maphand.c

Go to the documentation of this file.

/***********************************************************************
 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 "bitvector.h"
#include "fcintl.h"
#include "log.h"
#include "mem.h"
#include "rand.h"
#include "support.h"
 
/* common */
#include "ai.h"
#include "base.h"
#include "borders.h"
#include "events.h"
#include "game.h"
#include "map.h"
#include "movement.h"
#include "nation.h"
#include "packets.h"
#include "player.h"
#include "road.h"
#include "specialist.h"
#include "unit.h"
#include "unitlist.h"
#include "vision.h"
 
/* server */
#include "citytools.h"
#include "cityturn.h"
#include "notify.h"
#include "plrhand.h"
#include "sanitycheck.h"
#include "sernet.h"
#include "srv_main.h"
#include "unithand.h"
#include "unittools.h"
 
/* server/advisors */
#include "advdata.h"
 
/* server/generator */
#include "mapgen_utils.h"
 
#include "maphand.h"
 
/* Suppress send_tile_info() during game_load() */
static bool send_tile_suppressed = FALSE;
 
static void player_tile_init(struct tile *ptile, struct player *pplayer);
static void player_tile_free(struct tile *ptile, struct player *pplayer);
static bool give_tile_info_from_player_to_player(struct player *pfrom,
                                                 struct player *pdest,
                                                 struct tile *ptile);
static void shared_vision_change_seen(struct player *pplayer,
                                      struct tile *ptile,
                                      const v_radius_t change,
                                      bool can_reveal_tiles);
static void map_change_seen(struct player *pplayer,
                            struct tile *ptile,
                            const v_radius_t change,
                            bool can_reveal_tiles);
static void map_change_own_seen(struct player *pplayer,
                                struct tile *ptile,
                                const v_radius_t change);
static inline int map_get_seen(const struct player *pplayer,
                               const struct tile *ptile,
                               enum vision_layer vlayer);
static inline bool map_is_also_seen(const struct tile *ptile,
                                    const struct player *pplayer,
                                    enum vision_layer vlayer);
 
static bool is_tile_claimable(struct tile *ptile, struct tile *source,
                              struct player *pplayer);
 
/**********************************************************************/
static bool is_terrain_ecologically_wet(struct tile *ptile)
{
  return (is_terrain_class_near_tile(&(wld.map), ptile, TC_OCEAN)
          || tile_has_river(ptile)
          || count_river_near_tile(&(wld.map), ptile, nullptr) > 0);
}
 
/**********************************************************************/
void global_warming(int effect)
{
  climate_change(TRUE, effect);
  notify_player(nullptr, nullptr, E_GLOBAL_ECO, ftc_server,
                _("Global warming has occurred!"));
  notify_player(nullptr, nullptr, E_GLOBAL_ECO, ftc_server,
                _("Coastlines have been flooded and vast "
                  "ranges of grassland have become deserts."));
}
 
/**********************************************************************/
void nuclear_winter(int effect)
{
  climate_change(FALSE, effect);
  notify_player(nullptr, nullptr, E_GLOBAL_ECO, ftc_server,
                _("Nuclear winter has occurred!"));
  notify_player(nullptr, nullptr, E_GLOBAL_ECO, ftc_server,
                _("Wetlands have dried up and vast "
                  "ranges of grassland have become tundra."));
}
 
/**********************************************************************/
void climate_change(bool warming, int effect)
{
  int k = map_num_tiles();
  bool used[k];
  const struct civ_map *nmap = &(wld.map);
 
  memset(used, 0, sizeof(used));
 
  log_verbose("Climate change: %s (%d)",
              warming ? "Global warming" : "Nuclear winter", effect);
 
  while (effect > 0 && (k--) > 0) {
    struct terrain *old, *candidates[2], *new;
    struct tile *ptile;
    int i;
 
    do {
      /* We want to transform a tile at most once due to a climate change. */
      ptile = rand_map_pos(&(wld.map));
    } while (used[tile_index(ptile)]);
    used[tile_index(ptile)] = TRUE;
 
    old = tile_terrain(ptile);
    /* Prefer the transformation that's appropriate to the ambient moisture,
     * but be prepared to fall back in exceptional circumstances */
    {
      struct terrain *wetter, *drier;
 
      wetter = warming ? old->warmer_wetter_result : old->cooler_wetter_result;
      drier  = warming ? old->warmer_drier_result  : old->cooler_drier_result;
      if (is_terrain_ecologically_wet(ptile)) {
        candidates[0] = wetter;
        candidates[1] = drier;
      } else {
        candidates[0] = drier;
        candidates[1] = wetter;
      }
    }
 
    /* If the preferred transformation is ruled out for some exceptional reason
     * specific to this tile, fall back to the other, rather than letting this
     * tile be immune to change. */
    for (i = 0; i < 2; i++) {
      new = candidates[i];
 
      /* If the preferred transformation simply hasn't been specified
       * for this terrain at all, don't fall back to the other. */
      if (new == T_NONE) {
        break;
      }
 
      if (tile_city(ptile) != nullptr && terrain_has_flag(new, TER_NO_CITIES)) {
        /* do not change to a terrain with the flag TER_NO_CITIES if the tile
         * has a city */
        continue;
      }
 
      /* Only change between water and land at coastlines, and between
       * frozen and unfrozen at ice margin */
      if (!terrain_surroundings_allow_change(nmap, ptile, new)) {
        continue;
      }
 
      /* OK! */
      break;
    }
    if (i == 2) {
      /* Neither transformation was permitted. Give up. */
      continue;
    }
 
    if (new != T_NONE && old != new) {
      effect--;
 
      /* Check terrain changing activities.
         These would not be caught by the check if unit can continue activity
         after the terrain change has taken place, as the activity itself is still
         legal, but would be towards different terrain, and terrain types are not
         activity targets (target is nullptr) */
      unit_list_iterate(ptile->units, punit) {
        if (punit->activity_target == nullptr) {
          /* Target is always nullptr for terrain changing activities. */
          if (punit->activity == ACTIVITY_CULTIVATE
              || punit->activity == ACTIVITY_PLANT
              || punit->activity == ACTIVITY_TRANSFORM) {
            unit_activities_cancel(punit);
          }
        }
      } unit_list_iterate_end;
 
      /* Really change the terrain. */
      tile_change_terrain(ptile, new);
      check_terrain_change(ptile, old);
      update_tile_knowledge(ptile);
 
      tile_change_side_effects(ptile, FALSE);
 
    } else if (old == new) {
      /* This counts toward a climate change although nothing is changed. */
      effect--;
    }
  }
}
 
/**********************************************************************/
bool upgrade_city_extras(struct city *pcity, struct extra_type **gained)
{
  struct tile *ptile = pcity->tile;
  struct player *pplayer = city_owner(pcity);
  bool upgradet = FALSE;
 
  extra_type_iterate(pextra) {
    if (!tile_has_extra(ptile, pextra)) {
      if (extra_has_flag(pextra, EF_ALWAYS_ON_CITY_CENTER)
          || (extra_has_flag(pextra, EF_AUTO_ON_CITY_CENTER)
              && player_can_build_extra(pextra, pplayer, ptile)
              && !tile_has_conflicting_extra(ptile, pextra))) {
        tile_add_extra(pcity->tile, pextra);
        if (gained != nullptr) {
          if (upgradet) {
            *gained = nullptr;
          } else {
            *gained = pextra;
          }
        }
        upgradet = TRUE;
      }
    }
  } extra_type_iterate_end;
 
  return upgradet;
}
 
/**********************************************************************/
void upgrade_all_city_extras(struct player *pplayer, bool discovery)
{
  int cities_upgradet = 0;
  struct extra_type *upgradet = nullptr;
  bool multiple_types = FALSE;
  int cities_total = city_list_size(pplayer->cities);
  int percent;
 
  conn_list_do_buffer(pplayer->connections);
 
  city_list_iterate(pplayer->cities, pcity) {
    struct extra_type *new_upgrade;
 
    if (upgrade_city_extras(pcity, &new_upgrade)) {
      update_tile_knowledge(pcity->tile);
      cities_upgradet++;
      if (new_upgrade == nullptr) {
        /* This single city alone had multiple types */
        multiple_types = TRUE;
      } else if (upgradet == nullptr) {
        /* First gained */
        upgradet = new_upgrade;
      } else if (upgradet != new_upgrade) {
        /* Different type from what another city got. */
        multiple_types = TRUE;
      }
    }
  } city_list_iterate_end;
 
  if (cities_total > 0) {
    percent = cities_upgradet * 100 / cities_total;
  } else {
    percent = 0;
  }
 
  if (cities_upgradet > 0) {
    if (discovery) {
      if (percent >= 75) {
        notify_player(pplayer, nullptr, E_TECH_GAIN, ftc_server,
                      _("New hope sweeps like fire through the country as "
                        "the discovery of new infrastructure building technology "
                        "is announced."));
      }
    } else {
      if (percent >= 75) {
        notify_player(pplayer, nullptr, E_TECH_GAIN, ftc_server,
                      _("The people are pleased to hear that your "
                        "scientists finally know about new infrastructure building "
                        "technology."));
      }
    }
 
    if (multiple_types) {
      notify_player(pplayer, nullptr, E_TECH_GAIN, ftc_server,
                    _("Workers spontaneously gather and upgrade all "
                      "possible cities with better infrastructure."));
    } else {
      notify_player(pplayer, nullptr, E_TECH_GAIN, ftc_server,
                    _("Workers spontaneously gather and upgrade all "
                      "possible cities with %s."),
                    extra_name_translation(upgradet));
    }
  }
 
  conn_list_do_unbuffer(pplayer->connections);
}
 
/**********************************************************************/
bool really_gives_vision(struct player *me, struct player *them)
{
  return BV_ISSET(me->server.really_gives_vision, player_index(them));
}
 
/**********************************************************************/
static void buffer_shared_vision(struct player *pplayer)
{
  players_iterate(pplayer2) {
    if (really_gives_vision(pplayer, pplayer2)) {
      conn_list_compression_freeze(pplayer2->connections);
      conn_list_do_buffer(pplayer2->connections);
    }
  } players_iterate_end;
  conn_list_compression_freeze(pplayer->connections);
  conn_list_do_buffer(pplayer->connections);
}
 
