aiair.c

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/***********************************************************************
 Freeciv - Copyright (C) 2002 - The Freeciv Team
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
***********************************************************************/
 
#ifdef HAVE_CONFIG_H
#include <fc_config.h>
#endif
 
/* utility */
#include "log.h"
 
/* common */
#include "combat.h"
#include "game.h"
#include "map.h"
#include "movement.h"
#include "player.h"
#include "pf_tools.h"
#include "unit.h"
 
/* server */
#include "citytools.h"
#include "maphand.h"
#include "srv_log.h"
#include "unithand.h"
#include "unittools.h"
 
/* server/advisors */
#include "advbuilding.h"
#include "advgoto.h"
 
/* ai */
#include "handicaps.h"
 
/* ai/default */
#include "aiplayer.h"
#include "ailog.h"
#include "aitools.h"
#include "aiunit.h"
#include "daicity.h"
 
#include "aiair.h"
 
/******************************************************************/
static inline int regen_turns(struct unit *punit, struct tile *ptile,
                              int lost_hp)
{
  struct tile *real_tile = unit_tile(punit);
  int res, regen, recov;
 
  punit->tile = ptile;
  /* unit_list_prepend(ptile, punit); ... (handle "MaxUnitsOnTile" etc.) */
  regen = hp_gain_coord(punit);
  recov = get_unit_bonus(punit, EFT_UNIT_RECOVER);
  if (lost_hp - recov <= 0) {
    res = 0;
  } else {
    res = 1 + (lost_hp - recov) / (recov + regen);
  }
  punit->tile = real_tile;
 
  return res;
}
 
/******************************************************************/
static struct tile *find_nearest_airbase(struct unit *punit,
                                         struct pf_path **path)
{
  struct player *pplayer = unit_owner(punit);
  struct pf_parameter parameter;
  struct pf_map *pfm;
  struct tile *best = NULL;
  int lost_hp = unit_type_get(punit)->hp - punit->hp;
  int best_regt = FC_INFINITY;
  const struct civ_map *nmap = &(wld.map);
 
  pft_fill_unit_parameter(&parameter, nmap, punit);
  parameter.omniscience = !has_handicap(pplayer, H_MAP);
  pfm = pf_map_new(&parameter);
 
  pf_map_move_costs_iterate(pfm, ptile, move_cost, TRUE) {
    if (move_cost > punit->moves_left) {
      /* Too far! */
      break;
    }
 
    if (is_refuel_point(ptile, pplayer, punit)) {
      if (lost_hp > 0) {
        int regt = regen_turns(punit, ptile, lost_hp);
 
        if (regt <= 0) {
          /* Nothing better to search */
          best = ptile;
          break;
        } else if (!best || regt < best_regt) {
          /* Regenerates faster */
          best_regt = regt;
          best = ptile;
        }
      } else {
        best = ptile;
        break;
      }
    }
  } pf_map_move_costs_iterate_end;
 
  if (path && best) {
    *path = pf_map_path(pfm, best);
  }
  pf_map_destroy(pfm);
  return best;
}
 
/******************************************************************/
static bool dai_should_we_air_attack_tile(struct ai_type *ait,
                                          struct unit *punit, struct tile *ptile)
{
  struct city *acity = tile_city(ptile);
 
  /* For a virtual unit (punit->id == 0), all targets are good */
  /* TODO: There is a danger of producing too many units that will not
   * attack anything. Production should not happen if there is an idle
   * unit of the same type nearby */
  if (acity && punit->id != 0
      && def_ai_city_data(acity, ait)->invasion.occupy == 0
      && !unit_can_take_over(punit)) {
    /* No units capable of occupying are invading */
    log_debug("Don't want to attack %s, although we could",
              city_name_get(acity));
    return FALSE;
  }
 
  return TRUE;
}
 
/******************************************************************/
static adv_want dai_evaluate_tile_for_air_attack(struct unit *punit,
                                                 struct tile *dst_tile)
{
  struct unit *pdefender;
  /* Unit costs in shields */
  int balanced_cost, unit_cost, victim_cost = 0;
  /* Unit stats */
  int unit_attack, victim_defense;
  /* Final answer */
  adv_want profit;
  /* Time spent in the air */
  int sortie_time;
  struct civ_map *nmap = &(wld.map);
 
