follow_path(ferry, path, ptile);
    if (alive && unit_tile(passenger) != ptile) {
      /* Ferry has stopped; it is at the landing beach or
       * has run out of movement points */
      struct tile *next_tile;
 
      if (!pf_path_advance(path, unit_tile(passenger))) {
        /* Somehow we got thrown away from our route.
         * This can happen if our movement caused alliance breakup. */
        return unit_is_alive(pass_id);
      }
      next_tile = path->positions[1].tile;
      if (!is_ocean_tile(next_tile)) {
        int ferry_id = ferry->id;
 
        UNIT_LOG(LOG_DEBUG, passenger, "Our boat has arrived "
                 "[%d](moves left: %d)", ferry->id, ferry->moves_left);
        UNIT_LOG(LOG_DEBUG, passenger, "Disembarking to (%d,%d)",
                 TILE_XY(next_tile));
        /* Land leg */
        alive = adv_follow_path(passenger, path, ptile);
        /* Movement of the passenger outside the ferry can cause also
         * ferry to die. That has happened at least when passenger
         * destroyed city cutting the civ1-style channel (cities in
         * a chain) ferry was in. */
        if (unit_is_alive(ferry_id) && 0 < ferry->moves_left
            && (!alive || unit_tile(ferry) != unit_tile(passenger))) {
          /* The passenger is no longer on the ferry,
           * and the ferry can still act.
           * Give a chance for another passenger to take command
           * of the ferry.
           */
          UNIT_LOG(LOG_DEBUG, ferry, "Activating passengers");
          dai_activate_passengers(ait, ferry);
 
          /* It is theoretically possible passenger died here due to
           * autoattack against another passing unit at its location. */
          alive = unit_is_alive(pass_id);
        }
      }
      /* else at sea */
    } else if (alive) {
      /* Arrived all the way to the destination by boat. Deboard. */
      if (can_unit_exist_at_tile(parameter->land.map, passenger, ptile)) {
        unit_transport_unload_send(passenger);
      }
    }
    /* else dead */
  } else {
    /* Not always an error; enemy units might block all paths. */
    UNIT_LOG(LOG_DEBUG, passenger, "no path to destination");
  }
 
  pf_path_destroy(path);
  pf_map_destroy(pfm);
 
  return alive;
}
 
/**********************************************************************/
bool aiferry_goto_amphibious(struct ai_type *ait, struct unit *ferry,
                             struct unit *passenger, struct tile *ptile)
{
  struct pft_amphibious parameter;
  struct adv_risk_cost land_risk_cost;
  struct adv_risk_cost sea_risk_cost;
 
  dai_fill_unit_param(ait, &parameter.land, &land_risk_cost, passenger, ptile);
  if (parameter.land.get_TB != no_fights) {
    /* Use the ferry to go around danger areas: */
    parameter.land.get_TB = no_intermediate_fights;
  }
  dai_fill_unit_param(ait, &parameter.sea, &sea_risk_cost, ferry, ptile);
  pft_fill_amphibious_parameter(&parameter);
 
  /* Move as far along the path to the destination as we can;
   * that is, ignore the presence of enemy units when computing the
   * path */
  parameter.combined.get_zoc = NULL;
 
  return dai_amphibious_goto_constrained(ait, ferry, passenger, ptile,
                                         &parameter);
}
 
/**********************************************************************/
bool aiferry_gobyboat(struct ai_type *ait, struct player *pplayer,
                      struct unit *punit, struct tile *dest_tile, bool with_bodyguard)
{
  struct civ_map *nmap = &(wld.map);
 
  if (!unit_transported(punit)) {
    /* We are not on a boat and we cannot walk */
    int boatid;
    struct unit *ferryboat = NULL;
    int cap = with_bodyguard ? 2 : 1;
    bool board_success = FALSE;
 
    UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "will have to go to (%d,%d) by boat",
             TILE_XY(dest_tile));
 
    if (!is_terrain_class_near_tile(nmap, unit_tile(punit), TC_OCEAN)) {
      struct pf_path *path_to_ferry = NULL;
 
      boatid = aiferry_find_boat(ait, punit, cap, &path_to_ferry);
      if (boatid <= 0) {
        UNIT_LOG(LOGLEVEL_GOBYBOAT, punit,
                 "in ai_gothere cannot find any boats.");
        def_ai_unit_data(punit, ait)->done = TRUE; /* Nothing to do */
        return FALSE;
      }
 
      ferryboat = game_unit_by_number(boatid);
      UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "found boat[%d](%d,%d), going there", 
               boatid, TILE_XY(unit_tile(ferryboat)));
      /* The path can be amphibious so we will stop at the coast.  
       * It might not lead _onto_ the boat. */
      if (!adv_unit_execute_path(punit, path_to_ferry)) { 
        /* Died. */
        pf_path_destroy(path_to_ferry);
        return FALSE;
      }
      pf_path_destroy(path_to_ferry);
    }
 
    if (!is_terrain_class_near_tile(nmap, unit_tile(punit), TC_OCEAN)) {
      /* Still haven't reached the coast */
      return FALSE;
    }
 
    /* We are on the coast, look around for a boat */
    boatid = aiferry_find_boat_nearby(ait, punit, cap);
    if (boatid <= 0) {
      UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "requesting a boat.");
      aiferry_request_boat(ait, punit);
      return FALSE;
    }
 
    /* Ok, a boat found, try boarding it */
    ferryboat = game_unit_by_number(boatid);
    UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "found a nearby boat[%d](%d,%d)",
             ferryboat->id, TILE_XY(unit_tile(ferryboat)));
    /* Setting ferry now in hope it won't run away even 
     * if we can't board it right now */
    aiferry_psngr_meet_boat(ait, punit, ferryboat);
 
    if (is_tiles_adjacent(unit_tile(punit), unit_tile(ferryboat))) {
      (void) dai_unit_move(ait, punit, unit_tile(ferryboat));
    }
 
    /* FIXME: check if action is enabled. */
    if (!can_unit_load(punit, ferryboat)) {
      /* Something prevented us from boarding */
      /* FIXME: this is probably a serious bug, but we just skip past
       * it and continue. */
      UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "couldn't board boat[%d](%d,%d)",
               ferryboat->id, TILE_XY(unit_tile(ferryboat)));
      return FALSE;
    }
 
    action_by_result_iterate(paction, ACTRES_TRANSPORT_BOARD) {
      enum gen_action act_id = action_id(paction);
 
      if (action_prob_possible(action_prob_vs_unit(nmap, punit, act_id,
                                                   ferryboat))) {
        if (unit_perform_action(pplayer,
                                punit->id, ferryboat->id, 0, "",
                                act_id, ACT_REQ_PLAYER)) {
          board_success = TRUE;
          break;
        }
      }
    } action_by_result_iterate_end;
 
    if (!board_success) {
      /* No action enabler active.
       * TODO: Try to predict this failure so that the units wouldn't
       *       waste turns to travel to the rendezvous point. */
      UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "boarding boat[%d](%d,%d) not enabled",
               ferryboat->id, TILE_XY(unit_tile(ferryboat)));
 
      return FALSE;
    }
 
    fc_assert(unit_transported(punit));
  }
 
  if (unit_transported(punit)) {
    /* We are on a boat, ride it! */
    struct unit *ferryboat = unit_transport_get(punit);
 
    /* Check if we are the passenger-in-charge */
    if (is_boat_free(ait, ferryboat, punit, 0)) {
      struct unit *bodyguard = aiguard_guard_of(ait, punit);
 
      UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, 
               "got boat[%d](moves left: %d), going (%d,%d)",
               ferryboat->id, ferryboat->moves_left, TILE_XY(dest_tile));
      aiferry_psngr_meet_boat(ait, punit, ferryboat);
 
      punit->goto_tile = dest_tile;
      /* Grab bodyguard */
      if (bodyguard
          && !same_pos(unit_tile(punit), unit_tile(bodyguard))) {
        if (!goto_is_sane(bodyguard, unit_tile(punit))
            || !dai_unit_goto(ait, bodyguard, unit_tile(punit))) {
          /* Bodyguard can't get there or died en route */
          aiguard_request_guard(ait, punit);
          bodyguard = NULL;
        } else if (bodyguard->moves_left <= 0) {
          /* Wait for me, I'm cooooming!! */
          UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "waiting for bodyguard");
          def_ai_unit_data(punit, ait)->done = TRUE;
          return FALSE;
        } else {
          /* Crap bodyguard. Got stuck somewhere. Ditch it! */
          UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "ditching useless bodyguard");
          aiguard_request_guard(ait, punit);
          dai_unit_new_task(ait, bodyguard, AIUNIT_NONE, NULL);
          bodyguard = NULL;
        }
      }
      if (bodyguard) {
        fc_assert(same_pos(unit_tile(punit), unit_tile(bodyguard)));
 
        /* Bodyguard either uses the same boat or none at all. */
        action_by_result_iterate(paction, ACTRES_TRANSPORT_BOARD) {
          enum gen_action act_id = action_id(paction);
 
          if (action_prob_possible(action_prob_vs_unit(nmap, bodyguard,
                                                       act_id,
                                                       ferryboat))) {
            if (unit_perform_action(pplayer,
                                    bodyguard->id, ferryboat->id, 0, "",
                                    act_id, ACT_REQ_PLAYER)) {
              break;
            }
          }
        } action_by_result_iterate_end;
      }
 
      if (!aiferry_goto_amphibious(ait, ferryboat, punit, dest_tile)) {
        /* Died */
        return FALSE;
      }
      if (same_pos(unit_tile(punit), dest_tile)) {
        /* Arrived */
        unit_activity_handling(punit, ACTIVITY_IDLE);
      } else {
        /* We are in still transit */
        def_ai_unit_data(punit, ait)->done = TRUE;
        return FALSE;
      }
    } else {
      /* Waiting for the boss to load and move us */
      UNIT_LOG(LOGLEVEL_GOBYBOAT, punit, "Cannot command boat [%d],"
               " its boss is [%d]", 
               ferryboat->id, def_ai_unit_data(ferryboat, ait)->passenger);
      return FALSE;
    }
  }
 
  return TRUE;
}
 
 
/* ===================== Boat management ================================= */
 
/**********************************************************************/
static bool aiferry_findcargo(struct ai_type *ait, struct unit *pferry)
{
  /* Path-finding stuff */
  struct pf_map *pfm;
  struct pf_parameter parameter;
  int passengers = dai_plr_data_get(ait, unit_owner(pferry),
                                    NULL)->stats.passengers;
  struct player *pplayer;
  const struct civ_map *nmap = &(wld.map);
 
  if (passengers <= 0) {
    /* No passengers anywhere */
    return FALSE;
  }
 
  UNIT_LOG(LOGLEVEL_FERRY, pferry, "Ferryboat is looking for cargo.");
 
  pplayer = unit_owner(pferry);
  pft_fill_unit_overlap_param(&parameter, nmap, pferry);
  parameter.omniscience = !has_handicap(pplayer, H_MAP);
  /* If we have omniscience, we use it, since paths to some places
   * might be "blocked" by unknown. We don't want to fight though */
  parameter.get_TB = no_fights;
 
  pfm = pf_map_new(&parameter);
  pf_map_tiles_iterate(pfm, ptile, TRUE) {
    unit_list_iterate(ptile->units, aunit) {
      struct unit_ai *unit_data = def_ai_unit_data(aunit, ait);
 
      if (unit_owner(pferry) == unit_owner(aunit) 
          && (unit_data->ferryboat == FERRY_WANTED
              || unit_data->ferryboat == pferry->id)) {
        UNIT_LOG(LOGLEVEL_FERRY, pferry, 
                 "Found a potential cargo %s[%d](%d,%d), going there",
                 unit_rule_name(aunit),
                 aunit->id,
                 TILE_XY(unit_tile(aunit)));
        pferry->goto_tile = unit_tile(aunit);
        /* Exchange phone numbers */
        aiferry_psngr_meet_boat(ait, aunit, pferry);
        pf_map_destroy(pfm);
        return TRUE;
      }
    } unit_list_iterate_end;
  } pf_map_tiles_iterate_end;
 
