station_cmd.cpp

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/* $Id$ */

/*
 * 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 "bridge_map.h"
#include "cmd_helper.h"
#include "viewport_func.h"
#include "command_func.h"
#include "town.h"
#include "news_func.h"
#include "train.h"
#include "ship.h"
#include "roadveh.h"
#include "industry.h"
#include "newgrf_cargo.h"
#include "newgrf_debug.h"
#include "newgrf_station.h"
#include "newgrf_canal.h" /* For the buoy */
#include "pathfinder/yapf/yapf_cache.h"
#include "road_internal.h" /* For drawing catenary/checking road removal */
#include "autoslope.h"
#include "water.h"
#include "strings_func.h"
#include "clear_func.h"
#include "date_func.h"
#include "vehicle_func.h"
#include "string_func.h"
#include "animated_tile_func.h"
#include "elrail_func.h"
#include "station_base.h"
#include "roadstop_base.h"
#include "newgrf_railtype.h"
#include "waypoint_base.h"
#include "waypoint_func.h"
#include "pbs.h"
#include "debug.h"
#include "core/random_func.hpp"
#include "company_base.h"
#include "table/airporttile_ids.h"
#include "newgrf_airporttiles.h"
#include "order_backup.h"
#include "newgrf_house.h"
#include "company_gui.h"
#include "linkgraph/linkgraph_base.h"
#include "linkgraph/refresh.h"
#include "widgets/station_widget.h"

#include "table/strings.h"

#include "safeguards.h"

/* static */ const FlowStat::SharesMap FlowStat::empty_sharesmap;

bool IsHangar(TileIndex t)
{
  assert(IsTileType(t, MP_STATION));

  /* If the tile isn't an airport there's no chance it's a hangar. */
  if (!IsAirport(t)) return false;

  const Station *st = Station::GetByTile(t);
  const AirportSpec *as = st->airport.GetSpec();

  for (uint i = 0; i < as->nof_depots; i++) {
    if (st->airport.GetHangarTile(i) == t) return true;
  }

  return false;
}

template <class T>
CommandCost GetStationAround(TileArea ta, StationID closest_station, CompanyID company, T **st)
{
  ta.tile -= TileDiffXY(1, 1);
  ta.w    += 2;
  ta.h    += 2;

  /* check around to see if there are any stations there owned by the company */
  TILE_AREA_LOOP(tile_cur, ta) {
    if (IsTileType(tile_cur, MP_STATION)) {
      StationID t = GetStationIndex(tile_cur);
      if (!T::IsValidID(t) || Station::Get(t)->owner != company) continue;
      if (closest_station == INVALID_STATION) {
        closest_station = t;
      } else if (closest_station != t) {
        return_cmd_error(STR_ERROR_ADJOINS_MORE_THAN_ONE_EXISTING);
      }
    }
  }
  *st = (closest_station == INVALID_STATION) ? NULL : T::Get(closest_station);
  return CommandCost();
}

typedef bool (*CMSAMatcher)(TileIndex tile);

static int CountMapSquareAround(TileIndex tile, CMSAMatcher cmp)
{
  int num = 0;

  for (int dx = -3; dx <= 3; dx++) {
    for (int dy = -3; dy <= 3; dy++) {
      TileIndex t = TileAddWrap(tile, dx, dy);
      if (t != INVALID_TILE && cmp(t)) num++;
    }
  }

  return num;
}

static bool CMSAMine(TileIndex tile)
{
  /* No industry */
  if (!IsTileType(tile, MP_INDUSTRY)) return false;

  const Industry *ind = Industry::GetByTile(tile);

  /* No extractive industry */
  if ((GetIndustrySpec(ind->type)->life_type & INDUSTRYLIFE_EXTRACTIVE) == 0) return false;

  for (uint i = 0; i < lengthof(ind->produced_cargo); i++) {
    /* The industry extracts something non-liquid, i.e. no oil or plastic, so it is a mine.
     * Also the production of passengers and mail is ignored. */
    if (ind->produced_cargo[i] != CT_INVALID &&
        (CargoSpec::Get(ind->produced_cargo[i])->classes & (CC_LIQUID | CC_PASSENGERS | CC_MAIL)) == 0) {
      return true;
    }
  }

  return false;
}

static bool CMSAWater(TileIndex tile)
{
  return IsTileType(tile, MP_WATER) && IsWater(tile);
}

static bool CMSATree(TileIndex tile)
{
  return IsTileType(tile, MP_TREES);
}

#define M(x) ((x) - STR_SV_STNAME)

enum StationNaming {
  STATIONNAMING_RAIL,
  STATIONNAMING_ROAD,
  STATIONNAMING_AIRPORT,
  STATIONNAMING_OILRIG,
  STATIONNAMING_DOCK,
  STATIONNAMING_HELIPORT,
};

struct StationNameInformation {
  uint32 free_names; 
  bool *indtypes;    
};

static bool FindNearIndustryName(TileIndex tile, void *user_data)
{
  /* All already found industry types */
  StationNameInformation *sni = (StationNameInformation*)user_data;
  if (!IsTileType(tile, MP_INDUSTRY)) return false;

  /* If the station name is undefined it means that it doesn't name a station */
  IndustryType indtype = GetIndustryType(tile);
  if (GetIndustrySpec(indtype)->station_name == STR_UNDEFINED) return false;

  /* In all cases if an industry that provides a name is found two of
   * the standard names will be disabled. */
  sni->free_names &= ~(1 << M(STR_SV_STNAME_OILFIELD) | 1 << M(STR_SV_STNAME_MINES));
  return !sni->indtypes[indtype];
}

static StringID GenerateStationName(Station *st, TileIndex tile, StationNaming name_class)
{
  static const uint32 _gen_station_name_bits[] = {
    0,                                       // STATIONNAMING_RAIL
    0,                                       // STATIONNAMING_ROAD
    1U << M(STR_SV_STNAME_AIRPORT),          // STATIONNAMING_AIRPORT
    1U << M(STR_SV_STNAME_OILFIELD),         // STATIONNAMING_OILRIG
    1U << M(STR_SV_STNAME_DOCKS),            // STATIONNAMING_DOCK
    1U << M(STR_SV_STNAME_HELIPORT),         // STATIONNAMING_HELIPORT
  };

  const Town *t = st->town;
  uint32 free_names = UINT32_MAX;

  bool indtypes[NUM_INDUSTRYTYPES];
  memset(indtypes, 0, sizeof(indtypes));

  const Station *s;
  FOR_ALL_STATIONS(s) {
    if (s != st && s->town == t) {
      if (s->indtype != IT_INVALID) {
        indtypes[s->indtype] = true;
        StringID name = GetIndustrySpec(s->indtype)->station_name;
        if (name != STR_UNDEFINED) {
          /* Filter for other industrytypes with the same name */
          for (IndustryType it = 0; it < NUM_INDUSTRYTYPES; it++) {
            const IndustrySpec *indsp = GetIndustrySpec(it);
            if (indsp->enabled && indsp->station_name == name) indtypes[it] = true;
          }
        }
        continue;
      }
      uint str = M(s->string_id);
      if (str <= 0x20) {
        if (str == M(STR_SV_STNAME_FOREST)) {
          str = M(STR_SV_STNAME_WOODS);
        }
        ClrBit(free_names, str);
      }
    }
  }

  TileIndex indtile = tile;
  StationNameInformation sni = { free_names, indtypes };
  if (CircularTileSearch(&indtile, 7, FindNearIndustryName, &sni)) {
    /* An industry has been found nearby */
    IndustryType indtype = GetIndustryType(indtile);
    const IndustrySpec *indsp = GetIndustrySpec(indtype);
    /* STR_NULL means it only disables oil rig/mines */
    if (indsp->station_name != STR_NULL) {
      st->indtype = indtype;
      return STR_SV_STNAME_FALLBACK;
    }
  }

  /* Oil rigs/mines name could be marked not free by looking for a near by industry. */
  free_names = sni.free_names;

  /* check default names */
  uint32 tmp = free_names & _gen_station_name_bits[name_class];
  if (tmp != 0) return STR_SV_STNAME + FindFirstBit(tmp);

  /* check mine? */
  if (HasBit(free_names, M(STR_SV_STNAME_MINES))) {
    if (CountMapSquareAround(tile, CMSAMine) >= 2) {
      return STR_SV_STNAME_MINES;
    }
  }

  /* check close enough to town to get central as name? */
  if (DistanceMax(tile, t->xy) < 8) {
    if (HasBit(free_names, M(STR_SV_STNAME))) return STR_SV_STNAME;

    if (HasBit(free_names, M(STR_SV_STNAME_CENTRAL))) return STR_SV_STNAME_CENTRAL;
  }

  /* Check lakeside */
  if (HasBit(free_names, M(STR_SV_STNAME_LAKESIDE)) &&
      DistanceFromEdge(tile) < 20 &&
      CountMapSquareAround(tile, CMSAWater) >= 5) {
    return STR_SV_STNAME_LAKESIDE;
  }

  /* Check woods */
  if (HasBit(free_names, M(STR_SV_STNAME_WOODS)) && (
        CountMapSquareAround(tile, CMSATree) >= 8 ||
        CountMapSquareAround(tile, IsTileForestIndustry) >= 2)
      ) {
    return _settings_game.game_creation.landscape == LT_TROPIC ? STR_SV_STNAME_FOREST : STR_SV_STNAME_WOODS;
  }

  /* check elevation compared to town */
  int z = GetTileZ(tile);
  int z2 = GetTileZ(t->xy);
  if (z < z2) {
    if (HasBit(free_names, M(STR_SV_STNAME_VALLEY))) return STR_SV_STNAME_VALLEY;
  } else if (z > z2) {
    if (HasBit(free_names, M(STR_SV_STNAME_HEIGHTS))) return STR_SV_STNAME_HEIGHTS;
  }

  /* check direction compared to town */
  static const int8 _direction_and_table[] = {
    ~( (1 << M(STR_SV_STNAME_WEST))  | (1 << M(STR_SV_STNAME_EAST)) | (1 << M(STR_SV_STNAME_NORTH)) ),
    ~( (1 << M(STR_SV_STNAME_SOUTH)) | (1 << M(STR_SV_STNAME_WEST)) | (1 << M(STR_SV_STNAME_NORTH)) ),
    ~( (1 << M(STR_SV_STNAME_SOUTH)) | (1 << M(STR_SV_STNAME_EAST)) | (1 << M(STR_SV_STNAME_NORTH)) ),
    ~( (1 << M(STR_SV_STNAME_SOUTH)) | (1 << M(STR_SV_STNAME_WEST)) | (1 << M(STR_SV_STNAME_EAST)) ),
  };

  free_names &= _direction_and_table[
    (TileX(tile) < TileX(t->xy)) +
    (TileY(tile) < TileY(t->xy)) * 2];

  tmp = free_names & ((1 << 1) | (1 << 2) | (1 << 3) | (1 << 4) | (1 << 6) | (1 << 7) | (1 << 12) | (1 << 26) | (1 << 27) | (1 << 28) | (1 << 29) | (1 << 30));
  return (tmp == 0) ? STR_SV_STNAME_FALLBACK : (STR_SV_STNAME + FindFirstBit(tmp));
}
#undef M

static Station *GetClosestDeletedStation(TileIndex tile)
{
  uint threshold = 8;
  Station *best_station = NULL;
  Station *st;

  FOR_ALL_STATIONS(st) {
    if (!st->IsInUse() && st->owner == _current_company) {
      uint cur_dist = DistanceManhattan(tile, st->xy);

      if (cur_dist < threshold) {
        threshold = cur_dist;
        best_station = st;
      }
    }
  }

  return best_station;
}


void Station::GetTileArea(TileArea *ta, StationType type) const
{
  switch (type) {
    case STATION_RAIL:
      *ta = this->train_station;
      return;

    case STATION_AIRPORT:
      *ta = this->airport;
      return;

    case STATION_TRUCK:
      *ta = this->truck_station;
      return;

    case STATION_BUS:
      *ta = this->bus_station;
      return;

    case STATION_DOCK:
    case STATION_OILRIG:
      ta->tile = this->dock_tile;
      break;

    default: NOT_REACHED();
  }

  ta->w = 1;
  ta->h = 1;
}

void Station::UpdateVirtCoord()
{
  Point pt = RemapCoords2(TileX(this->xy) * TILE_SIZE, TileY(this->xy) * TILE_SIZE);

  pt.y -= 32 * ZOOM_LVL_BASE;
  if ((this->facilities & FACIL_AIRPORT) && this->airport.type == AT_OILRIG) pt.y -= 16 * ZOOM_LVL_BASE;

  SetDParam(0, this->index);
  SetDParam(1, this->facilities);
  this->sign.UpdatePosition(pt.x, pt.y, STR_VIEWPORT_STATION);

  SetWindowDirty(WC_STATION_VIEW, this->index);
}

void UpdateAllStationVirtCoords()
{
  BaseStation *st;

  FOR_ALL_BASE_STATIONS(st) {
    st->UpdateVirtCoord();
  }
}

static CargoTypes GetAcceptanceMask(const Station *st)
{
  CargoTypes mask = 0;

  for (CargoID i = 0; i < NUM_CARGO; i++) {
    if (HasBit(st->goods[i].status, GoodsEntry::GES_ACCEPTANCE)) SetBit(mask, i);
  }
  return mask;
}

static void ShowRejectOrAcceptNews(const Station *st, uint num_items, CargoID *cargo, StringID msg)
{
  for (uint i = 0; i < num_items; i++) {
    SetDParam(i + 1, CargoSpec::Get(cargo[i])->name);
  }