#define PROB_MULTIPLIER 100 /* Should unify with those in combat.c */
 
  if (!can_unit_attack_tile(punit, NULL, dst_tile)
      || !(pdefender = get_defender(nmap, punit, dst_tile))) {
    return 0;
  }
 
  /* Ok, we can attack, but is it worth it? */
 
  /* Cost of our unit */
  unit_cost = unit_build_shield_cost_base(punit);
  /* This is to say "wait, ill unit will get better!" */
  unit_cost = unit_cost * unit_type_get(punit)->hp / punit->hp; 
 
  /* Determine cost of enemy units */
  victim_cost = stack_cost(punit, pdefender);
  if (0 == victim_cost) {
    return 0;
  }
 
  /* Missile would die 100% so we adjust the victim_cost -- GB */
  if (utype_can_do_action(unit_type_get(punit), ACTION_SUICIDE_ATTACK)) {
    /* Assume that the attack will be a suicide attack even if a regular
     * attack may be legal. */
    victim_cost -= unit_build_shield_cost_base(punit);
  }
 
  unit_attack = (int) (PROB_MULTIPLIER
                       * unit_win_chance(nmap, punit, pdefender));
 
  victim_defense = PROB_MULTIPLIER - unit_attack;
 
  balanced_cost = build_cost_balanced(unit_type_get(punit));
 
  sortie_time
    = (utype_pays_mp_for_action_estimate(nmap,
                                         action_by_number(ACTION_ATTACK),
                                         unit_type_get(punit), unit_owner(punit),
                                         /* Assume that dst_tile is closer to the tile the actor
                                          * unit will attack from than its current tile. */
                                         dst_tile,
                                         dst_tile) >= MAX_MOVE_FRAGS ? 1 : 0);
 
  profit = kill_desire(victim_cost, unit_attack, unit_cost, victim_defense, 1)
    - SHIELD_WEIGHTING + 2 * TRADE_WEIGHTING;
  if (profit > 0) {
    profit = military_amortize(unit_owner(punit), 
                               game_city_by_number(punit->homecity),
                               profit, sortie_time, balanced_cost);
    log_debug("%s at (%d, %d) is a worthy target with profit " ADV_WANT_PRINTF,
              unit_rule_name(pdefender), TILE_XY(dst_tile), profit);
  } else {
    log_debug("%s(%d, %d): %s at (%d, %d) is unworthy with profit " ADV_WANT_PRINTF,
              unit_rule_name(punit), TILE_XY(unit_tile(punit)),
              unit_rule_name(pdefender), TILE_XY(dst_tile), profit);
    profit = 0;
  }
 
  return profit;
}
 
/******************************************************************/
static adv_want find_something_to_bomb(struct ai_type *ait, struct unit *punit,
                                       struct pf_path **path, struct tile **pptile)
{
  struct player *pplayer = unit_owner(punit);
  struct pf_parameter parameter;
  struct pf_map *pfm;
  struct tile *best_tile = NULL;
  adv_want best = 0;
  const struct civ_map *nmap = &(wld.map);
 
  pft_fill_unit_parameter(&parameter, nmap, punit);
  parameter.omniscience = !has_handicap(pplayer, H_MAP);
  pfm = pf_map_new(&parameter);
 
  /* Let's find something to bomb */
  pf_map_move_costs_iterate(pfm, ptile, move_cost, FALSE) {
    if (move_cost >= punit->moves_left) {
      /* Too far! */
      break;
    }
 
    if (has_handicap(pplayer, H_MAP) && !map_is_known(ptile, pplayer)) {
      /* The target tile is unknown */
      continue;
    }
 
    if (has_handicap(pplayer, H_FOG) 
        && !map_is_known_and_seen(ptile, pplayer, V_MAIN)) {
      /* The tile is fogged */
      continue;
    }
 
    if (is_enemy_unit_tile(ptile, pplayer)
        && dai_should_we_air_attack_tile(ait, punit, ptile)
        && can_unit_attack_tile(punit, NULL, ptile)) {
      adv_want new_best = dai_evaluate_tile_for_air_attack(punit, ptile);
 
      if (new_best > best) {
        best_tile = ptile;
        best = new_best;
        log_debug("%s wants to attack tile (%d, %d)",
                  unit_rule_name(punit), TILE_XY(ptile));
      }
    }
  } pf_map_move_costs_iterate_end;
 
