Split "Establish Embassy".

[freeciv.git] / server / advisors / advdata.c

/***********************************************************************
 Freeciv - Copyright (C) 2002 - The Freeciv Project
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
***********************************************************************/

#ifdef HAVE_CONFIG_H
#include <fc_config.h>
#endif

/* utility */
#include "log.h"
#include "mem.h"

/* common */
#include "actions.h"
#include "ai.h"
#include "city.h"
#include "effects.h"
#include "game.h"
#include "government.h"
#include "map.h"
#include "movement.h"
#include "research.h"
#include "unit.h"
#include "unitlist.h"

/* common/aicore */
#include "aisupport.h"
#include "path_finding.h"
#include "pf_tools.h"

/* server */
#include "cityturn.h"
#include "diplhand.h"
#include "maphand.h"
#include "plrhand.h"
#include "srv_log.h"
#include "unittools.h"

/* server/advisors */
#include "advbuilding.h"
#include "advcity.h"
#include "advtools.h"
#include "autosettlers.h"

/* ai */
#include "handicaps.h"

#include "advdata.h"

static void adv_dipl_new(const struct player *plr1,
                         const struct player *plr2);
static void adv_dipl_free(const struct player *plr1,
                          const struct player *plr2);
static struct adv_dipl *adv_dipl_get(const struct player *plr1,
                                     const struct player *plr2);

/**************************************************************************
  Precalculates some important data about the improvements in the game
  that we use later in ai/aicity.c.  We mark improvements as 'calculate'
  if we want to run a full test on them, as 'estimate' if we just want
  to do some guesses on them, or as 'unused' is they are useless to us.
  Then we find the largest range of calculatable effects in the
  improvement and record it for later use.
**************************************************************************/
static void adv_data_city_impr_calc(struct player *pplayer,
                                    struct adv_data *adv)
{
  int count[ADV_IMPR_LAST];

  memset(count, 0, sizeof(count));

  improvement_iterate(pimprove) {
    struct universal source = {
      .kind = VUT_IMPROVEMENT,
      .value = {.building = pimprove}
    };

    adv->impr_calc[improvement_index(pimprove)] = ADV_IMPR_ESTIMATE;

    /* Find largest extension */
    effect_list_iterate(get_req_source_effects(&source), peffect) {
      switch (peffect->type) {
#if 0
      /* TODO */
      case EFT_FORCE_CONTENT:
      case EFT_FORCE_CONTENT_PCT:
      case EFT_MAKE_CONTENT:
      case EFT_MAKE_CONTENT_MIL:
      case EFT_MAKE_CONTENT_MIL_PER:
      case EFT_MAKE_CONTENT_PCT:
      case EFT_MAKE_HAPPY:
#endif
      case EFT_CAPITAL_CITY:
      case EFT_POLLU_POP_PCT:
      case EFT_POLLU_POP_PCT_2:
      case EFT_POLLU_PROD_PCT:
      case EFT_OUTPUT_BONUS:
      case EFT_OUTPUT_BONUS_2:
      case EFT_OUTPUT_WASTE_PCT:
      case EFT_UPKEEP_FREE:
        requirement_vector_iterate(&peffect->reqs, preq) {
          if (VUT_IMPROVEMENT == preq->source.kind
              && preq->source.value.building == pimprove) {
            if (adv->impr_calc[improvement_index(pimprove)] != ADV_IMPR_CALCULATE_FULL) {
              adv->impr_calc[improvement_index(pimprove)] = ADV_IMPR_CALCULATE;
            }
            if (preq->range > adv->impr_range[improvement_index(pimprove)]) {
              adv->impr_range[improvement_index(pimprove)] = preq->range;
            }
          }
        } requirement_vector_iterate_end;
        break;
      case EFT_OUTPUT_ADD_TILE:
      case EFT_OUTPUT_PER_TILE:
      case EFT_OUTPUT_INC_TILE:
        requirement_vector_iterate(&peffect->reqs, preq) {
          if (VUT_IMPROVEMENT == preq->source.kind
              && preq->source.value.building == pimprove) {
            adv->impr_calc[improvement_index(pimprove)] = ADV_IMPR_CALCULATE_FULL;
            if (preq->range > adv->impr_range[improvement_index(pimprove)]) {
              adv->impr_range[improvement_index(pimprove)] = preq->range;
            }
          }
        } requirement_vector_iterate_end;
      break;
      default:
      /* Nothing! */
      break;
      }
    } effect_list_iterate_end;
  } improvement_iterate_end;
}