  SetDParam(0, st->index);
  AddNewsItem(msg, NT_ACCEPTANCE, NF_INCOLOUR | NF_SMALL, NR_STATION, st->index);
}

CargoArray GetProductionAroundTiles(TileIndex tile, int w, int h, int rad)
{
  CargoArray produced;

  int x = TileX(tile);
  int y = TileY(tile);

  /* expand the region by rad tiles on each side
   * while making sure that we remain inside the board. */
  int x2 = min(x + w + rad, MapSizeX());
  int x1 = max(x - rad, 0);

  int y2 = min(y + h + rad, MapSizeY());
  int y1 = max(y - rad, 0);

  assert(x1 < x2);
  assert(y1 < y2);
  assert(w > 0);
  assert(h > 0);

  TileArea ta(TileXY(x1, y1), TileXY(x2 - 1, y2 - 1));

  /* Loop over all tiles to get the produced cargo of
   * everything except industries */
  TILE_AREA_LOOP(tile, ta) AddProducedCargo(tile, produced);

  /* Loop over the industries. They produce cargo for
   * anything that is within 'rad' from their bounding
   * box. As such if you have e.g. a oil well the tile
   * area loop might not hit an industry tile while
   * the industry would produce cargo for the station.
   */
  const Industry *i;
  FOR_ALL_INDUSTRIES(i) {
    if (!ta.Intersects(i->location)) continue;

    for (uint j = 0; j < lengthof(i->produced_cargo); j++) {
      CargoID cargo = i->produced_cargo[j];
      if (cargo != CT_INVALID) produced[cargo]++;
    }
  }

  return produced;
}

CargoArray GetAcceptanceAroundTiles(TileIndex tile, int w, int h, int rad, CargoTypes *always_accepted)
{
  CargoArray acceptance;
  if (always_accepted != NULL) *always_accepted = 0;

  int x = TileX(tile);
  int y = TileY(tile);

  /* expand the region by rad tiles on each side
   * while making sure that we remain inside the board. */
  int x2 = min(x + w + rad, MapSizeX());
  int y2 = min(y + h + rad, MapSizeY());
  int x1 = max(x - rad, 0);
  int y1 = max(y - rad, 0);

  assert(x1 < x2);
  assert(y1 < y2);
  assert(w > 0);
  assert(h > 0);

  for (int yc = y1; yc != y2; yc++) {
    for (int xc = x1; xc != x2; xc++) {
      TileIndex tile = TileXY(xc, yc);
      AddAcceptedCargo(tile, acceptance, always_accepted);
    }
  }

  return acceptance;
}

void UpdateStationAcceptance(Station *st, bool show_msg)
{
  /* old accepted goods types */
  CargoTypes old_acc = GetAcceptanceMask(st);

  /* And retrieve the acceptance. */
  CargoArray acceptance;
  if (!st->rect.IsEmpty()) {
    acceptance = GetAcceptanceAroundTiles(
      TileXY(st->rect.left, st->rect.top),
      st->rect.right  - st->rect.left + 1,
      st->rect.bottom - st->rect.top  + 1,
      st->GetCatchmentRadius(),
      &st->always_accepted
    );
  }

  /* Adjust in case our station only accepts fewer kinds of goods */
  for (CargoID i = 0; i < NUM_CARGO; i++) {
    uint amt = acceptance[i];

    /* Make sure the station can accept the goods type. */
    bool is_passengers = IsCargoInClass(i, CC_PASSENGERS);
    if ((!is_passengers && !(st->facilities & ~FACIL_BUS_STOP)) ||
        (is_passengers && !(st->facilities & ~FACIL_TRUCK_STOP))) {
      amt = 0;
    }

    GoodsEntry &ge = st->goods[i];
    SB(ge.status, GoodsEntry::GES_ACCEPTANCE, 1, amt >= 8);
    if (LinkGraph::IsValidID(ge.link_graph)) {
      (*LinkGraph::Get(ge.link_graph))[ge.node].SetDemand(amt / 8);
    }
  }

  /* Only show a message in case the acceptance was actually changed. */
  CargoTypes new_acc = GetAcceptanceMask(st);
  if (old_acc == new_acc) return;

  /* show a message to report that the acceptance was changed? */
  if (show_msg && st->owner == _local_company && st->IsInUse()) {
    /* List of accept and reject strings for different number of
     * cargo types */
    static const StringID accept_msg[] = {
      STR_NEWS_STATION_NOW_ACCEPTS_CARGO,
      STR_NEWS_STATION_NOW_ACCEPTS_CARGO_AND_CARGO,
    };
    static const StringID reject_msg[] = {
      STR_NEWS_STATION_NO_LONGER_ACCEPTS_CARGO,
      STR_NEWS_STATION_NO_LONGER_ACCEPTS_CARGO_OR_CARGO,
    };

    /* Array of accepted and rejected cargo types */
    CargoID accepts[2] = { CT_INVALID, CT_INVALID };
    CargoID rejects[2] = { CT_INVALID, CT_INVALID };
    uint num_acc = 0;
    uint num_rej = 0;

    /* Test each cargo type to see if its acceptance has changed */
    for (CargoID i = 0; i < NUM_CARGO; i++) {
      if (HasBit(new_acc, i)) {
        if (!HasBit(old_acc, i) && num_acc < lengthof(accepts)) {
          /* New cargo is accepted */
          accepts[num_acc++] = i;
        }
      } else {
        if (HasBit(old_acc, i) && num_rej < lengthof(rejects)) {
          /* Old cargo is no longer accepted */
          rejects[num_rej++] = i;
        }
      }
    }

    /* Show news message if there are any changes */
    if (num_acc > 0) ShowRejectOrAcceptNews(st, num_acc, accepts, accept_msg[num_acc - 1]);
    if (num_rej > 0) ShowRejectOrAcceptNews(st, num_rej, rejects, reject_msg[num_rej - 1]);
  }

  /* redraw the station view since acceptance changed */
  SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_ACCEPT_RATING_LIST);
}

static void UpdateStationSignCoord(BaseStation *st)
{
  const StationRect *r = &st->rect;

  if (r->IsEmpty()) return; // no tiles belong to this station

  /* clamp sign coord to be inside the station rect */
  st->xy = TileXY(ClampU(TileX(st->xy), r->left, r->right), ClampU(TileY(st->xy), r->top, r->bottom));
  st->UpdateVirtCoord();

  if (!Station::IsExpected(st)) return;
  Station *full_station = Station::From(st);
  for (CargoID c = 0; c < NUM_CARGO; ++c) {
    LinkGraphID lg = full_station->goods[c].link_graph;
    if (!LinkGraph::IsValidID(lg)) continue;
    (*LinkGraph::Get(lg))[full_station->goods[c].node].UpdateLocation(st->xy);
  }
}

static CommandCost BuildStationPart(Station **st, DoCommandFlag flags, bool reuse, TileArea area, StationNaming name_class)
{
  /* Find a deleted station close to us */
  if (*st == NULL && reuse) *st = GetClosestDeletedStation(area.tile);

  if (*st != NULL) {
    if ((*st)->owner != _current_company) {
      return_cmd_error(CMD_ERROR);
    }

    CommandCost ret = (*st)->rect.BeforeAddRect(area.tile, area.w, area.h, StationRect::ADD_TEST);
    if (ret.Failed()) return ret;
  } else {
    /* allocate and initialize new station */
    if (!Station::CanAllocateItem()) return_cmd_error(STR_ERROR_TOO_MANY_STATIONS_LOADING);

    if (flags & DC_EXEC) {
      *st = new Station(area.tile);

      (*st)->town = ClosestTownFromTile(area.tile, UINT_MAX);
      (*st)->string_id = GenerateStationName(*st, area.tile, name_class);

      if (Company::IsValidID(_current_company)) {
        SetBit((*st)->town->have_ratings, _current_company);
      }
    }
  }
  return CommandCost();
}

static void DeleteStationIfEmpty(BaseStation *st)
{
  if (!st->IsInUse()) {
    st->delete_ctr = 0;
    InvalidateWindowData(WC_STATION_LIST, st->owner, 0);
  }
  /* station remains but it probably lost some parts - station sign should stay in the station boundaries */
  UpdateStationSignCoord(st);
}

void Station::AfterStationTileSetChange(bool adding, StationType type)
{
  this->UpdateVirtCoord();
  this->RecomputeIndustriesNear();
  DirtyCompanyInfrastructureWindows(this->owner);
  if (adding) InvalidateWindowData(WC_STATION_LIST, this->owner, 0);

  switch (type) {
    case STATION_RAIL:
      SetWindowWidgetDirty(WC_STATION_VIEW, this->index, WID_SV_TRAINS);
      break;
    case STATION_AIRPORT:
      break;
    case STATION_TRUCK:
    case STATION_BUS:
      SetWindowWidgetDirty(WC_STATION_VIEW, this->index, WID_SV_ROADVEHS);
      break;
    case STATION_DOCK:
      SetWindowWidgetDirty(WC_STATION_VIEW, this->index, WID_SV_SHIPS);
      break;
    default: NOT_REACHED();
  }

  if (adding) {
    UpdateStationAcceptance(this, false);
    InvalidateWindowData(WC_SELECT_STATION, 0, 0);
  } else {
    DeleteStationIfEmpty(this);
  }

}

CommandCost ClearTile_Station(TileIndex tile, DoCommandFlag flags);

CommandCost CheckBuildableTile(TileIndex tile, uint invalid_dirs, int &allowed_z, bool allow_steep, bool check_bridge = true)
{
  if (check_bridge && IsBridgeAbove(tile)) {
    return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
  }

  CommandCost ret = EnsureNoVehicleOnGround(tile);
  if (ret.Failed()) return ret;

  int z;
  Slope tileh = GetTileSlope(tile, &z);

  /* Prohibit building if
   *   1) The tile is "steep" (i.e. stretches two height levels).
   *   2) The tile is non-flat and the build_on_slopes switch is disabled.
   */
  if ((!allow_steep && IsSteepSlope(tileh)) ||
      ((!_settings_game.construction.build_on_slopes) && tileh != SLOPE_FLAT)) {
    return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
  }

  CommandCost cost(EXPENSES_CONSTRUCTION);
  int flat_z = z + GetSlopeMaxZ(tileh);
  if (tileh != SLOPE_FLAT) {
    /* Forbid building if the tile faces a slope in a invalid direction. */
    for (DiagDirection dir = DIAGDIR_BEGIN; dir != DIAGDIR_END; dir++) {
      if (HasBit(invalid_dirs, dir) && !CanBuildDepotByTileh(dir, tileh)) {
        return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
      }
    }
    cost.AddCost(_price[PR_BUILD_FOUNDATION]);
  }

  /* The level of this tile must be equal to allowed_z. */
  if (allowed_z < 0) {
    /* First tile. */
    allowed_z = flat_z;
  } else if (allowed_z != flat_z) {
    return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
  }

  return cost;
}

static CommandCost CheckFlatLandAirport(AirportTileTableIterator tile_iter, DoCommandFlag flags)
{
  CommandCost cost(EXPENSES_CONSTRUCTION);
  int allowed_z = -1;

  for (; tile_iter != INVALID_TILE; ++tile_iter) {
    CommandCost ret = CheckBuildableTile(tile_iter, 0, allowed_z, true);
    if (ret.Failed()) return ret;
    cost.AddCost(ret);

    ret = DoCommand(tile_iter, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
    if (ret.Failed()) return ret;
    cost.AddCost(ret);
  }

  return cost;
}

static CommandCost CheckFlatLandRailStation(TileArea tile_area, DoCommandFlag flags, Axis axis, StationID *station, RailType rt, SmallVector<Train *, 4> &affected_vehicles, StationClassID spec_class, byte spec_index, byte plat_len, byte numtracks)
{
  CommandCost cost(EXPENSES_CONSTRUCTION);
  int allowed_z = -1;
  uint invalid_dirs = 5 << axis;

  const StationSpec *statspec = StationClass::Get(spec_class)->GetSpec(spec_index);
  bool slope_cb = statspec != NULL && HasBit(statspec->callback_mask, CBM_STATION_SLOPE_CHECK);

  TILE_AREA_LOOP(tile_cur, tile_area) {
    CommandCost ret = CheckBuildableTile(tile_cur, invalid_dirs, allowed_z, false);
    if (ret.Failed()) return ret;
    cost.AddCost(ret);

    if (slope_cb) {
      /* Do slope check if requested. */
      ret = PerformStationTileSlopeCheck(tile_area.tile, tile_cur, statspec, axis, plat_len, numtracks);
      if (ret.Failed()) return ret;
    }