  /* False positive can happen if we cannot find a route to the passenger
   * because of an internal sea or enemy blocking the route */
  UNIT_LOG(LOGLEVEL_FERRY, pferry,
           "AI Passengers counting reported false positive %d", passengers);
  pf_map_destroy(pfm);
  return FALSE;
}
 
/**********************************************************************/
static bool aiferry_find_interested_city(struct ai_type *ait,
                                         struct unit *pferry)
{
  /* Path-finding stuff */
  struct pf_map *pfm;
  struct pf_parameter parameter;
  /* Early termination condition */
  int turns_horizon = FC_INFINITY;
  /* Future return value */
  bool needed = FALSE;
  const struct civ_map *nmap = &(wld.map);
 
  UNIT_LOG(LOGLEVEL_FERRY, pferry, "Ferry looking for a city that needs it");
 
  pft_fill_unit_parameter(&parameter, nmap, pferry);
  /* We are looking for our own cities, no need to look into the unknown */
  parameter.get_TB = no_fights_or_unknown;
  parameter.omniscience = FALSE;
  pfm = pf_map_new(&parameter);
 
  pf_map_positions_iterate(pfm, pos, TRUE) {
    struct city *pcity;
 
    if (pos.turn >= turns_horizon) {
      /* Won't be able to find anything better than what we have */
      break;
    }
 
    pcity = tile_city(pos.tile);
    
    if (pcity && city_owner(pcity) == unit_owner(pferry)
        && (def_ai_city_data(pcity, ait)->choice.need_boat 
            || (VUT_UTYPE == pcity->production.kind
                && utype_has_role(pcity->production.value.utype,
                                  L_FERRYBOAT)))) {
      bool really_needed = TRUE;
      int turns = city_production_turns_to_build(pcity, TRUE);
 
      UNIT_LOG(LOGLEVEL_FERRY, pferry, "%s (%d, %d) looks promising...", 
               city_name_get(pcity), TILE_XY(pcity->tile));
 
      if (pos.turn > turns
          && VUT_UTYPE == pcity->production.kind
          && utype_has_role(pcity->production.value.utype, L_FERRYBOAT)) {
        UNIT_LOG(LOGLEVEL_FERRY, pferry, "%s is NOT suitable: "
                 "will finish building its own ferry too soon",
                 city_name_get(pcity));
        continue;
      }
 
      if (turns >= turns_horizon) {
        UNIT_LOG(LOGLEVEL_FERRY, pferry, "%s is NOT suitable: "
                 "has just started building",
                 city_name_get(pcity));
        continue;
      }
 
      unit_list_iterate(pos.tile->units, aunit) {
        if (aunit != pferry && unit_owner(aunit) == unit_owner(pferry)
            && unit_has_type_role(aunit, L_FERRYBOAT)) {
 
          UNIT_LOG(LOGLEVEL_FERRY, pferry, "%s is NOT suitable: "
                   "has another ferry",
                   city_name_get(pcity));
          really_needed = FALSE;
          break;
        }
      } unit_list_iterate_end;
 
      if (really_needed) {
        UNIT_LOG(LOGLEVEL_FERRY, pferry, "will go to %s unless we "
                 "find something better",
                 city_name_get(pcity));
        pferry->goto_tile = pos.tile;
        turns_horizon = turns;
        needed = TRUE;
      }
    }
  } pf_map_positions_iterate_end;
 
  pf_map_destroy(pfm);
  return needed;
}
 
/**********************************************************************/
void dai_manage_ferryboat(struct ai_type *ait, struct player *pplayer,
                          struct unit *punit)
{
  struct city *pcity;
  int sanity = punit->id;
  struct unit_ai *unit_data;
  int bossid;
  const struct unit_type *ptype;
 