/**************************************************************************
  Check if the player still takes advantage of EFT_TECH_PARASITE.
  Research is useless if there are still techs which may be given to the
  player for free.
**************************************************************************/
static bool player_has_really_useful_tech_parasite(struct player* pplayer)
{
  struct research *presearch, *aresearch;
  int players_needed = get_player_bonus(pplayer, EFT_TECH_PARASITE);

  if (players_needed == 0) {
    return FALSE;
  }

  presearch = research_get(pplayer);
  advance_index_iterate(A_FIRST, tech) {
    int players_having;

    if (!research_invention_gettable(presearch, tech,
                                     game.info.tech_parasite_allow_holes)
        || TECH_KNOWN == research_invention_state(presearch, tech)) {
      continue;
    }

    players_having = 0;

    players_iterate_alive(aplayer) {
      if (aplayer == pplayer) {
        continue;
      }

      aresearch = research_get(aplayer);
      if (TECH_KNOWN == research_invention_state(aresearch, tech)
          || aresearch->researching == tech) {
        players_having++;
        if (players_having >= players_needed) {
          return TRUE;
        }
      }
    } players_iterate_alive_end;
  } advance_index_iterate_end;
  return FALSE;
}

/**************************************************************************
  Analyze rulesets. Must be run after rulesets are loaded, unlike
  _init, which must be run before savegames are loaded, which is usually
  before rulesets.
**************************************************************************/
void adv_data_analyze_rulesets(struct player *pplayer)
{
  struct adv_data *adv = pplayer->server.adv;

  fc_assert_ret(adv != NULL);

  adv_data_city_impr_calc(pplayer, adv);
}

/**************************************************************************
  This function is called each turn to initialize pplayer->ai.stats.units.
**************************************************************************/
static void count_my_units(struct player *pplayer)
{
  struct adv_data *adv = adv_data_get(pplayer, NULL);

  memset(&adv->stats.units, 0, sizeof(adv->stats.units));

  unit_list_iterate(pplayer->units, punit) {
    struct unit_class *pclass = unit_class_get(punit);

    adv->stats.units.byclass[uclass_index(pclass)]++;

    if (unit_has_type_flag(punit, UTYF_COAST_STRICT)) {
      adv->stats.units.coast_strict++;
    }
    if (uclass_has_flag(pclass, UCF_MISSILE)) {
      adv->stats.units.missiles++;
    }
    if (unit_can_do_action(punit, ACTION_PARADROP)) {
      adv->stats.units.paratroopers++;
    }
    if (utype_can_do_action(punit->utype, ACTION_AIRLIFT)) {
      adv->stats.units.airliftable++;
    }
    if (can_upgrade_unittype(pplayer, unit_type_get(punit)) >= 0) {
      adv->stats.units.upgradeable++;
    }
  } unit_list_iterate_end;
}

/**************************************************************************
  Return whether data phase is currently open. Data phase is open
  between adv_data_phase_init() and adv_data_phase_done() calls.
**************************************************************************/
bool is_adv_data_phase_open(struct player *pplayer)
{
  struct adv_data *adv = pplayer->server.adv;

  return adv->phase_is_initialized;
}

/**************************************************************************
  Make and cache lots of calculations needed for other functions.

  Returns TRUE if new data was created, FALSE if data existed already.

  Note: We use map.num_continents here rather than pplayer->num_continents
  because we are omniscient and don't care about such trivialities as who
  can see what.

  FIXME: We should try to find the lowest common defence strength of our
  defending units, and ignore enemy units that are incapable of harming 
  us, instead of just checking attack strength > 1.
**************************************************************************/
bool adv_data_phase_init(struct player *pplayer, bool is_new_phase)
{
  struct adv_data *adv = pplayer->server.adv;
  int i;
  int nuke_units;
  bool danger_of_nukes;

  fc_assert_ret_val(adv != NULL, FALSE);

  if (adv->phase_is_initialized) {
    return FALSE;
  }
  adv->phase_is_initialized = TRUE;

  TIMING_LOG(AIT_AIDATA, TIMER_START);

  nuke_units = num_role_units(action_id_get_role(ACTION_NUKE));
  danger_of_nukes = FALSE;