  /* Return the best values. */
  if (pptile) {
    *pptile = best_tile;
  }
  if (path) {
    *path = best_tile ? pf_map_path(pfm, best_tile) : NULL;
  }
 
  pf_map_destroy(pfm);
 
  return best;
}
 
/******************************************************************/
static struct tile *dai_find_strategic_airbase(struct ai_type *ait,
                                               struct unit *punit,
                                               struct pf_path **path)
{
  struct player *pplayer = unit_owner(punit);
  struct pf_parameter parameter;
  struct pf_map *pfm;
  struct tile *best_tile = NULL;
  struct city *pcity;
  struct unit *pvirtual = NULL;
  adv_want best_worth = 0, target_worth;
  int lost_hp = unit_type_get(punit)->hp - punit->hp;
  int regen_turns_min = FC_INFINITY;
  bool defend = FALSE; /* Used only for lost_hp > 0 */
  bool refuel_start = FALSE; /* Used for not a "grave danger" start */
  const struct civ_map *nmap = &(wld.map);
 
  /* Consider staying at the current position
   * before we generate the map, maybe we should not */
  if (is_unit_being_refueled(punit)) {
    /* We suppose here for speed that the recovery effect is global.
     * It's so in the standard rulesets but might be not elsewhere */
    int recov = get_unit_bonus(punit, EFT_UNIT_RECOVER);
    int regen = hp_gain_coord(punit);
    const struct tile *ptile = unit_tile(punit);
 
    if (lost_hp > 0 && regen + recov > 0) {
      regen_turns_min =
        punit->moved ? lost_hp - recov : lost_hp - (regen + recov);
      if (regen_turns_min <= 0) {
        if (lost_hp - recov > 0) {
          /* Probably, nothing can repair us faster */
          log_debug("Repairment of %s is almost finished, stays here",
                    unit_rule_name(punit));
          def_ai_unit_data(punit, ait)->done = TRUE;
          return NULL;
        } else {
          regen_turns_min = 0;
        }
      } else {
        regen_turns_min /= regen + recov;
        regen_turns_min += 1;
      }
    }
    pcity = tile_city(ptile);
    if (pcity
        && def_ai_city_data(pcity, ait)->grave_danger
           > (unit_list_size(ptile->units) - 1) << 1) {
      if (lost_hp <= 0 || regen_turns_min <= 1) {
        log_debug("%s stays defending %s",
                  unit_rule_name(punit), city_name_get(pcity));
        return NULL;
      } else {
        /* We may find a city in grave danger that restores faster */
        defend = TRUE;
      }
    } else {
      refuel_start = TRUE;
    }
  }
 
  pft_fill_unit_parameter(&parameter, nmap, punit);
  parameter.omniscience = !has_handicap(pplayer, H_MAP);
  pfm = pf_map_new(&parameter);
  pf_map_move_costs_iterate(pfm, ptile, move_cost, FALSE) {
    bool chg_for_regen = FALSE;
 
    if (move_cost >= punit->moves_left) {
      break; /* Too far! */
    }
 
    if (!is_refuel_point(ptile, pplayer, punit)) {
      continue; /* Cannot refuel here. */
    }
 
    if (lost_hp > 0) {
      /* Don't fly to a point where we'll regenerate longer */
      int regen_tn = regen_turns(punit, ptile, lost_hp);
 
      if (regen_turns_min < regen_tn) {
        log_debug("%s knows a better repair base than %d,%d",
                  unit_rule_name(punit), TILE_XY(ptile));
        continue;
      } else if (regen_turns_min > regen_tn) {
        regen_turns_min = regen_tn;
        best_tile = ptile;
        best_worth = 0; /* to be calculated if necessary */
        chg_for_regen = TRUE;
      }
    }
 
