disaster_vehicle.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD 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, version 2.
 * OpenTTD 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. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#include "stdafx.h"
 
#include "aircraft.h"
#include "disaster_vehicle.h"
#include "industry.h"
#include "station_base.h"
#include "command_func.h"
#include "news_func.h"
#include "town.h"
#include "company_func.h"
#include "strings_func.h"
#include "viewport_func.h"
#include "vehicle_func.h"
#include "sound_func.h"
#include "effectvehicle_func.h"
#include "roadveh.h"
#include "train.h"
#include "ai/ai.hpp"
#include "game/game.hpp"
#include "company_base.h"
#include "core/random_func.hpp"
#include "core/backup_type.hpp"
#include "landscape_cmd.h"
#include "timer/timer.h"
#include "timer/timer_game_economy.h"
 
#include "table/strings.h"
 
#include "safeguards.h"
 
uint16_t _disaster_delay;
 
static void DisasterClearSquare(TileIndex tile)
{
  if (EnsureNoVehicleOnGround(tile).Failed()) return;
 
  switch (GetTileType(tile)) {
    case MP_RAILWAY:
      if (Company::IsHumanID(GetTileOwner(tile)) && !IsRailDepot(tile)) {
        Backup<CompanyID> cur_company(_current_company, OWNER_WATER, FILE_LINE);
        Command<CMD_LANDSCAPE_CLEAR>::Do(DC_EXEC, tile);
        cur_company.Restore();
 
        /* update signals in buffer */
        UpdateSignalsInBuffer();
      }
      break;
 
    case MP_HOUSE: {
      Backup<CompanyID> cur_company(_current_company, OWNER_NONE, FILE_LINE);
      Command<CMD_LANDSCAPE_CLEAR>::Do(DC_EXEC, tile);
      cur_company.Restore();
      break;
    }
 
    case MP_TREES:
    case MP_CLEAR:
      DoClearSquare(tile);
      break;
 
    default:
      break;
  }
}
 
static const SpriteID _disaster_images_1[] = {SPR_BLIMP, SPR_BLIMP, SPR_BLIMP, SPR_BLIMP, SPR_BLIMP, SPR_BLIMP, SPR_BLIMP, SPR_BLIMP};
static const SpriteID _disaster_images_2[] = {SPR_UFO_SMALL_SCOUT, SPR_UFO_SMALL_SCOUT, SPR_UFO_SMALL_SCOUT, SPR_UFO_SMALL_SCOUT, SPR_UFO_SMALL_SCOUT, SPR_UFO_SMALL_SCOUT, SPR_UFO_SMALL_SCOUT, SPR_UFO_SMALL_SCOUT};
static const SpriteID _disaster_images_3[] = {SPR_F_15, SPR_F_15, SPR_F_15, SPR_F_15, SPR_F_15, SPR_F_15, SPR_F_15, SPR_F_15};
static const SpriteID _disaster_images_4[] = {SPR_SUB_SMALL_NE, SPR_SUB_SMALL_NE, SPR_SUB_SMALL_SE, SPR_SUB_SMALL_SE, SPR_SUB_SMALL_SW, SPR_SUB_SMALL_SW, SPR_SUB_SMALL_NW, SPR_SUB_SMALL_NW};
static const SpriteID _disaster_images_5[] = {SPR_SUB_LARGE_NE, SPR_SUB_LARGE_NE, SPR_SUB_LARGE_SE, SPR_SUB_LARGE_SE, SPR_SUB_LARGE_SW, SPR_SUB_LARGE_SW, SPR_SUB_LARGE_NW, SPR_SUB_LARGE_NW};
static const SpriteID _disaster_images_6[] = {SPR_UFO_HARVESTER, SPR_UFO_HARVESTER, SPR_UFO_HARVESTER, SPR_UFO_HARVESTER, SPR_UFO_HARVESTER, SPR_UFO_HARVESTER, SPR_UFO_HARVESTER, SPR_UFO_HARVESTER};
static const SpriteID _disaster_images_7[] = {SPR_XCOM_SKYRANGER, SPR_XCOM_SKYRANGER, SPR_XCOM_SKYRANGER, SPR_XCOM_SKYRANGER, SPR_XCOM_SKYRANGER, SPR_XCOM_SKYRANGER, SPR_XCOM_SKYRANGER, SPR_XCOM_SKYRANGER};
static const SpriteID _disaster_images_8[] = {SPR_AH_64A, SPR_AH_64A, SPR_AH_64A, SPR_AH_64A, SPR_AH_64A, SPR_AH_64A, SPR_AH_64A, SPR_AH_64A};
static const SpriteID _disaster_images_9[] = {SPR_ROTOR_MOVING_1, SPR_ROTOR_MOVING_1, SPR_ROTOR_MOVING_1, SPR_ROTOR_MOVING_1, SPR_ROTOR_MOVING_1, SPR_ROTOR_MOVING_1, SPR_ROTOR_MOVING_1, SPR_ROTOR_MOVING_1};
 