  /*** Threats ***/

  adv->num_continents    = wld.map.num_continents;
  adv->num_oceans        = wld.map.num_oceans;
  adv->threats.continent = fc_calloc(adv->num_continents + 1, sizeof(bool));
  adv->threats.invasions = FALSE;
  adv->threats.nuclear   = 0; /* none */
  adv->threats.ocean     = fc_calloc(adv->num_oceans + 1, sizeof(bool));
  adv->threats.igwall    = FALSE;

  players_iterate(aplayer) {
    if (!adv_is_player_dangerous(pplayer, aplayer)) {
      continue;
    }

    /* The idea is that if there aren't any hostile cities on
     * our continent, the danger of land attacks is not big
     * enough to warrant city walls. Concentrate instead on 
     * coastal fortresses and hunting down enemy transports. */
    city_list_iterate(aplayer->cities, acity) {
      Continent_id continent = tile_continent(acity->tile);
      if (continent >= 0) {
        adv->threats.continent[continent] = TRUE;
      }
    } city_list_iterate_end;

    unit_list_iterate(aplayer->units, punit) {
      const struct unit_class *pclass = unit_class_get(punit);

      if (unit_type_get(punit)->adv.igwall) {
        adv->threats.igwall = TRUE;
      }

      if (pclass->adv.sea_move != MOVE_NONE) {
        /* If the enemy has not started sailing yet, or we have total
         * control over the seas, don't worry, keep attacking. */
        if (uclass_has_flag(pclass, UCF_CAN_OCCUPY_CITY)) {
          /* Enemy represents a cross-continental threat! */
          adv->threats.invasions = TRUE;
        } else if (get_transporter_capacity(punit) > 0) {
          unit_class_iterate(cargoclass) {
            if (uclass_has_flag(cargoclass, UCF_CAN_OCCUPY_CITY)
                && can_unit_type_transport(unit_type_get(punit), cargoclass)) {
              /* Enemy can transport some threatening units! */
              adv->threats.invasions = TRUE;
              break;
            }
          } unit_class_iterate_end;
        }

        /* The idea is that while our enemies don't have any offensive
         * seaborne units, we don't have to worry. Go on the offensive! */
        if (unit_type_get(punit)->attack_strength > 1) {
          if (is_ocean_tile(unit_tile(punit))) {
            Continent_id continent = tile_continent(unit_tile(punit));
            adv->threats.ocean[-continent] = TRUE;
          } else {
            adjc_iterate(unit_tile(punit), tile2) {
              if (is_ocean_tile(tile2)) {
                Continent_id continent = tile_continent(tile2);
                adv->threats.ocean[-continent] = TRUE;
              }
            } adjc_iterate_end;
          }
        } 
        continue;
      }

      /* If our enemy builds missiles, worry about missile defence. */
      if (uclass_has_flag(unit_class_get(punit), UCF_MISSILE)
          && unit_type_get(punit)->attack_strength > 1) {
        adv->threats.missile = TRUE;
      }

      /* If he builds nukes, worry a lot. */
      if (unit_can_do_action(punit, ACTION_NUKE)) {
        danger_of_nukes = TRUE;
      }
    } unit_list_iterate_end;

    /* Check for nuke capability */
    for (i = 0; i < nuke_units; i++) {
      struct unit_type *nuke =
          get_role_unit(action_id_get_role(ACTION_NUKE), i);

      if (can_player_build_unit_direct(aplayer, nuke)) { 
        adv->threats.nuclear = 1;
      }
    }
  } players_iterate_end;

  /* Increase from fear to terror if opponent actually has nukes */
  if (danger_of_nukes) {
    adv->threats.nuclear++; /* sum of both fears */
  }

  /*** Exploration ***/

  adv->explore.land_done = TRUE;
  adv->explore.sea_done = TRUE;
  adv->explore.continent = fc_calloc(adv->num_continents + 1, sizeof(bool));
  adv->explore.ocean = fc_calloc(adv->num_oceans + 1, sizeof(bool));

  whole_map_iterate(&(wld.map), ptile) {
    Continent_id continent = tile_continent(ptile);