    if ((pcity = tile_city(ptile))
        /* Two defenders per attacker is enough,
         * at least considering that planes are usually
         * expensive and weak city defenders */
        && def_ai_city_data(pcity, ait)->grave_danger
           > unit_list_size(ptile->units) << 1) {
      if (lost_hp <= 0) {
        best_tile = ptile;
        break; /* Fly there immediately!! */
      } else {
        if (!defend) {
          /* We maybe have equally regenerating base but not in danger */
          best_tile = ptile;
          defend = TRUE;
        }
        continue;
      }
    } else if (defend) {
      if (chg_for_regen) {
        /* We better regenerate faster and take a revenge a bit later */
        defend = FALSE;
      } else {
        /* We already have a base in grave danger that restores not worse */
        continue;
      }
    }
 
    if (!pvirtual) {
      pvirtual =
        unit_virtual_create(pplayer,
                            player_city_by_number(pplayer, punit->homecity),
                            unit_type_get(punit), punit->veteran);
      if (refuel_start) {
        /* What worth really worth moving out? */
        adv_want start_worth;
 
        unit_tile_set(pvirtual, unit_tile(punit));
        start_worth = find_something_to_bomb(ait, pvirtual, NULL, NULL);
        best_worth = MAX(start_worth, 0);
      }
    }
 
    unit_tile_set(pvirtual, ptile);
    target_worth = find_something_to_bomb(ait, pvirtual, NULL, NULL);
    if (target_worth > best_worth) {
      /* It's either a first find or it's better than the previous. */
      best_worth = target_worth;
      best_tile = ptile;
      /* We can still look for something better. */
    }
  } pf_map_move_costs_iterate_end;
 
  if (pvirtual) {
    unit_virtual_destroy(pvirtual);
  }
 
  if (path) {
    /* Stores the path. */
    *path = best_tile ? pf_map_path(pfm, best_tile) : NULL;
  }
  pf_map_destroy(pfm);
 
  return best_tile;
}
 
/******************************************************************/
void dai_manage_airunit(struct ai_type *ait, struct player *pplayer,
                        struct unit *punit)
{
  struct tile *dst_tile = unit_tile(punit);
  /* Loop prevention */
  int moves = punit->moves_left;
  int id = punit->id;
  struct pf_parameter parameter;
  struct pf_map *pfm;
  struct pf_path *path;
 
  CHECK_UNIT(punit);
 
  if (!is_unit_being_refueled(punit)) {
    /* We are out in the open, what shall we do? */
    if (punit->activity == ACTIVITY_GOTO
        /* We are on a GOTO.  Check if it will get us anywhere */
        && NULL != punit->goto_tile
        && !same_pos(unit_tile(punit), punit->goto_tile)
        && is_refuel_point(punit->goto_tile, pplayer, punit)) {
      pfm = pf_map_new(&parameter);
      path = pf_map_path(pfm, punit->goto_tile);
      if (path) {
        bool alive = adv_follow_path(punit, path, punit->goto_tile);
 
        pf_path_destroy(path);
        pf_map_destroy(pfm);
        if (alive && punit->moves_left > 0) {
          /* Maybe do something else. */
          dai_manage_airunit(ait, pplayer, punit);
        }
        return;
      }
      pf_map_destroy(pfm);
    } else if ((dst_tile = find_nearest_airbase(punit, &path))) {
      /* Go refuelling */
      if (!adv_follow_path(punit, path, dst_tile)) {
        pf_path_destroy(path);
        return; /* The unit died. */
      }
      pf_path_destroy(path);
    } else {
      if (punit->fuel == 1) {
        UNIT_LOG(LOG_DEBUG, punit, "Oops, fallin outta the sky");
      }
      def_ai_unit_data(punit, ait)->done = TRUE; /* Won't help trying again */
      return;
    }
 
