daicity.c

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/***********************************************************************
 Freeciv - Copyright (C) 1996 - A Kjeldberg, L Gregersen, P Unold
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
***********************************************************************/
 
#ifdef HAVE_CONFIG_H
#include <fc_config.h>
#endif
 
#include <string.h>
#include <math.h> /* pow */
 
/* utility */
#include "rand.h"
#include "registry.h"
 
/* common */
#include "actions.h"
#include "game.h"
#include "government.h"
#include "map.h"
#include "research.h"
#include "specialist.h"
 
/* server */
#include "cityhand.h"
#include "citytools.h"
#include "cityturn.h"
#include "notify.h"
#include "plrhand.h"
#include "srv_log.h"
#include "unithand.h"
#include "unittools.h"
 
/* server/advisors */
#include "advdata.h"
#include "advtools.h"
#include "autoworkers.h"
#include "advbuilding.h"
#include "infracache.h"
 
/* ai */
#include "aitraits.h"
#include "difficulty.h"
#include "handicaps.h"
 
/* ai/default */
#include "daidata.h"
#include "daidiplomacy.h"
#include "daidomestic.h"
#include "daihand.h"
#include "daimilitary.h"
#include "daieffects.h"
#include "daiplayer.h"
#include "daisettler.h"
#include "daitools.h"
 
#include "daicity.h"
 
#define LOG_BUY LOG_DEBUG
#define LOG_EMERGENCY LOG_VERBOSE
#define LOG_WANT LOG_VERBOSE
 
/* TODO:  AI_CITY_RECALC_SPEED should be configurable to ai difficulty.
          -kauf  */
#define AI_CITY_RECALC_SPEED 5
 
#define AI_BA_RECALC_SPEED 5
 
#define SPECVEC_TAG tech
#define SPECVEC_TYPE struct advance *
#include "specvec.h"
 
#define SPECVEC_TAG impr
#define SPECVEC_TYPE const struct impr_type *
#include "specvec.h"
 
/* Iterate over cities within a certain range around a given city
 * (city_here) that exist within a given city list. */
#define city_range_iterate(city_here, list, range, city)                \
{                                                                       \
  city_list_iterate(list, city) {                                       \
    if (range == REQ_RANGE_PLAYER                                       \
        || range == REQ_RANGE_TEAM                                      \
        || range == REQ_RANGE_ALLIANCE                                  \
        || (range == REQ_RANGE_TRADE_ROUTE                              \
         && (city == city_here                                          \
             || have_cities_trade_route(city, city_here)))              \
     || ((range == REQ_RANGE_CITY || range == REQ_RANGE_LOCAL)          \
      && city == city_here)                                             \
     || (range == REQ_RANGE_CONTINENT                                   \
      && tile_continent(city->tile) ==                                  \
         tile_continent(city_here->tile))) {
 
#define city_range_iterate_end                                          \
    }                                                                   \
  } city_list_iterate_end;                                              \
}
 
#define CITY_EMERGENCY(pcity)                                           \
 (pcity->surplus[O_SHIELD] < 0 || city_unhappy(pcity)                   \
  || pcity->food_stock + pcity->surplus[O_FOOD] < 0)
 
static void dai_city_sell_noncritical(struct city *pcity,
                                      bool redundant_only);
static void resolve_city_emergency(struct ai_type *ait,
                                   struct player *pplayer,
                                   struct city *pcity);
 
/**********************************************************************/
static void want_tech_for_improvement_effect(struct ai_type *ait,
                                             struct player *pplayer,
                                             const struct city *pcity,
                                             const struct impr_type *pimprove,
                                             const struct advance *tech,
                                             adv_want building_want)
{
  /* The conversion factor was determined by experiment,
   * and might need adjustment. See also dai_tech_effect_values()
   */
  const adv_want tech_want
    = building_want * def_ai_city_data(pcity, ait)->building_wait * 14 / 8;
#if 0
  /* This logging is relatively expensive,
   * so activate it only while necessary. */
  TECH_LOG(LOG_DEBUG, pplayer, tech,
           "wanted by %s for building: %d -> %d",
           city_name_get(pcity), improvement_rule_name(pimprove),
           building_want, tech_want);
#endif /* 0 */
  if (tech) {
    def_ai_player_data(pplayer, ait)->tech_want[advance_index(tech)]
      += tech_want;
  }
}
 
/**********************************************************************/
void want_techs_for_improvement_effect(struct ai_type *ait,
                                       struct player *pplayer,
                                       const struct city *pcity,
                                       const struct impr_type *pimprove,
                                       struct tech_vector *needed_techs,
                                       adv_want building_want)
{
  int t;
  int n_needed_techs = tech_vector_size(needed_techs);
 
  for (t = 0; t < n_needed_techs; t++) {
    want_tech_for_improvement_effect(ait, pplayer, pcity, pimprove,
                                     *tech_vector_get(needed_techs, t),
                                     building_want);
  }
}
 
/**********************************************************************/
void dont_want_tech_obsoleting_impr(struct ai_type *ait,
                                    struct player *pplayer,
                                    const struct city *pcity,
                                    const struct impr_type *pimprove,
                                    adv_want building_want)
{
  requirement_vector_iterate(&pimprove->obsolete_by, pobs) {
    if (pobs->source.kind == VUT_ADVANCE && pobs->present) {
      want_tech_for_improvement_effect(ait, pplayer, pcity, pimprove,
                                       pobs->source.value.advance,
                                       -building_want);
    }
  } requirement_vector_iterate_end;
}
 
/**********************************************************************/
static void dai_barbarian_choose_build(struct player *pplayer,
                                       struct city *pcity,
                                       struct adv_choice *choice)
{
  struct unit_type *bestunit = nullptr;
  int i, bestattack = 0;
  const struct civ_map *nmap = &(wld.map);
 
  /* Choose the best unit among the basic ones */
  for (i = 0; i < num_role_units(L_BARBARIAN_BUILD); i++) {
    struct unit_type *iunit = get_role_unit(L_BARBARIAN_BUILD, i);
 
    if (iunit->attack_strength > bestattack
        && can_city_build_unit_now(nmap, pcity, iunit,
                                   RPT_CERTAIN)) {
      bestunit = iunit;
      bestattack = iunit->attack_strength;
    }
  }
 
  /* Choose among those made available through other civ's research */
  for (i = 0; i < num_role_units(L_BARBARIAN_BUILD_TECH); i++) {
    struct unit_type *iunit = get_role_unit(L_BARBARIAN_BUILD_TECH, i);
 
    if (iunit->attack_strength > bestattack
        && can_city_build_unit_now(nmap, pcity, iunit,
                                   RPT_CERTAIN)) {
      bestunit = iunit;
      bestattack = iunit->attack_strength;
    }
  }
 
  /* If found anything, put it into the choice */
  if (bestunit) {
    choice->value.utype = bestunit;
    /* "Overriding military emergency" indicator */
    choice->want   = DAI_WANT_MILITARY_EMERGENCY;
    choice->type   = CT_ATTACKER;
    adv_choice_set_use(choice, "barbarian");
  } else {
    log_base(LOG_WANT, "Barbarians don't know what to build!");
  }
}
 
/**********************************************************************/
static void dai_city_choose_build(struct ai_type *ait,
                                  struct player *pplayer,
                                  struct city *pcity)
{
  struct adv_choice *newchoice;
  struct adv_data *adv = adv_data_get(pplayer, nullptr);
  struct ai_city *city_data = def_ai_city_data(pcity, ait);
  const struct civ_map *nmap = &(wld.map);
 
  if (has_handicap(pplayer, H_AWAY)
      && !city_built_last_turn(pcity)
      && city_data->urgency == 0) {
    /* Don't change existing productions unless we have to. */
    return;
  }
 
  if (is_barbarian(pplayer)) {
    dai_barbarian_choose_build(pplayer, pcity, &(city_data->choice));
  } else {
    if ((city_data->choice.want < DAI_WANT_MILITARY_EMERGENCY
         || city_data->urgency == 0)
        && !(dai_on_war_footing(ait, pplayer) && city_data->choice.want > 0
             && pcity->id != adv->wonder_city)) {
      newchoice = domestic_advisor_choose_build(ait, pplayer, pcity);
      adv_choice_copy(&(city_data->choice),
                      adv_better_choice(&(city_data->choice), newchoice));
      adv_free_choice(newchoice);
    }
  }
 
  /* Fallbacks */
  if (city_data->choice.want == 0) {
    /* Fallbacks do happen with techlevel 0, which is now default. -- Per */
    CITY_LOG(LOG_WANT, pcity, "Falling back - didn't want to build soldiers,"
             " workers, caravans, settlers, or buildings!");
    city_data->choice.want = 1;
    if (best_role_unit(pcity, action_id_get_role(ACTION_TRADE_ROUTE))) {
      city_data->choice.value.utype
        = best_role_unit(pcity, action_id_get_role(ACTION_TRADE_ROUTE));
      city_data->choice.type = CT_CIVILIAN;
      adv_choice_set_use(&(city_data->choice), "fallback trade route");
    } else {
      unsigned int our_def = assess_defense_quadratic(ait, pcity);
 
      if (our_def == 0
          && dai_process_defender_want(ait, nmap, pplayer, pcity, 1,
                                       &(city_data->choice), 0)) {
        adv_choice_set_use(&(city_data->choice), "fallback defender");
        CITY_LOG(LOG_DEBUG, pcity, "Building fallback defender");
      } else if (best_role_unit(pcity, UTYF_WORKERS)) {
        city_data->choice.value.utype
          = dai_role_utype_for_terrain_class(pcity, UTYF_WORKERS, TC_LAND);
        city_data->choice.type = CT_CIVILIAN;
        adv_choice_set_use(&(city_data->choice), "fallback worker");
      } else {
        CITY_LOG(LOG_ERROR, pcity, "Cannot even build a fallback "
                 "(caravan/coinage/settlers). Fix the ruleset!");
        city_data->choice.want = 0;
      }
    }
  }
 
  if (city_data->choice.want != 0) {
    struct universal build_new;
 