/**********************************************************************/
static void unbuffer_shared_vision(struct player *pplayer)
{
  players_iterate(pplayer2) {
    if (really_gives_vision(pplayer, pplayer2)) {
      conn_list_do_unbuffer(pplayer2->connections);
      conn_list_compression_thaw(pplayer2->connections);
    }
  } players_iterate_end;
  conn_list_do_unbuffer(pplayer->connections);
  conn_list_compression_thaw(pplayer->connections);
}
 
/**********************************************************************/
void give_map_from_player_to_player(struct player *pfrom, struct player *pdest)
{
  buffer_shared_vision(pdest);
 
  whole_map_iterate(&(wld.map), ptile) {
    give_tile_info_from_player_to_player(pfrom, pdest, ptile);
  } whole_map_iterate_end;
 
  unbuffer_shared_vision(pdest);
  city_thaw_workers_queue();
  sync_cities();
}
 
/**********************************************************************/
void give_seamap_from_player_to_player(struct player *pfrom, struct player *pdest)
{
  buffer_shared_vision(pdest);
 
  whole_map_iterate(&(wld.map), ptile) {
    if (is_ocean_tile(ptile)) {
      give_tile_info_from_player_to_player(pfrom, pdest, ptile);
    }
  } whole_map_iterate_end;
 
  unbuffer_shared_vision(pdest);
  city_thaw_workers_queue();
  sync_cities();
}
 
/**********************************************************************/
void give_citymap_from_player_to_player(struct city *pcity,
                                        struct player *pfrom, struct player *pdest)
{
  struct tile *pcenter = city_tile(pcity);
  const struct civ_map *nmap = &(wld.map);
 
  buffer_shared_vision(pdest);
 
  city_tile_iterate(nmap, city_map_radius_sq_get(pcity), pcenter, ptile) {
    give_tile_info_from_player_to_player(pfrom, pdest, ptile);
  } city_tile_iterate_end;
 
  unbuffer_shared_vision(pdest);
  city_thaw_workers_queue();
  sync_cities();
}
 
/**********************************************************************/
void send_all_known_tiles(struct conn_list *dest)
{
  int tiles_sent;
 
  if (!dest) {
    dest = game.est_connections;
  }
 
  /* Send whole map piece by piece to each player to balance the load
     of the send buffers better */
  tiles_sent = 0;
  conn_list_do_buffer(dest);
 
  whole_map_iterate(&(wld.map), ptile) {
    tiles_sent++;
    if ((tiles_sent % MAP_NATIVE_WIDTH) == 0) {
      conn_list_do_unbuffer(dest);
      flush_packets();
      conn_list_do_buffer(dest);
    }
 
    send_tile_info(dest, ptile, FALSE);
  } whole_map_iterate_end;
 
  conn_list_do_unbuffer(dest);
  flush_packets();
}
 
/**********************************************************************/
bool send_tile_suppression(bool now)
{
  bool formerly = send_tile_suppressed;
 
  send_tile_suppressed = now;
  return formerly;
}
 
/**********************************************************************/
void send_tile_info(struct conn_list *dest, struct tile *ptile,
                    bool send_unknown)
{
  struct packet_tile_info info;
  const struct player *owner;
  const struct player *eowner;
 
  if (dest == nullptr) {
    CALL_FUNC_EACH_AI(tile_info, ptile);
  }
 
  if (send_tile_suppressed) {
    return;
  }
 
  if (!dest) {
    dest = game.est_connections;
  }
 
  info.tile = tile_index(ptile);
 
  if (ptile->spec_sprite) {
    sz_strlcpy(info.spec_sprite, ptile->spec_sprite);
  } else {
    info.spec_sprite[0] = '\0';
  }
 
  conn_list_iterate(dest, pconn) {
    struct player *pplayer = pconn->playing;
    bool known;
 
    if (pplayer == nullptr && !pconn->observer) {
      continue;
    }
 
    if (pplayer != nullptr) {
      known = map_is_known(ptile, pplayer);
    }
 
    if (pplayer == nullptr
        || (known && map_is_also_seen(ptile, pplayer, V_MAIN))) {
      struct extra_type *resource;
 
      info.known = TILE_KNOWN_SEEN;
      info.continent = tile_continent(ptile);
      owner = tile_owner(ptile);
      eowner = extra_owner(ptile);
      info.owner = (owner ? player_number(owner) : MAP_TILE_OWNER_NULL);
      info.extras_owner = (eowner ? player_number(eowner) : MAP_TILE_OWNER_NULL);
      info.worked = (tile_worked(ptile) != nullptr)
                     ? tile_worked(ptile)->id
                     : IDENTITY_NUMBER_ZERO;
 
      info.terrain = (tile_terrain(ptile) != nullptr)
                      ? terrain_number(tile_terrain(ptile))
                      : terrain_count();
 
      resource = tile_resource(ptile);
      if (resource != nullptr
          && (pplayer == nullptr
              || player_knows_extra_exist(pplayer, resource, ptile))) {
        info.resource = extra_number(resource);
      } else {
        info.resource = MAX_EXTRA_TYPES;
      }
 
      info.placing = (ptile->placing != nullptr)
                      ? extra_number(ptile->placing)
                      : -1;
      info.place_turn = (ptile->placing != nullptr)
                         ? game.info.turn + ptile->infra_turns
                         : 0;
 
      if (pplayer != nullptr) {
        dbv_to_bv(info.extras.vec, &(map_get_player_tile(ptile, pplayer)->extras));
      } else {
        info.extras = ptile->extras;
      }
 
      if (ptile->label != nullptr) {
        /* Always leave final '\0' in place */
        strncpy(info.label, ptile->label, sizeof(info.label) - 1);
      } else {
        info.label[0] = '\0';
      }
 
      info.altitude = ptile->altitude;
 
      send_packet_tile_info(pconn, &info);
    } else if (pplayer != nullptr && known) {
      struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
      struct vision_site *psite = map_get_playermap_site(plrtile);
 
      info.known = TILE_KNOWN_UNSEEN;
      info.continent = tile_continent(ptile);
      owner = (game.server.foggedborders
               ? plrtile->owner
               : tile_owner(ptile));
      eowner = plrtile->extras_owner;
      info.owner = (owner ? player_number(owner) : MAP_TILE_OWNER_NULL);
      info.extras_owner = (eowner ? player_number(eowner) : MAP_TILE_OWNER_NULL);
      info.worked = (psite != nullptr)
                    ? psite->identity
                    : IDENTITY_NUMBER_ZERO;
 
      info.terrain = (plrtile->terrain != nullptr)
                      ? terrain_number(plrtile->terrain)
                      : terrain_count();
      info.resource = (plrtile->resource != nullptr)
                       ? extra_number(plrtile->resource)
                       : MAX_EXTRA_TYPES;
      info.placing = -1;
      info.place_turn = 0;
 
      dbv_to_bv(info.extras.vec, &(plrtile->extras));
 
      /* Labels never change, so they are not subject to fog of war */
      if (ptile->label != nullptr) {
        sz_strlcpy(info.label, ptile->label);
      } else {
        info.label[0] = '\0';
      }
 
      info.altitude = ptile->altitude;
 
      send_packet_tile_info(pconn, &info);
    } else if (send_unknown) {
      info.known = TILE_UNKNOWN;
      info.continent = 0;
      info.owner = MAP_TILE_OWNER_NULL;
      info.extras_owner = MAP_TILE_OWNER_NULL;
      info.worked = IDENTITY_NUMBER_ZERO;
 
      info.terrain = terrain_count();
      info.resource = MAX_EXTRA_TYPES;
      info.placing = -1;
      info.place_turn = 0;
 
      BV_CLR_ALL(info.extras);
 
      info.label[0] = '\0';
 
      info.altitude = 0;
 
      send_packet_tile_info(pconn, &info);
    }
  }
  conn_list_iterate_end;
}
 
/**********************************************************************/
static bool unit_is_on_layer(const struct unit *punit,
                             enum vision_layer vlayer)
{
  return unit_type_get(punit)->vlayer == vlayer;
}
 
/**********************************************************************/
void send_map_info(struct conn_list *dest)
{
  struct packet_map_info minfo;
 
  minfo.xsize = MAP_NATIVE_WIDTH;
  minfo.ysize = MAP_NATIVE_HEIGHT;
  minfo.topology_id = wld.map.topology_id;
  minfo.wrap_id = wld.map.wrap_id;
  minfo.north_latitude = wld.map.north_latitude;
  minfo.south_latitude = wld.map.south_latitude;
  minfo.altitude_info = wld.map.altitude_info;
 
  lsend_packet_map_info(dest, &minfo);
}
 
/**********************************************************************/
static void shared_vision_change_seen(struct player *pplayer,
                                      struct tile *ptile,
                                      const v_radius_t change,
                                      bool can_reveal_tiles)
{
  map_change_own_seen(pplayer, ptile, change);
  map_change_seen(pplayer, ptile, change, can_reveal_tiles);
 
  players_iterate(pplayer2) {
    if (really_gives_vision(pplayer, pplayer2)) {
      map_change_seen(pplayer2, ptile, change, can_reveal_tiles);
    }
  } players_iterate_end;
}
 
/**********************************************************************/
void map_vision_update(struct player *pplayer, struct tile *ptile,
                       const v_radius_t old_radius_sq,
                       const v_radius_t new_radius_sq,
                       bool can_reveal_tiles)
{
  v_radius_t change;
  int max_radius;
 
  if (old_radius_sq[V_MAIN] == new_radius_sq[V_MAIN]
      && old_radius_sq[V_INVIS] == new_radius_sq[V_INVIS]
      && old_radius_sq[V_SUBSURFACE] == new_radius_sq[V_SUBSURFACE]) {
    return;
  }
 
  /* Determines 'max_radius' value. */
  max_radius = 0;
  vision_layer_iterate(v) {
    if (max_radius < old_radius_sq[v]) {
      max_radius = old_radius_sq[v];
    }
    if (max_radius < new_radius_sq[v]) {
      max_radius = new_radius_sq[v];
    }
  } vision_layer_iterate_end;
 