static const SpriteID * const _disaster_images[] = {
  _disaster_images_1, _disaster_images_1,                     
  _disaster_images_2, _disaster_images_2,                     
  _disaster_images_3, _disaster_images_3,                     
  _disaster_images_8, _disaster_images_8, _disaster_images_9, 
  _disaster_images_6, _disaster_images_6,                     
  _disaster_images_7, _disaster_images_7,                     
  _disaster_images_4, _disaster_images_5,                     
};
 
void DisasterVehicle::UpdateImage()
{
  SpriteID img = this->image_override;
  if (img == 0) img = _disaster_images[this->subtype][this->direction];
  this->sprite_cache.sprite_seq.Set(img);
}
 
DisasterVehicle::DisasterVehicle(int x, int y, Direction direction, DisasterSubType subtype, VehicleID big_ufo_destroyer_target) :
    SpecializedVehicleBase(), big_ufo_destroyer_target(big_ufo_destroyer_target)
{
  this->vehstatus = VS_UNCLICKABLE;
 
  this->x_pos = x;
  this->y_pos = y;
  switch (subtype) {
    case ST_ZEPPELINER:
    case ST_SMALL_UFO:
    case ST_AIRPLANE:
    case ST_HELICOPTER:
    case ST_BIG_UFO:
    case ST_BIG_UFO_DESTROYER:
      GetAircraftFlightLevelBounds(this, &this->z_pos, nullptr);
      break;
 
    case ST_HELICOPTER_ROTORS:
      GetAircraftFlightLevelBounds(this, &this->z_pos, nullptr);
      this->z_pos += ROTOR_Z_OFFSET;
      break;
 
    case ST_SMALL_SUBMARINE:
    case ST_BIG_SUBMARINE:
      this->z_pos = 0;
      break;
 
    case ST_ZEPPELINER_SHADOW:
    case ST_SMALL_UFO_SHADOW:
    case ST_AIRPLANE_SHADOW:
    case ST_HELICOPTER_SHADOW:
    case ST_BIG_UFO_SHADOW:
    case ST_BIG_UFO_DESTROYER_SHADOW:
      this->z_pos = 0;
      this->vehstatus |= VS_SHADOW;
      break;
  }
 
  this->direction = direction;
  this->tile = TileVirtXY(x, y);
  this->subtype = subtype;
  this->UpdateDeltaXY();
  this->owner = OWNER_NONE;
  this->image_override = 0;
  this->state = 0;
 
  this->UpdateImage();
  this->UpdatePositionAndViewport();
}
 
void DisasterVehicle::UpdatePosition(int x, int y, int z)
{
  this->x_pos = x;
  this->y_pos = y;
  this->z_pos = z;
  this->tile = TileVirtXY(x, y);
 
  this->UpdateImage();
  this->UpdatePositionAndViewport();
 
  DisasterVehicle *u = this->Next();
  if (u != nullptr) {
    int safe_x = Clamp(x, 0, Map::MaxX() * TILE_SIZE);
    int safe_y = Clamp(y - 1, 0, Map::MaxY() * TILE_SIZE);
 
    u->x_pos = x;
    u->y_pos = y - 1 - (std::max(z - GetSlopePixelZ(safe_x, safe_y), 0) >> 3);
    safe_y = Clamp(u->y_pos, 0, Map::MaxY() * TILE_SIZE);
    u->z_pos = GetSlopePixelZ(safe_x, safe_y);
    u->direction = this->direction;
 
    u->UpdateImage();
    u->UpdatePositionAndViewport();
 
    if ((u = u->Next()) != nullptr) {
      u->x_pos = x;
      u->y_pos = y;
      u->z_pos = z + ROTOR_Z_OFFSET;
      u->UpdatePositionAndViewport();
    }
  }
}
 
static bool DisasterTick_Zeppeliner(DisasterVehicle *v)
{
  v->tick_counter++;
 
  if (v->state < 2) {
    if (HasBit(v->tick_counter, 0)) return true;
 