    /* if station is set, then we have special handling to allow building on top of already existing stations.
     * so station points to INVALID_STATION if we can build on any station.
     * Or it points to a station if we're only allowed to build on exactly that station. */
    if (station != NULL && IsTileType(tile_cur, MP_STATION)) {
      if (!IsRailStation(tile_cur)) {
        return ClearTile_Station(tile_cur, DC_AUTO); // get error message
      } else {
        StationID st = GetStationIndex(tile_cur);
        if (*station == INVALID_STATION) {
          *station = st;
        } else if (*station != st) {
          return_cmd_error(STR_ERROR_ADJOINS_MORE_THAN_ONE_EXISTING);
        }
      }
    } else {
      /* Rail type is only valid when building a railway station; if station to
       * build isn't a rail station it's INVALID_RAILTYPE. */
      if (rt != INVALID_RAILTYPE &&
          IsPlainRailTile(tile_cur) && !HasSignals(tile_cur) &&
          HasPowerOnRail(GetRailType(tile_cur), rt)) {
        /* Allow overbuilding if the tile:
         *  - has rail, but no signals
         *  - it has exactly one track
         *  - the track is in line with the station
         *  - the current rail type has power on the to-be-built type (e.g. convert normal rail to el rail)
         */
        TrackBits tracks = GetTrackBits(tile_cur);
        Track track = RemoveFirstTrack(&tracks);
        Track expected_track = HasBit(invalid_dirs, DIAGDIR_NE) ? TRACK_X : TRACK_Y;

        if (tracks == TRACK_BIT_NONE && track == expected_track) {
          /* Check for trains having a reservation for this tile. */
          if (HasBit(GetRailReservationTrackBits(tile_cur), track)) {
            Train *v = GetTrainForReservation(tile_cur, track);
            if (v != NULL) {
              *affected_vehicles.Append() = v;
            }
          }
          CommandCost ret = DoCommand(tile_cur, 0, track, flags, CMD_REMOVE_SINGLE_RAIL);
          if (ret.Failed()) return ret;
          cost.AddCost(ret);
          /* With flags & ~DC_EXEC CmdLandscapeClear would fail since the rail still exists */
          continue;
        }
      }
      ret = DoCommand(tile_cur, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
      if (ret.Failed()) return ret;
      cost.AddCost(ret);
    }
  }

  return cost;
}

static CommandCost CheckFlatLandRoadStop(TileArea tile_area, DoCommandFlag flags, uint invalid_dirs, bool is_drive_through, bool is_truck_stop, Axis axis, StationID *station, RoadTypes rts)
{
  CommandCost cost(EXPENSES_CONSTRUCTION);
  int allowed_z = -1;

  TILE_AREA_LOOP(cur_tile, tile_area) {
    CommandCost ret = CheckBuildableTile(cur_tile, invalid_dirs, allowed_z, !is_drive_through);
    if (ret.Failed()) return ret;
    cost.AddCost(ret);

    /* If station is set, then we have special handling to allow building on top of already existing stations.
     * Station points to INVALID_STATION if we can build on any station.
     * Or it points to a station if we're only allowed to build on exactly that station. */
    if (station != NULL && IsTileType(cur_tile, MP_STATION)) {
      if (!IsRoadStop(cur_tile)) {
        return ClearTile_Station(cur_tile, DC_AUTO); // Get error message.
      } else {
        if (is_truck_stop != IsTruckStop(cur_tile) ||
            is_drive_through != IsDriveThroughStopTile(cur_tile)) {
          return ClearTile_Station(cur_tile, DC_AUTO); // Get error message.
        }
        /* Drive-through station in the wrong direction. */
        if (is_drive_through && IsDriveThroughStopTile(cur_tile) && DiagDirToAxis(GetRoadStopDir(cur_tile)) != axis){
          return_cmd_error(STR_ERROR_DRIVE_THROUGH_DIRECTION);
        }
        StationID st = GetStationIndex(cur_tile);
        if (*station == INVALID_STATION) {
          *station = st;
        } else if (*station != st) {
          return_cmd_error(STR_ERROR_ADJOINS_MORE_THAN_ONE_EXISTING);
        }
      }
    } else {
      bool build_over_road = is_drive_through && IsNormalRoadTile(cur_tile);
      /* Road bits in the wrong direction. */
      RoadBits rb = IsNormalRoadTile(cur_tile) ? GetAllRoadBits(cur_tile) : ROAD_NONE;
      if (build_over_road && (rb & (axis == AXIS_X ? ROAD_Y : ROAD_X)) != 0) {
        /* Someone was pedantic and *NEEDED* three fracking different error messages. */
        switch (CountBits(rb)) {
          case 1:
            return_cmd_error(STR_ERROR_DRIVE_THROUGH_DIRECTION);

          case 2:
            if (rb == ROAD_X || rb == ROAD_Y) return_cmd_error(STR_ERROR_DRIVE_THROUGH_DIRECTION);
            return_cmd_error(STR_ERROR_DRIVE_THROUGH_CORNER);

          default: // 3 or 4
            return_cmd_error(STR_ERROR_DRIVE_THROUGH_JUNCTION);
        }
      }

      RoadTypes cur_rts = IsNormalRoadTile(cur_tile) ? GetRoadTypes(cur_tile) : ROADTYPES_NONE;
      uint num_roadbits = 0;
      if (build_over_road) {
        /* There is a road, check if we can build road+tram stop over it. */
        if (HasBit(cur_rts, ROADTYPE_ROAD)) {
          Owner road_owner = GetRoadOwner(cur_tile, ROADTYPE_ROAD);
          if (road_owner == OWNER_TOWN) {
            if (!_settings_game.construction.road_stop_on_town_road) return_cmd_error(STR_ERROR_DRIVE_THROUGH_ON_TOWN_ROAD);
          } else if (!_settings_game.construction.road_stop_on_competitor_road && road_owner != OWNER_NONE) {
            CommandCost ret = CheckOwnership(road_owner);
            if (ret.Failed()) return ret;
          }
          num_roadbits += CountBits(GetRoadBits(cur_tile, ROADTYPE_ROAD));
        }

        if (GetDisallowedRoadDirections(cur_tile) != DRD_NONE) return_cmd_error(STR_ERROR_DRIVE_THROUGH_ON_ONEWAY_ROAD);

        /* There is a tram, check if we can build road+tram stop over it. */
        if (HasBit(cur_rts, ROADTYPE_TRAM)) {
          Owner tram_owner = GetRoadOwner(cur_tile, ROADTYPE_TRAM);
          if (Company::IsValidID(tram_owner) &&
              (!_settings_game.construction.road_stop_on_competitor_road ||
              /* Disallow breaking end-of-line of someone else
               * so trams can still reverse on this tile. */
              HasExactlyOneBit(GetRoadBits(cur_tile, ROADTYPE_TRAM)))) {
            CommandCost ret = CheckOwnership(tram_owner);
            if (ret.Failed()) return ret;
          }
          num_roadbits += CountBits(GetRoadBits(cur_tile, ROADTYPE_TRAM));
        }

        /* Take into account existing roadbits. */
        rts |= cur_rts;
      } else {
        ret = DoCommand(cur_tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
        if (ret.Failed()) return ret;
        cost.AddCost(ret);
      }

      uint roadbits_to_build = CountBits(rts) * 2 - num_roadbits;
      cost.AddCost(_price[PR_BUILD_ROAD] * roadbits_to_build);
    }
  }

  return cost;
}

CommandCost CanExpandRailStation(const BaseStation *st, TileArea &new_ta, Axis axis)
{
  TileArea cur_ta = st->train_station;

  /* determine new size of train station region.. */
  int x = min(TileX(cur_ta.tile), TileX(new_ta.tile));
  int y = min(TileY(cur_ta.tile), TileY(new_ta.tile));
  new_ta.w = max(TileX(cur_ta.tile) + cur_ta.w, TileX(new_ta.tile) + new_ta.w) - x;
  new_ta.h = max(TileY(cur_ta.tile) + cur_ta.h, TileY(new_ta.tile) + new_ta.h) - y;
  new_ta.tile = TileXY(x, y);

  /* make sure the final size is not too big. */
  if (new_ta.w > _settings_game.station.station_spread || new_ta.h > _settings_game.station.station_spread) {
    return_cmd_error(STR_ERROR_STATION_TOO_SPREAD_OUT);
  }

  return CommandCost();
}

static inline byte *CreateSingle(byte *layout, int n)
{
  int i = n;
  do *layout++ = 0; while (--i);
  layout[((n - 1) >> 1) - n] = 2;
  return layout;
}

static inline byte *CreateMulti(byte *layout, int n, byte b)
{
  int i = n;
  do *layout++ = b; while (--i);
  if (n > 4) {
    layout[0 - n] = 0;
    layout[n - 1 - n] = 0;
  }
  return layout;
}

void GetStationLayout(byte *layout, int numtracks, int plat_len, const StationSpec *statspec)
{
  if (statspec != NULL && statspec->lengths >= plat_len &&
      statspec->platforms[plat_len - 1] >= numtracks &&
      statspec->layouts[plat_len - 1][numtracks - 1]) {
    /* Custom layout defined, follow it. */
    memcpy(layout, statspec->layouts[plat_len - 1][numtracks - 1],
      plat_len * numtracks);
    return;
  }

  if (plat_len == 1) {
    CreateSingle(layout, numtracks);
  } else {
    if (numtracks & 1) layout = CreateSingle(layout, plat_len);
    numtracks >>= 1;

    while (--numtracks >= 0) {
      layout = CreateMulti(layout, plat_len, 4);
      layout = CreateMulti(layout, plat_len, 6);
    }
  }
}

template <class T, StringID error_message>
CommandCost FindJoiningBaseStation(StationID existing_station, StationID station_to_join, bool adjacent, TileArea ta, T **st)
{
  assert(*st == NULL);
  bool check_surrounding = true;

  if (_settings_game.station.adjacent_stations) {
    if (existing_station != INVALID_STATION) {
      if (adjacent && existing_station != station_to_join) {
        /* You can't build an adjacent station over the top of one that
         * already exists. */
        return_cmd_error(error_message);
      } else {
        /* Extend the current station, and don't check whether it will
         * be near any other stations. */
        *st = T::GetIfValid(existing_station);
        check_surrounding = (*st == NULL);
      }
    } else {
      /* There's no station here. Don't check the tiles surrounding this
       * one if the company wanted to build an adjacent station. */
      if (adjacent) check_surrounding = false;
    }
  }

  if (check_surrounding) {
    /* Make sure there is no more than one other station around us that is owned by us. */
    CommandCost ret = GetStationAround(ta, existing_station, _current_company, st);
    if (ret.Failed()) return ret;
  }

  /* Distant join */
  if (*st == NULL && station_to_join != INVALID_STATION) *st = T::GetIfValid(station_to_join);

  return CommandCost();
}

static CommandCost FindJoiningStation(StationID existing_station, StationID station_to_join, bool adjacent, TileArea ta, Station **st)
{
  return FindJoiningBaseStation<Station, STR_ERROR_MUST_REMOVE_RAILWAY_STATION_FIRST>(existing_station, station_to_join, adjacent, ta, st);
}

CommandCost FindJoiningWaypoint(StationID existing_waypoint, StationID waypoint_to_join, bool adjacent, TileArea ta, Waypoint **wp)
{
  return FindJoiningBaseStation<Waypoint, STR_ERROR_MUST_REMOVE_RAILWAYPOINT_FIRST>(existing_waypoint, waypoint_to_join, adjacent, ta, wp);
}

static void FreeTrainReservation(Train *v)
{
  FreeTrainTrackReservation(v);
  if (IsRailStationTile(v->tile)) SetRailStationPlatformReservation(v->tile, TrackdirToExitdir(v->GetVehicleTrackdir()), false);
  v = v->Last();
  if (IsRailStationTile(v->tile)) SetRailStationPlatformReservation(v->tile, TrackdirToExitdir(ReverseTrackdir(v->GetVehicleTrackdir())), false);
}

static void RestoreTrainReservation(Train *v)
{
  if (IsRailStationTile(v->tile)) SetRailStationPlatformReservation(v->tile, TrackdirToExitdir(v->GetVehicleTrackdir()), true);
  TryPathReserve(v, true, true);
  v = v->Last();
  if (IsRailStationTile(v->tile)) SetRailStationPlatformReservation(v->tile, TrackdirToExitdir(ReverseTrackdir(v->GetVehicleTrackdir())), true);
}

CommandCost CmdBuildRailStation(TileIndex tile_org, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  /* Unpack parameters */
  RailType rt    = Extract<RailType, 0, 6>(p1);
  Axis axis      = Extract<Axis, 6, 1>(p1);
  byte numtracks = GB(p1,  8, 8);
  byte plat_len  = GB(p1, 16, 8);
  bool adjacent  = HasBit(p1, 24);

  StationClassID spec_class = Extract<StationClassID, 0, 8>(p2);
  byte spec_index           = GB(p2, 8, 8);
  StationID station_to_join = GB(p2, 16, 16);

  /* Does the authority allow this? */
  CommandCost ret = CheckIfAuthorityAllowsNewStation(tile_org, flags);
  if (ret.Failed()) return ret;

  if (!ValParamRailtype(rt)) return CMD_ERROR;

  /* Check if the given station class is valid */
  if ((uint)spec_class >= StationClass::GetClassCount() || spec_class == STAT_CLASS_WAYP) return CMD_ERROR;
  if (spec_index >= StationClass::Get(spec_class)->GetSpecCount()) return CMD_ERROR;
  if (plat_len == 0 || numtracks == 0) return CMD_ERROR;

  int w_org, h_org;
  if (axis == AXIS_X) {
    w_org = plat_len;
    h_org = numtracks;
  } else {
    h_org = plat_len;
    w_org = numtracks;
  }

  bool reuse = (station_to_join != NEW_STATION);
  if (!reuse) station_to_join = INVALID_STATION;
  bool distant_join = (station_to_join != INVALID_STATION);

  if (distant_join && (!_settings_game.station.distant_join_stations || !Station::IsValidID(station_to_join))) return CMD_ERROR;

  if (h_org > _settings_game.station.station_spread || w_org > _settings_game.station.station_spread) return CMD_ERROR;