    if (is_ocean_tile(ptile)) {
      if (adv->explore.sea_done && has_handicap(pplayer, H_TARGETS) 
          && !map_is_known(ptile, pplayer)) {
        /* We're not done there. */
        adv->explore.sea_done = FALSE;
        adv->explore.ocean[-continent] = TRUE;
      }
      /* skip rest, which is land only */
      continue;
    }
    if (adv->explore.continent[tile_continent(ptile)]) {
      /* we don't need more explaining, we got the point */
      continue;
    }
    if (tile_has_cause_extra(ptile, EC_HUT) 
        && (!has_handicap(pplayer, H_HUTS)
             || map_is_known(ptile, pplayer))) {
      adv->explore.land_done = FALSE;
      adv->explore.continent[continent] = TRUE;
      continue;
    }
    if (has_handicap(pplayer, H_TARGETS) && !map_is_known(ptile, pplayer)) {
      /* this AI must explore */
      adv->explore.land_done = FALSE;
      adv->explore.continent[continent] = TRUE;
    }
  } whole_map_iterate_end;

  /*** Statistics ***/

  adv->stats.cities = fc_calloc(adv->num_continents + 1, sizeof(int));
  adv->stats.average_production = 0;
  city_list_iterate(pplayer->cities, pcity) {
    Continent_id continent = tile_continent(pcity->tile);
    if (continent >= 0) {
      adv->stats.cities[continent]++;
    }
    adv->stats.average_production += pcity->surplus[O_SHIELD];
  } city_list_iterate_end;
  adv->stats.average_production /= MAX(1, city_list_size(pplayer->cities));

  /*** Diplomacy ***/

  players_iterate(aplayer) {
    struct adv_dipl *dip = adv_dipl_get(pplayer, aplayer);

    dip->allied_with_enemy = FALSE;
    players_iterate(check_pl) {
      if (pplayers_allied(aplayer, check_pl)
          && player_diplstate_get(pplayer, check_pl)->type == DS_WAR) {
        dip->allied_with_enemy = TRUE;
      }
    } players_iterate_end;
  } players_iterate_end;

  adv->dipl.spacerace_leader = player_leading_spacerace();

  adv->dipl.production_leader = NULL;
  players_iterate(aplayer) {
    if (adv->dipl.production_leader == NULL
        || adv->dipl.production_leader->score.mfg < aplayer->score.mfg) {
      adv->dipl.production_leader = aplayer;
    }
  } players_iterate_end;

  /*** Priorities ***/

  /* NEVER set these to zero! Weight values are usually multiplied by 
   * these values, so be careful with them. They are used in city 
   * and government calculations, and food and shields should be 
   * slightly bigger because we only look at surpluses there. They
   * are all WAGs. */
  adv->food_priority = FOOD_WEIGHTING;
  adv->shield_priority = SHIELD_WEIGHTING;
  if (adv_wants_science(pplayer)) {
    adv->luxury_priority = 1;
    adv->science_priority = TRADE_WEIGHTING;
  } else {
    adv->luxury_priority = TRADE_WEIGHTING;
    adv->science_priority = 1;
  }
  adv->gold_priority = TRADE_WEIGHTING;
  adv->happy_priority = 1;
  adv->unhappy_priority = TRADE_WEIGHTING; /* danger */
  adv->angry_priority = TRADE_WEIGHTING * 3; /* grave danger */
  adv->pollution_priority = POLLUTION_WEIGHTING;

  /* Research want */
  if (is_future_tech(research_get(pplayer)->researching)
      || player_has_really_useful_tech_parasite(pplayer)) {
    adv->wants_science = FALSE;
  } else {
    adv->wants_science = TRUE;
  }
  
  /* max num cities
   * The idea behind this code is that novice players don't understand that
   * expansion is critical and find it very annoying.
   * With the following code AI players will try to be only a bit better 
   * than the best human players. This should lead to more exciting games
   * for the beginners.
   */
  if (has_handicap(pplayer, H_EXPANSION)) {
    bool found_human = FALSE;
    adv->max_num_cities = 3;
    players_iterate_alive(aplayer) {
      if (aplayer == pplayer || is_ai(aplayer)) {
        continue;
      }
      adv->max_num_cities = MAX(adv->max_num_cities,
                                city_list_size(aplayer->cities) + 3);
      found_human = TRUE;
    } players_iterate_alive_end;
    if (!found_human) {
      adv->max_num_cities = MAP_INDEX_SIZE;
    }
  } else {
    adv->max_num_cities = MAP_INDEX_SIZE;
  }

  count_my_units(pplayer);

  TIMING_LOG(AIT_AIDATA, TIMER_STOP);