#ifdef FREECIV_DEBUG
  log_debug("Updating vision at (%d, %d) in a radius of %d.",
            TILE_XY(ptile), max_radius);
  vision_layer_iterate(v) {
    log_debug("  vision layer %d is changing from %d to %d.",
              v, old_radius_sq[v], new_radius_sq[v]);
  } vision_layer_iterate_end;
#endif /* FREECIV_DEBUG */
 
  buffer_shared_vision(pplayer);
  circle_dxyr_iterate(&(wld.map), ptile, max_radius, tile1, dx, dy, dr) {
    vision_layer_iterate(v) {
      if (dr > old_radius_sq[v] && dr <= new_radius_sq[v]) {
        change[v] = 1;
      } else if (dr > new_radius_sq[v] && dr <= old_radius_sq[v]) {
        change[v] = -1;
      } else {
        change[v] = 0;
      }
    } vision_layer_iterate_end;
    shared_vision_change_seen(pplayer, tile1, change, can_reveal_tiles);
  } circle_dxyr_iterate_end;
  unbuffer_shared_vision(pplayer);
}
 
/**********************************************************************/
void map_set_border_vision(struct player *pplayer,
                           const bool is_enabled)
{
  const v_radius_t radius_sq = V_RADIUS(is_enabled ? 1 : -1, 0, 0);
 
  if (pplayer->server.border_vision == is_enabled) {
    /* No change. Changing the seen count beyond what already exists would
     * be a bug. */
    return;
  }
 
  /* Set the new border seer value. */
  pplayer->server.border_vision = is_enabled;
 
  whole_map_iterate(&(wld.map), ptile) {
    if (pplayer == ptile->owner) {
      /* The tile is within the player's borders. */
      shared_vision_change_seen(pplayer, ptile, radius_sq, TRUE);
    }
  } whole_map_iterate_end;
}
 
/**********************************************************************/
void map_show_tile(struct player *src_player, struct tile *ptile)
{
  log_debug("Showing %i,%i to %s", TILE_XY(ptile), player_name(src_player));
 
#ifndef FREECIV_NDEBUG
  static int recurse = 0;
 
  fc_assert(recurse == 0);
 
  recurse++;
#endif /* !FREECIV_NDEBUG */
 
  players_iterate(pplayer) {
    if (pplayer == src_player || really_gives_vision(src_player, pplayer)) {
      struct city *pcity;
 
      if (!map_is_known_and_seen(ptile, pplayer, V_MAIN)) {
        map_set_known(ptile, pplayer);
 
        /* As the tile may be fogged send_tile_info won't always do this for us */
        update_player_tile_knowledge(pplayer, ptile);
        update_player_tile_last_seen(pplayer, ptile);
 
        send_tile_info(pplayer->connections, ptile, FALSE);
 
        /* Remove old cities that exist no more */
        reality_check_city(pplayer, ptile);
 
        if ((pcity = tile_city(ptile))) {
          /* As the tile may be fogged send_city_info won't do this for us */
          update_dumb_city(pplayer, pcity);
          send_city_info(pplayer, pcity);
        }
 
        vision_layer_iterate(v) {
          if (0 < map_get_seen(pplayer, ptile, v)) {
            unit_list_iterate(ptile->units, punit) {
              if (unit_is_on_layer(punit, v)) {
                send_unit_info(pplayer->connections, punit);
              }
            } unit_list_iterate_end;
          }
        } vision_layer_iterate_end;
      }
    }
  } players_iterate_end;
 
#ifndef FREECIV_NDEBUG
  recurse--;
#endif
}
 
/**********************************************************************/
void map_hide_tile(struct player *src_player, struct tile *ptile)
{
  log_debug("Hiding %d,%d to %s", TILE_XY(ptile), player_name(src_player));
 
#ifndef FREECIV_NDEBUG
  static int recurse = 0;
 
  fc_assert(recurse == 0);
 
  recurse++;
#endif /* !FREECIV_NDEBUG */
 
  players_iterate(pplayer) {
    if (pplayer == src_player || really_gives_vision(src_player, pplayer)) {
      if (map_is_known(ptile, pplayer)) {
        if (0 < map_get_seen(pplayer, ptile, V_MAIN)) {
          update_player_tile_last_seen(pplayer, ptile);
        }
 
        /* Remove city. */
        remove_dumb_city(pplayer, ptile);
 
        /* Remove units. */
        vision_layer_iterate(v) {
          if (0 < map_get_seen(pplayer, ptile, v)) {
            unit_list_iterate(ptile->units, punit) {
              if (unit_is_on_layer(punit, v)) {
                unit_goes_out_of_sight(pplayer, punit);
              }
            } unit_list_iterate_end;
          }
        } vision_layer_iterate_end;
      }
 
      map_clear_known(ptile, pplayer);
 
      send_tile_info(pplayer->connections, ptile, TRUE);
    }
  } players_iterate_end;
 
#ifndef FREECIV_NDEBUG
  recurse--;
#endif
}
 
/**********************************************************************/
void map_show_circle(struct player *pplayer, struct tile *ptile, int radius_sq)
{
  buffer_shared_vision(pplayer);
 
  circle_iterate(&(wld.map), ptile, radius_sq, tile1) {
    map_show_tile(pplayer, tile1);
  } circle_iterate_end;
 
  unbuffer_shared_vision(pplayer);
}
 
/**********************************************************************/
void map_show_all(struct player *pplayer)
{
  buffer_shared_vision(pplayer);
 
  whole_map_iterate(&(wld.map), ptile) {
    map_show_tile(pplayer, ptile);
  } whole_map_iterate_end;
 
  unbuffer_shared_vision(pplayer);
}
 
/**********************************************************************/
bool map_is_known(const struct tile *ptile, const struct player *pplayer)
{
  if (pplayer->tile_known.vec == nullptr) {
    /* Player map not initialized yet */
    return FALSE;
  }
 
  return dbv_isset(&pplayer->tile_known, tile_index(ptile));
}
 
/**********************************************************************/
static inline bool map_is_also_seen(const struct tile *ptile,
                                    const struct player *pplayer,
                                    enum vision_layer vlayer)
{
  return map_get_seen(pplayer, ptile, vlayer) > 0;
}
 
/**********************************************************************/
bool map_is_known_and_seen(const struct tile *ptile,
                           const struct player *pplayer,
                           enum vision_layer vlayer)
{
  return map_is_known(ptile, pplayer) && map_is_also_seen(ptile, pplayer, vlayer);
}
 
/**********************************************************************/
static inline int map_get_seen(const struct player *pplayer,
                               const struct tile *ptile,
                               enum vision_layer vlayer)
{
  return map_get_player_tile(ptile, pplayer)->seen_count[vlayer];
}
 
/**********************************************************************/
void map_change_seen(struct player *pplayer,
                     struct tile *ptile,
                     const v_radius_t change,
                     bool can_reveal_tiles)
{
  struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
  bool revealing_tile = FALSE;
 
#ifdef FREECIV_DEBUG
  log_debug("%s() for player %s (nb %d) at (%d, %d).",
            __FUNCTION__, player_name(pplayer), player_number(pplayer),
            TILE_XY(ptile));
  vision_layer_iterate(v) {
    log_debug("  vision layer %d is changing from %d to %d.",
              v, plrtile->seen_count[v], plrtile->seen_count[v] + change[v]);
  } vision_layer_iterate_end;
#endif /* FREECIV_DEBUG */
 
  /* Removes units out of vision. First, check invisible layers because
   * we must remove all units before fog of war because clients expect
   * the tile is empty when it is fogged. */
  if (0 > change[V_INVIS]
      && plrtile->seen_count[V_INVIS] == -change[V_INVIS]) {
    log_debug("(%d, %d): hiding invisible units to player %s (nb %d).",
              TILE_XY(ptile), player_name(pplayer), player_number(pplayer));
 
    unit_list_iterate(ptile->units, punit) {
      if (unit_is_on_layer(punit, V_INVIS)
          && can_player_see_unit(pplayer, punit)
          && (plrtile->seen_count[V_MAIN] + change[V_MAIN] <= 0
              || !pplayers_allied(pplayer, unit_owner(punit)))) {
        /* Allied units on seen tiles (V_MAIN) are always seen.
         * That's how can_player_see_unit_at() works. */
        unit_goes_out_of_sight(pplayer, punit);
      }
    } unit_list_iterate_end;
  }
  if (0 > change[V_SUBSURFACE]
      && plrtile->seen_count[V_SUBSURFACE] == -change[V_SUBSURFACE]) {
    log_debug("(%d, %d): hiding subsurface units to player %s (nb %d).",
              TILE_XY(ptile), player_name(pplayer), player_number(pplayer));
 
    unit_list_iterate(ptile->units, punit) {
      if (unit_is_on_layer(punit, V_SUBSURFACE)
          && can_player_see_unit(pplayer, punit)) {
        unit_goes_out_of_sight(pplayer, punit);
      }
    } unit_list_iterate_end;
  }
 
  if (0 > change[V_MAIN]
      && plrtile->seen_count[V_MAIN] == -change[V_MAIN]) {
    log_debug("(%d, %d): hiding visible units to player %s (nb %d).",
              TILE_XY(ptile), player_name(pplayer), player_number(pplayer));
 
    unit_list_iterate(ptile->units, punit) {
      if (unit_is_on_layer(punit, V_MAIN)
          && can_player_see_unit(pplayer, punit)) {
        unit_goes_out_of_sight(pplayer, punit);
      }
    } unit_list_iterate_end;
  }
 
  vision_layer_iterate(v) {
    /* Avoid underflow. */
    fc_assert(0 <= change[v] || -change[v] <= plrtile->seen_count[v]);
    plrtile->seen_count[v] += change[v];
  } vision_layer_iterate_end;
 