  /* these values are those that will be stored in train_tile and station_platforms */
  TileArea new_location(tile_org, w_org, h_org);

  /* Make sure the area below consists of clear tiles. (OR tiles belonging to a certain rail station) */
  StationID est = INVALID_STATION;
  SmallVector<Train *, 4> affected_vehicles;
  /* Clear the land below the station. */
  CommandCost cost = CheckFlatLandRailStation(new_location, flags, axis, &est, rt, affected_vehicles, spec_class, spec_index, plat_len, numtracks);
  if (cost.Failed()) return cost;
  /* Add construction expenses. */
  cost.AddCost((numtracks * _price[PR_BUILD_STATION_RAIL] + _price[PR_BUILD_STATION_RAIL_LENGTH]) * plat_len);
  cost.AddCost(numtracks * plat_len * RailBuildCost(rt));

  Station *st = NULL;
  ret = FindJoiningStation(est, station_to_join, adjacent, new_location, &st);
  if (ret.Failed()) return ret;

  ret = BuildStationPart(&st, flags, reuse, new_location, STATIONNAMING_RAIL);
  if (ret.Failed()) return ret;

  if (st != NULL && st->train_station.tile != INVALID_TILE) {
    CommandCost ret = CanExpandRailStation(st, new_location, axis);
    if (ret.Failed()) return ret;
  }

  /* Check if we can allocate a custom stationspec to this station */
  const StationSpec *statspec = StationClass::Get(spec_class)->GetSpec(spec_index);
  int specindex = AllocateSpecToStation(statspec, st, (flags & DC_EXEC) != 0);
  if (specindex == -1) return_cmd_error(STR_ERROR_TOO_MANY_STATION_SPECS);

  if (statspec != NULL) {
    /* Perform NewStation checks */

    /* Check if the station size is permitted */
    if (HasBit(statspec->disallowed_platforms, min(numtracks - 1, 7)) || HasBit(statspec->disallowed_lengths, min(plat_len - 1, 7))) {
      return CMD_ERROR;
    }

    /* Check if the station is buildable */
    if (HasBit(statspec->callback_mask, CBM_STATION_AVAIL)) {
      uint16 cb_res = GetStationCallback(CBID_STATION_AVAILABILITY, 0, 0, statspec, NULL, INVALID_TILE);
      if (cb_res != CALLBACK_FAILED && !Convert8bitBooleanCallback(statspec->grf_prop.grffile, CBID_STATION_AVAILABILITY, cb_res)) return CMD_ERROR;
    }
  }

  if (flags & DC_EXEC) {
    TileIndexDiff tile_delta;
    byte *layout_ptr;
    byte numtracks_orig;
    Track track;

    st->train_station = new_location;
    st->AddFacility(FACIL_TRAIN, new_location.tile);

    st->rect.BeforeAddRect(tile_org, w_org, h_org, StationRect::ADD_TRY);

    if (statspec != NULL) {
      /* Include this station spec's animation trigger bitmask
       * in the station's cached copy. */
      st->cached_anim_triggers |= statspec->animation.triggers;
    }

    tile_delta = (axis == AXIS_X ? TileDiffXY(1, 0) : TileDiffXY(0, 1));
    track = AxisToTrack(axis);

    layout_ptr = AllocaM(byte, numtracks * plat_len);
    GetStationLayout(layout_ptr, numtracks, plat_len, statspec);

    numtracks_orig = numtracks;

    Company *c = Company::Get(st->owner);
    TileIndex tile_track = tile_org;
    do {
      TileIndex tile = tile_track;
      int w = plat_len;
      do {
        byte layout = *layout_ptr++;
        if (IsRailStationTile(tile) && HasStationReservation(tile)) {
          /* Check for trains having a reservation for this tile. */
          Train *v = GetTrainForReservation(tile, AxisToTrack(GetRailStationAxis(tile)));
          if (v != NULL) {
            *affected_vehicles.Append() = v;
            FreeTrainReservation(v);
          }
        }

        /* Railtype can change when overbuilding. */
        if (IsRailStationTile(tile)) {
          if (!IsStationTileBlocked(tile)) c->infrastructure.rail[GetRailType(tile)]--;
          c->infrastructure.station--;
        }

        /* Remove animation if overbuilding */
        DeleteAnimatedTile(tile);
        byte old_specindex = HasStationTileRail(tile) ? GetCustomStationSpecIndex(tile) : 0;
        MakeRailStation(tile, st->owner, st->index, axis, layout & ~1, rt);
        /* Free the spec if we overbuild something */
        DeallocateSpecFromStation(st, old_specindex);

        SetCustomStationSpecIndex(tile, specindex);
        SetStationTileRandomBits(tile, GB(Random(), 0, 4));
        SetAnimationFrame(tile, 0);

        if (!IsStationTileBlocked(tile)) c->infrastructure.rail[rt]++;
        c->infrastructure.station++;

        if (statspec != NULL) {
          /* Use a fixed axis for GetPlatformInfo as our platforms / numtracks are always the right way around */
          uint32 platinfo = GetPlatformInfo(AXIS_X, GetStationGfx(tile), plat_len, numtracks_orig, plat_len - w, numtracks_orig - numtracks, false);

          /* As the station is not yet completely finished, the station does not yet exist. */
          uint16 callback = GetStationCallback(CBID_STATION_TILE_LAYOUT, platinfo, 0, statspec, NULL, tile);
          if (callback != CALLBACK_FAILED) {
            if (callback < 8) {
              SetStationGfx(tile, (callback & ~1) + axis);
            } else {
              ErrorUnknownCallbackResult(statspec->grf_prop.grffile->grfid, CBID_STATION_TILE_LAYOUT, callback);
            }
          }

          /* Trigger station animation -- after building? */
          TriggerStationAnimation(st, tile, SAT_BUILT);
        }

        tile += tile_delta;
      } while (--w);
      AddTrackToSignalBuffer(tile_track, track, _current_company);
      YapfNotifyTrackLayoutChange(tile_track, track);
      tile_track += tile_delta ^ TileDiffXY(1, 1); // perpendicular to tile_delta
    } while (--numtracks);

    for (uint i = 0; i < affected_vehicles.Length(); ++i) {
      /* Restore reservations of trains. */
      RestoreTrainReservation(affected_vehicles[i]);
    }

    /* Check whether we need to expand the reservation of trains already on the station. */
    TileArea update_reservation_area;
    if (axis == AXIS_X) {
      update_reservation_area = TileArea(tile_org, 1, numtracks_orig);
    } else {
      update_reservation_area = TileArea(tile_org, numtracks_orig, 1);
    }

    TILE_AREA_LOOP(tile, update_reservation_area) {
      /* Don't even try to make eye candy parts reserved. */
      if (IsStationTileBlocked(tile)) continue;

      DiagDirection dir = AxisToDiagDir(axis);
      TileIndexDiff tile_offset = TileOffsByDiagDir(dir);
      TileIndex platform_begin = tile;
      TileIndex platform_end = tile;

      /* We can only account for tiles that are reachable from this tile, so ignore primarily blocked tiles while finding the platform begin and end. */
      for (TileIndex next_tile = platform_begin - tile_offset; IsCompatibleTrainStationTile(next_tile, platform_begin); next_tile -= tile_offset) {
        platform_begin = next_tile;
      }
      for (TileIndex next_tile = platform_end + tile_offset; IsCompatibleTrainStationTile(next_tile, platform_end); next_tile += tile_offset) {
        platform_end = next_tile;
      }

      /* If there is at least on reservation on the platform, we reserve the whole platform. */
      bool reservation = false;
      for (TileIndex t = platform_begin; !reservation && t <= platform_end; t += tile_offset) {
        reservation = HasStationReservation(t);
      }

      if (reservation) {
        SetRailStationPlatformReservation(platform_begin, dir, true);
      }
    }

    st->MarkTilesDirty(false);
    st->AfterStationTileSetChange(true, STATION_RAIL);
  }

  return cost;
}

static void MakeRailStationAreaSmaller(BaseStation *st)
{
  TileArea ta = st->train_station;

restart:

  /* too small? */
  if (ta.w != 0 && ta.h != 0) {
    /* check the left side, x = constant, y changes */
    for (uint i = 0; !st->TileBelongsToRailStation(ta.tile + TileDiffXY(0, i));) {
      /* the left side is unused? */
      if (++i == ta.h) {
        ta.tile += TileDiffXY(1, 0);
        ta.w--;
        goto restart;
      }
    }

    /* check the right side, x = constant, y changes */
    for (uint i = 0; !st->TileBelongsToRailStation(ta.tile + TileDiffXY(ta.w - 1, i));) {
      /* the right side is unused? */
      if (++i == ta.h) {
        ta.w--;
        goto restart;
      }
    }

    /* check the upper side, y = constant, x changes */
    for (uint i = 0; !st->TileBelongsToRailStation(ta.tile + TileDiffXY(i, 0));) {
      /* the left side is unused? */
      if (++i == ta.w) {
        ta.tile += TileDiffXY(0, 1);
        ta.h--;
        goto restart;
      }
    }

    /* check the lower side, y = constant, x changes */
    for (uint i = 0; !st->TileBelongsToRailStation(ta.tile + TileDiffXY(i, ta.h - 1));) {
      /* the left side is unused? */
      if (++i == ta.w) {
        ta.h--;
        goto restart;
      }
    }
  } else {
    ta.Clear();
  }

  st->train_station = ta;
}

template <class T>
CommandCost RemoveFromRailBaseStation(TileArea ta, SmallVector<T *, 4> &affected_stations, DoCommandFlag flags, Money removal_cost, bool keep_rail)
{
  /* Count of the number of tiles removed */
  int quantity = 0;
  CommandCost total_cost(EXPENSES_CONSTRUCTION);
  /* Accumulator for the errors seen during clearing. If no errors happen,
   * and the quantity is 0 there is no station. Otherwise it will be one
   * of the other error that got accumulated. */
  CommandCost error;

  /* Do the action for every tile into the area */
  TILE_AREA_LOOP(tile, ta) {
    /* Make sure the specified tile is a rail station */
    if (!HasStationTileRail(tile)) continue;

    /* If there is a vehicle on ground, do not allow to remove (flood) the tile */
    CommandCost ret = EnsureNoVehicleOnGround(tile);
    error.AddCost(ret);
    if (ret.Failed()) continue;

    /* Check ownership of station */
    T *st = T::GetByTile(tile);
    if (st == NULL) continue;

    if (_current_company != OWNER_WATER) {
      CommandCost ret = CheckOwnership(st->owner);
      error.AddCost(ret);
      if (ret.Failed()) continue;
    }

    /* If we reached here, the tile is valid so increase the quantity of tiles we will remove */
    quantity++;

    if (keep_rail || IsStationTileBlocked(tile)) {
      /* Don't refund the 'steel' of the track when we keep the
       *  rail, or when the tile didn't have any rail at all. */
      total_cost.AddCost(-_price[PR_CLEAR_RAIL]);
    }

    if (flags & DC_EXEC) {
      /* read variables before the station tile is removed */
      uint specindex = GetCustomStationSpecIndex(tile);
      Track track = GetRailStationTrack(tile);
      Owner owner = GetTileOwner(tile);
      RailType rt = GetRailType(tile);
      Train *v = NULL;

      if (HasStationReservation(tile)) {
        v = GetTrainForReservation(tile, track);
        if (v != NULL) FreeTrainReservation(v);
      }

      bool build_rail = keep_rail && !IsStationTileBlocked(tile);
      if (!build_rail && !IsStationTileBlocked(tile)) Company::Get(owner)->infrastructure.rail[rt]--;

      DoClearSquare(tile);
      DeleteNewGRFInspectWindow(GSF_STATIONS, tile);
      if (build_rail) MakeRailNormal(tile, owner, TrackToTrackBits(track), rt);
      Company::Get(owner)->infrastructure.station--;
      DirtyCompanyInfrastructureWindows(owner);

      st->rect.AfterRemoveTile(st, tile);
      AddTrackToSignalBuffer(tile, track, owner);
      YapfNotifyTrackLayoutChange(tile, track);

      DeallocateSpecFromStation(st, specindex);

      affected_stations.Include(st);

      if (v != NULL) RestoreTrainReservation(v);
    }
  }

  if (quantity == 0) return error.Failed() ? error : CommandCost(STR_ERROR_THERE_IS_NO_STATION);

  for (T **stp = affected_stations.Begin(); stp != affected_stations.End(); stp++) {
    T *st = *stp;

    /* now we need to make the "spanned" area of the railway station smaller
     * if we deleted something at the edges.
     * we also need to adjust train_tile. */
    MakeRailStationAreaSmaller(st);
    UpdateStationSignCoord(st);

    /* if we deleted the whole station, delete the train facility. */
    if (st->train_station.tile == INVALID_TILE) {
      st->facilities &= ~FACIL_TRAIN;
      SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_TRAINS);
      st->UpdateVirtCoord();
      DeleteStationIfEmpty(st);
    }
  }

  total_cost.AddCost(quantity * removal_cost);
  return total_cost;
}

CommandCost CmdRemoveFromRailStation(TileIndex start, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  TileIndex end = p1 == 0 ? start : p1;
  if (start >= MapSize() || end >= MapSize()) return CMD_ERROR;