    ADV_CHOICE_ASSERT(city_data->choice);
 
#ifdef ADV_CHOICE_TRACK
    if (city_data->choice.log_if_chosen) {
      log_normal("%s wants %s for %s with desire " ADV_WANT_PRINTF ".",
                 city_name_get(pcity),
                 adv_choice_rule_name(&city_data->choice),
                 city_data->choice.use,
                 city_data->choice.want);
    }
#endif /* ADV_CHOICE_TRACK */
 
    CITY_LOG(LOG_DEBUG, pcity, "wants %s with desire " ADV_WANT_PRINTF ".",
             adv_choice_rule_name(&city_data->choice),
             city_data->choice.want);
 
    switch (city_data->choice.type) {
    case CT_CIVILIAN:
    case CT_ATTACKER:
    case CT_DEFENDER:
      build_new.kind = VUT_UTYPE;
      build_new.value.utype = city_data->choice.value.utype;
      break;
    case CT_BUILDING:
      build_new.kind = VUT_IMPROVEMENT;
      build_new.value.building = city_data->choice.value.building;
      break;
    case CT_NONE:
      build_new.kind = VUT_NONE;
      break;
    case CT_LAST:
      build_new.kind = universals_n_invalid();
      break;
    };
 
    change_build_target(pplayer, pcity, &build_new,
                        E_CITY_PRODUCTION_CHANGED);
  }
}
 
/**********************************************************************/
static void try_to_sell_stuff(struct player *pplayer, struct city *pcity)
{
  improvement_iterate(pimprove) {
    if (can_city_sell_building(pcity, pimprove)
        && !building_has_effect(pimprove, EFT_DEFEND_BONUS)) {
      /* Selling walls to buy defenders is counterproductive -- Syela */
      really_handle_city_sell(pplayer, pcity, pimprove);
      break;
    }
  } improvement_iterate_end;
}
 
/**********************************************************************/
static void increase_maxbuycost(struct player *pplayer, int new_value)
{
  pplayer->ai_common.maxbuycost = MAX(pplayer->ai_common.maxbuycost, new_value);
}
 
/**********************************************************************/
static void dai_upgrade_units(struct city *pcity, int limit, bool military)
{
  action_id upgrade_actions[MAX_NUM_ACTIONS];
  struct player *pplayer = city_owner(pcity);
  int expenses;
 
  {
    /* Find upgrade unit actions */
    int i = 0;
    action_array_add_all_by_result(upgrade_actions, &i, ACTRES_UPGRADE_UNIT);
    action_array_end(upgrade_actions, i);
  }
 
  dai_calc_data(pplayer, nullptr, &expenses, nullptr);
 
  unit_list_iterate(pcity->tile->units, punit) {
    if (pcity->owner == punit->owner) {
      /* Only upgrade units you own, not allied ones */
 
      const struct unit_type *old_type = unit_type_get(punit);
      const struct unit_type *punittype
        = can_upgrade_unittype(pplayer, old_type);
 
      if (military && !IS_ATTACKER(old_type)) {
        /* Only upgrade military units this round */
        continue;
      } else if (!military && IS_ATTACKER(old_type)) {
        /* Only civilians or transports this round */
        continue;
      }
 
      if (punittype == nullptr) {
        continue;
      }
 
      action_array_iterate(upgrade_actions, act_id) {
        if (action_ever_possible(act_id)) {
          const struct action *paction = action_by_number(act_id);
          int cost = unit_upgrade_price(pplayer, old_type, punittype);
          int real_limit = limit;
 
          /* Sinking Triremes are DANGEROUS!!
           * We'll do anything to upgrade 'em. */
          /* FIXME: This assumes rules to be quite close to civ/2.
           * Of the supplied rulesets those are the only ones with
           * UTYF_COAST unit, but... */
          if (unit_has_type_flag(punit, UTYF_COAST)) {
            real_limit = expenses;
          }
          if (pplayer->economic.gold - cost > real_limit) {
            CITY_LOG(LOG_BUY, pcity, "Upgraded %s to %s for %d (%s)",
                     unit_rule_name(punit),
                     utype_rule_name(punittype),
                     cost,
                     military ? "military" : "civilian");
            unit_do_action(city_owner(pcity), punit->id,
                           pcity->id, 0, "",
                           paction->id);
          } else {
            increase_maxbuycost(pplayer, cost);
          }
        }
      } action_array_iterate_end;
    }
  } unit_list_iterate_end;
}
 
/**********************************************************************/
static void unit_do_disband_trad(struct player *owner, struct unit *punit,
                                 const enum action_requester requester)
{
  const int punit_id_stored = punit->id;
  const struct civ_map *nmap = &(wld.map);
 
  fc_assert_ret(owner == unit_owner(punit));
 
  /* Help Wonder gives 100% of the shields used to produce the unit to the
   * city where it is located. */
  if (unit_can_do_action(punit, ACTION_HELP_WONDER)) {
    struct city *tgt_city;
 
    /* Only a city at the same tile as the unit can benefit. */
    tgt_city = tile_city(unit_tile(punit));
 
    if (tgt_city
        && is_action_enabled_unit_on_city(nmap, ACTION_HELP_WONDER,
                                          punit, tgt_city)) {
      if (unit_perform_action(owner, punit->id, tgt_city->id,
                              0, nullptr, ACTION_HELP_WONDER, requester)) {
        /* No shields wasted. The unit did Help Wonder. */
        return;
      }
 
      if (!unit_is_alive(punit_id_stored)) {
        /* The unit is gone. Maybe it was killed in Lua? */
        return;
      }
    }
  }
 
  /* Disbanding a unit inside a city gives it 50% of the shields used to
   * produce the unit. */
  if (unit_can_do_action(punit, ACTION_DISBAND_UNIT_RECOVER)) {
    struct city *tgt_city;
 
    /* Only a city at the same tile as the unit can benefit. */
    tgt_city = tile_city(unit_tile(punit));
 
    if (tgt_city
        && is_action_enabled_unit_on_city(nmap, ACTION_DISBAND_UNIT_RECOVER,
                                          punit, tgt_city)) {
      if (unit_perform_action(owner, punit->id, tgt_city->id,
                              0, nullptr, ACTION_DISBAND_UNIT_RECOVER,
                              requester)) {
        /* The unit did Disband Unit Recover. 50% of the shields wasted. */
        return;
      }
 
      if (!unit_is_alive(punit_id_stored)) {
        /* The unit is gone. Maybe it was killed in Lua? */
        return;
      }
    }
  }
 
  /* Try to disband even if all shields will be wasted. */
  if (unit_can_do_action(punit, ACTION_DISBAND_UNIT)) {
    if (is_action_enabled_unit_on_self(nmap, ACTION_DISBAND_UNIT, punit)) {
      if (unit_perform_action(owner, punit->id, punit->id,
                              0, nullptr, ACTION_DISBAND_UNIT, requester)) {
        /* All shields wasted. The unit did Disband Unit. */
        return;
      }
    }
  }
}
 
/**********************************************************************/
static void dai_spend_gold(struct ai_type *ait, struct player *pplayer)
{
  struct adv_choice bestchoice;
  int cached_limit = dai_gold_reserve(pplayer);
  int expenses;
  bool war_footing = dai_on_war_footing(ait, pplayer);
 
  /* Disband explorers that are at home but don't serve a purpose.
   * FIXME: This is a hack, and should be removed once we
   * learn how to ferry explorers to new land. */
  city_list_iterate(pplayer->cities, pcity) {
    struct tile *ptile = pcity->tile;
    unit_list_iterate_safe(ptile->units, punit) {
      if (unit_has_type_role(punit, L_EXPLORER)
          && pcity->id == punit->homecity
          && def_ai_city_data(pcity, ait)->urgency == 0) {
        CITY_LOG(LOG_BUY, pcity, "disbanding %s to increase production",
                 unit_rule_name(punit));
        unit_do_disband_trad(pplayer, punit, ACT_REQ_PLAYER);
      }
    } unit_list_iterate_safe_end;
  } city_list_iterate_end;
 
  dai_calc_data(pplayer, nullptr, &expenses, nullptr);
 
  do {
    bool expensive; /* Don't buy when it costs x2 unless we must */
    int buycost;
    int limit = cached_limit; /* cached_limit is our gold reserve */
    struct city *pcity = nullptr;
    struct ai_city *city_data;
 
    /* Find highest wanted item on the buy list */
    adv_init_choice(&bestchoice);
    city_list_iterate(pplayer->cities, acity) {
      struct ai_city *acity_data = def_ai_city_data(acity, ait);
 
      if (acity_data->choice.want
          > bestchoice.want && ai_fuzzy(pplayer, TRUE)) {
        adv_choice_copy(&bestchoice, &(acity_data->choice));
        pcity = acity;
      }
    } city_list_iterate_end;
 
    /* We found nothing, so we're done */
    if (pcity == nullptr) {
      break;
    }
 
    city_data = def_ai_city_data(pcity, ait);
 
    /* Not dealing with this city a second time */
    city_data->choice.want = -1;
 