  /* V_MAIN vision ranges must always be more than invisible ranges
   * (see comment in common/vision.h), so we assume that the V_MAIN
   * seen count cannot be inferior to V_INVIS or V_SUBSURFACE seen count.
   * Moreover, when the fog of war is disabled, V_MAIN has an extra
   * seen count point. */
  fc_assert(plrtile->seen_count[V_INVIS] + !game.info.fogofwar
            <= plrtile->seen_count[V_MAIN]);
  fc_assert(plrtile->seen_count[V_SUBSURFACE] + !game.info.fogofwar
            <= plrtile->seen_count[V_MAIN]);
 
  if (!map_is_known(ptile, pplayer)) {
    if (0 < plrtile->seen_count[V_MAIN] && can_reveal_tiles) {
      log_debug("(%d, %d): revealing tile to player %s (nb %d).",
                TILE_XY(ptile), player_name(pplayer),
                player_number(pplayer));
 
      map_set_known(ptile, pplayer);
      revealing_tile = TRUE;
    } else {
      return;
    }
  }
 
  /* Fog the tile. */
  if (0 > change[V_MAIN] && 0 == plrtile->seen_count[V_MAIN]) {
    struct city *pcity;
 
    log_debug("(%d, %d): fogging tile for player %s (nb %d).",
              TILE_XY(ptile), player_name(pplayer), player_number(pplayer));
 
    pcity = ptile->worked;
 
    if (pcity != nullptr && city_owner(pcity) == pplayer) {
      city_map_update_empty(pcity, ptile);
      pcity->specialists[DEFAULT_SPECIALIST]++;
      if (pcity->server.needs_arrange == CNA_NOT) {
        pcity->server.needs_arrange = CNA_NORMAL;
      }
    }
 
    update_player_tile_last_seen(pplayer, ptile);
    if (game.server.foggedborders) {
      plrtile->owner = tile_owner(ptile);
    }
    plrtile->extras_owner = extra_owner(ptile);
    send_tile_info(pplayer->connections, ptile, FALSE);
  }
 
  if ((revealing_tile && 0 < plrtile->seen_count[V_MAIN])
      || (0 < change[V_MAIN]
          /* plrtile->seen_count[V_MAIN] Always set to 1
            * when the fog of war is disabled. */
          && (change[V_MAIN] + !game.info.fogofwar
              == (plrtile->seen_count[V_MAIN])))) {
    struct city *pcity;
 
    log_debug("(%d, %d): unfogging tile for player %s (nb %d).",
              TILE_XY(ptile), player_name(pplayer), player_number(pplayer));
 
    /* Send info about the tile itself.
     * It has to be sent first because the client needs correct
     * continent number before it can handle following packets
     */
    update_player_tile_knowledge(pplayer, ptile);
    send_tile_info(pplayer->connections, ptile, FALSE);
 
    /* Discover units. */
    unit_list_iterate(ptile->units, punit) {
      /* Be sure not to revive dead unit on client when it's not yet
       * removed from the tile. This could happen when "unit_lost" lua script
       * somehow causes tile of the dead unit to unfog again. */
      if (unit_is_on_layer(punit, V_MAIN)
          && !punit->server.dying) {
        send_unit_info(pplayer->connections, punit);
      }
    } unit_list_iterate_end;
 
    /* Discover cities. */
    reality_check_city(pplayer, ptile);
 
    if ((pcity = tile_city(ptile)) != nullptr) {
      send_city_info(pplayer, pcity);
    }
  }
 
  if ((revealing_tile && 0 < plrtile->seen_count[V_INVIS])
      || (0 < change[V_INVIS]
          && change[V_INVIS] == plrtile->seen_count[V_INVIS])) {
    log_debug("(%d, %d): revealing invisible units to player %s (nb %d).",
              TILE_XY(ptile), player_name(pplayer),
              player_number(pplayer));
    /* Discover units. */
    unit_list_iterate(ptile->units, punit) {
      if (unit_is_on_layer(punit, V_INVIS)) {
        send_unit_info(pplayer->connections, punit);
      }
    } unit_list_iterate_end;
  }
  if ((revealing_tile && 0 < plrtile->seen_count[V_SUBSURFACE])
      || (0 < change[V_SUBSURFACE]
          && change[V_SUBSURFACE] == plrtile->seen_count[V_SUBSURFACE])) {
    log_debug("(%d, %d): revealing subsurface units to player %s (nb %d).",
              TILE_XY(ptile), player_name(pplayer),
              player_number(pplayer));
    /* Discover units. */
    unit_list_iterate(ptile->units, punit) {
      if (unit_is_on_layer(punit, V_SUBSURFACE)) {
        send_unit_info(pplayer->connections, punit);
      }
    } unit_list_iterate_end;
  }
}
 
/**********************************************************************/
static inline int player_tile_own_seen(const struct player_tile *plrtile,
                                       enum vision_layer vlayer)
{
  return plrtile->own_seen[vlayer];
}
 
/**********************************************************************/
static void map_change_own_seen(struct player *pplayer,
                                struct tile *ptile,
                                const v_radius_t change)
{
  struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
 
  vision_layer_iterate(v) {
    plrtile->own_seen[v] += change[v];
  } vision_layer_iterate_end;
}
 
/**********************************************************************/
void change_playertile_site(struct player_tile *ptile,
                            struct vision_site *new_site)
{
  if (ptile->site == new_site) {
    /* Do nothing. */
    return;
  }
 
  if (ptile->site != nullptr) {
    /* Releasing old site from tile */
    vision_site_destroy(ptile->site);
  }
 
  ptile->site = new_site;
}
 
/**********************************************************************/
void map_set_known(struct tile *ptile, struct player *pplayer)
{
  dbv_set(&pplayer->tile_known, tile_index(ptile));
}
 
/**********************************************************************/
void map_clear_known(struct tile *ptile, struct player *pplayer)
{
  dbv_clr(&pplayer->tile_known, tile_index(ptile));
}
 
/**********************************************************************/
void map_know_and_see_all(struct player *pplayer)
{
  const v_radius_t radius_sq = V_RADIUS(1, 1, 1);
 
  buffer_shared_vision(pplayer);
  whole_map_iterate(&(wld.map), ptile) {
    map_change_seen(pplayer, ptile, radius_sq, TRUE);
  } whole_map_iterate_end;
  unbuffer_shared_vision(pplayer);
}
 
/**********************************************************************/
void show_map_to_all(void)
{
  players_iterate(pplayer) {
    map_know_and_see_all(pplayer);
  } players_iterate_end;
}
 
/**********************************************************************/
void player_map_init(struct player *pplayer)
{
  pplayer->server.private_map
    = fc_realloc(pplayer->server.private_map,
                 MAP_INDEX_SIZE * sizeof(*pplayer->server.private_map));
 
  whole_map_iterate(&(wld.map), ptile) {
    player_tile_init(ptile, pplayer);
  } whole_map_iterate_end;
 
  dbv_init(&pplayer->tile_known, MAP_INDEX_SIZE);
}
 
/**********************************************************************/
void player_map_free(struct player *pplayer)
{
  if (!pplayer->server.private_map) {
    return;
  }
 
  whole_map_iterate(&(wld.map), ptile) {
    player_tile_free(ptile, pplayer);
  } whole_map_iterate_end;
 
  free(pplayer->server.private_map);
  pplayer->server.private_map = nullptr;
 
  dbv_free(&pplayer->tile_known);
}
 
/**********************************************************************/
void remove_player_from_maps(struct player *pplayer)
{
  /* only after removing borders! */
  conn_list_do_buffer(game.est_connections);
  whole_map_iterate(&(wld.map), ptile) {
    /* Clear all players' knowledge about the removed player, and free
     * data structures (including those in removed player's player map). */
    bool reality_changed = FALSE;
 
    players_iterate(aplayer) {
      struct player_tile *aplrtile;
      bool changed = FALSE;
 
      if (!aplayer->server.private_map) {
        continue;
      }
      aplrtile = map_get_player_tile(ptile, aplayer);
 
      /* Free vision sites (cities) for removed and other players */
      if (aplrtile && aplrtile->site
          && vision_site_owner(aplrtile->site) == pplayer) {
        change_playertile_site(aplrtile, nullptr);
        changed = TRUE;
      }
 
      /* Remove references to player from others' maps */
      if (aplrtile->owner == pplayer) {
        aplrtile->owner = nullptr;
        changed = TRUE;
      }
      if (aplrtile->extras_owner == pplayer) {
        aplrtile->extras_owner = nullptr;
        changed = TRUE;
      }
 
      /* Must ensure references to dying player are gone from clients
       * before player is destroyed */
      if (changed) {
        /* This will use player tile if fogged */
        send_tile_info(pplayer->connections, ptile, FALSE);
      }
    } players_iterate_end;
 
    /* Clear removed player's knowledge */
    if (pplayer->tile_known.vec) {
      map_clear_known(ptile, pplayer);
    }
 
    /* Free all claimed tiles. */
    if (tile_owner(ptile) == pplayer) {
      tile_set_owner(ptile, nullptr, nullptr);
      reality_changed = TRUE;
    }
    if (extra_owner(ptile) == pplayer) {
      ptile->extras_owner = nullptr;
      reality_changed = TRUE;
    }
 
    if (reality_changed) {
      /* Update anyone who can see the tile (e.g. global observers) */
      send_tile_info(nullptr, ptile, FALSE);
    }
  } whole_map_iterate_end;
 
  conn_list_do_unbuffer(game.est_connections);
}
 
/**********************************************************************/
static void player_tile_init(struct tile *ptile, struct player *pplayer)
{
  struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
 
  plrtile->terrain = T_UNKNOWN;
  plrtile->resource = nullptr;
  plrtile->owner = nullptr;
  plrtile->extras_owner = nullptr;
  plrtile->site = nullptr;
  dbv_init(&(plrtile->extras), extra_count());
  if (!game.server.last_updated_year) {
    plrtile->last_updated = game.info.turn;
  } else {
    plrtile->last_updated = game.info.year;
  }
 
  plrtile->seen_count[V_MAIN] = !game.server.fogofwar_old;
  plrtile->seen_count[V_INVIS] = 0;
  plrtile->seen_count[V_SUBSURFACE] = 0;
  memcpy(plrtile->own_seen, plrtile->seen_count, sizeof(v_radius_t));
}
 