  TileArea ta(start, end);
  SmallVector<Station *, 4> affected_stations;

  CommandCost ret = RemoveFromRailBaseStation(ta, affected_stations, flags, _price[PR_CLEAR_STATION_RAIL], HasBit(p2, 0));
  if (ret.Failed()) return ret;

  /* Do all station specific functions here. */
  for (Station **stp = affected_stations.Begin(); stp != affected_stations.End(); stp++) {
    Station *st = *stp;

    if (st->train_station.tile == INVALID_TILE) SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_TRAINS);
    st->MarkTilesDirty(false);
    st->RecomputeIndustriesNear();
  }

  /* Now apply the rail cost to the number that we deleted */
  return ret;
}

CommandCost CmdRemoveFromRailWaypoint(TileIndex start, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  TileIndex end = p1 == 0 ? start : p1;
  if (start >= MapSize() || end >= MapSize()) return CMD_ERROR;

  TileArea ta(start, end);
  SmallVector<Waypoint *, 4> affected_stations;

  return RemoveFromRailBaseStation(ta, affected_stations, flags, _price[PR_CLEAR_WAYPOINT_RAIL], HasBit(p2, 0));
}


template <class T>
CommandCost RemoveRailStation(T *st, DoCommandFlag flags, Money removal_cost)
{
  /* Current company owns the station? */
  if (_current_company != OWNER_WATER) {
    CommandCost ret = CheckOwnership(st->owner);
    if (ret.Failed()) return ret;
  }

  /* determine width and height of platforms */
  TileArea ta = st->train_station;

  assert(ta.w != 0 && ta.h != 0);

  CommandCost cost(EXPENSES_CONSTRUCTION);
  /* clear all areas of the station */
  TILE_AREA_LOOP(tile, ta) {
    /* only remove tiles that are actually train station tiles */
    if (st->TileBelongsToRailStation(tile)) {
      SmallVector<T*, 4> affected_stations; // dummy
      CommandCost ret = RemoveFromRailBaseStation(TileArea(tile, 1, 1), affected_stations, flags, removal_cost, false);
      if (ret.Failed()) return ret;
      cost.AddCost(ret);
    }
  }

  return cost;
}

static CommandCost RemoveRailStation(TileIndex tile, DoCommandFlag flags)
{
  /* if there is flooding, remove platforms tile by tile */
  if (_current_company == OWNER_WATER) {
    return DoCommand(tile, 0, 0, DC_EXEC, CMD_REMOVE_FROM_RAIL_STATION);
  }

  Station *st = Station::GetByTile(tile);
  CommandCost cost = RemoveRailStation(st, flags, _price[PR_CLEAR_STATION_RAIL]);

  if (flags & DC_EXEC) st->RecomputeIndustriesNear();

  return cost;
}

static CommandCost RemoveRailWaypoint(TileIndex tile, DoCommandFlag flags)
{
  /* if there is flooding, remove waypoints tile by tile */
  if (_current_company == OWNER_WATER) {
    return DoCommand(tile, 0, 0, DC_EXEC, CMD_REMOVE_FROM_RAIL_WAYPOINT);
  }

  return RemoveRailStation(Waypoint::GetByTile(tile), flags, _price[PR_CLEAR_WAYPOINT_RAIL]);
}


static RoadStop **FindRoadStopSpot(bool truck_station, Station *st)
{
  RoadStop **primary_stop = (truck_station) ? &st->truck_stops : &st->bus_stops;

  if (*primary_stop == NULL) {
    /* we have no roadstop of the type yet, so write a "primary stop" */
    return primary_stop;
  } else {
    /* there are stops already, so append to the end of the list */
    RoadStop *stop = *primary_stop;
    while (stop->next != NULL) stop = stop->next;
    return &stop->next;
  }
}

static CommandCost RemoveRoadStop(TileIndex tile, DoCommandFlag flags);

static CommandCost FindJoiningRoadStop(StationID existing_stop, StationID station_to_join, bool adjacent, TileArea ta, Station **st)
{
  return FindJoiningBaseStation<Station, STR_ERROR_MUST_REMOVE_ROAD_STOP_FIRST>(existing_stop, station_to_join, adjacent, ta, st);
}

CommandCost CmdBuildRoadStop(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  bool type = HasBit(p2, 0);
  bool is_drive_through = HasBit(p2, 1);
  RoadTypes rts = Extract<RoadTypes, 2, 2>(p2);
  StationID station_to_join = GB(p2, 16, 16);
  bool reuse = (station_to_join != NEW_STATION);
  if (!reuse) station_to_join = INVALID_STATION;
  bool distant_join = (station_to_join != INVALID_STATION);

  uint8 width = (uint8)GB(p1, 0, 8);
  uint8 length = (uint8)GB(p1, 8, 8);

  /* Check if the requested road stop is too big */
  if (width > _settings_game.station.station_spread || length > _settings_game.station.station_spread) return_cmd_error(STR_ERROR_STATION_TOO_SPREAD_OUT);
  /* Check for incorrect width / length. */
  if (width == 0 || length == 0) return CMD_ERROR;
  /* Check if the first tile and the last tile are valid */
  if (!IsValidTile(tile) || TileAddWrap(tile, width - 1, length - 1) == INVALID_TILE) return CMD_ERROR;

  TileArea roadstop_area(tile, width, length);

  if (distant_join && (!_settings_game.station.distant_join_stations || !Station::IsValidID(station_to_join))) return CMD_ERROR;

  if (!HasExactlyOneBit(rts) || !HasRoadTypesAvail(_current_company, rts)) return CMD_ERROR;

  /* Trams only have drive through stops */
  if (!is_drive_through && HasBit(rts, ROADTYPE_TRAM)) return CMD_ERROR;

  DiagDirection ddir;
  Axis axis;
  if (is_drive_through) {
    /* By definition axis is valid, due to there being 2 axes and reading 1 bit. */
    axis = Extract<Axis, 6, 1>(p2);
    ddir = AxisToDiagDir(axis);
  } else {
    /* By definition ddir is valid, due to there being 4 diagonal directions and reading 2 bits. */
    ddir = Extract<DiagDirection, 6, 2>(p2);
    axis = DiagDirToAxis(ddir);
  }

  CommandCost ret = CheckIfAuthorityAllowsNewStation(tile, flags);
  if (ret.Failed()) return ret;

  /* Total road stop cost. */
  CommandCost cost(EXPENSES_CONSTRUCTION, roadstop_area.w * roadstop_area.h * _price[type ? PR_BUILD_STATION_TRUCK : PR_BUILD_STATION_BUS]);
  StationID est = INVALID_STATION;
  ret = CheckFlatLandRoadStop(roadstop_area, flags, is_drive_through ? 5 << axis : 1 << ddir, is_drive_through, type, axis, &est, rts);
  if (ret.Failed()) return ret;
  cost.AddCost(ret);

  Station *st = NULL;
  ret = FindJoiningRoadStop(est, station_to_join, HasBit(p2, 5), roadstop_area, &st);
  if (ret.Failed()) return ret;

  /* Check if this number of road stops can be allocated. */
  if (!RoadStop::CanAllocateItem(roadstop_area.w * roadstop_area.h)) return_cmd_error(type ? STR_ERROR_TOO_MANY_TRUCK_STOPS : STR_ERROR_TOO_MANY_BUS_STOPS);

  ret = BuildStationPart(&st, flags, reuse, roadstop_area, STATIONNAMING_ROAD);
  if (ret.Failed()) return ret;

  if (flags & DC_EXEC) {
    /* Check every tile in the area. */
    TILE_AREA_LOOP(cur_tile, roadstop_area) {
      RoadTypes cur_rts = GetRoadTypes(cur_tile);
      Owner road_owner = HasBit(cur_rts, ROADTYPE_ROAD) ? GetRoadOwner(cur_tile, ROADTYPE_ROAD) : _current_company;
      Owner tram_owner = HasBit(cur_rts, ROADTYPE_TRAM) ? GetRoadOwner(cur_tile, ROADTYPE_TRAM) : _current_company;

      if (IsTileType(cur_tile, MP_STATION) && IsRoadStop(cur_tile)) {
        RemoveRoadStop(cur_tile, flags);
      }

      RoadStop *road_stop = new RoadStop(cur_tile);
      /* Insert into linked list of RoadStops. */
      RoadStop **currstop = FindRoadStopSpot(type, st);
      *currstop = road_stop;

      if (type) {
        st->truck_station.Add(cur_tile);
      } else {
        st->bus_station.Add(cur_tile);
      }

      /* Initialize an empty station. */
      st->AddFacility((type) ? FACIL_TRUCK_STOP : FACIL_BUS_STOP, cur_tile);

      st->rect.BeforeAddTile(cur_tile, StationRect::ADD_TRY);

      RoadStopType rs_type = type ? ROADSTOP_TRUCK : ROADSTOP_BUS;
      if (is_drive_through) {
        /* Update company infrastructure counts. If the current tile is a normal
         * road tile, count only the new road bits needed to get a full diagonal road. */
        RoadType rt;
        FOR_EACH_SET_ROADTYPE(rt, cur_rts | rts) {
          Company *c = Company::GetIfValid(rt == ROADTYPE_ROAD ? road_owner : tram_owner);
          if (c != NULL) {
            c->infrastructure.road[rt] += 2 - (IsNormalRoadTile(cur_tile) && HasBit(cur_rts, rt) ? CountBits(GetRoadBits(cur_tile, rt)) : 0);
            DirtyCompanyInfrastructureWindows(c->index);
          }
        }

        MakeDriveThroughRoadStop(cur_tile, st->owner, road_owner, tram_owner, st->index, rs_type, rts | cur_rts, axis);
        road_stop->MakeDriveThrough();
      } else {
        /* Non-drive-through stop never overbuild and always count as two road bits. */
        Company::Get(st->owner)->infrastructure.road[FIND_FIRST_BIT(rts)] += 2;
        MakeRoadStop(cur_tile, st->owner, st->index, rs_type, rts, ddir);
      }
      Company::Get(st->owner)->infrastructure.station++;

      MarkTileDirtyByTile(cur_tile);
    }
  }

  if (st != NULL) {
    st->AfterStationTileSetChange(true, type ? STATION_TRUCK: STATION_BUS);
  }
  return cost;
}


static Vehicle *ClearRoadStopStatusEnum(Vehicle *v, void *)
{
  if (v->type == VEH_ROAD) {
    /* Okay... we are a road vehicle on a drive through road stop.
     * But that road stop has just been removed, so we need to make
     * sure we are in a valid state... however, vehicles can also
     * turn on road stop tiles, so only clear the 'road stop' state
     * bits and only when the state was 'in road stop', otherwise
     * we'll end up clearing the turn around bits. */
    RoadVehicle *rv = RoadVehicle::From(v);
    if (HasBit(rv->state, RVS_IN_DT_ROAD_STOP)) rv->state &= RVSB_ROAD_STOP_TRACKDIR_MASK;
  }

  return NULL;
}


static CommandCost RemoveRoadStop(TileIndex tile, DoCommandFlag flags)
{
  Station *st = Station::GetByTile(tile);

  if (_current_company != OWNER_WATER) {
    CommandCost ret = CheckOwnership(st->owner);
    if (ret.Failed()) return ret;
  }

  bool is_truck = IsTruckStop(tile);

  RoadStop **primary_stop;
  RoadStop *cur_stop;
  if (is_truck) { // truck stop
    primary_stop = &st->truck_stops;
    cur_stop = RoadStop::GetByTile(tile, ROADSTOP_TRUCK);
  } else {
    primary_stop = &st->bus_stops;
    cur_stop = RoadStop::GetByTile(tile, ROADSTOP_BUS);
  }

  assert(cur_stop != NULL);

  /* don't do the check for drive-through road stops when company bankrupts */
  if (IsDriveThroughStopTile(tile) && (flags & DC_BANKRUPT)) {
    /* remove the 'going through road stop' status from all vehicles on that tile */
    if (flags & DC_EXEC) FindVehicleOnPos(tile, NULL, &ClearRoadStopStatusEnum);
  } else {
    CommandCost ret = EnsureNoVehicleOnGround(tile);
    if (ret.Failed()) return ret;
  }

  if (flags & DC_EXEC) {
    if (*primary_stop == cur_stop) {
      /* removed the first stop in the list */
      *primary_stop = cur_stop->next;
      /* removed the only stop? */
      if (*primary_stop == NULL) {
        st->facilities &= (is_truck ? ~FACIL_TRUCK_STOP : ~FACIL_BUS_STOP);
      }
    } else {
      /* tell the predecessor in the list to skip this stop */
      RoadStop *pred = *primary_stop;
      while (pred->next != cur_stop) pred = pred->next;
      pred->next = cur_stop->next;
    }

    /* Update company infrastructure counts. */
    RoadType rt;
    FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
      Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
      if (c != NULL) {
        c->infrastructure.road[rt] -= 2;
        DirtyCompanyInfrastructureWindows(c->index);
      }
    }
    Company::Get(st->owner)->infrastructure.station--;
    DirtyCompanyInfrastructureWindows(st->owner);

    if (IsDriveThroughStopTile(tile)) {
      /* Clears the tile for us */
      cur_stop->ClearDriveThrough();
    } else {
      DoClearSquare(tile);
    }

    delete cur_stop;