    GetNewVehiclePosResult gp = GetNewVehiclePos(v);
 
    v->UpdatePosition(gp.x, gp.y, GetAircraftFlightLevel(v));
 
    if (v->state == 1) {
      if (++v->age == 38) {
        v->state = 2;
        v->age = 0;
      }
 
      if (GB(v->tick_counter, 0, 3) == 0) CreateEffectVehicleRel(v, 0, -17, 2, EV_CRASH_SMOKE);
 
    } else if (v->state == 0) {
      if (IsValidTile(v->tile) && IsAirportTile(v->tile)) {
        v->state = 1;
        v->age = 0;
 
        SetDParam(0, GetStationIndex(v->tile));
        AddTileNewsItem(STR_NEWS_DISASTER_ZEPPELIN, NT_ACCIDENT, v->tile);
        AI::NewEvent(GetTileOwner(v->tile), new ScriptEventDisasterZeppelinerCrashed(GetStationIndex(v->tile)));
      }
    }
 
    if (v->y_pos >= (int)((Map::SizeY() + 9) * TILE_SIZE - 1)) {
      delete v;
      return false;
    }
 
    return true;
  }
 
  if (v->state > 2) {
    if (++v->age <= 13320) return true;
 
    if (IsValidTile(v->tile) && IsAirportTile(v->tile)) {
      Station *st = Station::GetByTile(v->tile);
      CLRBITS(st->airport.flags, RUNWAY_IN_block);
      AI::NewEvent(GetTileOwner(v->tile), new ScriptEventDisasterZeppelinerCleared(st->index));
    }
 
    v->UpdatePosition(v->x_pos, v->y_pos, GetAircraftFlightLevel(v));
    delete v;
    return false;
  }
 
  int x = v->x_pos;
  int y = v->y_pos;
  int z = GetSlopePixelZ(x, y);
  if (z < v->z_pos) z = v->z_pos - 1;
  v->UpdatePosition(x, y, z);
 
  if (++v->age == 1) {
    CreateEffectVehicleRel(v, 0, 7, 8, EV_EXPLOSION_LARGE);
    if (_settings_client.sound.disaster) SndPlayVehicleFx(SND_12_EXPLOSION, v);
    v->image_override = SPR_BLIMP_CRASHING;
  } else if (v->age == 70) {
    v->image_override = SPR_BLIMP_CRASHED;
  } else if (v->age <= 300) {
    if (GB(v->tick_counter, 0, 3) == 0) {
      uint32_t r = Random();
 
      CreateEffectVehicleRel(v,
        GB(r, 0, 4) - 7,
        GB(r, 4, 4) - 7,
        GB(r, 8, 3) + 5,
        EV_EXPLOSION_SMALL);
    }
  } else if (v->age == 350) {
    v->state = 3;
    v->age = 0;
  }
 
  if (IsValidTile(v->tile) && IsAirportTile(v->tile)) {
    SETBITS(Station::GetByTile(v->tile)->airport.flags, RUNWAY_IN_block);
  }
 
  return true;
}
 
static bool DisasterTick_Ufo(DisasterVehicle *v)
{
  v->image_override = (HasBit(++v->tick_counter, 3)) ? SPR_UFO_SMALL_SCOUT_DARKER : SPR_UFO_SMALL_SCOUT;
 
  if (v->state == 0) {
    /* Fly around randomly */
    int x = TileX(v->dest_tile) * TILE_SIZE;
    int y = TileY(v->dest_tile) * TILE_SIZE;
    if (Delta(x, v->x_pos) + Delta(y, v->y_pos) >= (int)TILE_SIZE) {
      v->direction = GetDirectionTowards(v, x, y);
      GetNewVehiclePosResult gp = GetNewVehiclePos(v);
      v->UpdatePosition(gp.x, gp.y, GetAircraftFlightLevel(v));
      return true;
    }
    if (++v->age < 6) {
      v->dest_tile = RandomTile();
      return true;
    }
    v->state = 1;
 
    uint n = 0; // Total number of targetable road vehicles.
    for (const Company *c : Company::Iterate()) {
      n += c->group_all[VEH_ROAD].num_vehicle;
    }
 
    if (n == 0) {
      /* If there are no targetable road vehicles, destroy the UFO. */
      delete v;
      return false;
    }
 
    n = RandomRange(n); // Choose one of them.
    for (const RoadVehicle *u : RoadVehicle::Iterate()) {
      /* Find (n+1)-th road vehicle. */
      if (u->IsFrontEngine() && (n-- == 0)) {
        /* Target it. */
        v->dest_tile = u->index;
        v->age = 0;
        break;
      }
    }
 
    return true;
  } else {
    /* Target a vehicle */
    RoadVehicle *u = RoadVehicle::Get(v->dest_tile.base());
    assert(u != nullptr && u->type == VEH_ROAD && u->IsFrontEngine());
 