/**********************************************************************/
static void player_tile_free(struct tile *ptile, struct player *pplayer)
{
  struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
 
  if (plrtile->site != nullptr) {
    vision_site_destroy(plrtile->site);
  }
 
  dbv_free(&(plrtile->extras));
}
 
/**********************************************************************/
struct vision_site *map_get_player_city(const struct tile *ptile,
                                        const struct player *pplayer)
{
  struct vision_site *psite = map_get_player_site(ptile, pplayer);
 
  fc_assert_ret_val(psite == nullptr || psite->location == ptile, nullptr);
 
  return psite;
}
 
/**********************************************************************/
struct player_tile *map_get_player_tile(const struct tile *ptile,
                                        const struct player *pplayer)
{
  fc_assert_ret_val(pplayer->server.private_map, nullptr);
 
  return pplayer->server.private_map + tile_index(ptile);
}
 
/**********************************************************************/
bool update_player_tile_knowledge(struct player *pplayer, struct tile *ptile)
{
  struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
 
  if (plrtile->terrain != ptile->terrain
      || !bv_match_dbv(&(plrtile->extras), ptile->extras.vec)
      || plrtile->resource != ptile->resource
      || plrtile->owner != tile_owner(ptile)
      || plrtile->extras_owner != extra_owner(ptile)) {
    plrtile->terrain = ptile->terrain;
    extra_type_iterate(pextra) {
      if (player_knows_extra_exist(pplayer, pextra, ptile)) {
        dbv_set(&(plrtile->extras), extra_number(pextra));
      } else {
        dbv_clr(&(plrtile->extras), extra_number(pextra));
      }
    } extra_type_iterate_end;
    if (ptile->resource != nullptr
        && player_knows_extra_exist(pplayer, ptile->resource, ptile)) {
      plrtile->resource = ptile->resource;
    } else {
      plrtile->resource = nullptr;
    }
    plrtile->owner = tile_owner(ptile);
    plrtile->extras_owner = extra_owner(ptile);
 
    return TRUE;
  }
 
  return FALSE;
}
 
/**********************************************************************/
void update_tile_knowledge(struct tile *ptile)
{
  if (server_state() == S_S_INITIAL) {
    return;
  }
 
  /* Players */
  players_iterate(pplayer) {
    if (map_is_known_and_seen(ptile, pplayer, V_MAIN)) {
      if (update_player_tile_knowledge(pplayer, ptile)) {
        send_tile_info(pplayer->connections, ptile, FALSE);
      }
    }
  } players_iterate_end;
 
  /* Global observers */
  conn_list_iterate(game.est_connections, pconn) {
    struct player *pplayer = pconn->playing;
 
    if (pplayer == nullptr && pconn->observer) {
      send_tile_info(pconn->self, ptile, FALSE);
    }
  } conn_list_iterate_end;
}
 
/**********************************************************************/
void update_player_tile_last_seen(struct player *pplayer,
                                  struct tile *ptile)
{
  if (!game.server.last_updated_year) {
    map_get_player_tile(ptile, pplayer)->last_updated = game.info.turn;
  } else {
    map_get_player_tile(ptile, pplayer)->last_updated = game.info.year;
  }
}
 
/**********************************************************************/
static bool really_give_tile_info_from_player_to_player(struct player *pfrom,
                                                        struct player *pdest,
                                                        struct tile *ptile)
{
  if (!map_is_known_and_seen(ptile, pdest, V_MAIN)) {
    /* I can just hear people scream as they try to comprehend this if :).
     * Let me try in words:
     * 1) if the tile is seen by pfrom the info is sent to pdest
     *  OR
     * 2) if the tile is known by pfrom AND (they have more recent info
     *     OR it is not known by pdest)
     */
    if (map_is_known_and_seen(ptile, pfrom, V_MAIN)
        || (map_is_known(ptile, pfrom)
            && (((map_get_player_tile(ptile, pfrom)->last_updated
                  > map_get_player_tile(ptile, pdest)->last_updated))
                || !map_is_known(ptile, pdest)))) {
      struct player_tile *from_tile, *dest_tile;
 
      from_tile = map_get_player_tile(ptile, pfrom);
      dest_tile = map_get_player_tile(ptile, pdest);
      /* Update and send tile knowledge */
      map_set_known(ptile, pdest);
      dest_tile->terrain = from_tile->terrain;
      dbv_copy(&(dest_tile->extras), &(from_tile->extras));
      dest_tile->resource = from_tile->resource;
      dest_tile->owner    = from_tile->owner;
      dest_tile->extras_owner = from_tile->extras_owner;
      dest_tile->last_updated = from_tile->last_updated;
      send_tile_info(pdest->connections, ptile, FALSE);
 
      /* Update and send city knowledge */
      /* Remove outdated cities */
      if (dest_tile->site) {
        if (!from_tile->site) {
          /* As the city was gone on the newer from_tile
             it will be removed by this function */
          reality_check_city(pdest, ptile);
        } else { /* We have a dest_city. update */
          if (from_tile->site->identity
              != dest_tile->site->identity) {
            /* As the city was gone on the newer from_tile
               it will be removed by this function */
            reality_check_city(pdest, ptile);
          }
        }
      }
 
      /* Set and send new city info */
      if (from_tile->site) {
        if (!dest_tile->site) {
          /* We cannot assign new vision site with change_playertile_site(),
           * since location is not yet set up for new site */
          dest_tile->site = vision_site_copy(from_tile->site);
        }
        /* Note that we don't care if receiver knows vision source city
         * or not. */
        send_city_info_at_tile(pdest, pdest->connections, nullptr, ptile);
      }
 
      city_map_update_tile_frozen(ptile);
 
      return TRUE;
    }
  }
 
  return FALSE;
}
 
/**********************************************************************/
static void really_give_map_from_player_to_player(struct player *pfrom,
                                                  struct player *pdest)
{
  whole_map_iterate(&(wld.map), ptile) {
    really_give_tile_info_from_player_to_player(pfrom, pdest, ptile);
  } whole_map_iterate_end;
 
  city_thaw_workers_queue();
  sync_cities();
}
 
/**********************************************************************/
static bool give_tile_info_from_player_to_player(struct player *pfrom,
                                                 struct player *pdest,
                                                 struct tile *ptile)
{
  bool updt = really_give_tile_info_from_player_to_player(pfrom, pdest, ptile);
 
  players_iterate(pplayer2) {
    if (really_gives_vision(pdest, pplayer2)) {
      updt |= really_give_tile_info_from_player_to_player(pfrom, pplayer2, ptile);
    }
  } players_iterate_end;
 
  return updt;
}
 
/**********************************************************************/
static void create_vision_dependencies(void)
{
  int added;
 
  players_iterate(pplayer) {
    pplayer->server.really_gives_vision = pplayer->gives_shared_vision;
  } players_iterate_end;
 
  /* In words: This terminates when it has run a round without adding
     a dependency. One loop only propagates dependencies one level deep,
     which is why we keep doing it as long as changes occur. */
  do {
    added = 0;
    players_iterate(pplayer) {
      players_iterate(pplayer2) {
        if (really_gives_vision(pplayer, pplayer2)
            && pplayer != pplayer2) {
          players_iterate(pplayer3) {
            if (really_gives_vision(pplayer2, pplayer3)
                && !really_gives_vision(pplayer, pplayer3)
                && pplayer != pplayer3) {
              BV_SET(pplayer->server.really_gives_vision, player_index(pplayer3));
              added++;
            }
          } players_iterate_end;
        }
      } players_iterate_end;
    } players_iterate_end;
  } while (added > 0);
}
 
/**********************************************************************/
void give_shared_vision(struct player *pfrom, struct player *pto)
{
  bv_player save_vision[player_slot_count()];
 
  if (pfrom == pto) {
    return;
  }
 
  if (gives_shared_vision(pfrom, pto)) {
    log_error("Trying to give shared vision from %s to %s, "
              "but that vision is already given!",
              player_name(pfrom), player_name(pto));
    return;
  }
 
  players_iterate(pplayer) {
    save_vision[player_index(pplayer)] = pplayer->server.really_gives_vision;
  } players_iterate_end;
 
  BV_SET(pfrom->gives_shared_vision, player_index(pto));
  create_vision_dependencies();
  log_debug("giving shared vision from %s to %s",
            player_name(pfrom), player_name(pto));
 
  players_iterate(pplayer) {
    buffer_shared_vision(pplayer);
    players_iterate(pplayer2) {
      if (really_gives_vision(pplayer, pplayer2)
          && !BV_ISSET(save_vision[player_index(pplayer)],
                       player_index(pplayer2))) {
        log_debug("really giving shared vision from %s to %s",
                  player_name(pplayer), player_name(pplayer2));
        whole_map_iterate(&(wld.map), ptile) {
          const struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
          const v_radius_t change =
              V_RADIUS(player_tile_own_seen(plrtile, V_MAIN),
                       player_tile_own_seen(plrtile, V_INVIS),
                       player_tile_own_seen(plrtile, V_SUBSURFACE));
 
          if (0 < change[V_MAIN] || 0 < change[V_INVIS]) {
            map_change_seen(pplayer2, ptile, change,
                            map_is_known(ptile, pplayer));
          }
        } whole_map_iterate_end;
 
        /* Squares that are not seen, but which pfrom may have more recent
           knowledge of */
        really_give_map_from_player_to_player(pplayer, pplayer2);
      }
    } players_iterate_end;
    unbuffer_shared_vision(pplayer);
  } players_iterate_end;
 
  if (S_S_RUNNING == server_state()) {
    send_player_info_c(pfrom, nullptr);
  }
}
 
/**********************************************************************/
void remove_shared_vision(struct player *pfrom, struct player *pto)
{
  bv_player save_vision[player_slot_count()];
 
  fc_assert_ret(pfrom != pto);
  if (!gives_shared_vision(pfrom, pto)) {
    log_error("Tried removing the shared vision from %s to %s, "
              "but it did not exist in the first place!",
              player_name(pfrom), player_name(pto));
    return;
  }
 
  players_iterate(pplayer) {
    save_vision[player_index(pplayer)] = pplayer->server.really_gives_vision;
  } players_iterate_end;
 
  log_debug("removing shared vision from %s to %s",
            player_name(pfrom), player_name(pto));
 