  } else if (punit->fuel == unit_type_get(punit)->fuel) {
    /* We only leave a refuel point when we are on full fuel */
 
    if (find_something_to_bomb(ait, punit, &path, &dst_tile) > 0) {
      /* Found target, coordinates are in punit's goto_dest.
       * TODO: separate attacking into a function, check for the best 
       * tile to attack from */
      fc_assert_ret(path != NULL && dst_tile != NULL);
      if (!adv_follow_path(punit, path, dst_tile)) {
        pf_path_destroy(path);
        return; /* The unit died. */
      }
      pf_path_destroy(path);
      unit_activity_handling(punit, ACTIVITY_IDLE);
    } else if ((dst_tile = dai_find_strategic_airbase(ait, punit, &path))) {
      log_debug("%s will fly to (%i, %i) (%s) to fight there",
                unit_rule_name(punit), TILE_XY(dst_tile),
                tile_city(dst_tile) ? city_name_get(tile_city(dst_tile)) : "");
      def_ai_unit_data(punit, ait)->done = TRUE; /* Wait for next turn */
      if (!adv_follow_path(punit, path, dst_tile)) {
        pf_path_destroy(path);
        return; /* The unit died. */
      }
      pf_path_destroy(path);
    } else {
      log_debug("%s cannot find anything to kill and is staying put", 
                unit_rule_name(punit));
      def_ai_unit_data(punit, ait)->done = TRUE;
      unit_activity_handling(punit, ACTIVITY_IDLE);
    }
  }
 
  if ((punit = game_unit_by_number(id)) != NULL && punit->moves_left > 0
      && punit->moves_left != moves) {
    /* We have moved this turn, might have ended up stuck out in the fields
     * so, as a safety measure, let's manage again */
    dai_manage_airunit(ait, pplayer, punit);
  }
 
}
 
/******************************************************************/
bool dai_choose_attacker_air(struct ai_type *ait, struct player *pplayer,
                             struct city *pcity, struct adv_choice *choice,
                             bool allow_gold_upkeep)
{
  bool want_something = FALSE;
  const struct civ_map *nmap = &(wld.map);
 
  /* This AI doesn't know how to build planes */
  if (has_handicap(pplayer, H_NOPLANES)) {
    return FALSE;
  }
 
  /* military_advisor_choose_build() does something idiotic,
   * this function should not be called if there is danger... */
  if (choice->want >= DAI_WANT_MILITARY_EMERGENCY
      && choice->type != CT_ATTACKER) {
    return FALSE;
  }
 
  if (!player_knows_techs_with_flag(pplayer, TF_BUILD_AIRBORNE)) {
    return FALSE;
  }
 
  unit_type_iterate(punittype) {
    struct unit_class *pclass = utype_class(punittype);
 
    if (pclass->adv.land_move == MOVE_NONE
        || pclass->adv.sea_move == MOVE_NONE
        || uclass_has_flag(pclass, UCF_TERRAIN_SPEED)
        || unit_type_is_losing_hp(pplayer, punittype)) {
      /* We don't consider this a plane */
      continue;
    }
 
    if (!allow_gold_upkeep && utype_upkeep_cost(punittype, pplayer, O_GOLD) > 0) {
      continue;
    }
 
    if (can_city_build_unit_now(nmap, pcity, punittype)) {
      struct unit *virtual_unit =
       unit_virtual_create(
          pplayer, pcity, punittype,
          city_production_unit_veteran_level(pcity, punittype));
      adv_want profit = find_something_to_bomb(ait, virtual_unit, NULL, NULL);
 
      if (profit > choice->want) {
        /* Update choice */
        choice->want = profit;
        choice->value.utype = punittype;
        choice->type = CT_ATTACKER;
        choice->need_boat = FALSE;
        adv_choice_set_use(choice, "offensive air");
        want_something = TRUE;
        log_debug("%s wants to build %s (want = " ADV_WANT_PRINTF ")",
                  city_name_get(pcity), utype_rule_name(punittype), profit);
      } else {
        log_debug("%s doesn't want to build %s (want = " ADV_WANT_PRINTF ")",
                  city_name_get(pcity), utype_rule_name(punittype), profit);
      }
      unit_virtual_destroy(virtual_unit);
    }
  } unit_type_iterate_end;
 
  return want_something;
}