    ADV_CHOICE_ASSERT(bestchoice);
 
    /* Try upgrade units at danger location (high want is usually danger) */
    if (city_data->urgency > 1) {
      if (bestchoice.type == CT_BUILDING
       && is_wonder(bestchoice.value.building)) {
        CITY_LOG(LOG_BUY, pcity, "Wonder being built in dangerous position!");
      } else {
        /* If we have urgent want, spend more */
        int upgrade_limit = limit;
 
        if (city_data->urgency > 1) {
          upgrade_limit = expenses;
        }
        /* Upgrade only military units now */
        dai_upgrade_units(pcity, upgrade_limit, TRUE);
      }
    }
 
    if (pcity->anarchy != 0 && bestchoice.type != CT_BUILDING) {
      continue; /* Nothing we can do */
    }
 
    /* Cost to complete production */
    buycost = city_production_buy_gold_cost(pcity);
 
    if (buycost <= 0) {
      continue; /* Already completed */
    }
 
    if (is_unit_choice_type(bestchoice.type)
        && utype_is_cityfounder(bestchoice.value.utype)) {
      if (get_city_bonus(pcity, EFT_SHRINK_FOOD) <= 0
          && bestchoice.value.utype->pop_cost > 0
          && city_size_get(pcity) <= bestchoice.value.utype->pop_cost) {
        /* Don't buy settlers in cities that cannot afford
         * the population cost. */
        /* This used to check also if city is about to grow to required size
         * next turn and allow buying of settlers in that case, but current
         * order of end/start turn activities is such that settler building
         * fails already before city grows. */
        continue;
      } else if (city_list_size(pplayer->cities) > 6) {
        /* Don't waste precious money buying settlers late game
         * since this raises taxes, and we want science. Adjust this
         * again when our tax algorithm is smarter. */
        continue;
      } else if (war_footing) {
        continue;
      }
    } else {
      /* We are not a settler. Therefore we increase the cash need we
       * balance our buy desire with to keep cash at hand for emergencies
       * and for upgrades */
      limit *= 2;
    }
 
    /* It costs x2 to buy something with no shields contributed */
    expensive = (pcity->shield_stock == 0)
                || (pplayer->economic.gold - buycost < limit);
 
    if (bestchoice.type == CT_ATTACKER
        && buycost
           > utype_build_shield_cost(pcity, nullptr,
                                     bestchoice.value.utype) * 2
        && !war_footing) {
       /* Too expensive for an offensive unit */
       continue;
    }
 
    /* FIXME: Here Syela wanted some code to check if
     * pcity was doomed, and we should therefore attempt
     * to sell everything in it of non-military value */
 
    if (pplayer->economic.gold - expenses >= buycost
        && (!expensive
            || (city_data->grave_danger != 0
                && assess_defense(ait, pcity) == 0)
            || (bestchoice.want > 200 && city_data->urgency > 1))) {
      /* Buy stuff */
      CITY_LOG(LOG_BUY, pcity,
               "Crash buy of %s for %d (want " ADV_WANT_PRINTF ")",
               adv_choice_rule_name(&bestchoice),
               buycost,
               bestchoice.want);
      really_handle_city_buy(pplayer, pcity);
    } else if (city_data->grave_danger != 0
               && bestchoice.type == CT_DEFENDER
               && assess_defense(ait, pcity) == 0) {
      /* We have no gold but MUST have a defender */
      CITY_LOG(LOG_BUY, pcity, "must have %s but can't afford it (%d < %d)!",
               adv_choice_rule_name(&bestchoice),
               pplayer->economic.gold,
               buycost);
      try_to_sell_stuff(pplayer, pcity);
      if (pplayer->economic.gold - expenses >= buycost) {
        CITY_LOG(LOG_BUY, pcity, "now we can afford it (sold something)");
        really_handle_city_buy(pplayer, pcity);
      }
      increase_maxbuycost(pplayer, buycost);
    }
  } while (TRUE);
 
  if (!war_footing) {
    /* Civilian upgrades now */
    city_list_iterate(pplayer->cities, pcity) {
      dai_upgrade_units(pcity, cached_limit, FALSE);
    } city_list_iterate_end;
  }
 
  log_base(LOG_BUY, "%s wants to keep %d in reserve (tax factor %d)",
           player_name(pplayer), cached_limit,
           pplayer->ai_common.maxbuycost);
}
 
/**********************************************************************/
static int unit_food_upkeep(struct unit *punit)
{
  int upkeep = unit_upkeep_cost(punit, O_FOOD);
 
  if (punit->id != 0 && punit->homecity == 0) {
    upkeep = 0; /* Thanks, Peter */
  }
 
  return upkeep;
}
 
/**********************************************************************/
static int unit_foodbox_cost(struct unit *punit)
{
  int pop_cost = unit_type_get(punit)->pop_cost;
 
  if (pop_cost <= 0) {
    return 0;
  }
 
  if (punit->id == 0) {
    /* It is a virtual unit, so must start in a city... */
    struct city *pcity = tile_city(unit_tile(punit));
    int size = city_size_get(pcity);
    int cost = 0;
    int i;
 
    /* The default is to lose 100%. The granary bonus reduces this. */
    int foodloss_pct = 100 - city_shrink_granary_savings(pcity);
 
    foodloss_pct = CLIP(0, foodloss_pct, 100);
    fc_assert_ret_val(pcity != nullptr, -1);
    fc_assert(size >= pop_cost);
 
    for (i = pop_cost; i > 0 ; i--) {
      cost += city_granary_size(size--);
    }
    cost = cost * foodloss_pct / 100;
 
    return cost;
  }
 
  return 30;
}
 
/**********************************************************************/
static void contemplate_terrain_improvements(struct ai_type *ait,
                                             struct city *pcity)
{
  struct unit *virtualunit;
  int want;
  enum unit_activity best_act;
  struct extra_type *best_target;
  struct tile *best_tile = nullptr; /* May be accessed by log_*() calls. */
  struct tile *pcenter = city_tile(pcity);
  struct player *pplayer = city_owner(pcity);
  struct adv_data *adv = adv_data_get(pplayer, nullptr);
  struct ai_plr *ai = dai_plr_data_get(ait, pplayer, nullptr);
  struct unit_type *utype;
  Continent_id place = tile_continent(pcenter);
  struct ai_city *city_data = def_ai_city_data(pcity, ait);
  struct dai_private_data *private = (struct dai_private_data *)ait->private;
  const struct civ_map *nmap = &(wld.map);
 
  if (!private->contemplace_workers) {
    /* AI type uses custom method to set worker want and type. */
    return;
  }
 
  city_data->worker_want = 0; /* Make sure old want does not stay if
                               * we don't want now */
 
  utype = dai_role_utype_for_terrain_class(pcity, UTYF_WORKERS, TC_LAND);
 
  if (utype == nullptr) {
    log_debug("No UTYF_WORKERS role unit available");
    return;
  }
 
  /* Create a localized "virtual" unit to do operations with. */
  virtualunit = unit_virtual_create(pplayer, pcity, utype, 0);
  /* Advisors data space not allocated as it's not needed in the
     lifetime of the virtualunit. */
  unit_tile_set(virtualunit, pcenter);
  want = worker_evaluate_improvements(nmap, virtualunit,
                                      &best_act, &best_target,
                                      &best_tile,
                                      nullptr, nullptr);
  if (unit_type_get(virtualunit)->pop_cost >= city_size_get(pcity)) {
    /* We don't like disbanding the city as a side effect */
    unit_virtual_destroy(virtualunit);
 
    return;
  }
  /* We consider unit_food_upkeep with only half FOOD_WEIGHTING to
   * balance the fact that unit can improve many tiles during its
   * lifetime, and want is calculated for just one of them.
   * Having full FOOD_WEIGHT here would mean that tile improvement of
   * +1 food would give just zero want for settler. Other weights
   * are lower, so +1 shield - unit food upkeep would be negative. */
  want = (want - unit_food_upkeep(virtualunit) * FOOD_WEIGHTING / 2) * 100
         / (40 + unit_foodbox_cost(virtualunit));
  unit_virtual_destroy(virtualunit);
 
  /* Massage our desire based on available statistics to prevent
   * overflooding with worker type units if they come cheap in
   * the ruleset */
  if (place >= 0) {
    want /= MAX(1, ai->stats.workers[place] / (adv->stats.cities[place] + 1));
    want -= ai->stats.workers[place];
  } else {
    want /= MAX(1, ai->stats.ocean_workers[-place]
                   / (adv->stats.ocean_cities[-place] + 1));
    want -= ai->stats.ocean_workers[-place];
  }
  want = MAX(want, 0);
 
  if (place >= 0) {
    CITY_LOG(LOG_DEBUG, pcity, "wants %s with want %d to do %s at (%d,%d), "
             "we have %d workers and %d cities on the continent",
             utype_rule_name(utype),
             want,
             get_activity_text(best_act),
             TILE_XY(best_tile),
             ai->stats.workers[place],
             adv->stats.cities[place]);
  } else {
    CITY_LOG(LOG_DEBUG, pcity, "wants %s with want %d to do %s at (%d,%d), "
             "we have %d workers and %d cities on the ocean",
             utype_rule_name(utype),
             want,
             get_activity_text(best_act),
             TILE_XY(best_tile),
             ai->stats.ocean_workers[-place],
             adv->stats.ocean_cities[-place]);
  }
 
  fc_assert(want >= 0);
 
  city_data->worker_want = want;
  city_data->worker_type
    = dai_role_utype_for_terrain_class(pcity, UTYF_WORKERS,
                                       place >= 0 ? TC_LAND : TC_OCEAN);
}
 