  /* Government */
  TIMING_LOG(AIT_GOVERNMENT, TIMER_START);
  adv_best_government(pplayer);
  TIMING_LOG(AIT_GOVERNMENT, TIMER_STOP);

  return TRUE;
}

/**************************************************************************
  Clean up our mess.
**************************************************************************/
void adv_data_phase_done(struct player *pplayer)
{
  struct adv_data *adv = pplayer->server.adv;

  fc_assert_ret(adv != NULL);

  if (!adv->phase_is_initialized) {
    return;
  }

  free(adv->explore.ocean);
  adv->explore.ocean = NULL;

  free(adv->explore.continent);
  adv->explore.continent = NULL;

  free(adv->threats.continent);
  adv->threats.continent = NULL;

  free(adv->threats.ocean);
  adv->threats.ocean = NULL;

  free(adv->stats.cities);
  adv->stats.cities = NULL;

  adv->num_continents = 0;
  adv->num_oceans     = 0;

  adv->phase_is_initialized = FALSE;
}

/**************************************************************************
  Return a pointer to our data.
  If caller_closes is set, data phase will be opened even if it's
  currently closed, and the boolean will be set accordingly to tell caller
  that phase needs closing.
**************************************************************************/
struct adv_data *adv_data_get(struct player *pplayer, bool *caller_closes)
{
  struct adv_data *adv = pplayer->server.adv;

  fc_assert_ret_val(adv != NULL, NULL);

  /* It's certainly indication of bug causing problems
     if this adv_data_get() gets called between adv_data_phase_done() and
     adv_data_phase_init(), since we may end up calling those
     functions if number of known continents has changed.

     Consider following case:
       Correct call order would be:
       a) adv_data_phase_init()
       b)   adv_data_get() -> adv_data_phase_done()
       c)   adv_data_get() -> adv_data_phase_init()
       d) adv_data_phase_done()
       e) do something
       f) adv_data_phase_init()

       In (e) data phase would be closed and data would be
       correctly initialized at (f), which is probably beginning
       next turn.

       Buggy version where adv_data_get() (b&c) gets called after (d):
       a) adv_data_phase_init()
       d) adv_data_phase_done()
       b)   adv_data_get() -> adv_data_phase_done()
       c)   adv_data_get() -> adv_data_phase_init()
       e) do something
       f) adv_data_phase_init()

       Now in (e) data phase would be open. When adv_data_phase_init()
       then finally gets called and it really should recreate data
       to match situation of new turn, it detects that data phase
       is already initialized and does nothing.

       So, this assertion is here for a reason!

       Code below tries to fix the situation best it can if such a bug is
       encountered. Since we are probably going to trust that to be enough
       instead of making intrusive fixes for actual bug in stable branch,
       do not assert for non-debug builds of stable versions. */
#if defined(FREECIV_DEBUG) || defined(IS_DEVEL_VERSION)
  fc_assert(caller_closes != NULL || adv->phase_is_initialized);
#endif

  if (caller_closes != NULL) {
    *caller_closes = FALSE;
  }

  if (adv->num_continents != wld.map.num_continents
      || adv->num_oceans != wld.map.num_oceans) {
    /* we discovered more continents, recalculate! */

    if (adv->phase_is_initialized) {
      /* Only call these in this order if inside data phase.
         This is blanket "fix" for all cases where adv_data_get() is called
         at illegal time. This at least minimize bad effects of such calls. */
      adv_data_phase_done(pplayer);
      adv_data_phase_init(pplayer, FALSE);
    } else {
      /* Call them in "wrong" order so we return recalculated data to caller,
         but leave data phase closed.
         This is blanket "fix" for all cases where adv_data_get() is called
         at illegal time. This at least minimize bad effects of such calls.

         Arguably this is not buggy at all but works just as designed in
         case of being called in alternate movement mode for players
         other than currently moving one (for diplomacy between the two,
         for example) */
      log_debug("%s advisor data phase closed when adv_data_get() called",
                player_name(pplayer));
      adv_data_phase_init(pplayer, FALSE);
      if (caller_closes != NULL) {
        *caller_closes = TRUE;
      } else {
        adv_data_phase_done(pplayer);
      }
    }
  } else {
    if (!adv->phase_is_initialized && caller_closes != NULL) {
      adv_data_phase_init(pplayer, FALSE);
      *caller_closes = TRUE;
    }
  }

  return adv;
}

/**************************************************************************
  Allocate memory for advisor data. Save to call multiple times.
**************************************************************************/
void adv_data_init(struct player *pplayer)
{
  struct adv_data *adv;