  CHECK_UNIT(punit);
 
  /* Try to recover hitpoints if we are in a city, before we do anything */
  if (punit->hp < unit_type_get(punit)->hp
      && (pcity = tile_city(unit_tile(punit)))) {
    UNIT_LOG(LOGLEVEL_FERRY, punit, "waiting in %s to recover hitpoints", 
             city_name_get(pcity));
    def_ai_unit_data(punit, ait)->done = TRUE;
    return;
  }
 
  /* Check if we are an empty barbarian boat and so not needed */
  if (is_barbarian(pplayer) && get_transporter_occupancy(punit) == 0) {
    wipe_unit(punit, ULR_RETIRED, NULL);
    return;
  }
 
  unit_data = def_ai_unit_data(punit, ait);
 
  bossid = unit_data->passenger; /* Old boss */
 
  do {
    /* Do we have the passenger-in-charge on board? */
    if (unit_data->passenger > 0) {
      struct unit *psngr = game_unit_by_number(unit_data->passenger);
 
      /* If the passenger-in-charge is adjacent, we should wait for it to 
       * board.  We will pass control to it later. */
      if (!psngr
          || real_map_distance(unit_tile(punit), unit_tile(psngr)) > 1) {
        UNIT_LOG(LOGLEVEL_FERRY, punit, 
                 "recorded passenger[%d] is not on board, checking for "
                 "others", unit_data->passenger);
        unit_data->passenger = FERRY_ABANDON_BOSS;
      }
    }
 
    if (unit_data->passenger == FERRY_AVAILABLE
        || unit_data->passenger == FERRY_ABANDON_BOSS) {
      struct unit *candidate = NULL;
 
      /* Try to select passenger-in-charge from among our passengers */
      unit_list_iterate(punit->transporting, aunit) {
        if (unit_owner(aunit) != pplayer) {
          /* We used to check if ferryboat was set to us or to
           * FERRY_WANTED too, but this was a bit strict. Especially
           * when we don't save these values in a savegame. */
          continue;
        }
 
        if (def_ai_unit_data(aunit, ait)->task != AIUNIT_ESCORT) {
          candidate = aunit;
          break;
        } else {
          /* Bodyguards shouldn't be in charge of boats so continue looking */
          candidate = aunit;
        }
      } unit_list_iterate_end;
      
      if (candidate) {
        UNIT_LOG(LOGLEVEL_FERRY, punit, 
                 "appointed %s[%d] our passenger-in-charge",
                 unit_rule_name(candidate),
                 candidate->id);
        bossid = candidate->id;
        aiferry_psngr_meet_boat(ait, candidate, punit);
      }
    }
 
    if (unit_data->passenger > 0) {
      struct unit *boss = game_unit_by_number(bossid);
 
      fc_assert_ret(NULL != boss);
 
      if (unit_has_type_flag(boss, UTYF_SETTLERS)
          || unit_is_cityfounder(boss)) {
        /* Temporary hack: settlers all go in the end, forcing them 
         * earlier might mean uninitialised cache, so just wait for them */
        return;
      }
 
      UNIT_LOG(LOGLEVEL_FERRY, punit, "passing control to %s[%d]",
                unit_rule_name(boss),
                boss->id);
      dai_manage_unit(ait, pplayer, boss);
    