    uint dist = Delta(v->x_pos, u->x_pos) + Delta(v->y_pos, u->y_pos);
 
    if (dist < TILE_SIZE && !(u->vehstatus & VS_HIDDEN) && u->breakdown_ctr == 0) {
      u->breakdown_ctr = 3;
      u->breakdown_delay = 140;
    }
 
    v->direction = GetDirectionTowards(v, u->x_pos, u->y_pos);
    GetNewVehiclePosResult gp = GetNewVehiclePos(v);
 
    int z = v->z_pos;
    if (dist <= TILE_SIZE && z > u->z_pos) z--;
    v->UpdatePosition(gp.x, gp.y, z);
 
    if (z <= u->z_pos && (u->vehstatus & VS_HIDDEN) == 0) {
      v->age++;
      if (u->crashed_ctr == 0) {
        u->Crash();
 
        AddTileNewsItem(STR_NEWS_DISASTER_SMALL_UFO, NT_ACCIDENT, u->tile);
 
        AI::NewEvent(u->owner, new ScriptEventVehicleCrashed(u->index, u->tile, ScriptEventVehicleCrashed::CRASH_RV_UFO));
        Game::NewEvent(new ScriptEventVehicleCrashed(u->index, u->tile, ScriptEventVehicleCrashed::CRASH_RV_UFO));
      }
    }
 
    /* Destroy? */
    if (v->age > 50) {
      CreateEffectVehicleRel(v, 0, 7, 8, EV_EXPLOSION_LARGE);
      if (_settings_client.sound.disaster) SndPlayVehicleFx(SND_12_EXPLOSION, v);
      delete v;
      return false;
    }
  }
 
  return true;
}
 
static void DestructIndustry(Industry *i)
{
  for (TileIndex tile = 0; tile != Map::Size(); tile++) {
    if (i->TileBelongsToIndustry(tile)) {
      ResetIndustryConstructionStage(tile);
      MarkTileDirtyByTile(tile);
    }
  }
}
 
static bool DisasterTick_Aircraft(DisasterVehicle *v, uint16_t image_override, bool leave_at_top, StringID news_message, IndustryBehaviour industry_flag)
{
  v->tick_counter++;
  v->image_override = (v->state == 1 && HasBit(v->tick_counter, 2)) ? image_override : 0;
 
  GetNewVehiclePosResult gp = GetNewVehiclePos(v);
  v->UpdatePosition(gp.x, gp.y, GetAircraftFlightLevel(v));
 
  if ((leave_at_top && gp.x < (-10 * (int)TILE_SIZE)) || (!leave_at_top && gp.x > (int)(Map::SizeX() * TILE_SIZE + 9 * TILE_SIZE) - 1)) {
    delete v;
    return false;
  }
 
  if (v->state == 2) {
    if (GB(v->tick_counter, 0, 2) == 0) {
      Industry *i = Industry::Get(v->dest_tile.base()); // Industry destructor calls ReleaseDisastersTargetingIndustry, so this is valid
      int x = TileX(i->location.tile) * TILE_SIZE;
      int y = TileY(i->location.tile) * TILE_SIZE;
      uint32_t r = Random();
 
      CreateEffectVehicleAbove(
        GB(r,  0, 6) + x,
        GB(r,  6, 6) + y,
        GB(r, 12, 4),
        EV_EXPLOSION_SMALL);
 
      if (++v->age >= 55) v->state = 3;
    }
  } else if (v->state == 1) {
    if (++v->age == 112) {
      v->state = 2;
      v->age = 0;
 
      Industry *i = Industry::Get(v->dest_tile.base()); // Industry destructor calls ReleaseDisastersTargetingIndustry, so this is valid
      DestructIndustry(i);
 
      SetDParam(0, i->town->index);
      AddIndustryNewsItem(news_message, NT_ACCIDENT, i->index);
      if (_settings_client.sound.disaster) SndPlayTileFx(SND_12_EXPLOSION, i->location.tile);
    }
  } else if (v->state == 0) {
    int x = v->x_pos + ((leave_at_top ? -15 : 15) * TILE_SIZE);
    int y = v->y_pos;
 
    if ((uint)x > Map::MaxX() * TILE_SIZE - 1) return true;
 
    TileIndex tile = TileVirtXY(x, y);
    if (!IsTileType(tile, MP_INDUSTRY)) return true;
 