  if (pplayer->server.adv == NULL) {
    pplayer->server.adv = fc_calloc(1, sizeof(*pplayer->server.adv));
  }
  adv = pplayer->server.adv;

  adv->government_want = NULL;

  adv->dipl.adv_dipl_slots = fc_calloc(player_slot_count(),
                                       sizeof(*adv->dipl.adv_dipl_slots));
  player_slots_iterate(pslot) {
    struct adv_dipl **dip_slot =
      adv->dipl.adv_dipl_slots + player_slot_index(pslot);
    *dip_slot = NULL;
  } player_slots_iterate_end;

  players_iterate(aplayer) {
    adv_dipl_new(pplayer, aplayer);
    if (aplayer != pplayer) {
      adv_dipl_new(aplayer, pplayer);
    }
  } players_iterate_end;

  adv_data_default(pplayer);
}

/**************************************************************************
  Initialize with sane values.
**************************************************************************/
void adv_data_default(struct player *pplayer)
{
  struct adv_data *adv = pplayer->server.adv;

  fc_assert_ret(adv != NULL);

  adv->govt_reeval = 0;
  adv->government_want = fc_realloc(adv->government_want,
                                   (government_count() + 1)
                                    * sizeof(*adv->government_want));
  memset(adv->government_want, 0,
         (government_count() + 1) * sizeof(*adv->government_want));

  adv->wonder_city = 0;

  adv->wants_science = TRUE;
  adv->celebrate = FALSE;
  adv->max_num_cities = 10000;
}

/**************************************************************************
  Free memory for advisor data.
**************************************************************************/
void adv_data_close(struct player *pplayer)
{
  struct adv_data *adv = pplayer->server.adv;

  fc_assert_ret(NULL != adv);

  adv_data_phase_done(pplayer);

  if (adv->government_want != NULL) {
    free(adv->government_want);
  }

  if (adv->dipl.adv_dipl_slots != NULL) {
    players_iterate(aplayer) {
      adv_dipl_free(pplayer, aplayer);
      if (aplayer != pplayer) {
        adv_dipl_free(aplayer, pplayer);
      }
    } players_iterate_end;
    FC_FREE(adv->dipl.adv_dipl_slots);
  }

  if (adv != NULL) {
    free(adv);
  }

  pplayer->server.adv = NULL;
}

/****************************************************************************
  Allocate new advisor diplomacy slot
****************************************************************************/
static void adv_dipl_new(const struct player *plr1,
                         const struct player *plr2)
{
  struct adv_dipl **dip_slot =
    plr1->server.adv->dipl.adv_dipl_slots + player_index(plr2);

  *dip_slot = fc_calloc(1, sizeof(struct adv_dipl));
}

/****************************************************************************
  Free resources allocated for diplomacy information between two players.
****************************************************************************/
static void adv_dipl_free(const struct player *plr1,
                          const struct player *plr2)
{
  struct adv_dipl **dip_slot =
    plr1->server.adv->dipl.adv_dipl_slots + player_index(plr2);

  if (*dip_slot != NULL) {
    FC_FREE(*dip_slot);
    *dip_slot = NULL;
  }
}

/**************************************************************************
  Returns diplomatic state type between two players
**************************************************************************/
static struct adv_dipl *adv_dipl_get(const struct player *plr1,
                                     const struct player *plr2)
{
  struct adv_dipl **dip_slot =
    plr1->server.adv->dipl.adv_dipl_slots + player_index(plr2);

  return *dip_slot;
}

/**************************************************************************
  Find best government to aim for.
  We do it by setting our government to all possible values and calculating
  our GDP (total ai_eval_calc_city) under this government.  If the very
  best of the governments is not available to us (it is not yet discovered),
  we record it in the goal.gov structure with the aim of wanting the
  necessary tech more.  The best of the available governments is recorded 
  in goal.revolution.  We record the want of each government, and only
  recalculate this data every ai->govt_reeval_turns turns.