/**********************************************************************/
void dai_manage_cities(struct ai_type *ait, struct player *pplayer)
{
  pplayer->ai_common.maxbuycost = 0;
 
  TIMING_LOG(AIT_EMERGENCY, TIMER_START);
  city_list_iterate(pplayer->cities, pcity) {
    if (CITY_EMERGENCY(pcity)
        || city_granary_size(city_size_get(pcity)) == pcity->food_stock) {
      /* Having a full granary isn't an emergency, but we want to rearrange */
      auto_arrange_workers(pcity); /* This usually helps */
    }
    if (CITY_EMERGENCY(pcity)) {
      /* Fix critical shortages or unhappiness */
      resolve_city_emergency(ait, pplayer, pcity);
    }
    dai_city_sell_noncritical(pcity, TRUE);
    sync_cities();
  } city_list_iterate_end;
  if (pplayer->economic.tax >= 30 /* Otherwise expect it to increase tax */
      && player_get_expected_income(pplayer) < -(pplayer->economic.gold)) {
    int count = city_list_size(pplayer->cities);
    struct city *sellers[count + 1];
    int i;
 
    /* Randomized order */
    count = 0;
    city_list_iterate(pplayer->cities, pcity) {
      sellers[count++] = pcity;
    } city_list_iterate_end;
 
    for (i = 0; i < count; i++) {
      int replace = fc_rand(count);
      struct city *tmp;
 
      tmp = sellers[i];
      sellers[i] = sellers[replace];
      sellers[replace] = tmp;
    }
 
    i = 0;
    while (player_get_expected_income(pplayer) < -(pplayer->economic.gold)
           && i < count) {
      dai_city_sell_noncritical(sellers[i++], FALSE);
    }
  }
  TIMING_LOG(AIT_EMERGENCY, TIMER_STOP);
 
  TIMING_LOG(AIT_BUILDINGS, TIMER_START);
  building_advisor(pplayer);
  TIMING_LOG(AIT_BUILDINGS, TIMER_STOP);
 
  /* Initialize the infrastructure cache, which is used shortly. */
  initialize_infrastructure_cache(pplayer);
  city_list_iterate(pplayer->cities, pcity) {
    struct ai_city *city_data = def_ai_city_data(pcity, ait);
    struct adv_choice *choice;
 
    if (city_data->choice.want <= 0) {
      /* Note that this function mungs the seamap, but we don't care */
      TIMING_LOG(AIT_CITY_MILITARY, TIMER_START);
      choice = military_advisor_choose_build(ait, &(wld.map), pplayer, pcity,
                                             nullptr);
      adv_choice_copy(&(city_data->choice), choice);
      adv_free_choice(choice);
      TIMING_LOG(AIT_CITY_MILITARY, TIMER_STOP);
    }
    if (dai_on_war_footing(ait, pplayer) && city_data->choice.want > 0) {
      city_data->worker_want = 0;
      city_data->founder_want = 0;
      city_data->founder_turn = game.info.turn; /* Do not consider zero we set
                                                 * here a valid value,
                                                 * if real want is needed.
                                                 * Recalculate immediately
                                                 * in such situation. */
      continue; /* Go, soldiers! */
    }
    /* Will record its findings in pcity->worker_want */
    TIMING_LOG(AIT_CITY_TERRAIN, TIMER_START);
    contemplate_terrain_improvements(ait, pcity);
    TIMING_LOG(AIT_CITY_TERRAIN, TIMER_STOP);
 
    TIMING_LOG(AIT_CITY_SETTLERS, TIMER_START);
    if (city_data->founder_turn <= game.info.turn) {
      /* Will record its findings in pcity->founder_want */
      contemplate_new_city(ait, pcity);
      /* Avoid recalculating all the time.. */
      /* This means AI is not very opportunistic if there happens to open up
       * spot for a new city. */
      city_data->founder_turn
        = game.info.turn + fc_rand(AI_CITY_RECALC_SPEED) + AI_CITY_RECALC_SPEED;
    } else if (pcity->server.debug) {
      /* Recalculate every turn */
      contemplate_new_city(ait, pcity);
    }
    TIMING_LOG(AIT_CITY_SETTLERS, TIMER_STOP);
    ADV_CHOICE_ASSERT(city_data->choice);
  } city_list_iterate_end;
  /* Reset auto settler state for the next run. */
  dai_auto_settler_reset(ait, pplayer);
 
  city_list_iterate(pplayer->cities, pcity) {
    dai_city_choose_build(ait, pplayer, pcity);
 
    /* Initialize for next turn */
    def_ai_city_data(pcity, ait)->choice.want = -1;
  } city_list_iterate_end;
 
  dai_spend_gold(ait, pplayer);
}
 
/**********************************************************************/
static bool building_crucial(const struct player *plr,
                             struct impr_type *pimprove,
                             const struct city *pcity)
{
#if 0 /* This check will become more complicated now. */
  if (ai_wants_no_science(plr)
      && building_has_effect(pimprove, EFT_SCIENCE_BONUS)) {
    return FALSE;
  }
#endif /* 0 */
 
  if (building_has_effect(pimprove, EFT_DEFEND_BONUS)
        /* selling city walls is really, really dumb -- Syela */
      || is_improvement_productive(pcity, pimprove)) {
    return TRUE;
  }
 
  return FALSE;
}
 
/**********************************************************************/
static void dai_city_sell_noncritical(struct city *pcity,
                                      bool redundant_only)
{
  struct player *pplayer = city_owner(pcity);
 
  city_built_iterate(pcity, pimprove) {
    if (can_city_sell_building(pcity, pimprove)
        && !building_crucial(pplayer, pimprove, pcity)
        && (!redundant_only || is_improvement_redundant(pcity, pimprove))) {
      int gain = impr_sell_gold(pimprove);
 
      notify_player(pplayer, pcity->tile, E_IMP_SOLD, ftc_server,
                    PL_("%s is selling %s for %d.",
                        "%s is selling %s for %d.", gain),
                    city_link(pcity),
                    improvement_name_translation(pimprove),
                    gain);
      do_sell_building(pplayer, pcity, pimprove, "sold");
 
      return; /* Max 1 building each turn */
    }
  } city_built_iterate_end;
}
 
/**********************************************************************/
static void resolve_city_emergency(struct ai_type *ait,
                                   struct player *pplayer,
                                   struct city *pcity)
{
  struct tile *pcenter = city_tile(pcity);
  const struct civ_map *nmap = &(wld.map);
 
  log_base(LOG_EMERGENCY,
           "Emergency in %s (%s, angry%d, unhap%d food%d, prod%d)",
           city_name_get(pcity),
           city_unhappy(pcity) ? "unhappy" : "content",
           pcity->feel[CITIZEN_ANGRY][FEELING_FINAL],
           pcity->feel[CITIZEN_UNHAPPY][FEELING_FINAL],
           pcity->surplus[O_FOOD],
           pcity->surplus[O_SHIELD]);
 
  city_tile_iterate(nmap, city_map_radius_sq_get(pcity), pcenter, atile) {
    struct city *acity = tile_worked(atile);
 
    if (acity && acity != pcity && city_owner(acity) == city_owner(pcity))  {
      log_base(LOG_EMERGENCY, "%s taking over %s square in (%d, %d)",
               city_name_get(pcity), city_name_get(acity), TILE_XY(atile));
 
#ifndef FREECIV_NDEBUG
      int ax, ay;
#endif
      fc_assert_action(city_base_to_city_map(&ax, &ay, acity, atile),
                       continue);
 
      if (is_free_worked(acity, atile)) {
        /* Can't remove a worker here. */
        continue;
      }
 
      city_map_update_empty(acity, atile);
      acity->specialists[DEFAULT_SPECIALIST]++;
      city_freeze_workers_queue(acity);
    }
  } city_tile_iterate_end;
 
  auto_arrange_workers(pcity);
 
  if (!CITY_EMERGENCY(pcity)) {
    log_base(LOG_EMERGENCY, "Emergency in %s resolved", city_name_get(pcity));
    goto cleanup;
  }
 
  unit_list_iterate_safe(pcity->units_supported, punit) {
    if (city_unhappy(pcity)
        && (utype_happy_cost(unit_type_get(punit), pplayer) > 0
            && (unit_being_aggressive(nmap, punit) || is_field_unit(punit)))
        && def_ai_unit_data(punit, ait)->passenger == 0) {
      UNIT_LOG(LOG_EMERGENCY, punit, "is causing unrest, disbanded");
      /* TODO: If Help Wonder stops blocking Disband Unit there may be
       * cases where Disband Unit should be selected. Example: Field unit
       * in allied city that is building a wonder that makes the ally win
       * without sharing the victory. */
      /* TODO: Should the unit try to find legal targets at adjacent tiles?
       * Should it consider other self eliminating actions than the
       * components of the traditional disband? */
      unit_do_disband_trad(pplayer, punit, ACT_REQ_PLAYER);
      city_refresh(pcity);
    }
  } unit_list_iterate_safe_end;
 
  if (CITY_EMERGENCY(pcity)) {
    log_base(LOG_EMERGENCY, "Emergency in %s remains unresolved",
             city_name_get(pcity));
  } else {
    log_base(LOG_EMERGENCY,
             "Emergency in %s resolved by disbanding unit(s)",
             city_name_get(pcity));
  }
 
  cleanup:
  city_thaw_workers_queue();
  sync_cities();
}
 
/**********************************************************************/
void dai_city_alloc(struct ai_type *ait, struct city *pcity)
{
  struct ai_city *city_data = fc_calloc(1, sizeof(struct ai_city));
 
  city_data->building_wait = BUILDING_WAIT_MINIMUM;
  adv_init_choice(&(city_data->choice));
 
  city_set_ai_data(pcity, ait, city_data);
}
 
/**********************************************************************/
void dai_city_free(struct ai_type *ait, struct city *pcity)
{
  struct ai_city *city_data = def_ai_city_data(pcity, ait);
 
  if (city_data != nullptr) {
    adv_deinit_choice(&(city_data->choice));
    city_set_ai_data(pcity, ait, nullptr);
    FC_FREE(city_data);
  }
}
 