    /* Make sure no vehicle is going to the old roadstop */
    RoadVehicle *v;
    FOR_ALL_ROADVEHICLES(v) {
      if (v->First() == v && v->current_order.IsType(OT_GOTO_STATION) &&
          v->dest_tile == tile) {
        v->SetDestTile(v->GetOrderStationLocation(st->index));
      }
    }

    st->rect.AfterRemoveTile(st, tile);

    st->AfterStationTileSetChange(false, is_truck ? STATION_TRUCK: STATION_BUS);

    /* Update the tile area of the truck/bus stop */
    if (is_truck) {
      st->truck_station.Clear();
      for (const RoadStop *rs = st->truck_stops; rs != NULL; rs = rs->next) st->truck_station.Add(rs->xy);
    } else {
      st->bus_station.Clear();
      for (const RoadStop *rs = st->bus_stops; rs != NULL; rs = rs->next) st->bus_station.Add(rs->xy);
    }
  }

  return CommandCost(EXPENSES_CONSTRUCTION, _price[is_truck ? PR_CLEAR_STATION_TRUCK : PR_CLEAR_STATION_BUS]);
}

CommandCost CmdRemoveRoadStop(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  uint8 width = (uint8)GB(p1, 0, 8);
  uint8 height = (uint8)GB(p1, 8, 8);
  bool keep_drive_through_roads = !HasBit(p2, 1);

  /* Check for incorrect width / height. */
  if (width == 0 || height == 0) return CMD_ERROR;
  /* Check if the first tile and the last tile are valid */
  if (!IsValidTile(tile) || TileAddWrap(tile, width - 1, height - 1) == INVALID_TILE) return CMD_ERROR;
  /* Bankrupting company is not supposed to remove roads, there may be road vehicles. */
  if (!keep_drive_through_roads && (flags & DC_BANKRUPT)) return CMD_ERROR;

  TileArea roadstop_area(tile, width, height);

  CommandCost cost(EXPENSES_CONSTRUCTION);
  CommandCost last_error(STR_ERROR_THERE_IS_NO_STATION);
  bool had_success = false;

  TILE_AREA_LOOP(cur_tile, roadstop_area) {
    /* Make sure the specified tile is a road stop of the correct type */
    if (!IsTileType(cur_tile, MP_STATION) || !IsRoadStop(cur_tile) || (uint32)GetRoadStopType(cur_tile) != GB(p2, 0, 1)) continue;

    /* Save information on to-be-restored roads before the stop is removed. */
    RoadTypes rts = ROADTYPES_NONE;
    RoadBits road_bits = ROAD_NONE;
    Owner road_owner[] = { OWNER_NONE, OWNER_NONE };
    assert_compile(lengthof(road_owner) == ROADTYPE_END);
    if (IsDriveThroughStopTile(cur_tile)) {
      RoadType rt;
      FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(cur_tile)) {
        road_owner[rt] = GetRoadOwner(cur_tile, rt);
        /* If we don't want to preserve our roads then restore only roads of others. */
        if (keep_drive_through_roads || road_owner[rt] != _current_company) SetBit(rts, rt);
      }
      road_bits = AxisToRoadBits(DiagDirToAxis(GetRoadStopDir(cur_tile)));
    }

    CommandCost ret = RemoveRoadStop(cur_tile, flags);
    if (ret.Failed()) {
      last_error = ret;
      continue;
    }
    cost.AddCost(ret);
    had_success = true;

    /* Restore roads. */
    if ((flags & DC_EXEC) && rts != ROADTYPES_NONE) {
      MakeRoadNormal(cur_tile, road_bits, rts, ClosestTownFromTile(cur_tile, UINT_MAX)->index,
          road_owner[ROADTYPE_ROAD], road_owner[ROADTYPE_TRAM]);

      /* Update company infrastructure counts. */
      RoadType rt;
      FOR_EACH_SET_ROADTYPE(rt, rts) {
        Company *c = Company::GetIfValid(GetRoadOwner(cur_tile, rt));
        if (c != NULL) {
          c->infrastructure.road[rt] += CountBits(road_bits);
          DirtyCompanyInfrastructureWindows(c->index);
        }
      }
    }
  }

  return had_success ? cost : last_error;
}

static uint GetMinimalAirportDistanceToTile(TileIterator &it, TileIndex town_tile)
{
  uint mindist = UINT_MAX;

  for (TileIndex cur_tile = it; cur_tile != INVALID_TILE; cur_tile = ++it) {
    mindist = min(mindist, DistanceManhattan(town_tile, cur_tile));
  }

  return mindist;
}

uint8 GetAirportNoiseLevelForTown(const AirportSpec *as, TileIterator &it, TileIndex town_tile)
{
  /* 0 cannot be accounted, and 1 is the lowest that can be reduced from town.
   * So no need to go any further*/
  if (as->noise_level < 2) return as->noise_level;

  uint distance = GetMinimalAirportDistanceToTile(it, town_tile);

  /* The steps for measuring noise reduction are based on the "magical" (and arbitrary) 8 base distance
   * adding the town_council_tolerance 4 times, as a way to graduate, depending of the tolerance.
   * Basically, it says that the less tolerant a town is, the bigger the distance before
   * an actual decrease can be granted */
  uint8 town_tolerance_distance = 8 + (_settings_game.difficulty.town_council_tolerance * 4);

  /* now, we want to have the distance segmented using the distance judged bareable by town
   * This will give us the coefficient of reduction the distance provides. */
  uint noise_reduction = distance / town_tolerance_distance;

  /* If the noise reduction equals the airport noise itself, don't give it for free.
   * Otherwise, simply reduce the airport's level. */
  return noise_reduction >= as->noise_level ? 1 : as->noise_level - noise_reduction;
}

Town *AirportGetNearestTown(const AirportSpec *as, const TileIterator &it)
{
  Town *t, *nearest = NULL;
  uint add = as->size_x + as->size_y - 2; // GetMinimalAirportDistanceToTile can differ from DistanceManhattan by this much
  uint mindist = UINT_MAX - add; // prevent overflow
  FOR_ALL_TOWNS(t) {
    if (DistanceManhattan(t->xy, it) < mindist + add) { // avoid calling GetMinimalAirportDistanceToTile too often
      TileIterator *copy = it.Clone();
      uint dist = GetMinimalAirportDistanceToTile(*copy, t->xy);
      delete copy;
      if (dist < mindist) {
        nearest = t;
        mindist = dist;
      }
    }
  }

  return nearest;
}


void UpdateAirportsNoise()
{
  Town *t;
  const Station *st;

  FOR_ALL_TOWNS(t) t->noise_reached = 0;

  FOR_ALL_STATIONS(st) {
    if (st->airport.tile != INVALID_TILE && st->airport.type != AT_OILRIG) {
      const AirportSpec *as = st->airport.GetSpec();
      AirportTileIterator it(st);
      Town *nearest = AirportGetNearestTown(as, it);
      nearest->noise_reached += GetAirportNoiseLevelForTown(as, it, nearest->xy);
    }
  }
}

CommandCost CmdBuildAirport(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  StationID station_to_join = GB(p2, 16, 16);
  bool reuse = (station_to_join != NEW_STATION);
  if (!reuse) station_to_join = INVALID_STATION;
  bool distant_join = (station_to_join != INVALID_STATION);
  byte airport_type = GB(p1, 0, 8);
  byte layout = GB(p1, 8, 8);

  if (distant_join && (!_settings_game.station.distant_join_stations || !Station::IsValidID(station_to_join))) return CMD_ERROR;

  if (airport_type >= NUM_AIRPORTS) return CMD_ERROR;

  CommandCost ret = CheckIfAuthorityAllowsNewStation(tile, flags);
  if (ret.Failed()) return ret;

  /* Check if a valid, buildable airport was chosen for construction */
  const AirportSpec *as = AirportSpec::Get(airport_type);
  if (!as->IsAvailable() || layout >= as->num_table) return CMD_ERROR;

  Direction rotation = as->rotation[layout];
  int w = as->size_x;
  int h = as->size_y;
  if (rotation == DIR_E || rotation == DIR_W) Swap(w, h);
  TileArea airport_area = TileArea(tile, w, h);

  if (w > _settings_game.station.station_spread || h > _settings_game.station.station_spread) {
    return_cmd_error(STR_ERROR_STATION_TOO_SPREAD_OUT);
  }

  AirportTileTableIterator iter(as->table[layout], tile);
  CommandCost cost = CheckFlatLandAirport(iter, flags);
  if (cost.Failed()) return cost;

  /* The noise level is the noise from the airport and reduce it to account for the distance to the town center. */
  Town *nearest = AirportGetNearestTown(as, iter);
  uint newnoise_level = GetAirportNoiseLevelForTown(as, iter, nearest->xy);

  /* Check if local auth would allow a new airport */
  StringID authority_refuse_message = STR_NULL;
  Town *authority_refuse_town = NULL;

  if (_settings_game.economy.station_noise_level) {
    /* do not allow to build a new airport if this raise the town noise over the maximum allowed by town */
    if ((nearest->noise_reached + newnoise_level) > nearest->MaxTownNoise()) {
      authority_refuse_message = STR_ERROR_LOCAL_AUTHORITY_REFUSES_NOISE;
      authority_refuse_town = nearest;
    }
  } else {
    Town *t = ClosestTownFromTile(tile, UINT_MAX);
    uint num = 0;
    const Station *st;
    FOR_ALL_STATIONS(st) {
      if (st->town == t && (st->facilities & FACIL_AIRPORT) && st->airport.type != AT_OILRIG) num++;
    }
    if (num >= 2) {
      authority_refuse_message = STR_ERROR_LOCAL_AUTHORITY_REFUSES_AIRPORT;
      authority_refuse_town = t;
    }
  }

  if (authority_refuse_message != STR_NULL) {
    SetDParam(0, authority_refuse_town->index);
    return_cmd_error(authority_refuse_message);
  }

  Station *st = NULL;
  ret = FindJoiningStation(INVALID_STATION, station_to_join, HasBit(p2, 0), airport_area, &st);
  if (ret.Failed()) return ret;

  /* Distant join */
  if (st == NULL && distant_join) st = Station::GetIfValid(station_to_join);

  ret = BuildStationPart(&st, flags, reuse, airport_area, (GetAirport(airport_type)->flags & AirportFTAClass::AIRPLANES) ? STATIONNAMING_AIRPORT : STATIONNAMING_HELIPORT);
  if (ret.Failed()) return ret;

  if (st != NULL && st->airport.tile != INVALID_TILE) {
    return_cmd_error(STR_ERROR_TOO_CLOSE_TO_ANOTHER_AIRPORT);
  }

  for (AirportTileTableIterator iter(as->table[layout], tile); iter != INVALID_TILE; ++iter) {
    cost.AddCost(_price[PR_BUILD_STATION_AIRPORT]);
  }

  if (flags & DC_EXEC) {
    /* Always add the noise, so there will be no need to recalculate when option toggles */
    nearest->noise_reached += newnoise_level;

    st->AddFacility(FACIL_AIRPORT, tile);
    st->airport.type = airport_type;
    st->airport.layout = layout;
    st->airport.flags = 0;
    st->airport.rotation = rotation;

    st->rect.BeforeAddRect(tile, w, h, StationRect::ADD_TRY);

    for (AirportTileTableIterator iter(as->table[layout], tile); iter != INVALID_TILE; ++iter) {
      MakeAirport(iter, st->owner, st->index, iter.GetStationGfx(), WATER_CLASS_INVALID);
      SetStationTileRandomBits(iter, GB(Random(), 0, 4));
      st->airport.Add(iter);

      if (AirportTileSpec::Get(GetTranslatedAirportTileID(iter.GetStationGfx()))->animation.status != ANIM_STATUS_NO_ANIMATION) AddAnimatedTile(iter);
    }

    /* Only call the animation trigger after all tiles have been built */
    for (AirportTileTableIterator iter(as->table[layout], tile); iter != INVALID_TILE; ++iter) {
      AirportTileAnimationTrigger(st, iter, AAT_BUILT);
    }

    UpdateAirplanesOnNewStation(st);

    Company::Get(st->owner)->infrastructure.airport++;

    st->AfterStationTileSetChange(true, STATION_AIRPORT);
    InvalidateWindowData(WC_STATION_VIEW, st->index, -1);

    if (_settings_game.economy.station_noise_level) {
      SetWindowDirty(WC_TOWN_VIEW, st->town->index);
    }
  }

  return cost;
}

static CommandCost RemoveAirport(TileIndex tile, DoCommandFlag flags)
{
  Station *st = Station::GetByTile(tile);

  if (_current_company != OWNER_WATER) {
    CommandCost ret = CheckOwnership(st->owner);
    if (ret.Failed()) return ret;
  }

  tile = st->airport.tile;

  CommandCost cost(EXPENSES_CONSTRUCTION);

  const Aircraft *a;
  FOR_ALL_AIRCRAFT(a) {
    if (!a->IsNormalAircraft()) continue;
    if (a->targetairport == st->index && a->state != FLYING) return CMD_ERROR;
  }

  if (flags & DC_EXEC) {
    const AirportSpec *as = st->airport.GetSpec();
    /* The noise level is the noise from the airport and reduce it to account for the distance to the town center.
     * And as for construction, always remove it, even if the setting is not set, in order to avoid the
     * need of recalculation */
    AirportTileIterator it(st);
    Town *nearest = AirportGetNearestTown(as, it);
    nearest->noise_reached -= GetAirportNoiseLevelForTown(as, it, nearest->xy);
  }

  TILE_AREA_LOOP(tile_cur, st->airport) {
    if (!st->TileBelongsToAirport(tile_cur)) continue;