  Note: Call this _before_ doing taxes!
**************************************************************************/
void adv_best_government(struct player *pplayer)
{
  struct adv_data *adv = adv_data_get(pplayer, NULL);
  int best_val = 0;
  struct government *current_gov = government_of_player(pplayer);

  adv->goal.govt.gov = current_gov;
  adv->goal.govt.val = 0;
  adv->goal.govt.req = A_UNSET;
  adv->goal.revolution = current_gov;

  if (has_handicap(pplayer, H_AWAY) || !pplayer->is_alive) {
    return;
  }

  if (adv->govt_reeval == 0) {
    const struct research *presearch = research_get(pplayer);

    governments_iterate(gov) {
      adv_want val = 0;
      bool override = FALSE;

      if (gov == game.government_during_revolution) {
        continue; /* pointless */
      }
      if (gov->ai.better
          && can_change_to_government(pplayer, gov->ai.better)) {
        continue; /* we have better governments available */
      }

      CALL_PLR_AI_FUNC(gov_value, pplayer, pplayer, gov, &val, &override);

      if (!override) {
        int dist;
        adv_want bonus = 0; /* in percentage */
        int revolution_turns;

        pplayer->government = gov;
        /* Ideally we should change tax rates here, but since
         * this is a rather big CPU operation, we'd rather not. */
        check_player_max_rates(pplayer);
        city_list_iterate(pplayer->cities, acity) {
          auto_arrange_workers(acity);
        } city_list_iterate_end;
        city_list_iterate(pplayer->cities, pcity) {
          val += adv_eval_calc_city(pcity, adv);
        } city_list_iterate_end;

        /* Bonuses for non-economic abilities. We increase val by
         * a very small amount here to choose govt in cases where
         * we have no cities yet. */
        bonus += get_player_bonus(pplayer, EFT_VETERAN_BUILD) > 0 ? 3 : 0;

        /* TODO: Individual and well balanced value. */
        action_iterate(act) {
          if (!action_immune_government(gov, act)) {
            /* This government doesn't provide immunity againt this
             * action. */
            continue;
          }

          switch((enum gen_action)act) {
          case ACTION_ATTACK:
          case ACTION_SPY_INCITE_CITY:
          case ACTION_CONQUER_CITY:
            bonus += 4;
            break;
          case ACTION_SPY_BRIBE_UNIT:
            bonus += 2;
            break;
          case ACTION_SPY_INVESTIGATE_CITY:
          case ACTION_INV_CITY_SPEND:
          case ACTION_SPY_POISON:
          case ACTION_SPY_STEAL_GOLD:
          case ACTION_SPY_SABOTAGE_CITY:
          case ACTION_SPY_TARGETED_SABOTAGE_CITY:
          case ACTION_SPY_STEAL_TECH:
          case ACTION_SPY_TARGETED_STEAL_TECH:
          case ACTION_SPY_SABOTAGE_UNIT:
          case ACTION_CAPTURE_UNITS:
          case ACTION_STEAL_MAPS:
          case ACTION_BOMBARD:
          case ACTION_SPY_NUKE:
          case ACTION_NUKE:
          case ACTION_DESTROY_CITY:
          case ACTION_EXPEL_UNIT:
            /* Being a target of this is usually undesireable */
            /* TODO: Individual and well balanced values. */
            bonus += 0.1;
            break;

          case ACTION_MARKETPLACE:
          case ACTION_FOUND_CITY:
          case ACTION_DISBAND_UNIT:
          case ACTION_PARADROP:
            /* Wants the ability to do this to it self. Don't want others
             * to target it. Do nothing since action_immune_government()
             * doesn't separate based on who the actor is. */
            break;

          case ACTION_ESTABLISH_EMBASSY:
          case ACTION_ESTABLISH_EMBASSY_STAY:
          case ACTION_TRADE_ROUTE:
          case ACTION_JOIN_CITY:
          case ACTION_HELP_WONDER:
          case ACTION_RECYCLE_UNIT:
          case ACTION_HOME_CITY:
          case ACTION_UPGRADE_UNIT:
          case ACTION_AIRLIFT:
          case ACTION_HEAL_UNIT:
            /* Could be good. An embassy gives permanent contact. A trade
             * route gives gold per turn. Join city gives population. Help
             * wonder gives shields. */
            /* TODO: Individual and well balanced values. */
            break;

          case ACTION_COUNT:
            /* Invalid */
            fc_assert(act != ACTION_COUNT);
            break;
          }
        } action_iterate_end;

        bonus += get_player_bonus(pplayer, EFT_INSPIRE_PARTISANS) > 0 ? 3 : 0;
        bonus += get_player_bonus(pplayer, EFT_RAPTURE_GROW) > 0 ? 2 : 0;
        bonus += get_player_bonus(pplayer, EFT_FANATICS) > 0 ? 3 : 0;
        bonus += get_player_bonus(pplayer, EFT_OUTPUT_INC_TILE) * 8;

        revolution_turns = get_player_bonus(pplayer, EFT_REVOLUTION_UNHAPPINESS);
        if (revolution_turns > 0) {
          bonus -= 6 / revolution_turns;
        }

        val += (val * bonus) / 100;