    IndustryID ind = GetIndustryIndex(tile);
    v->dest_tile = ind;
 
    if (GetIndustrySpec(Industry::Get(ind)->type)->behaviour & industry_flag) {
      v->state = 1;
      v->age = 0;
    }
  }
 
  return true;
}
 
static bool DisasterTick_Airplane(DisasterVehicle *v)
{
  return DisasterTick_Aircraft(v, SPR_F_15_FIRING, true, STR_NEWS_DISASTER_AIRPLANE_OIL_REFINERY, INDUSTRYBEH_AIRPLANE_ATTACKS);
}
 
static bool DisasterTick_Helicopter(DisasterVehicle *v)
{
  return DisasterTick_Aircraft(v, SPR_AH_64A_FIRING, false, STR_NEWS_DISASTER_HELICOPTER_FACTORY, INDUSTRYBEH_CHOPPER_ATTACKS);
}
 
static bool DisasterTick_Helicopter_Rotors(DisasterVehicle *v)
{
  v->tick_counter++;
  if (HasBit(v->tick_counter, 0)) return true;
 
  SpriteID &cur_image = v->sprite_cache.sprite_seq.seq[0].sprite;
  if (++cur_image > SPR_ROTOR_MOVING_3) cur_image = SPR_ROTOR_MOVING_1;
 
  v->UpdatePositionAndViewport();
 
  return true;
}
 
static bool DisasterTick_Big_Ufo(DisasterVehicle *v)
{
  v->tick_counter++;
 
  if (v->state == 1) {
    int x = TileX(v->dest_tile) * TILE_SIZE + TILE_SIZE / 2;
    int y = TileY(v->dest_tile) * TILE_SIZE + TILE_SIZE / 2;
    if (Delta(v->x_pos, x) + Delta(v->y_pos, y) >= 8) {
      v->direction = GetDirectionTowards(v, x, y);
 
      GetNewVehiclePosResult gp = GetNewVehiclePos(v);
      v->UpdatePosition(gp.x, gp.y, GetAircraftFlightLevel(v));
      return true;
    }
 
    if (!IsValidTile(v->dest_tile)) {
      /* Make sure we don't land outside the map. */
      delete v;
      return false;
    }
 
    int z = GetSlopePixelZ(v->x_pos, v->y_pos);
    if (z < v->z_pos) {
      v->UpdatePosition(v->x_pos, v->y_pos, v->z_pos - 1);
      return true;
    }
 
    v->state = 2;
 
    for (Vehicle *target : Vehicle::Iterate()) {
      if (target->IsGroundVehicle()) {
        if (Delta(target->x_pos, v->x_pos) + Delta(target->y_pos, v->y_pos) <= 12 * (int)TILE_SIZE) {
          target->breakdown_ctr = 5;
          target->breakdown_delay = 0xF0;
        }
      }
    }
 
    Town *t = ClosestTownFromTile(v->dest_tile, UINT_MAX);
    SetDParam(0, t->index);
    AddTileNewsItem(STR_NEWS_DISASTER_BIG_UFO, NT_ACCIDENT, v->tile);
 
    if (!Vehicle::CanAllocateItem(2)) {
      delete v;
      return false;
    }
    DisasterVehicle *u = new DisasterVehicle(-6 * (int)TILE_SIZE, v->y_pos, DIR_SW, ST_BIG_UFO_DESTROYER, v->index);
    DisasterVehicle *w = new DisasterVehicle(-6 * (int)TILE_SIZE, v->y_pos, DIR_SW, ST_BIG_UFO_DESTROYER_SHADOW);
    u->SetNext(w);
  } else if (v->state == 0) {
    int x = TileX(v->dest_tile) * TILE_SIZE;
    int y = TileY(v->dest_tile) * TILE_SIZE;
    if (Delta(x, v->x_pos) + Delta(y, v->y_pos) >= (int)TILE_SIZE) {
      v->direction = GetDirectionTowards(v, x, y);
      GetNewVehiclePosResult gp = GetNewVehiclePos(v);
      v->UpdatePosition(gp.x, gp.y, GetAircraftFlightLevel(v));
      return true;
    }
 
    if (++v->age < 6) {
      v->dest_tile = RandomTile();
      return true;
    }
    v->state = 1;
 
    const auto is_valid_target = [](const Train *t) {
      return t->IsFrontEngine() // Only the engines
        && Company::IsHumanID(t->owner) // Don't break AIs
        && IsPlainRailTile(t->tile) // No tunnels
        && (t->vehstatus & VS_CRASHED) == 0; // Not crashed
    };
 
    uint n = 0; // Total number of targetable trains.
    for (const Train *t : Train::Iterate()) {
      if (is_valid_target(t)) n++;
    }
 
    if (n == 0) {
      /* If there are no targetable trains, destroy the UFO. */
      delete v;
      return false;
    }
 
    n = RandomRange(n); // Choose one of them.
    for (const Train *t : Train::Iterate()) {
      /* Find (n+1)-th train. */
      if (is_valid_target(t) && (n-- == 0)) {
        /* Target it. */
        v->dest_tile = t->tile;
        v->age = 0;
        break;
      }
    }
  }
 
  return true;
}
 
static bool DisasterTick_Big_Ufo_Destroyer(DisasterVehicle *v)
{
  v->tick_counter++;
 