    CommandCost ret = EnsureNoVehicleOnGround(tile_cur);
    if (ret.Failed()) return ret;

    cost.AddCost(_price[PR_CLEAR_STATION_AIRPORT]);

    if (flags & DC_EXEC) {
      if (IsHangarTile(tile_cur)) OrderBackup::Reset(tile_cur, false);
      DeleteAnimatedTile(tile_cur);
      DoClearSquare(tile_cur);
      DeleteNewGRFInspectWindow(GSF_AIRPORTTILES, tile_cur);
    }
  }

  if (flags & DC_EXEC) {
    /* Clear the persistent storage. */
    delete st->airport.psa;

    for (uint i = 0; i < st->airport.GetNumHangars(); ++i) {
      DeleteWindowById(
        WC_VEHICLE_DEPOT, st->airport.GetHangarTile(i)
      );
    }

    st->rect.AfterRemoveRect(st, st->airport);

    st->airport.Clear();
    st->facilities &= ~FACIL_AIRPORT;

    InvalidateWindowData(WC_STATION_VIEW, st->index, -1);

    if (_settings_game.economy.station_noise_level) {
      SetWindowDirty(WC_TOWN_VIEW, st->town->index);
    }

    Company::Get(st->owner)->infrastructure.airport--;

    st->AfterStationTileSetChange(false, STATION_AIRPORT);

    DeleteNewGRFInspectWindow(GSF_AIRPORTS, st->index);
  }

  return cost;
}

CommandCost CmdOpenCloseAirport(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  if (!Station::IsValidID(p1)) return CMD_ERROR;
  Station *st = Station::Get(p1);

  if (!(st->facilities & FACIL_AIRPORT) || st->owner == OWNER_NONE) return CMD_ERROR;

  CommandCost ret = CheckOwnership(st->owner);
  if (ret.Failed()) return ret;

  if (flags & DC_EXEC) {
    st->airport.flags ^= AIRPORT_CLOSED_block;
    SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_CLOSE_AIRPORT);
  }
  return CommandCost();
}

bool HasStationInUse(StationID station, bool include_company, CompanyID company)
{
  const Vehicle *v;
  FOR_ALL_VEHICLES(v) {
    if ((v->owner == company) == include_company) {
      const Order *order;
      FOR_VEHICLE_ORDERS(v, order) {
        if ((order->IsType(OT_GOTO_STATION) || order->IsType(OT_GOTO_WAYPOINT)) && order->GetDestination() == station) {
          return true;
        }
      }
    }
  }
  return false;
}

static const TileIndexDiffC _dock_tileoffs_chkaround[] = {
  {-1,  0},
  { 0,  0},
  { 0,  0},
  { 0, -1}
};
static const byte _dock_w_chk[4] = { 2, 1, 2, 1 };
static const byte _dock_h_chk[4] = { 1, 2, 1, 2 };

CommandCost CmdBuildDock(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  StationID station_to_join = GB(p2, 16, 16);
  bool reuse = (station_to_join != NEW_STATION);
  if (!reuse) station_to_join = INVALID_STATION;
  bool distant_join = (station_to_join != INVALID_STATION);

  if (distant_join && (!_settings_game.station.distant_join_stations || !Station::IsValidID(station_to_join))) return CMD_ERROR;

  DiagDirection direction = GetInclinedSlopeDirection(GetTileSlope(tile));
  if (direction == INVALID_DIAGDIR) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
  direction = ReverseDiagDir(direction);

  /* Docks cannot be placed on rapids */
  if (HasTileWaterGround(tile)) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);

  CommandCost ret = CheckIfAuthorityAllowsNewStation(tile, flags);
  if (ret.Failed()) return ret;

  if (IsBridgeAbove(tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

  ret = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
  if (ret.Failed()) return ret;

  TileIndex tile_cur = tile + TileOffsByDiagDir(direction);

  if (!IsTileType(tile_cur, MP_WATER) || !IsTileFlat(tile_cur)) {
    return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
  }

  if (IsBridgeAbove(tile_cur)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

  /* Get the water class of the water tile before it is cleared.*/
  WaterClass wc = GetWaterClass(tile_cur);

  ret = DoCommand(tile_cur, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
  if (ret.Failed()) return ret;

  tile_cur += TileOffsByDiagDir(direction);
  if (!IsTileType(tile_cur, MP_WATER) || !IsTileFlat(tile_cur)) {
    return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
  }

  TileArea dock_area = TileArea(tile + ToTileIndexDiff(_dock_tileoffs_chkaround[direction]),
      _dock_w_chk[direction], _dock_h_chk[direction]);

  /* middle */
  Station *st = NULL;
  ret = FindJoiningStation(INVALID_STATION, station_to_join, HasBit(p1, 0), dock_area, &st);
  if (ret.Failed()) return ret;

  /* Distant join */
  if (st == NULL && distant_join) st = Station::GetIfValid(station_to_join);

  ret = BuildStationPart(&st, flags, reuse, dock_area, STATIONNAMING_DOCK);
  if (ret.Failed()) return ret;

  if (st != NULL && st->dock_tile != INVALID_TILE) return_cmd_error(STR_ERROR_TOO_CLOSE_TO_ANOTHER_DOCK);

  if (flags & DC_EXEC) {
    st->dock_tile = tile;
    st->AddFacility(FACIL_DOCK, tile);

    st->rect.BeforeAddRect(dock_area.tile, dock_area.w, dock_area.h, StationRect::ADD_TRY);

    /* If the water part of the dock is on a canal, update infrastructure counts.
     * This is needed as we've unconditionally cleared that tile before. */
    if (wc == WATER_CLASS_CANAL) {
      Company::Get(st->owner)->infrastructure.water++;
    }
    Company::Get(st->owner)->infrastructure.station += 2;

    MakeDock(tile, st->owner, st->index, direction, wc);

    st->AfterStationTileSetChange(true, STATION_DOCK);
  }

  return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_STATION_DOCK]);
}

static CommandCost RemoveDock(TileIndex tile, DoCommandFlag flags)
{
  Station *st = Station::GetByTile(tile);
  CommandCost ret = CheckOwnership(st->owner);
  if (ret.Failed()) return ret;

  TileIndex docking_location = TILE_ADD(st->dock_tile, ToTileIndexDiff(GetDockOffset(st->dock_tile)));

  TileIndex tile1 = st->dock_tile;
  TileIndex tile2 = tile1 + TileOffsByDiagDir(GetDockDirection(tile1));

  ret = EnsureNoVehicleOnGround(tile1);
  if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile2);
  if (ret.Failed()) return ret;

  if (flags & DC_EXEC) {
    DoClearSquare(tile1);
    MarkTileDirtyByTile(tile1);
    MakeWaterKeepingClass(tile2, st->owner);

    st->rect.AfterRemoveTile(st, tile1);
    st->rect.AfterRemoveTile(st, tile2);

    st->dock_tile = INVALID_TILE;
    st->facilities &= ~FACIL_DOCK;

    Company::Get(st->owner)->infrastructure.station -= 2;

    st->AfterStationTileSetChange(false, STATION_DOCK);

    /* All ships that were going to our station, can't go to it anymore.
     * Just clear the order, then automatically the next appropriate order
     * will be selected and in case of no appropriate order it will just
     * wander around the world. */
    Ship *s;
    FOR_ALL_SHIPS(s) {
      if (s->current_order.IsType(OT_LOADING) && s->tile == docking_location) {
        s->LeaveStation();
      }

      if (s->dest_tile == docking_location) {
        s->SetDestTile(0);
        s->current_order.Free();
      }
    }
  }

  return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_STATION_DOCK]);
}

#include "table/station_land.h"

const DrawTileSprites *GetStationTileLayout(StationType st, byte gfx)
{
  return &_station_display_datas[st][gfx];
}

bool SplitGroundSpriteForOverlay(const TileInfo *ti, SpriteID *ground, RailTrackOffset *overlay_offset)
{
  bool snow_desert;
  switch (*ground) {
    case SPR_RAIL_TRACK_X:
    case SPR_MONO_TRACK_X:
    case SPR_MGLV_TRACK_X:
      snow_desert = false;
      *overlay_offset = RTO_X;
      break;

    case SPR_RAIL_TRACK_Y:
    case SPR_MONO_TRACK_Y:
    case SPR_MGLV_TRACK_Y:
      snow_desert = false;
      *overlay_offset = RTO_Y;
      break;

    case SPR_RAIL_TRACK_X_SNOW:
    case SPR_MONO_TRACK_X_SNOW:
    case SPR_MGLV_TRACK_X_SNOW:
      snow_desert = true;
      *overlay_offset = RTO_X;
      break;

    case SPR_RAIL_TRACK_Y_SNOW:
    case SPR_MONO_TRACK_Y_SNOW:
    case SPR_MGLV_TRACK_Y_SNOW:
      snow_desert = true;
      *overlay_offset = RTO_Y;
      break;

    default:
      return false;
  }

  if (ti != NULL) {
    /* Decide snow/desert from tile */
    switch (_settings_game.game_creation.landscape) {
      case LT_ARCTIC:
        snow_desert = (uint)ti->z > GetSnowLine() * TILE_HEIGHT;
        break;

      case LT_TROPIC:
        snow_desert = GetTropicZone(ti->tile) == TROPICZONE_DESERT;
        break;

      default:
        break;
    }
  }

  *ground = snow_desert ? SPR_FLAT_SNOW_DESERT_TILE : SPR_FLAT_GRASS_TILE;
  return true;
}

static void DrawTile_Station(TileInfo *ti)
{
  const NewGRFSpriteLayout *layout = NULL;
  DrawTileSprites tmp_rail_layout;
  const DrawTileSprites *t = NULL;
  RoadTypes roadtypes;
  int32 total_offset;
  const RailtypeInfo *rti = NULL;
  uint32 relocation = 0;
  uint32 ground_relocation = 0;
  BaseStation *st = NULL;
  const StationSpec *statspec = NULL;
  uint tile_layout = 0;

  if (HasStationRail(ti->tile)) {
    rti = GetRailTypeInfo(GetRailType(ti->tile));
    roadtypes = ROADTYPES_NONE;
    total_offset = rti->GetRailtypeSpriteOffset();

    if (IsCustomStationSpecIndex(ti->tile)) {
      /* look for customization */
      st = BaseStation::GetByTile(ti->tile);
      statspec = st->speclist[GetCustomStationSpecIndex(ti->tile)].spec;

      if (statspec != NULL) {
        tile_layout = GetStationGfx(ti->tile);

        if (HasBit(statspec->callback_mask, CBM_STATION_SPRITE_LAYOUT)) {
          uint16 callback = GetStationCallback(CBID_STATION_SPRITE_LAYOUT, 0, 0, statspec, st, ti->tile);
          if (callback != CALLBACK_FAILED) tile_layout = (callback & ~1) + GetRailStationAxis(ti->tile);
        }

        /* Ensure the chosen tile layout is valid for this custom station */
        if (statspec->renderdata != NULL) {
          layout = &statspec->renderdata[tile_layout < statspec->tiles ? tile_layout : (uint)GetRailStationAxis(ti->tile)];
          if (!layout->NeedsPreprocessing()) {
            t = layout;
            layout = NULL;
          }
        }
      }
    }
  } else {
    roadtypes = IsRoadStop(ti->tile) ? GetRoadTypes(ti->tile) : ROADTYPES_NONE;
    total_offset = 0;
  }

  StationGfx gfx = GetStationGfx(ti->tile);
  if (IsAirport(ti->tile)) {
    gfx = GetAirportGfx(ti->tile);
    if (gfx >= NEW_AIRPORTTILE_OFFSET) {
      const AirportTileSpec *ats = AirportTileSpec::Get(gfx);
      if (ats->grf_prop.spritegroup[0] != NULL && DrawNewAirportTile(ti, Station::GetByTile(ti->tile), gfx, ats)) {
        return;
      }
      /* No sprite group (or no valid one) found, meaning no graphics associated.
       * Use the substitute one instead */
      assert(ats->grf_prop.subst_id != INVALID_AIRPORTTILE);
      gfx = ats->grf_prop.subst_id;
    }
    switch (gfx) {
      case APT_RADAR_GRASS_FENCE_SW:
        t = &_station_display_datas_airport_radar_grass_fence_sw[GetAnimationFrame(ti->tile)];
        break;
      case APT_GRASS_FENCE_NE_FLAG:
        t = &_station_display_datas_airport_flag_grass_fence_ne[GetAnimationFrame(ti->tile)];
        break;
      case APT_RADAR_FENCE_SW:
        t = &_station_display_datas_airport_radar_fence_sw[GetAnimationFrame(ti->tile)];
        break;
      case APT_RADAR_FENCE_NE:
        t = &_station_display_datas_airport_radar_fence_ne[GetAnimationFrame(ti->tile)];
        break;
      case APT_GRASS_FENCE_NE_FLAG_2:
        t = &_station_display_datas_airport_flag_grass_fence_ne_2[GetAnimationFrame(ti->tile)];
        break;
    }
  }

  Owner owner = GetTileOwner(ti->tile);

  PaletteID palette;
  if (Company::IsValidID(owner)) {
    palette = COMPANY_SPRITE_COLOUR(owner);
  } else {
    /* Some stations are not owner by a company, namely oil rigs */
    palette = PALETTE_TO_GREY;
  }

  if (layout == NULL && (t == NULL || t->seq == NULL)) t = GetStationTileLayout(GetStationType(ti->tile), gfx);