/**********************************************************************/
void dai_city_save(struct ai_type *ait, const char *aitstr,
                   struct section_file *file, const struct city *pcity,
                   const char *citystr)
{
  struct ai_city *city_data = def_ai_city_data(pcity, ait);
 
  /* FIXME: Remove this when the urgency is properly recalculated. */
  secfile_insert_int(file, city_data->urgency, "%s.%s.urgency",
                     citystr, aitstr);
 
  /* Avoid fc_rand() recalculations on subsequent reload. */
  secfile_insert_int(file, city_data->building_turn, "%s.%s.building_turn",
                     citystr, aitstr);
  secfile_insert_int(file, city_data->building_wait, "%s.%s.building_wait",
                     citystr, aitstr);
 
  /* Avoid fc_rand() and expensive recalculations on subsequent reload. */
  secfile_insert_int(file, city_data->founder_turn, "%s.%s.founder_turn",
                     citystr, aitstr);
  secfile_insert_int(file, city_data->founder_want, "%s.%s.founder_want",
                     citystr, aitstr);
  secfile_insert_bool(file, city_data->founder_boat, "%s.%s.founder_boat",
                      citystr, aitstr);
}
 
/**********************************************************************/
void dai_city_load(struct ai_type *ait, const char *aitstr,
                   const struct section_file *file,
                   struct city *pcity, const char *citystr)
{
  struct ai_city *city_data = def_ai_city_data(pcity, ait);
 
  /* FIXME: Remove this when the urgency is properly recalculated. */
  city_data->urgency
    = secfile_lookup_int_default(file, 0, "%s.%s.urgency", citystr, aitstr);
 
  /* Avoid fc_rand() recalculations on subsequent reload. */
  city_data->building_turn
    = secfile_lookup_int_default(file, 0, "%s.%s.building_turn", citystr,
                                 aitstr);
  city_data->building_wait
    = secfile_lookup_int_default(file, BUILDING_WAIT_MINIMUM,
                                 "%s.%s.building_wait", citystr, aitstr);
 
  /* Avoid fc_rand() and expensive recalculations on subsequent reload. */
  city_data->founder_turn
    = secfile_lookup_int_default(file, 0, "%s.%s.founder_turn", citystr,
                                 aitstr);
  city_data->founder_want
    = secfile_lookup_int_default(file, 0, "%s.%s.founder_want", citystr,
                                 aitstr);
  city_data->founder_boat
    = secfile_lookup_bool_default(file, (city_data->founder_want < 0),
                                  "%s.%s.founder_boat", citystr, aitstr);
}
 
/**********************************************************************/
static int action_target_neg_util(action_id act_id,
                                  const struct city *pcity)
{
  struct action *paction = action_by_number(act_id);
 
  fc_assert_msg(action_id_exists(act_id),
                "Action %d don't exist.", act_id);
 
  if (action_get_target_kind(paction) != ATK_CITY) {
    /* Not city targeted in this ruleset. */
    return 0;
  }
 
  switch (paction->result) {
  case ACTRES_SPY_INCITE_CITY:
    /* Copied from the evaluation of the No_Incite effect */
    return MAX((game.server.diplchance * 2
                - game.server.incite_total_factor) / 2
               - game.server.incite_improvement_factor * 5
               - game.server.incite_unit_factor * 5, 0);
 
  /* Really bad for the city owner. */
  case ACTRES_SPY_NUKE:
  case ACTRES_CONQUER_CITY:
  /* The ai will never destroy their own city to keep it out of enemy
   * hands. If it starts supporting it this value should change. */
  case ACTRES_DESTROY_CITY:
    return 20;
 
  /* Bad for the city owner. */
  case ACTRES_SPY_POISON:
  case ACTRES_SPY_SPREAD_PLAGUE:
  case ACTRES_SPY_SABOTAGE_CITY:
  case ACTRES_SPY_TARGETED_SABOTAGE_CITY:
  case ACTRES_SPY_SABOTAGE_CITY_PRODUCTION:
  case ACTRES_STRIKE_BUILDING:
  case ACTRES_STRIKE_PRODUCTION:
  case ACTRES_SPY_STEAL_GOLD:
  case ACTRES_NUKE:
    /* TODO: Individual and well balanced values */
    return 10;
 
  /* Good for an enemy */
  case ACTRES_SPY_STEAL_TECH:
  case ACTRES_SPY_TARGETED_STEAL_TECH:
  case ACTRES_STEAL_MAPS:
    /* TODO: Individual and well balanced values */
    return 8;
 
  /* Could be worse */
  case ACTRES_ESTABLISH_EMBASSY:
  case ACTRES_SPY_INVESTIGATE_CITY:
  case ACTRES_MARKETPLACE:
  case ACTRES_SPY_ESCAPE:
    /* TODO: Individual and well balanced values */
    return 1;
 
  /* Good for the city owner in most cases. */
  case ACTRES_TRADE_ROUTE:
  case ACTRES_HELP_WONDER:
  case ACTRES_JOIN_CITY:
  case ACTRES_DISBAND_UNIT_RECOVER:
  case ACTRES_HOME_CITY:
  case ACTRES_UPGRADE_UNIT:
  case ACTRES_AIRLIFT:
    /* TODO: Individual and well balanced values */
    return -1;
 
  /* Ruleset defined actions. We have no idea what they do. */
  case ACTRES_NONE:
    return 0;
 
  /* Shouldn't happen. */
  case ACTRES_PARADROP_CONQUER:
    /* Against the tile so potential city effects are overlooked for now. */
  case ACTRES_SPY_BRIBE_UNIT:
  case ACTRES_SPY_BRIBE_STACK:
  case ACTRES_SPY_SABOTAGE_UNIT:
  case ACTRES_SPY_ATTACK:
  case ACTRES_EXPEL_UNIT:
  case ACTRES_DISBAND_UNIT:
  case ACTRES_CAPTURE_UNITS:
  case ACTRES_BOMBARD:
  case ACTRES_FOUND_CITY:
  case ACTRES_NUKE_UNITS:
  case ACTRES_PARADROP:
  case ACTRES_ATTACK:
  case ACTRES_WIPE_UNITS:
  case ACTRES_COLLECT_RANSOM:
  case ACTRES_HEAL_UNIT:
  case ACTRES_TRANSFORM_TERRAIN:
  case ACTRES_CULTIVATE:
  case ACTRES_PLANT:
  case ACTRES_PILLAGE:
  case ACTRES_CLEAN:
  case ACTRES_FORTIFY:
  case ACTRES_ROAD:
  case ACTRES_CONVERT:
  case ACTRES_BASE:
  case ACTRES_MINE:
  case ACTRES_IRRIGATE:
  case ACTRES_TRANSPORT_DEBOARD:
  case ACTRES_TRANSPORT_BOARD:
  case ACTRES_TRANSPORT_UNLOAD:
  case ACTRES_TRANSPORT_LOAD:
  case ACTRES_TRANSPORT_DISEMBARK:
  case ACTRES_TRANSPORT_EMBARK:
  case ACTRES_CONQUER_EXTRAS:
  case ACTRES_HUT_ENTER:
  case ACTRES_HUT_FRIGHTEN:
  case ACTRES_UNIT_MOVE:
  case ACTRES_TELEPORT:
  case ACTRES_TELEPORT_CONQUER:
  case ACTRES_HOMELESS:
  case ACTRES_ENABLER_CHECK:
    fc_assert_msg(action_id_get_target_kind(act_id) == ATK_CITY,
                  "Action not aimed at cities");
    break;
  }
 
  /* Wrong action. Ignore it. */
  return 0;
}
 
/**********************************************************************/
static bool adjust_wants_for_reqs(struct ai_type *ait,
                                  struct player *pplayer,
                                  struct city *pcity,
                                  const struct impr_type *pimprove,
                                  const adv_want v)
{
  bool all_met = TRUE;
  int n_needed_techs = 0;
  int n_needed_improvements = 0;
  struct tech_vector needed_techs;
  struct impr_vector needed_improvements;
 
  const struct req_context context = {
    .player = pplayer,
    .city = pcity,
    .tile = city_tile(pcity),
    .building = pimprove,
  };
 
  tech_vector_init(&needed_techs);
  impr_vector_init(&needed_improvements);
 
  requirement_vector_iterate(&pimprove->reqs, preq) {
    const bool active = is_req_active(&context, nullptr, preq, RPT_POSSIBLE);
 
    if (VUT_ADVANCE == preq->source.kind && preq->present && !active) {
      /* Found a missing technology requirement for this improvement. */
      tech_vector_append(&needed_techs, preq->source.value.advance);
    } else if (VUT_IMPROVEMENT == preq->source.kind && preq->present
               && !active) {
      /* Found a missing improvement requirement for this improvement.
       * For example, in the default ruleset a city must have a Library
       * before it can have a University. */
      impr_vector_append(&needed_improvements, preq->source.value.building);
    }
    all_met = all_met && active;
  } requirement_vector_iterate_end;
 