  GetNewVehiclePosResult gp = GetNewVehiclePos(v);
  v->UpdatePosition(gp.x, gp.y, GetAircraftFlightLevel(v));
 
  if (gp.x > (int)(Map::SizeX() * TILE_SIZE + 9 * TILE_SIZE) - 1) {
    delete v;
    return false;
  }
 
  if (v->state == 0) {
    Vehicle *u = Vehicle::Get(v->big_ufo_destroyer_target);
    if (Delta(v->x_pos, u->x_pos) > (int)TILE_SIZE) return true;
    v->state = 1;
 
    CreateEffectVehicleRel(u, 0, 7, 8, EV_EXPLOSION_LARGE);
    if (_settings_client.sound.disaster) SndPlayVehicleFx(SND_12_EXPLOSION, u);
 
    delete u;
 
    for (int i = 0; i != 80; i++) {
      uint32_t r = Random();
      CreateEffectVehicleAbove(
        GB(r, 0, 6) + v->x_pos - 32,
        GB(r, 5, 6) + v->y_pos - 32,
        0,
        EV_EXPLOSION_SMALL);
    }
 
    for (int dy = -3; dy < 3; dy++) {
      for (int dx = -3; dx < 3; dx++) {
        TileIndex tile = TileAddWrap(v->tile, dx, dy);
        if (tile != INVALID_TILE) DisasterClearSquare(tile);
      }
    }
  }
 
  return true;
}
 
static bool DisasterTick_Submarine(DisasterVehicle *v)
{
  v->tick_counter++;
 
  if (++v->age > 8880) {
    delete v;
    return false;
  }
 
  if (!HasBit(v->tick_counter, 0)) return true;
 
  TileIndex tile = v->tile + TileOffsByDiagDir(DirToDiagDir(v->direction));
  if (IsValidTile(tile)) {
    TrackBits trackbits = TrackStatusToTrackBits(GetTileTrackStatus(tile, TRANSPORT_WATER, 0));
    if (trackbits == TRACK_BIT_ALL && !Chance16(1, 90)) {
      GetNewVehiclePosResult gp = GetNewVehiclePos(v);
      v->UpdatePosition(gp.x, gp.y, v->z_pos);
      return true;
    }
  }
 
  v->direction = ChangeDir(v->direction, GB(Random(), 0, 1) ? DIRDIFF_90RIGHT : DIRDIFF_90LEFT);
 
  return true;
}
 
 
static bool DisasterTick_NULL(DisasterVehicle *)
{
  return true;
}
 
typedef bool DisasterVehicleTickProc(DisasterVehicle *v);
 
static DisasterVehicleTickProc * const _disastervehicle_tick_procs[] = {
  DisasterTick_Zeppeliner, DisasterTick_NULL,
  DisasterTick_Ufo,        DisasterTick_NULL,
  DisasterTick_Airplane,   DisasterTick_NULL,
  DisasterTick_Helicopter, DisasterTick_NULL, DisasterTick_Helicopter_Rotors,
  DisasterTick_Big_Ufo,    DisasterTick_NULL, DisasterTick_Big_Ufo_Destroyer,
  DisasterTick_NULL,
  DisasterTick_Submarine,
  DisasterTick_Submarine,
};
 
 
bool DisasterVehicle::Tick()
{
  return _disastervehicle_tick_procs[this->subtype](this);
}
 
typedef void DisasterInitProc();
 
 
static void Disaster_Zeppeliner_Init()
{
  if (!Vehicle::CanAllocateItem(2)) return;
 
  /* Pick a random place, unless we find a small airport */
  int x = TileX(Random()) * TILE_SIZE + TILE_SIZE / 2;
 
  for (const Station *st : Station::Iterate()) {
    if (st->airport.tile != INVALID_TILE && (st->airport.type == AT_SMALL || st->airport.type == AT_LARGE)) {
      x = (TileX(st->airport.tile) + 2) * TILE_SIZE;
      break;
    }
  }
 