        /* FIXME: handle reqs other than technologies. */
        dist = 0;
        requirement_vector_iterate(&gov->reqs, preq) {
          if (VUT_ADVANCE == preq->source.kind) {
            dist += MAX(1, research_goal_unknown_techs(presearch,
                                                       advance_number(preq->source.value.advance)));
          }
        } requirement_vector_iterate_end;
        val = amortize(val, dist);
      }

      adv->government_want[government_index(gov)] = val; /* Save want */
    } governments_iterate_end;
    /* Now reset our gov to it's real state. */
    pplayer->government = current_gov;
    city_list_iterate(pplayer->cities, acity) {
      auto_arrange_workers(acity);
    } city_list_iterate_end;
    if (player_is_cpuhog(pplayer)) {
      adv->govt_reeval = 1;
    } else {
      adv->govt_reeval = CLIP(5, city_list_size(pplayer->cities), 20);
    }
  }
  adv->govt_reeval--;

  /* Figure out which government is the best for us this turn. */
  governments_iterate(gov) {
    int gi = government_index(gov);
    if (adv->government_want[gi] > best_val 
        && can_change_to_government(pplayer, gov)) {
      best_val = adv->government_want[gi];
      adv->goal.revolution = gov;
    }
    if (adv->government_want[gi] > adv->goal.govt.val) {
      adv->goal.govt.gov = gov;
      adv->goal.govt.val = adv->government_want[gi];

      /* FIXME: handle reqs other than technologies. */
      adv->goal.govt.req = A_NONE;
      requirement_vector_iterate(&gov->reqs, preq) {
        if (VUT_ADVANCE == preq->source.kind) {
          adv->goal.govt.req = advance_number(preq->source.value.advance);
          break;
        }
      } requirement_vector_iterate_end;
    }
  } governments_iterate_end;
  /* Goodness of the ideal gov is calculated relative to the goodness of the
   * best of the available ones. */
  adv->goal.govt.val -= best_val;
}

/**************************************************************************
  Return whether science would help us at all.
**************************************************************************/
bool adv_wants_science(struct player *pplayer)
{
  return adv_data_get(pplayer, NULL)->wants_science;
}


/**********************************************************************
  There are some signs that a player might be dangerous: We are at 
  war with him, he has done lots of ignoble things to us, he is an 
  ally of one of our enemies (a ticking bomb to be sure), we don't like him,
  diplomatic state is neutral or we have cease fire.
***********************************************************************/
bool adv_is_player_dangerous(struct player *pplayer,
                             struct player *aplayer)
{
  struct adv_dipl *dip;
  enum diplstate_type ds;
  enum override_bool dang = NO_OVERRIDE;

  if (is_ai(pplayer)) {
    /* Give AI code possibility to decide itself */
    CALL_PLR_AI_FUNC(consider_plr_dangerous, pplayer, pplayer, aplayer, &dang);
  }

  if (dang == OVERRIDE_FALSE) {
    return FALSE;
  }

  if (dang == OVERRIDE_TRUE) {
    return TRUE;
  }

  if (pplayer == aplayer) {
    /* We always trust ourself */
    return FALSE;
  }
  
  ds = player_diplstate_get(pplayer, aplayer)->type;
  
  if (ds == DS_WAR || ds == DS_CEASEFIRE) {
    /* It's already a war or aplayer can declare it soon */
    return TRUE;
  }

  dip = adv_dipl_get(pplayer, aplayer);

  if (dip->allied_with_enemy) {
    /* Don't trust someone who will declare war on us soon */
    return TRUE;
  }

  if (player_diplstate_get(pplayer, aplayer)->has_reason_to_cancel > 0) {
    return TRUE;
  }

  if (pplayer->ai_common.love[player_index(aplayer)] < MAX_AI_LOVE / 10) {
    /* We don't trust players who we don't like. Note that 
     * aplayer's units inside pplayer's borders decreases AI's love */
    return TRUE;
  }
  
  return FALSE;
}