      if (!game_unit_by_number(sanity) || punit->moves_left <= 0) {
        return;
      }
      if (game_unit_by_number(bossid)) {
        if (same_pos(unit_tile(punit), unit_tile(boss))) {
          /* The boss decided to stay put on the ferry. We aren't moving. */
          UNIT_LOG(LOG_DEBUG, boss, "drove ferry - done for now");
          def_ai_unit_data(boss, ait)->done = TRUE;
          return;
        } else if (unit_data->passenger == bossid
                   && get_transporter_occupancy(punit) != 0) {
          /* The boss isn't on the ferry, has not passed control away,
           * and we have other passengers?
           * Forget about the boss. */
          unit_data->passenger = FERRY_ABANDON_BOSS;
        }
      }
      if (unit_data->passenger != bossid
          && unit_data->passenger != FERRY_ABANDON_BOSS) {
        /* Boss handling resulted in boss change. Run next round with new boss. */
        bossid = unit_data->passenger;
      }
    } else {
      /* Cannot select a passenger-in-charge */
      break;
    }
  } while (get_transporter_occupancy(punit) != 0);
 
  if (unit_data->passenger == FERRY_ABANDON_BOSS) {
    /* As nobody else wanted the control, restore it to old boss. */
    unit_data->passenger = bossid;
  }
 
  /* Not carrying anyone, even the ferryman */
 
  ptype = unit_type_get(punit);
 
  if (IS_ATTACKER(ptype) && punit->moves_left > 0) {
     /* AI used to build frigates to attack and then use them as ferries 
      * -- Syela */
    dai_unit_new_task(ait, punit, AIUNIT_NONE, NULL);
    UNIT_LOG(LOGLEVEL_FERRY, punit, "passing ferry over to attack code");
    dai_manage_military(ait, pplayer, punit);
    return;
  }
 
  UNIT_LOG(LOGLEVEL_FERRY, punit, "Ferryboat is not carrying anyone "
           "(moves left: %d).", punit->moves_left);
  aiferry_make_available(ait, punit);
  unit_activity_handling(punit, ACTIVITY_IDLE);
  dai_unit_new_task(ait, punit, AIUNIT_NONE, NULL);
  CHECK_UNIT(punit);
 
  /* Try to find passengers */
  if (aiferry_findcargo(ait, punit)) {
    UNIT_LOG(LOGLEVEL_FERRY, punit, "picking up cargo (moves left: %d)",
             punit->moves_left);
    if (dai_unit_goto(ait, punit, punit->goto_tile)) {
      if (is_tiles_adjacent(unit_tile(punit), punit->goto_tile)
          || same_pos(unit_tile(punit), punit->goto_tile)) {
        struct unit *cargo = game_unit_by_number(unit_data->passenger);
 
        /* See if passenger can jump on board! */
        fc_assert_ret(cargo != punit);
        dai_manage_unit(ait, pplayer, cargo);
      }
    }
    return;
  }
 
  /* Try to find a city that needs a ferry */
  if (aiferry_find_interested_city(ait, punit)) {
    if (same_pos(unit_tile(punit), punit->goto_tile)) {
      UNIT_LOG(LOGLEVEL_FERRY, punit, "staying in city that needs us");
      unit_data->done = TRUE;
      return;
    } else {
      UNIT_LOG(LOGLEVEL_FERRY, punit, "going to city that needs us");
      if (dai_unit_goto(ait, punit, punit->goto_tile)
          && same_pos(unit_tile(punit), punit->goto_tile)) {
        unit_data->done = TRUE; /* save some CPU */
      }
      return;
    }
  }
 
  UNIT_LOG(LOGLEVEL_FERRY, punit, "Passing control of ferry to explorer code");
  switch (manage_auto_explorer(punit)) {
  case MR_DEATH:
    /* don't use punit! */
    return;
  case MR_OK:
    /* FIXME: continue moving? */
    break;
  default:
    unit_data->done = TRUE;
    break;
  };
 
  if (punit->moves_left > 0) {
    struct city *safe_city = find_nearest_safe_city(punit);
 
    if (safe_city != NULL) {
      punit->goto_tile = safe_city->tile;
      UNIT_LOG(LOGLEVEL_FERRY, punit, "No work, going home");
      unit_data->done = TRUE;
      dai_unit_new_task(ait, punit, AIUNIT_NONE, NULL);
      (void) dai_unit_goto(ait, punit, safe_city->tile);
    }
  }
 
  return;
}