  /* If v is negative, the improvement is not worth building,
   * but there is no need to punish research of the technologies
   * that would make it available.
   */
  n_needed_techs = tech_vector_size(&needed_techs);
  if (0 < v && 0 < n_needed_techs) {
    /* Tell AI module how much we want this improvement and what techs are
     * required to get it. */
    const adv_want dv = v / n_needed_techs;
 
    want_techs_for_improvement_effect(ait, pplayer, pcity, pimprove,
                                      &needed_techs, dv);
  }
 
  /* If v is negative, the improvement is not worth building,
   * but there is no need to punish building the improvements
   * that would make it available.
   */
  n_needed_improvements = impr_vector_size(&needed_improvements);
  if (0 < v && 0 < n_needed_improvements) {
    /* Because we want this improvement,
     * we want the improvements that will make it possible */
    const adv_want dv = v / (n_needed_improvements * 4); /* WAG */
    int i;
 
    for (i = 0; i < n_needed_improvements; i++) {
      const struct impr_type *needed_impr
        = *impr_vector_get(&needed_improvements, i);
      /* TODO: increase the want for the needed_impr,
       * if we can build it now */
      /* Recurse */
      (void) adjust_wants_for_reqs(ait, pplayer, pcity, needed_impr, dv);
    }
  }
 
  /* TODO: use a similar method to increase wants for governments
   * that will make this improvement possible? */
 
  tech_vector_free(&needed_techs);
  impr_vector_free(&needed_improvements);
 
  return all_met;
}
 
/**********************************************************************/
adv_want dai_city_want(struct player *pplayer, struct city *acity,
                       struct adv_data *adv, struct impr_type *pimprove)
{
  adv_want want = 0;
  int prod[O_LAST], bonus[O_LAST], waste[O_LAST];
  const struct civ_map *nmap = &(wld.map);
 
  memset(prod, 0, O_LAST * sizeof(*prod));
  if (pimprove != nullptr
      && adv->impr_calc[improvement_index(pimprove)]
         == ADV_IMPR_CALCULATE_FULL) {
    struct tile *acenter = city_tile(acity);
    bool celebrating = base_city_celebrating(acity);
 
    /* The below calculation mostly duplicates get_worked_tile_output().
     * We do this only for buildings that we know may change tile
     * outputs. */
    city_tile_iterate(nmap, city_map_radius_sq_get(acity), acenter, ptile) {
      if (tile_worked(ptile) == acity) {
        output_type_iterate(o) {
          prod[o] += city_tile_output(acity, ptile, celebrating, o);
        } output_type_iterate_end;
      }
    } city_tile_iterate_end;
 
    add_specialist_output(acity, prod);
  } else {
    fc_assert(sizeof(*prod) == sizeof(*acity->citizen_base));
    memcpy(prod, acity->citizen_base, O_LAST * sizeof(*prod));
  }
 
  trade_routes_iterate(acity, proute) {
    prod[O_TRADE] += proute->value;
  } trade_routes_iterate_end;
  prod[O_GOLD] += get_city_tithes_bonus(acity);
  output_type_iterate(o) {
    bonus[o] = get_final_city_output_bonus(acity, o);
    waste[o] = city_waste(acity, o, prod[o] * bonus[o] / 100, nullptr);
  } output_type_iterate_end;
  add_tax_income(pplayer,
                 prod[O_TRADE] * bonus[O_TRADE] / 100 - waste[O_TRADE],
                 prod);
  output_type_iterate(o) {
    prod[o] = prod[o] * bonus[o] / 100 - waste[o];
  } output_type_iterate_end;
 
  city_built_iterate(acity, upkept) {
    prod[O_GOLD] -= city_improvement_upkeep(acity, upkept);
  } city_built_iterate_end;
  /* Unit upkeep isn't handled here.  Unless we do a full city_refresh it
   * won't be changed anyway. */
 
  want += prod[O_FOOD] * adv->food_priority;
  if (prod[O_SHIELD] != 0) {
    want += prod[O_SHIELD] * adv->shield_priority;
    want -= city_pollution(acity, prod[O_SHIELD]) * adv->pollution_priority;
  }
  want += prod[O_LUXURY] * adv->luxury_priority;
  want += prod[O_SCIENCE] * adv->science_priority;
  if (pplayer->economic.tax > 50) {
    /* Increased tax rate indicates that we've had gold shortage which
     * we are trying to fill with taxes. Consider gold more critical
     * than usually.
     * Smallest tax rate we can have here is
     * 60% -> factor (60 - 40) / 14.0 = 1.43 */
    want += prod[O_GOLD] * adv->gold_priority
            * (pplayer->economic.tax - 40) / 14.0;
  } else {
    want += prod[O_GOLD] * adv->gold_priority;
  }
 
  return want;
}
 
/**********************************************************************/
static adv_want base_want(struct ai_type *ait, struct player *pplayer,
                          struct city *pcity, struct impr_type *pimprove)
{
  struct adv_data *adv = adv_data_get(pplayer, nullptr);
  adv_want final_want = 0;
  int wonder_player_id = WONDER_NOT_OWNED;
  int wonder_city_id = WONDER_NOT_BUILT;
 
  if (adv->impr_calc[improvement_index(pimprove)] == ADV_IMPR_ESTIMATE) {
    return 0; /* Nothing to calculate here. */
  }
 
  if (!can_city_build_improvement_now(pcity, pimprove, RPT_CERTAIN)
      || (is_small_wonder(pimprove)
          && city_from_small_wonder(pplayer, pimprove) != nullptr)) {
    return 0;
  }
 
  if (is_wonder(pimprove)) {
    if (is_great_wonder(pimprove)) {
      wonder_player_id
        = game.info.great_wonder_owners[improvement_index(pimprove)];
    }
    wonder_city_id = pplayer->wonders[improvement_index(pimprove)];
  }
  /* Add the improvement */
  city_add_improvement(pcity, pimprove);
 
  /* Stir, then compare notes */
  city_range_iterate(pcity, pplayer->cities,
                     adv->impr_range[improvement_index(pimprove)], acity) {
    final_want += dai_city_want(pplayer, acity, adv, pimprove)
      - def_ai_city_data(acity, ait)->worth;
  } city_range_iterate_end;
 
  /* Restore */
  city_remove_improvement(pcity, pimprove);
  if (is_wonder(pimprove)) {
    if (is_great_wonder(pimprove)) {
      game.info.great_wonder_owners[improvement_index(pimprove)] =
          wonder_player_id;
    }
 
    pplayer->wonders[improvement_index(pimprove)] = wonder_city_id;
  }
 
  return final_want;
}
 
/**********************************************************************/
static void adjust_improvement_wants_by_effects(struct ai_type *ait,
                                                struct player *pplayer,
                                                struct city *pcity,
                                                struct impr_type *pimprove,
                                                const bool already)
{
  adv_want v = 0;
  int cities[REQ_RANGE_COUNT];
  int nplayers = normal_player_count();
  struct adv_data *ai = adv_data_get(pplayer, nullptr);
  bool capital = is_capital(pcity);
  bool can_build = TRUE;
  struct universal source = {
    .kind = VUT_IMPROVEMENT,
    .value = {.building = pimprove}
  };
  const bool is_convert = is_convert_improvement(pimprove);
  int turns = 9999;
  int place = tile_continent(pcity->tile);
 
  /* FIXME: Do we really need the effects check to be made *without*
   * passing the city tile? */
  const struct req_context effect_ctxt = {
    .player = pplayer,
    .city = pcity,
    .building = pimprove,
  };
 
  /* Do NOT pass building here, as the action might be about
   * targeting some completely different building, AND
   * the check to see if the action is possible before
   * the building is there is also ignoring the buildings.
   * We don't want those two results to differ for
   * an unrelated reason to what we are evaluating. */
  const struct req_context actenabler_ctxt = {
    .player = pplayer,
    .city = pcity,
    .tile = city_tile(pcity),
  };
 
  /* Remove team members from the equation */
  players_iterate(aplayer) {
    if (aplayer->team
        && aplayer->team == pplayer->team
        && aplayer != pplayer) {
      nplayers--;
    }
  } players_iterate_end;
 
  if (is_convert) {
    /* Since coinage-like improvements contains some entirely spurious
     * ruleset values, we need to hard-code a sensible want.
     * We must otherwise handle IG_CONVERT improvements like the others,
     * so the AI will research techs that make it available,
     * for rulesets that do not provide it from the start.
     */
    if (improvement_has_flag(pimprove, IF_GOLD)) {
      v += TRADE_WEIGHTING / 10;
    } else if (improvement_has_flag(pimprove, IF_INFRA)) {
      v += INFRA_WEIGHTING / 10;
    }
    /* Without relevant flags, base want remains 0. */
  } else {
    /* Base want is calculated above using a more direct approach. */
    v += base_want(ait, pplayer, pcity, pimprove);
    if (v != 0) {
      CITY_LOG(LOG_DEBUG, pcity,
               "%s base_want is " ADV_WANT_PRINTF " (range=%d)",
               improvement_rule_name(pimprove),
               v,
               ai->impr_range[improvement_index(pimprove)]);
    }
  }
 
  if (!is_convert) {
    /* Adjust by building cost */
    /* FIXME: ought to reduce by upkeep cost and amortise by building cost */
    v -= (impr_build_shield_cost(pcity, pimprove)
         / (pcity->surplus[O_SHIELD] * 10 + 1));
  }
 