  DisasterVehicle *v = new DisasterVehicle(x, 0, DIR_SE, ST_ZEPPELINER);
  /* Allocate shadow */
  DisasterVehicle *u = new DisasterVehicle(x, 0, DIR_SE, ST_ZEPPELINER_SHADOW);
  v->SetNext(u);
}
 
 
static void Disaster_Small_Ufo_Init()
{
  if (!Vehicle::CanAllocateItem(2)) return;
 
  int x = TileX(Random()) * TILE_SIZE + TILE_SIZE / 2;
  DisasterVehicle *v = new DisasterVehicle(x, 0, DIR_SE, ST_SMALL_UFO);
  v->dest_tile = TileXY(Map::SizeX() / 2, Map::SizeY() / 2);
 
  /* Allocate shadow */
  DisasterVehicle *u = new DisasterVehicle(x, 0, DIR_SE, ST_SMALL_UFO_SHADOW);
  v->SetNext(u);
}
 
 
/* Combat airplane which destroys an oil refinery */
static void Disaster_Airplane_Init()
{
  if (!Vehicle::CanAllocateItem(2)) return;
 
  Industry *found = nullptr;
 
  for (Industry *i : Industry::Iterate()) {
    if ((GetIndustrySpec(i->type)->behaviour & INDUSTRYBEH_AIRPLANE_ATTACKS) &&
        (found == nullptr || Chance16(1, 2))) {
      found = i;
    }
  }
 
  if (found == nullptr) return;
 
  /* Start from the bottom (south side) of the map */
  int x = (Map::SizeX() + 9) * TILE_SIZE - 1;
  int y = TileY(found->location.tile) * TILE_SIZE + 37;
 
  DisasterVehicle *v = new DisasterVehicle(x, y, DIR_NE, ST_AIRPLANE);
  DisasterVehicle *u = new DisasterVehicle(x, y, DIR_NE, ST_AIRPLANE_SHADOW);
  v->SetNext(u);
}
 
 
static void Disaster_Helicopter_Init()
{
  if (!Vehicle::CanAllocateItem(3)) return;
 
  Industry *found = nullptr;
 
  for (Industry *i : Industry::Iterate()) {
    if ((GetIndustrySpec(i->type)->behaviour & INDUSTRYBEH_CHOPPER_ATTACKS) &&
        (found == nullptr || Chance16(1, 2))) {
      found = i;
    }
  }
 
  if (found == nullptr) return;
 
  int x = -16 * (int)TILE_SIZE;
  int y = TileY(found->location.tile) * TILE_SIZE + 37;
 
  DisasterVehicle *v = new DisasterVehicle(x, y, DIR_SW, ST_HELICOPTER);
  DisasterVehicle *u = new DisasterVehicle(x, y, DIR_SW, ST_HELICOPTER_SHADOW);
  v->SetNext(u);
 
  DisasterVehicle *w = new DisasterVehicle(x, y, DIR_SW, ST_HELICOPTER_ROTORS);
  u->SetNext(w);
}
 
 
/* Big Ufo which lands on a piece of rail and will consequently be shot
 * down by a combat airplane, destroying the surroundings */
static void Disaster_Big_Ufo_Init()
{
  if (!Vehicle::CanAllocateItem(2)) return;
 
  int x = TileX(Random()) * TILE_SIZE + TILE_SIZE / 2;
  int y = Map::MaxX() * TILE_SIZE - 1;
 
  DisasterVehicle *v = new DisasterVehicle(x, y, DIR_NW, ST_BIG_UFO);
  v->dest_tile = TileXY(Map::SizeX() / 2, Map::SizeY() / 2);
 
  /* Allocate shadow */
  DisasterVehicle *u = new DisasterVehicle(x, y, DIR_NW, ST_BIG_UFO_SHADOW);
  v->SetNext(u);
}
 
 
static void Disaster_Submarine_Init(DisasterSubType subtype)
{
  if (!Vehicle::CanAllocateItem()) return;
 
  int y;
  Direction dir;
  uint32_t r = Random();
  int x = TileX(r) * TILE_SIZE + TILE_SIZE / 2;
 
  if (HasBit(r, 31)) {
    y = Map::MaxY() * TILE_SIZE - TILE_SIZE / 2 - 1;
    dir = DIR_NW;
  } else {
    y = TILE_SIZE / 2;
    if (_settings_game.construction.freeform_edges) y += TILE_SIZE;
    dir = DIR_SE;
  }
  if (!IsWaterTile(TileVirtXY(x, y))) return;
 
  new DisasterVehicle(x, y, dir, subtype);
}
 
/* Curious submarine #1, just floats around */
static void Disaster_Small_Submarine_Init()
{
  Disaster_Submarine_Init(ST_SMALL_SUBMARINE);
}
 