  BV_CLR(pfrom->gives_shared_vision, player_index(pto));
  create_vision_dependencies();
 
  players_iterate(pplayer) {
    buffer_shared_vision(pplayer);
    players_iterate(pplayer2) {
      if (!really_gives_vision(pplayer, pplayer2)
          && BV_ISSET(save_vision[player_index(pplayer)],
                      player_index(pplayer2))) {
        log_debug("really removing shared vision from %s to %s",
                  player_name(pplayer), player_name(pplayer2));
        whole_map_iterate(&(wld.map), ptile) {
          const struct player_tile *plrtile = map_get_player_tile(ptile, pplayer);
          const v_radius_t change =
              V_RADIUS(-player_tile_own_seen(plrtile, V_MAIN),
                       -player_tile_own_seen(plrtile, V_INVIS),
                       -player_tile_own_seen(plrtile, V_SUBSURFACE));
 
          if (0 > change[V_MAIN] || 0 > change[V_INVIS]) {
            map_change_seen(pplayer2, ptile, change, FALSE);
          }
        } whole_map_iterate_end;
      }
    } players_iterate_end;
    unbuffer_shared_vision(pplayer);
  } players_iterate_end;
 
  if (S_S_RUNNING == server_state()) {
    send_player_info_c(pfrom, nullptr);
  }
}
 
/**********************************************************************/
void enable_fog_of_war_player(struct player *pplayer)
{
  const v_radius_t radius_sq = V_RADIUS(-1, 0, 0);
 
  dlsend_packet_edit_fogofwar_state(pplayer->connections, TRUE);
 
  buffer_shared_vision(pplayer);
  whole_map_iterate(&(wld.map), ptile) {
    map_change_seen(pplayer, ptile, radius_sq, FALSE);
  } whole_map_iterate_end;
  unbuffer_shared_vision(pplayer);
}
 
/**********************************************************************/
void enable_fog_of_war(void)
{
  players_iterate(pplayer) {
    enable_fog_of_war_player(pplayer);
  } players_iterate_end;
}
 
/**********************************************************************/
void disable_fog_of_war_player(struct player *pplayer)
{
  const v_radius_t radius_sq = V_RADIUS(1, 0, 0);
 
  dlsend_packet_edit_fogofwar_state(pplayer->connections, FALSE);
 
  buffer_shared_vision(pplayer);
  whole_map_iterate(&(wld.map), ptile) {
    map_change_seen(pplayer, ptile, radius_sq, FALSE);
  } whole_map_iterate_end;
  unbuffer_shared_vision(pplayer);
}
 
/**********************************************************************/
void disable_fog_of_war(void)
{
  players_iterate(pplayer) {
    disable_fog_of_war_player(pplayer);
  } players_iterate_end;
}
 
/**********************************************************************/
static void ocean_to_land_fix_rivers(struct tile *ptile)
{
  cardinal_adjc_iterate(&(wld.map), ptile, tile1) {
    bool ocean_near = FALSE;
 
    cardinal_adjc_iterate(&(wld.map), tile1, tile2) {
      if (is_ocean_tile(tile2))
        ocean_near = TRUE;
    } cardinal_adjc_iterate_end;
 
    if (!ocean_near) {
      /* If ruleset has several river types defined, this
       * may cause same tile to contain more than one river. */
      extra_type_by_cause_iterate(EC_ROAD, priver) {
        if (tile_has_extra(tile1, priver)
            && road_has_flag(extra_road_get(priver), RF_RIVER)) {
          tile_add_extra(ptile, priver);
        }
      } extra_type_by_cause_iterate_end;
    }
  } cardinal_adjc_iterate_end;
}
 
/**********************************************************************/
static void terrain_change_bounce_single_unit(struct unit *punit,
                                              struct tile *from)
{
  bool unit_alive = TRUE;
  struct player *owner = unit_owner(punit);
 
  /* Look for a nearby safe tile */
  adjc_iterate(&(wld.map), from, ptile2) {
    if (can_unit_exist_at_tile(&(wld.map), punit, ptile2)
        && !is_non_allied_unit_tile(ptile2, owner,
                                    unit_has_type_flag(punit, UTYF_FLAGLESS))
        && !is_non_allied_city_tile(ptile2, owner)) {
      log_verbose("Moved %s %s due to changing terrain at (%d,%d).",
                  nation_rule_name(nation_of_unit(punit)),
                  unit_rule_name(punit), TILE_XY(unit_tile(punit)));
      notify_player(owner, unit_tile(punit),
                    E_UNIT_RELOCATED, ftc_server,
                    _("Moved your %s due to changing terrain."),
                    unit_link(punit));
 
      /* TODO: Should a unit be able to bounce to a transport like is
       * done below? What if the unit can't legally enter the transport,
       * say because the transport is Unreachable and the unit doesn't
       * have it in its embarks field or because "Transport Embark"
       * isn't enabled? Kept like it was to preserve the old rules for
       * now. -- Sveinung */
      unit_alive = unit_move(punit, ptile2, 0,
                             nullptr, TRUE, FALSE, FALSE, FALSE, FALSE);
      if (unit_alive && punit->activity == ACTIVITY_SENTRY) {
        unit_activity_handling(punit, ACTIVITY_IDLE, ACTION_NONE);
      }
      break;
    }
  } adjc_iterate_end;
 
  if (unit_alive && unit_tile(punit) == from) {
    /* If we get here we could not move punit. */
 
    /* Try to bounce transported units. */
    if (0 < get_transporter_occupancy(punit)) {
      struct unit_list *pcargo_units;
 
      pcargo_units = unit_transport_cargo(punit);
      unit_list_iterate_safe(pcargo_units, pcargo) {
        terrain_change_bounce_single_unit(pcargo, from);
      } unit_list_iterate_safe_end;
    }
  }
}
 
/**********************************************************************/
static void check_units_single_tile(struct tile *ptile)
{
  const struct civ_map *nmap = &(wld.map);
 
  unit_list_iterate_safe(ptile->units, punit) {
    int id = punit->id;
 
    /* Top-level transports only. Each handle their own cargo */
    if (!unit_transported(punit)
        && !can_unit_exist_at_tile(nmap, punit, ptile)) {
      terrain_change_bounce_single_unit(punit, ptile);
 
      if (unit_is_alive(id) && unit_tile(punit) == ptile) {
        log_verbose("Disbanded %s %s due to changing terrain "
                    "at (%d, %d).",
                    nation_rule_name(nation_of_unit(punit)),
                    unit_rule_name(punit), TILE_XY(ptile));
        notify_player(unit_owner(punit), ptile,
                      E_UNIT_LOST_MISC, ftc_server,
                      _("Disbanded your %s due to changing terrain."),
                      unit_tile_link(punit));
        wipe_unit(punit, ULR_NONNATIVE_TERR, nullptr);
      }
    }
  } unit_list_iterate_safe_end;
}
 
/**********************************************************************/
void bounce_units_on_terrain_change(struct tile *ptile)
{
  const struct civ_map *nmap = &(wld.map);
 
  /* Check this tile for direct effect on its units */
  check_units_single_tile(ptile);
  /* We have to check adjacent tiles too, in case units in cities are now
   * illegal (e.g., boat in a city that has become landlocked),
   * and in case of CoastStrict units losing their adjacent coast. */
  adjc_iterate(nmap, ptile, ptile2) {
    check_units_single_tile(ptile2);
  } adjc_iterate_end;
}
 
/**********************************************************************/
bool need_to_reassign_continents(const struct terrain *oldter,
                                 const struct terrain *newter)
{
  bool old_is_ocean, new_is_ocean;
 
  if (!oldter || !newter) {
    return FALSE;
  }
 
  old_is_ocean = is_ocean(oldter);
  new_is_ocean = is_ocean(newter);
 
  return (old_is_ocean && !new_is_ocean)
    || (!old_is_ocean && new_is_ocean);
}
 
/**********************************************************************/
void terrain_changed(struct tile *ptile)
{
  struct city *pcity = tile_city(ptile);
 
  if (pcity != nullptr) {
    /* Tile is city center and new terrain may support better extras. */
    upgrade_city_extras(pcity, nullptr);
  }
 
  bounce_units_on_terrain_change(ptile);
}
 
/**********************************************************************/
void fix_tile_on_terrain_change(struct tile *ptile,
                                struct terrain *oldter,
                                bool extend_rivers)
{
  if (is_ocean(oldter) && !is_ocean_tile(ptile)) {
    if (extend_rivers) {
      ocean_to_land_fix_rivers(ptile);
    }
    city_landlocked_sell_coastal_improvements(ptile);
  }
 
  terrain_changed(ptile);
}
 
/**********************************************************************/
void check_terrain_change(struct tile *ptile, struct terrain *oldter)
{
  struct terrain *newter = tile_terrain(ptile);
  struct tile *claimer;
  bool cont_reassigned = FALSE;
 
  /* Check if new terrain is a freshwater terrain next to non-freshwater.
   * In that case, the new terrain is *changed*. */
  if (is_ocean(newter) && terrain_has_flag(newter, TER_FRESHWATER)) {
    bool nonfresh = FALSE;
 
    adjc_iterate(&(wld.map), ptile, atile) {
      if (is_ocean(tile_terrain(atile))
          && !terrain_has_flag(tile_terrain(atile), TER_FRESHWATER)) {
        nonfresh = TRUE;
        break;
      }
    } adjc_iterate_end;
    if (nonfresh) {
      /* Need to pick a new, non-freshwater ocean type for this tile.
       * We don't want e.g. Deep Ocean to be propagated to this tile
       * and then to a whole lake by the flooding below, so we pick
       * the shallowest non-fresh oceanic type.
       * Prefer terrain that matches the frozenness of the target. */
      newter = most_shallow_ocean(terrain_has_flag(newter, TER_FROZEN));
      tile_change_terrain(ptile, newter);
    }
  }
 
  if (need_to_reassign_continents(oldter, newter)) {
    assign_continent_numbers();
    cont_reassigned = TRUE;
 
    phase_players_iterate(pplayer) {
      if (is_adv_data_phase_open(pplayer)) {
        /* Player is using continent numbers that they would assume to remain accurate.
         * Force refresh:
         * 1) Close the phase, so that it can be opened
         * 2) Open the phase, recalculating
         */
        adv_data_phase_done(pplayer);
        adv_data_phase_init(pplayer, FALSE);
      }
    } phase_players_iterate_end;
  }
 
  fix_tile_on_terrain_change(ptile, oldter, TRUE);
 