  /* Find number of cities per range.  */
  cities[REQ_RANGE_PLAYER] = city_list_size(pplayer->cities);
  /* kludge -- Number of *our* cities in these ranges. */
  cities[REQ_RANGE_WORLD] = cities[REQ_RANGE_ALLIANCE] = cities[REQ_RANGE_TEAM]
    = cities[REQ_RANGE_PLAYER];
 
  if (place < 0) {
    cities[REQ_RANGE_CONTINENT] = 1;
  } else {
    cities[REQ_RANGE_CONTINENT] = ai->stats.cities[place];
  }
 
  /* All the trade partners and the city being considered. */
  cities[REQ_RANGE_TRADE_ROUTE] = city_num_trade_routes(pcity) + 1;
 
  cities[REQ_RANGE_CITY] = cities[REQ_RANGE_LOCAL] = 1;
 
  /* Invalid building range */
  cities[REQ_RANGE_ADJACENT] = cities[REQ_RANGE_CADJACENT]
    = cities[REQ_RANGE_TILE] = 0;
 
  players_iterate(aplayer) {
    int potential = (aplayer->server.bulbs_last_turn
                     + city_list_size(aplayer->cities) + 1);
 
    if (potential > 0) {
      requirement_vector_iterate(&pimprove->obsolete_by, pobs) {
        if (pobs->source.kind == VUT_ADVANCE && pobs->present) {
          turns = MIN(turns,
                      research_goal_bulbs_required(research_get(aplayer),
                          advance_number(pobs->source.value.advance))
                      / (potential + 1));
        }
      } requirement_vector_iterate_end;
    }
  } players_iterate_end;
 
  effect_list_iterate(get_req_source_effects(&source), peffect) {
    enum req_range range = REQ_RANGE_MAX;
    bool active = TRUE;
    int n_needed_techs = 0;
    struct tech_vector needed_techs;
    bool present = TRUE;
    bool impossible_to_get = FALSE;
 
    tech_vector_init(&needed_techs);
 
    requirement_vector_iterate(&peffect->reqs, preq) {
      /* Check if all the requirements for the currently evaluated effect
       * are met, except for having the building that we are evaluating. */
      if (universal_fulfills_requirement(preq, &source) == ITF_YES) {
        if (preq->range < range) {
          /* More limited range */
          range = preq->range;
        }
        present = preq->present;
        continue;
      }
 
      if (!is_req_active(&effect_ctxt, nullptr, preq, RPT_POSSIBLE)) {
        active = FALSE;
        if (VUT_ADVANCE == preq->source.kind && preq->present) {
          /* This missing requirement is a missing tech requirement.
           * This will be for some additional effect
           * (For example, in the default ruleset, Mysticism increases
           * the effect of Temples). */
          tech_vector_append(&needed_techs, preq->source.value.advance);
        } else if (!dai_can_requirement_be_met_in_city(preq, pplayer, pcity)) {
          impossible_to_get = TRUE;
        }
      }
    } requirement_vector_iterate_end;
 
    n_needed_techs = tech_vector_size(&needed_techs);
    if ((active || n_needed_techs) && !impossible_to_get) {
      adv_want v1 = dai_effect_value(pplayer, ai, pcity, capital,
                                     turns, peffect, range, nplayers);
      /* v1 could be negative (the effect could be undesirable),
       * although it is usually positive.
       * For example, in the default ruleset, Communism decreases the
       * effectiveness of a Cathedral. */
 
      if (!present) {
        /* Building removes the effect */
        /* Currently v1 is (v + delta). Make it (v - delta) instead */
        v1 = -v1;
      }
 
      if (active) {
        v += v1;
      } else if (v1 > 0) {
        /* If value of the effect is negative, do not hold it against
         * the tech - having the tech won't force one to build the
         * building. */
 
        /* We might want the technology that will enable this
         * (additional) effect.
         * The better the effect, the more we want the technology.
         * We are more interested in (additional) effects that enhance
         * buildings we already have.
         */
        const int a = already? 5: 4; /* WAG */
        const adv_want dv = v1 * a / (4 * n_needed_techs);
 
        want_techs_for_improvement_effect(ait, pplayer, pcity, pimprove,
                                          &needed_techs, dv);
      }
    }
 
    tech_vector_free(&needed_techs);
  } effect_list_iterate_end;
 
  /* Can the city be the target of an action? */
  action_iterate (act_id) {
    bool is_possible;
    bool will_be_possible = FALSE;
    enum req_range max_range;
    int act_neg_util;
 
    /* Is the action relevant? */
    if (action_id_get_target_kind(act_id) != ATK_CITY) {
      continue;
    }
 
    /* No range found yet. Local is the most narrow range. */
    max_range = REQ_RANGE_LOCAL;
 
    /* Is it possible to do the action to the city right now?
     *
     * (DiplRel requirements are ignored since actor_player is nullptr) */
    is_possible = is_action_possible_on_city(act_id, nullptr, pcity);
 
    /* Will it be possible to do the action to the city if the building is
     * built? */
    action_enabler_list_iterate(action_enablers_for_action(act_id),
                                enabler) {
      bool active = TRUE;
      enum req_range range = REQ_RANGE_LOCAL;
 
      requirement_vector_iterate(&(enabler->target_reqs), preq) {
        if (universal_fulfills_requirement(preq, &source) == ITF_YES) {
          /* Pretend the building is there */
          if (preq->present) {
            range = preq->range; /* Assumption: Max one pr vector */
            continue;
          } else {
            active = FALSE;
            break;
          }
        } else if (!is_req_active(&actenabler_ctxt, nullptr,
                                  preq, RPT_POSSIBLE)) {
          active = FALSE;
          break;
        }
      } requirement_vector_iterate_end;
 
      if (active) {
        will_be_possible = TRUE;
 
        /* Store the widest range that enables the action. */
        if (max_range < range) {
          max_range = range;
        }
 
        /* Don't break the iteration even if the action is enabled. There
         * could be a wider range in an active action enabler not yet seen.
         */
      }
    } action_enabler_list_iterate_end;
 
    /* Will the building significantly change the ability to target
     * the city? */
    if (is_possible == will_be_possible) {
      continue;
    }
 
    /* How undesirable is it that the city may be a target? */
    act_neg_util = action_target_neg_util(act_id, pcity);
 
    /* Multiply the desire by number of cities in range.
     * Note: This is a simplification. If the action can be done or not
     * _may_ be uncanged or changed in the opposite direction in the other
     * cities in the range. */
    act_neg_util = cities[max_range] * act_neg_util;
 
    /* Consider the utility of being a potential target.
     * Remember: act_util is the negative utility of being a target. */
    if (will_be_possible) {
      v -= act_neg_util;
    } else {
      v += act_neg_util;
    }
  } action_iterate_end;
 
  if (already) {
    /* Discourage research of the technology that would make this building
     * obsolete. The bigger the desire for this building, the more
     * we want to discourage the technology. */
    dont_want_tech_obsoleting_impr(ait, pplayer, pcity, pimprove, v);
  } else {
    /* Increase the want for technologies that will enable
     * construction of this improvement, if necessary.
     */
    const bool all_met
      = adjust_wants_for_reqs(ait, pplayer, pcity, pimprove, v);
 
    can_build = can_build && all_met;
  }
 
  if (is_convert && can_build) {
    /* Could have a negative want for coinage-like improvements,
     * if we have some stock in a building already. */
    pcity->server.adv->building_want[improvement_index(pimprove)] += v;
  } else if (!already && can_build) {
    const struct research *presearch = research_get(pplayer);
 
    /* Convert the base 'want' into a building want
     * by applying various adjustments */
 
    /* Would it mean losing shields? */
    if ((VUT_UTYPE == pcity->production.kind
         || (is_wonder(pcity->production.value.building)
             && !is_wonder(pimprove))
         || (!is_wonder(pcity->production.value.building)
             && is_wonder(pimprove)))
        && pcity->turn_last_built != game.info.turn) {
      if (has_handicap(pplayer, H_PRODCHGPEN)) {
        v -= pcity->shield_stock * SHIELD_WEIGHTING / 4;
      } else {
        v -= pcity->shield_stock * SHIELD_WEIGHTING / 15;
      }
    }
 
    /* Reduce want if building gets obsoleted soon */
    requirement_vector_iterate(&pimprove->obsolete_by, pobs) {
      if (pobs->source.kind == VUT_ADVANCE && pobs->present) {
        int num_tech = research_goal_unknown_techs(presearch,
                             advance_number(pobs->source.value.advance));
 
        v -= v / MAX(1, num_tech);
      }
    } requirement_vector_iterate_end;
 
    /* Are we wonder city? Try to avoid building non-wonders very much. */
    if (pcity->id == ai->wonder_city && !is_wonder(pimprove)) {
      v /= 5;
    }
 
    /* Set */
    pcity->server.adv->building_want[improvement_index(pimprove)] += v;
  }
  /* Else we either have the improvement already,
   * or we can not build it (yet) */
}
 
/**********************************************************************/
static bool should_force_recalc(struct city *pcity)
{
  return city_built_last_turn(pcity)
      || (VUT_IMPROVEMENT == pcity->production.kind
       && !is_convert_improvement(pcity->production.value.building)
       && !dai_can_city_build_improvement_later
           (pcity, pcity->production.value.building));
}
 
/**********************************************************************/
void dai_build_adv_init(struct ai_type *ait, struct player *pplayer)
{
  struct adv_data *ai = adv_data_get(pplayer, nullptr);
 