 
/* Curious submarine #2, just floats around */
static void Disaster_Big_Submarine_Init()
{
  Disaster_Submarine_Init(ST_BIG_SUBMARINE);
}
 
 
static void Disaster_CoalMine_Init()
{
  int index = GB(Random(), 0, 4);
  uint m;
 
  for (m = 0; m < 15; m++) {
    for (const Industry *i : Industry::Iterate()) {
      if ((GetIndustrySpec(i->type)->behaviour & INDUSTRYBEH_CAN_SUBSIDENCE) && --index < 0) {
        SetDParam(0, i->town->index);
        AddTileNewsItem(STR_NEWS_DISASTER_COAL_MINE_SUBSIDENCE, NT_ACCIDENT, i->location.tile + TileDiffXY(1, 1)); // keep the news, even when the mine closes
 
        {
          TileIndex tile = i->location.tile;
          TileIndexDiff step = TileOffsByDiagDir((DiagDirection)GB(Random(), 0, 2));
 
          for (uint n = 0; n < 30; n++) {
            DisasterClearSquare(tile);
            tile += step;
            if (!IsValidTile(tile)) break;
          }
        }
        return;
      }
    }
  }
}
 
struct Disaster {
  DisasterInitProc *init_proc;      
  TimerGameCalendar::Year min_year; 
  TimerGameCalendar::Year max_year; 
};
 
static const Disaster _disasters[] = {
  {Disaster_Zeppeliner_Init,      1930, 1955}, // zeppeliner
  {Disaster_Small_Ufo_Init,       1940, 1970}, // ufo (small)
  {Disaster_Airplane_Init,        1960, 1990}, // airplane
  {Disaster_Helicopter_Init,      1970, 2000}, // helicopter
  {Disaster_Big_Ufo_Init,         2000, 2100}, // ufo (big)
  {Disaster_Small_Submarine_Init, 1940, 1965}, // submarine (small)
  {Disaster_Big_Submarine_Init,   1975, 2010}, // submarine (big)
  {Disaster_CoalMine_Init,        1950, 1985}, // coalmine
};
 
static void DoDisaster()
{
  byte buf[lengthof(_disasters)];
 
  byte j = 0;
  for (size_t i = 0; i != lengthof(_disasters); i++) {
    if (TimerGameCalendar::year >= _disasters[i].min_year && TimerGameCalendar::year < _disasters[i].max_year) buf[j++] = (byte)i;
  }
 
  if (j == 0) return;
 
  _disasters[buf[RandomRange(j)]].init_proc();
}
 
 
static void ResetDisasterDelay()
{
  _disaster_delay = GB(Random(), 0, 9) + 730;
}
 
static IntervalTimer<TimerGameEconomy> _economy_disaster_daily({TimerGameEconomy::DAY, TimerGameEconomy::Priority::DISASTER}, [](auto)
{
  if (--_disaster_delay != 0) return;
 
  ResetDisasterDelay();
 
  if (_settings_game.difficulty.disasters != 0) DoDisaster();
});
 
void StartupDisasters()
{
  ResetDisasterDelay();
}
 
void ReleaseDisastersTargetingIndustry(IndustryID i)
{
  for (DisasterVehicle *v : DisasterVehicle::Iterate()) {
    /* primary disaster vehicles that have chosen target */
    if (v->subtype == ST_AIRPLANE || v->subtype == ST_HELICOPTER) {
      /* if it has chosen target, and it is this industry (yes, dest_tile is IndustryID here), set order to "leaving map peacefully" */
      if (v->state > 0 && v->dest_tile == (uint32_t)i) v->state = 3;
    }
  }
}
 
void ReleaseDisastersTargetingVehicle(VehicleID vehicle)
{
  for (DisasterVehicle *v : DisasterVehicle::Iterate()) {
    /* primary disaster vehicles that have chosen target */
    if (v->subtype == ST_SMALL_UFO) {
      if (v->state != 0 && v->dest_tile == vehicle) {
        /* Revert to target-searching */
        v->state = 0;
        v->dest_tile = RandomTile();
        GetAircraftFlightLevelBounds(v, &v->z_pos, nullptr);
        v->age = 0;
      }
    }
  }
}
 
void DisasterVehicle::UpdateDeltaXY()
{
  this->x_offs        = -1;
  this->y_offs        = -1;
  this->x_extent      =  2;
  this->y_extent      =  2;
  this->z_extent      =  5;
}