  /* Check for saltwater filling freshwater lake */
  if (game.scenario.lake_flooding
      && is_ocean(newter) && !terrain_has_flag(newter, TER_FRESHWATER)) {
    adjc_iterate(&(wld.map), ptile, atile) {
      if (terrain_has_flag(tile_terrain(atile), TER_FRESHWATER)) {
        struct terrain *aold = tile_terrain(atile);
 
        tile_change_terrain(atile,
                            most_shallow_ocean(terrain_has_flag(aold,
                                                                TER_FROZEN)));
 
        /* Recursive, but as lakes are of limited size, this
         * won't recurse so much as to cause stack problems. */
        check_terrain_change(atile, aold);
        update_tile_knowledge(atile);
      }
    } adjc_iterate_end;
  }
 
  if (cont_reassigned) {
    send_all_known_tiles(nullptr);
  }
 
  claimer = tile_claimer(ptile);
  if (claimer != nullptr) {
    /* Make sure map_claim_border() conditions are still satisfied */
    if (!is_tile_claimable(ptile, claimer, tile_owner(ptile))) {
      map_clear_border(ptile);
    }
  }
 
  sanity_check_tile(ptile);
}
 
/**********************************************************************/
static bool is_tile_claimable(struct tile *ptile, struct tile *source,
                              struct player *pplayer)
{
  if (ptile == source) {
    /* Source itself is always claimable. */
    return TRUE;
  }
 
  return 0 < get_target_bonus_effects(nullptr,
                                      &(const struct req_context) {
                                        .tile = ptile,
                                        .player = pplayer,
                                      },
                                      &(const struct req_context) {
                                        .tile = source,
                                      },
                                      EFT_TILE_CLAIMABLE);
}
 
/**********************************************************************/
static void map_unit_homecity_enqueue(struct tile *ptile)
{
  unit_list_iterate(ptile->units, punit) {
    struct city *phome = game_city_by_number(punit->homecity);
 
    if (phome == nullptr) {
      continue;
    }
 
    city_refresh_queue_add(phome);
  } unit_list_iterate_end;
}
 
/**********************************************************************/
static void map_claim_border_ownership(struct tile *ptile,
                                       struct player *powner,
                                       struct tile *psource)
{
  struct player *ploser = tile_owner(ptile);
 
  if ((ploser != powner && ploser != nullptr)
      && (BORDERS_SEE_INSIDE == game.info.borders
          || BORDERS_EXPAND == game.info.borders
          || ploser->server.border_vision)) {
    const v_radius_t radius_sq = V_RADIUS(-1, 0, 0);
 
    shared_vision_change_seen(ploser, ptile, radius_sq, FALSE);
  }
 
  if (powner != nullptr
      && (BORDERS_SEE_INSIDE == game.info.borders
          || BORDERS_EXPAND == game.info.borders
          || powner->server.border_vision)) {
    const v_radius_t radius_sq = V_RADIUS(1, 0, 0);
 
    shared_vision_change_seen(powner, ptile, radius_sq, TRUE);
  }
 
  tile_set_owner(ptile, powner, psource);
 
  /* Needed only when foggedborders enabled, but we do it unconditionally
   * in case foggedborders ever gets enabled later. Better to have correct
   * information in player map just in case. */
  update_tile_knowledge(ptile);
 
  if (ploser != powner) {
    if (S_S_RUNNING == server_state() && game.info.happyborders != HB_DISABLED) {
      map_unit_homecity_enqueue(ptile);
    }
 
    if (!city_map_update_tile_frozen(ptile)) {
      send_tile_info(nullptr, ptile, FALSE);
    }
  }
}
 
/**********************************************************************/
void map_claim_ownership(struct tile *ptile, struct player *powner,
                         struct tile *psource, bool claim_bases)
{
  map_claim_border_ownership(ptile, powner, psource);
 
  if (claim_bases) {
    tile_claim_bases(ptile, powner);
  }
}
 
/**********************************************************************/
void tile_claim_bases(struct tile *ptile, struct player *powner)
{
  struct player *base_loser = extra_owner(ptile);
 
  /* This MUST be before potentially recursive call to map_claim_base(),
   * so that the recursive call will get new owner == base_loser and
   * abort recursion. */
  ptile->extras_owner = powner;
 
  extra_type_by_cause_iterate(EC_BASE, pextra) {
    map_claim_base(ptile, pextra, powner, base_loser);
  } extra_type_by_cause_iterate_end;
}
 
/**********************************************************************/
void map_clear_border(struct tile *ptile)
{
  int radius_sq = tile_border_source_radius_sq(ptile);
 
  circle_dxyr_iterate(&(wld.map), ptile, radius_sq, dtile, dx, dy, dr) {
    struct tile *claimer = tile_claimer(dtile);
 
    if (claimer == ptile) {
      map_claim_ownership(dtile, nullptr, nullptr, FALSE);
    }
  } circle_dxyr_iterate_end;
}
 
/**********************************************************************/
void map_update_border(struct tile *ptile, struct player *owner,
                       int old_radius_sq, int new_radius_sq)
{
  if (old_radius_sq == new_radius_sq) {
    /* No change */
    return;
  }
 
  if (BORDERS_DISABLED == game.info.borders) {
    return;
  }
 
  if (old_radius_sq < new_radius_sq) {
    map_claim_border(ptile, owner, new_radius_sq);
  } else {
    circle_dxyr_iterate(&(wld.map), ptile, old_radius_sq, dtile, dx, dy, dr) {
      if (dr > new_radius_sq) {
        struct tile *claimer = tile_claimer(dtile);
 
        if (claimer == ptile) {
          map_claim_ownership(dtile, nullptr, nullptr, FALSE);
        }
      }
    } circle_dxyr_iterate_end;
  }
}
 
/**********************************************************************/
void map_claim_border(struct tile *ptile, struct player *owner,
                      int radius_sq)
{
  if (BORDERS_DISABLED == game.info.borders) {
    return;
  }
 
  if (owner == nullptr) {
    /* Clear the border instead of claiming. Code below this block
     * cannot handle nullptr owner. */
    map_clear_border(ptile);
 
    return;
  }
 
  if (radius_sq < 0) {
    radius_sq = tile_border_source_radius_sq(ptile);
  }
 
  circle_dxyr_iterate(&(wld.map), ptile, radius_sq, dtile, dx, dy, dr) {
    struct tile *dclaimer = tile_claimer(dtile);
 
    if (dclaimer == ptile) {
      /* Already claimed by the ptile */
      continue;
    }
 
    if (dr != 0 && is_border_source(dtile)) {
      /* Do not claim border sources other than self */
      /* Note that this is extremely important at the moment for
       * base claiming to work correctly in case there's two
       * fortresses near each other. There could be infinite
       * recursion in them claiming each other. */
      continue;
    }
 
    if (!map_is_known(dtile, owner) && game.info.borders < BORDERS_EXPAND) {
      continue;
    }
 
    /* Always claim source itself (distance, dr, to it 0) */
    if (dr != 0 && dclaimer != nullptr && dclaimer != ptile) {
      struct city *ccity = tile_city(dclaimer);
      int strength_old, strength_new;
 
      if (ccity != nullptr) {
        /* Previously claimed by city */
        int city_x, city_y;
 
        map_distance_vector(&city_x, &city_y, ccity->tile, dtile);
 
        if (map_vector_to_sq_distance(city_x, city_y)
            <= city_map_radius_sq_get(ccity)
               + game.info.border_city_permanent_radius_sq) {
          /* Tile is within region permanently claimed by city */
          continue;
        }
      }
 
      strength_old = tile_border_strength(dtile, dclaimer);
      strength_new = tile_border_strength(dtile, ptile);
 
      if (strength_new <= strength_old) {
        /* Stronger shall prevail,
         * in case of equal strength older shall prevail */
        continue;
      }
    }
 
    /* Only certain tiles are claimable */
    if (is_tile_claimable(dtile, ptile, owner)) {
      map_claim_ownership(dtile, owner, ptile, dr == 0);
    }
  } circle_dxyr_iterate_end;
}
 
/**********************************************************************/
void map_calculate_borders(void)
{
  if (BORDERS_DISABLED == game.info.borders) {
    return;
  }
 
  if (wld.map.tiles == nullptr) {
    /* Map not yet initialized */
    return;
  }
 
  log_verbose("map_calculate_borders()");
 
  whole_map_iterate(&(wld.map), ptile) {
    if (is_border_source(ptile)) {
      map_claim_border(ptile, ptile->owner, -1);
    }
  } whole_map_iterate_end;
 
  log_verbose("map_calculate_borders() workers");
  city_thaw_workers_queue();
  city_refresh_queue_processing();
}
 
/**********************************************************************/
void map_claim_base(struct tile *ptile, struct extra_type *pextra,
                    struct player *powner, struct player *ploser)
{
  struct base_type *pbase;
  bv_player *could_see_unit = nullptr;
  int units_num = 0;
  int ul_size;
 
  if (!tile_has_extra(ptile, pextra)) {
    return;
  }
 
  if (pextra->eus != EUS_NORMAL) {
    ul_size = unit_list_size(ptile->units);
  } else {
    ul_size = 0;
  }
 
  int stored_units[ul_size + 1];
 
  if (ul_size > 0) {
    int i;
 
    could_see_unit = fc_malloc(sizeof(*could_see_unit) * ul_size);
 
    unit_list_iterate(ptile->units, aunit) {
      stored_units[units_num++] = aunit->id;
    } unit_list_iterate_end;
 
    fc_assert(units_num == ul_size);
 
    for (i = 0; i < units_num; i++) {
      struct unit *aunit = game_unit_by_number(stored_units[i]);
 