  /* Find current worth of cities and cache this. */
  city_list_iterate(pplayer->cities, pcity) {
    def_ai_city_data(pcity, ait)->worth = dai_city_want(pplayer, pcity, ai,
                                                        nullptr);
  } city_list_iterate_end;
}
 
/**********************************************************************/
void dai_build_adv_adjust(struct ai_type *ait, struct player *pplayer,
                          struct city *wonder_city)
{
  /* Clear old building wants.
   * Do this separately from the iteration over improvement types
   * because each iteration could actually update more than one improvement,
   * if improvements have improvements as requirements.
   */
  city_list_iterate(pplayer->cities, pcity) {
    struct ai_city *city_data = def_ai_city_data(pcity, ait);
 
    if (city_data->building_turn <= game.info.turn) {
      /* Do a scheduled recalculation this turn */
      improvement_iterate(pimprove) {
        pcity->server.adv->building_want[improvement_index(pimprove)] = 0;
      } improvement_iterate_end;
    } else if (should_force_recalc(pcity)) {
      /* Do an emergency recalculation this turn. */
      city_data->building_wait = city_data->building_turn
                                        - game.info.turn;
      city_data->building_turn = game.info.turn;
 
      improvement_iterate(pimprove) {
        pcity->server.adv->building_want[improvement_index(pimprove)] = 0;
      } improvement_iterate_end;
    }
  } city_list_iterate_end;
 
  improvement_iterate(pimprove) {
    if (can_player_build_improvement_later(pplayer, pimprove)) {
      city_list_iterate(pplayer->cities, pcity) {
        struct ai_city *city_data = def_ai_city_data(pcity, ait);
 
        if (pcity != wonder_city && is_wonder(pimprove)) {
          /* Only wonder city should build wonders! */
          pcity->server.adv->building_want[improvement_index(pimprove)] = 0;
        } else if (city_data->building_turn <= game.info.turn) {
          /* Building wants vary relatively slowly, so not worthwhile
           * recalculating them every turn.
           * We DO want to calculate (tech) wants because of buildings
           * we already have. */
          const bool already = city_has_building(pcity, pimprove);
          int idx = improvement_index(pimprove);
 
          adjust_improvement_wants_by_effects(ait, pplayer, pcity,
                                              pimprove, already);
 
          fc_assert(!(already
                      && 0 < pcity->server.adv->building_want[idx]));
 
          if (is_great_wonder(pimprove)) {
            /* Not only would we get the wonder, but we would also prevent
             * opponents from getting it. */
            pcity->server.adv->building_want[idx] *= 1.5;
 
            if (pcity->production.kind == VUT_IMPROVEMENT
                && is_great_wonder(pcity->production.value.building)) {
              /* If we already are building a great wonder, prefer continuing
               * to do so over stopping it */
              pcity->server.adv->building_want[idx] *= 1.25;
            }
          }
 
          /* If I am not an expansionist, I want buildings more than units */
          if (pcity->server.adv->building_want[idx] > 0) {
            pcity->server.adv->building_want[idx]
              = pcity->server.adv->building_want[idx]
                  * TRAIT_DEFAULT_VALUE
                  / ai_trait_get_value(TRAIT_EXPANSIONIST, pplayer);
          }
        }
        /* else wait until a later turn */
      } city_list_iterate_end;
    } else {
      /* An impossible improvement */
      city_list_iterate(pplayer->cities, pcity) {
        pcity->server.adv->building_want[improvement_index(pimprove)] = 0;
      } city_list_iterate_end;
    }
  } improvement_iterate_end;
 
#ifdef FREECIV_DEBUG
  /* This logging is relatively expensive, so activate only if necessary */
  city_list_iterate(pplayer->cities, pcity) {
    improvement_iterate(pimprove) {
      if (pcity->server.adv->building_want[improvement_index(pimprove)] != 0) {
        CITY_LOG(LOG_DEBUG, pcity, "want to build %s with " ADV_WANT_PRINTF,
                 improvement_rule_name(pimprove),
                 pcity->server.adv->building_want[improvement_index(pimprove)]);
      }
    } improvement_iterate_end;
  } city_list_iterate_end;
#endif /* FREECIV_DEBUG */
 
  /* Reset recalc counter */
  city_list_iterate(pplayer->cities, pcity) {
    struct ai_city *city_data = def_ai_city_data(pcity, ait);
 
    if (city_data->building_turn <= game.info.turn) {
      /* This will spread recalcs out so that no one turn end is
       * much longer than others */
      city_data->building_wait
        = fc_rand(AI_BA_RECALC_SPEED) + AI_BA_RECALC_SPEED;
      city_data->building_turn
        = game.info.turn + city_data->building_wait;
    }
  } city_list_iterate_end;
}
 
/**********************************************************************/
void dai_consider_wonder_city(struct ai_type *ait, struct city *pcity,
                              bool *result)
{
  if (def_ai_city_data(pcity, ait)->grave_danger > 0) {
    *result = FALSE;
  } else {
    *result = TRUE;
  }
}
 
/**********************************************************************/
static bool dai_cant_help_req(const struct req_context *context,
                              const struct requirement *req)
{
  switch (req->source.kind) {
  /* Unskilled in channel digging and merchantry */
  case VUT_TERRAIN:
  case VUT_EXTRA:
  case VUT_TILEDEF:
  case VUT_GOOD:
  case VUT_TERRAINCLASS:
  case VUT_TERRFLAG:
  case VUT_TERRAINALTER:
  case VUT_CITYTILE:
    return !is_req_active(context, nullptr, req, RPT_POSSIBLE);
  default:
    return is_req_preventing(context, nullptr, req, RPT_POSSIBLE) > REQUCH_NO;
  }
}
 
/**********************************************************************/
bool dai_can_city_build_improvement_later(const struct city *pcity,
                                          const struct impr_type *pimprove)
{
  const struct req_context city_ctxt = {
    .player = city_owner(pcity),
    .city = pcity,
    .tile = city_tile(pcity),
  };
 
  /* FIXME: AI may be too stupid to sell obsoleting improvements
   * from the city that are _not_ checked here. */
  if (!dai_can_player_build_improvement_later(city_owner(pcity),
                                              pimprove)) {
    return FALSE;
  }
  /* Check for requirements that aren't met and that are unchanging
   * (so they can never be met). */
  requirement_vector_iterate(&pimprove->reqs, preq) {
    if (dai_cant_help_req(&city_ctxt, preq)) {
      return FALSE;
    }
  } requirement_vector_iterate_end;
 
  return TRUE;
}
 
/**********************************************************************/
bool
dai_can_player_build_improvement_later(const struct player *p,
                                       const struct impr_type *pimprove)
{
  const struct req_context context = { .player = p };
 
  if (!valid_improvement(pimprove)) {
    return FALSE;
  }
  if (improvement_obsolete(p, pimprove, nullptr)) {
    return FALSE;
  }
  if (is_great_wonder(pimprove) && !great_wonder_is_available(pimprove)) {
    /* Can't build wonder if already built */
    return FALSE;
  }
 
  /* Check for requirements that aren't met and that are unchanging
   * (so they can never be met). */
  requirement_vector_iterate(&pimprove->reqs, preq) {
    if (preq->range >= REQ_RANGE_PLAYER
        && dai_cant_help_req(&context, preq)) {
      return FALSE;
    }
  } requirement_vector_iterate_end;
  /* FIXME: should check some "unchanging" reqs here - like if there's
   * a nation requirement, we can go ahead and check it now. */
 
  return TRUE;
}
 
/**********************************************************************/
Impr_type_id dai_find_source_building(struct city *pcity,
                                      enum effect_type effect_type,
                                      const struct unit_type *utype)
{
  int greatest_value = 0;
  const struct impr_type *best_building = nullptr;
  const struct req_context context = {
    .player = city_owner(pcity),
    .city = pcity,
    .tile = city_tile(pcity),
    .unittype = utype,
  };
 
  effect_list_iterate(get_effects(effect_type), peffect) {
    if (peffect->value > greatest_value) {
      const struct impr_type *building = nullptr;
      bool wrong_unit = FALSE;
 
      requirement_vector_iterate(&peffect->reqs, preq) {
        if (VUT_IMPROVEMENT == preq->source.kind && preq->present) {
          building = preq->source.value.building;
 
          if (!can_city_build_improvement_now(pcity, building, RPT_CERTAIN)
              || !is_improvement(building)) {
            building = nullptr;
            break;
          }
        } else if (VUT_IMPR_FLAG == preq->source.kind && preq->present) {
          /* TODO: Ruleset cache for buildings with specific flag */
          improvement_iterate(impr) {
            if (improvement_has_flag(impr, preq->source.value.impr_flag)) {
              if (can_city_build_improvement_now(pcity, impr, RPT_CERTAIN)
                  && is_improvement(impr)) {
                if (building == nullptr) {
                  building = impr;
                  break;
                }
              }
            }
          } improvement_iterate_end;
 
          if (building == nullptr) {
            break;
          }
        } else if (utype != nullptr
                   && !is_req_active(&context, nullptr, preq, RPT_POSSIBLE)) {
          /* Effect requires other kind of unit than what we are
           * interested about */
          wrong_unit = TRUE;
          break;
        }
      } requirement_vector_iterate_end;
      if (!wrong_unit && building != nullptr) {
        best_building = building;
        greatest_value = peffect->value;
      }
    }
  } effect_list_iterate_end;
 
  if (best_building) {
    return improvement_number(best_building);
  }
 
  return B_LAST;
}