      BV_CLR_ALL(could_see_unit[i]);
      players_iterate(aplayer) {
        if (can_player_see_unit(aplayer, aunit)) {
          BV_SET(could_see_unit[i], player_index(aplayer));
        }
      } players_iterate_end;
    }
  }
 
  pbase = extra_base_get(pextra);
 
  fc_assert_ret(pbase != nullptr);
 
  /* Transfer base provided vision to new owner */
  if (powner != nullptr) {
    const v_radius_t old_radius_sq = V_RADIUS(-1, -1, -1);
    const v_radius_t new_radius_sq = V_RADIUS(pbase->vision_main_sq,
                                              pbase->vision_invis_sq,
                                              pbase->vision_subs_sq);
 
    map_vision_update(powner, ptile, old_radius_sq, new_radius_sq,
                      game.server.vision_reveal_tiles);
  }
 
  if (ploser != nullptr) {
    const v_radius_t old_radius_sq = V_RADIUS(pbase->vision_main_sq,
                                              pbase->vision_invis_sq,
                                              pbase->vision_subs_sq);
    const v_radius_t new_radius_sq = V_RADIUS(-1, -1, -1);
 
    map_vision_update(ploser, ptile, old_radius_sq, new_radius_sq,
                      game.server.vision_reveal_tiles);
  }
 
  if (BORDERS_DISABLED != game.info.borders
      && territory_claiming_base(pbase) && powner != ploser) {
    /* Clear borders from old owner. New owner may not know all those
     * tiles and thus does not claim them when borders mode is less
     * than EXPAND. */
    if (ploser != nullptr) {
      /* Set this particular tile owner by nullptr so in recursion
       * both loser and owner will be nullptr. */
      map_claim_border_ownership(ptile, nullptr, ptile);
      map_clear_border(ptile);
    }
 
    /* We here first claim this tile ownership -> now on extra_owner()
     * will return new owner. Then we claim border, which will recursively
     * lead to this tile and base being claimed. But at that point
     * ploser == powner and above check will abort the recursion. */
    if (powner != nullptr) {
      map_claim_border_ownership(ptile, powner, ptile);
      map_claim_border(ptile, powner, -1);
    }
    city_thaw_workers_queue();
    city_refresh_queue_processing();
  }
 
  if (units_num > 0) {
    int i;
 
    for (i = 0; i < units_num; i++) {
      struct unit *aunit = game_unit_by_number(stored_units[i]);
 
      players_iterate(aplayer) {
        if (can_player_see_unit(aplayer, aunit)) {
          if (!BV_ISSET(could_see_unit[i], player_index(aplayer))) {
            send_unit_info(aplayer->connections, aunit);
          }
        } else {
          if (BV_ISSET(could_see_unit[i], player_index(aplayer))) {
            unit_goes_out_of_sight(aplayer, aunit);
          }
        }
      } players_iterate_end;
    }
 
    free(could_see_unit);
  }
}
 
/**********************************************************************/
void vision_change_sight(struct vision *vision, const v_radius_t radius_sq)
{
  map_vision_update(vision->player, vision->tile, vision->radius_sq,
                    radius_sq, vision->can_reveal_tiles);
  memcpy(vision->radius_sq, radius_sq, sizeof(v_radius_t));
}
 
/**********************************************************************/
void vision_clear_sight(struct vision *vision)
{
  const v_radius_t vision_radius_sq = V_RADIUS(-1, -1, -1);
 
  vision_change_sight(vision, vision_radius_sq);
 
  /* Owner of some city might have lost vision of a tile previously worked */
  players_iterate(pplayer) {
    city_list_iterate(pplayer->cities, pcity) {
      /* We are not interested about CNA_BROADCAST_PENDING, as the vision loss has
       * not set it, and whatever set it should take care of it. */
      if (pcity->server.needs_arrange == CNA_NORMAL) {
        city_refresh(pcity);
        auto_arrange_workers(pcity);
        pcity->server.needs_arrange = CNA_NOT;
      }
    } city_list_iterate_end;
  } players_iterate_end;
}
 
/**********************************************************************/
void create_extra(struct tile *ptile, struct extra_type *pextra,
                  struct player *pplayer)
{
  bool extras_removed = FALSE;
 
  extra_type_iterate(old_extra) {
    if (tile_has_extra(ptile, old_extra)
        && !can_extras_coexist(old_extra, pextra)) {
      destroy_extra(ptile, old_extra);
      extras_removed = TRUE;
    }
  } extra_type_iterate_end;
 
  if (pextra->eus != EUS_NORMAL) {
    unit_list_iterate(ptile->units, aunit) {
      if (is_native_extra_to_utype(pextra, unit_type_get(aunit))) {
        players_iterate(aplayer) {
          if (!pplayers_allied(pplayer, aplayer)
              && can_player_see_unit(aplayer, aunit)) {
            unit_goes_out_of_sight(aplayer, aunit);
          }
        } players_iterate_end;
      }
    } unit_list_iterate_end;
  }
 
  tile_add_extra(ptile, pextra);
 
  /* Watchtower might become effective. */
  unit_list_refresh_vision(ptile->units);
 
  if (pextra->data.base != nullptr) {
    /* Claim bases on tile */
    if (pplayer) {
      struct player *old_owner = extra_owner(ptile);
 
      /* Created base from nullptr -> pplayer */
      map_claim_base(ptile, pextra, pplayer, nullptr);
 
      if (old_owner != pplayer) {
        /* Existing bases from old_owner -> pplayer */
        extra_type_by_cause_iterate(EC_BASE, oldbase) {
          if (oldbase != pextra) {
            map_claim_base(ptile, oldbase, pplayer, old_owner);
          }
        } extra_type_by_cause_iterate_end;
 
        ptile->extras_owner = pplayer;
      }
    } else {
      /* Player who already owns bases on tile claims new base */
      map_claim_base(ptile, pextra, extra_owner(ptile), nullptr);
    }
  }
 
  if (extras_removed) {
    /* Maybe conflicting extra that was removed was the only thing
     * making tile native to some unit. */
    bounce_units_on_terrain_change(ptile);
  }
}
 
/**********************************************************************/
void destroy_extra(struct tile *ptile, struct extra_type *pextra)
{
  bv_player base_seen;
  bool real = tile_map_check(&(wld.map), ptile);
 
  /* Remember what players were able to see the base. */
  if (real) {
    BV_CLR_ALL(base_seen);
    players_iterate(pplayer) {
      if (map_is_known_and_seen(ptile, pplayer, V_MAIN)) {
        BV_SET(base_seen, player_index(pplayer));
      }
    } players_iterate_end;
  }
 
  if (real && is_extra_caused_by(pextra, EC_BASE)) {
    struct base_type *pbase = extra_base_get(pextra);
    struct player *owner = extra_owner(ptile);
 
    if (territory_claiming_base(pbase)) {
      map_clear_border(ptile);
    }
 
    if (owner != nullptr
        && (0 <= pbase->vision_main_sq || 0 <= pbase->vision_invis_sq)) {
      /* Base provides vision, but no borders. */
      const v_radius_t old_radius_sq =
        V_RADIUS(0 <= pbase->vision_main_sq ? pbase->vision_main_sq : -1,
                 0 <= pbase->vision_invis_sq ? pbase->vision_invis_sq : -1,
                 0 <= pbase->vision_subs_sq ? pbase->vision_subs_sq : -1);
      const v_radius_t new_radius_sq = V_RADIUS(-1, -1, -1);
 
      map_vision_update(owner, ptile, old_radius_sq, new_radius_sq,
                        game.server.vision_reveal_tiles);
    }
  }
 
  tile_remove_extra(ptile, pextra);
 
  if (real) {
    /* Remove base from vision of players which were able to see the base. */
    players_iterate(pplayer) {
      if (BV_ISSET(base_seen, player_index(pplayer))
          && update_player_tile_knowledge(pplayer, ptile)) {
        send_tile_info(pplayer->connections, ptile, FALSE);
      }
    } players_iterate_end;
 
    if (pextra->eus != EUS_NORMAL) {
      struct player *eowner = extra_owner(ptile);
 
      unit_list_iterate(ptile->units, aunit) {
        if (is_native_extra_to_utype(pextra, unit_type_get(aunit))) {
          players_iterate(aplayer) {
            if (can_player_see_unit(aplayer, aunit)
                && !pplayers_allied(aplayer, eowner)) {
              send_unit_info(aplayer->connections, aunit);
            }
          } players_iterate_end;
        }
      } unit_list_iterate_end;
    }
  }
}
 
/**********************************************************************/
bool give_distorted_map(struct player *pfrom, struct player *pto,
                        int prob, bool reveal_cities)
{
  bool updt = FALSE;
 
  buffer_shared_vision(pto);
 
  whole_map_iterate(&(wld.map), ptile) {
    if (fc_rand(100) < prob) {
      updt |= give_tile_info_from_player_to_player(pfrom, pto, ptile);
    } else if (reveal_cities && tile_city(ptile) != nullptr) {
      updt|= give_tile_info_from_player_to_player(pfrom, pto, ptile);
    }
  } whole_map_iterate_end;
 
  unbuffer_shared_vision(pto);
 
  return updt;
}
 
/**********************************************************************/
void tile_change_side_effects(struct tile *ptile, bool refresh_city)
{
  struct city *pcity = ptile->worked;
 
  /* Check the unit activities. */
  unit_activities_cancel_all_illegal_area(ptile);
 
  if (pcity != nullptr && !is_free_worked(pcity, ptile)
      && get_city_tile_output_bonus(pcity, ptile, nullptr,
                                    EFT_TILE_WORKABLE) <= 0) {
    city_map_update_empty(pcity, ptile);
    pcity->specialists[DEFAULT_SPECIALIST]++;
 
    if (refresh_city) {
      auto_arrange_workers(pcity);
      send_city_info(nullptr, pcity);
    }
  }
}