  /* don't show foundation for docks */
  if (ti->tileh != SLOPE_FLAT && !IsDock(ti->tile)) {
    if (statspec != NULL && HasBit(statspec->flags, SSF_CUSTOM_FOUNDATIONS)) {
      /* Station has custom foundations.
       * Check whether the foundation continues beyond the tile's upper sides. */
      uint edge_info = 0;
      int z;
      Slope slope = GetFoundationPixelSlope(ti->tile, &z);
      if (!HasFoundationNW(ti->tile, slope, z)) SetBit(edge_info, 0);
      if (!HasFoundationNE(ti->tile, slope, z)) SetBit(edge_info, 1);
      SpriteID image = GetCustomStationFoundationRelocation(statspec, st, ti->tile, tile_layout, edge_info);
      if (image == 0) goto draw_default_foundation;

      if (HasBit(statspec->flags, SSF_EXTENDED_FOUNDATIONS)) {
        /* Station provides extended foundations. */

        static const uint8 foundation_parts[] = {
          0, 0, 0, 0, // Invalid,  Invalid,   Invalid,   SLOPE_SW
          0, 1, 2, 3, // Invalid,  SLOPE_EW,  SLOPE_SE,  SLOPE_WSE
          0, 4, 5, 6, // Invalid,  SLOPE_NW,  SLOPE_NS,  SLOPE_NWS
          7, 8, 9     // SLOPE_NE, SLOPE_ENW, SLOPE_SEN
        };

        AddSortableSpriteToDraw(image + foundation_parts[ti->tileh], PAL_NONE, ti->x, ti->y, 16, 16, 7, ti->z);
      } else {
        /* Draw simple foundations, built up from 8 possible foundation sprites. */

        /* Each set bit represents one of the eight composite sprites to be drawn.
         * 'Invalid' entries will not drawn but are included for completeness. */
        static const uint8 composite_foundation_parts[] = {
          /* Invalid  (00000000), Invalid   (11010001), Invalid   (11100100), SLOPE_SW  (11100000) */
             0x00,                0xD1,                 0xE4,                 0xE0,
          /* Invalid  (11001010), SLOPE_EW  (11001001), SLOPE_SE  (11000100), SLOPE_WSE (11000000) */
             0xCA,                0xC9,                 0xC4,                 0xC0,
          /* Invalid  (11010010), SLOPE_NW  (10010001), SLOPE_NS  (11100100), SLOPE_NWS (10100000) */
             0xD2,                0x91,                 0xE4,                 0xA0,
          /* SLOPE_NE (01001010), SLOPE_ENW (00001001), SLOPE_SEN (01000100) */
             0x4A,                0x09,                 0x44
        };

        uint8 parts = composite_foundation_parts[ti->tileh];

        /* If foundations continue beyond the tile's upper sides then
         * mask out the last two pieces. */
        if (HasBit(edge_info, 0)) ClrBit(parts, 6);
        if (HasBit(edge_info, 1)) ClrBit(parts, 7);

        if (parts == 0) {
          /* We always have to draw at least one sprite to make sure there is a boundingbox and a sprite with the
           * correct offset for the childsprites.
           * So, draw the (completely empty) sprite of the default foundations. */
          goto draw_default_foundation;
        }

        StartSpriteCombine();
        for (int i = 0; i < 8; i++) {
          if (HasBit(parts, i)) {
            AddSortableSpriteToDraw(image + i, PAL_NONE, ti->x, ti->y, 16, 16, 7, ti->z);
          }
        }
        EndSpriteCombine();
      }

      OffsetGroundSprite(31, 1);
      ti->z += ApplyPixelFoundationToSlope(FOUNDATION_LEVELED, &ti->tileh);
    } else {
draw_default_foundation:
      DrawFoundation(ti, FOUNDATION_LEVELED);
    }
  }

  if (IsBuoy(ti->tile)) {
    DrawWaterClassGround(ti);
    SpriteID sprite = GetCanalSprite(CF_BUOY, ti->tile);
    if (sprite != 0) total_offset = sprite - SPR_IMG_BUOY;
  } else if (IsDock(ti->tile) || (IsOilRig(ti->tile) && IsTileOnWater(ti->tile))) {
    if (ti->tileh == SLOPE_FLAT) {
      DrawWaterClassGround(ti);
    } else {
      assert(IsDock(ti->tile));
      TileIndex water_tile = ti->tile + TileOffsByDiagDir(GetDockDirection(ti->tile));
      WaterClass wc = GetWaterClass(water_tile);
      if (wc == WATER_CLASS_SEA) {
        DrawShoreTile(ti->tileh);
      } else {
        DrawClearLandTile(ti, 3);
      }
    }
  } else {
    if (layout != NULL) {
      /* Sprite layout which needs preprocessing */
      bool separate_ground = HasBit(statspec->flags, SSF_SEPARATE_GROUND);
      uint32 var10_values = layout->PrepareLayout(total_offset, rti->fallback_railtype, 0, 0, separate_ground);
      uint8 var10;
      FOR_EACH_SET_BIT(var10, var10_values) {
        uint32 var10_relocation = GetCustomStationRelocation(statspec, st, ti->tile, var10);
        layout->ProcessRegisters(var10, var10_relocation, separate_ground);
      }
      tmp_rail_layout.seq = layout->GetLayout(&tmp_rail_layout.ground);
      t = &tmp_rail_layout;
      total_offset = 0;
    } else if (statspec != NULL) {
      /* Simple sprite layout */
      ground_relocation = relocation = GetCustomStationRelocation(statspec, st, ti->tile, 0);
      if (HasBit(statspec->flags, SSF_SEPARATE_GROUND)) {
        ground_relocation = GetCustomStationRelocation(statspec, st, ti->tile, 1);
      }
      ground_relocation += rti->fallback_railtype;
    }

    SpriteID image = t->ground.sprite;
    PaletteID pal  = t->ground.pal;
    RailTrackOffset overlay_offset;
    if (rti != NULL && rti->UsesOverlay() && SplitGroundSpriteForOverlay(ti, &image, &overlay_offset)) {
      SpriteID ground = GetCustomRailSprite(rti, ti->tile, RTSG_GROUND);
      DrawGroundSprite(image, PAL_NONE);
      DrawGroundSprite(ground + overlay_offset, PAL_NONE);

      if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasStationReservation(ti->tile)) {
        SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
        DrawGroundSprite(overlay + overlay_offset, PALETTE_CRASH);
      }
    } else {
      image += HasBit(image, SPRITE_MODIFIER_CUSTOM_SPRITE) ? ground_relocation : total_offset;
      if (HasBit(pal, SPRITE_MODIFIER_CUSTOM_SPRITE)) pal += ground_relocation;
      DrawGroundSprite(image, GroundSpritePaletteTransform(image, pal, palette));

      /* PBS debugging, draw reserved tracks darker */
      if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasStationRail(ti->tile) && HasStationReservation(ti->tile)) {
        const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
        DrawGroundSprite(GetRailStationAxis(ti->tile) == AXIS_X ? rti->base_sprites.single_x : rti->base_sprites.single_y, PALETTE_CRASH);
      }
    }
  }

  if (HasStationRail(ti->tile) && HasRailCatenaryDrawn(GetRailType(ti->tile))) DrawRailCatenary(ti);

  if (HasBit(roadtypes, ROADTYPE_TRAM)) {
    Axis axis = GetRoadStopDir(ti->tile) == DIAGDIR_NE ? AXIS_X : AXIS_Y;
    DrawGroundSprite((HasBit(roadtypes, ROADTYPE_ROAD) ? SPR_TRAMWAY_OVERLAY : SPR_TRAMWAY_TRAM) + (axis ^ 1), PAL_NONE);
    DrawRoadCatenary(ti, axis == AXIS_X ? ROAD_X : ROAD_Y);
  }

  if (IsRailWaypoint(ti->tile)) {
    /* Don't offset the waypoint graphics; they're always the same. */
    total_offset = 0;
  }

  DrawRailTileSeq(ti, t, TO_BUILDINGS, total_offset, relocation, palette);
}

void StationPickerDrawSprite(int x, int y, StationType st, RailType railtype, RoadType roadtype, int image)
{
  int32 total_offset = 0;
  PaletteID pal = COMPANY_SPRITE_COLOUR(_local_company);
  const DrawTileSprites *t = GetStationTileLayout(st, image);
  const RailtypeInfo *rti = NULL;

  if (railtype != INVALID_RAILTYPE) {
    rti = GetRailTypeInfo(railtype);
    total_offset = rti->GetRailtypeSpriteOffset();
  }

  SpriteID img = t->ground.sprite;
  RailTrackOffset overlay_offset;
  if (rti != NULL && rti->UsesOverlay() && SplitGroundSpriteForOverlay(NULL, &img, &overlay_offset)) {
    SpriteID ground = GetCustomRailSprite(rti, INVALID_TILE, RTSG_GROUND);
    DrawSprite(img, PAL_NONE, x, y);
    DrawSprite(ground + overlay_offset, PAL_NONE, x, y);
  } else {
    DrawSprite(img + total_offset, HasBit(img, PALETTE_MODIFIER_COLOUR) ? pal : PAL_NONE, x, y);
  }

  if (roadtype == ROADTYPE_TRAM) {
    DrawSprite(SPR_TRAMWAY_TRAM + (t->ground.sprite == SPR_ROAD_PAVED_STRAIGHT_X ? 1 : 0), PAL_NONE, x, y);
  }

  /* Default waypoint has no railtype specific sprites */
  DrawRailTileSeqInGUI(x, y, t, st == STATION_WAYPOINT ? 0 : total_offset, 0, pal);
}

static int GetSlopePixelZ_Station(TileIndex tile, uint x, uint y)
{
  return GetTileMaxPixelZ(tile);
}

static Foundation GetFoundation_Station(TileIndex tile, Slope tileh)
{
  return FlatteningFoundation(tileh);
}

static void GetTileDesc_Station(TileIndex tile, TileDesc *td)
{
  td->owner[0] = GetTileOwner(tile);
  if (IsDriveThroughStopTile(tile)) {
    Owner road_owner = INVALID_OWNER;
    Owner tram_owner = INVALID_OWNER;
    RoadTypes rts = GetRoadTypes(tile);
    if (HasBit(rts, ROADTYPE_ROAD)) road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);
    if (HasBit(rts, ROADTYPE_TRAM)) tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);

    /* Is there a mix of owners? */
    if ((tram_owner != INVALID_OWNER && tram_owner != td->owner[0]) ||
        (road_owner != INVALID_OWNER && road_owner != td->owner[0])) {
      uint i = 1;
      if (road_owner != INVALID_OWNER) {
        td->owner_type[i] = STR_LAND_AREA_INFORMATION_ROAD_OWNER;
        td->owner[i] = road_owner;
        i++;
      }
      if (tram_owner != INVALID_OWNER) {
        td->owner_type[i] = STR_LAND_AREA_INFORMATION_TRAM_OWNER;
        td->owner[i] = tram_owner;
      }
    }
  }
  td->build_date = BaseStation::GetByTile(tile)->build_date;

  if (HasStationTileRail(tile)) {
    const StationSpec *spec = GetStationSpec(tile);

    if (spec != NULL) {
      td->station_class = StationClass::Get(spec->cls_id)->name;
      td->station_name  = spec->name;

      if (spec->grf_prop.grffile != NULL) {
        const GRFConfig *gc = GetGRFConfig(spec->grf_prop.grffile->grfid);
        td->grf = gc->GetName();
      }
    }

    const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(tile));
    td->rail_speed = rti->max_speed;
    td->railtype = rti->strings.name;
  }

  if (IsAirport(tile)) {
    const AirportSpec *as = Station::GetByTile(tile)->airport.GetSpec();
    td->airport_class = AirportClass::Get(as->cls_id)->name;
    td->airport_name = as->name;

    const AirportTileSpec *ats = AirportTileSpec::GetByTile(tile);
    td->airport_tile_name = ats->name;

    if (as->grf_prop.grffile != NULL) {
      const GRFConfig *gc = GetGRFConfig(as->grf_prop.grffile->grfid);
      td->grf = gc->GetName();
    } else if (ats->grf_prop.grffile != NULL) {
      const GRFConfig *gc = GetGRFConfig(ats->grf_prop.grffile->grfid);
      td->grf = gc->GetName();
    }
  }

  StringID str;
  switch (GetStationType(tile)) {
    default: NOT_REACHED();
    case STATION_RAIL:     str = STR_LAI_STATION_DESCRIPTION_RAILROAD_STATION; break;
    case STATION_AIRPORT:
      str = (IsHangar(tile) ? STR_LAI_STATION_DESCRIPTION_AIRCRAFT_HANGAR : STR_LAI_STATION_DESCRIPTION_AIRPORT);
      break;
    case STATION_TRUCK:    str = STR_LAI_STATION_DESCRIPTION_TRUCK_LOADING_AREA; break;
    case STATION_BUS:      str = STR_LAI_STATION_DESCRIPTION_BUS_STATION; break;
    case STATION_OILRIG:   str = STR_INDUSTRY_NAME_OIL_RIG; break;
    case STATION_DOCK:     str = STR_LAI_STATION_DESCRIPTION_SHIP_DOCK; break;
    case STATION_BUOY:     str = STR_LAI_STATION_DESCRIPTION_BUOY; break;
    case STATION_WAYPOINT: str = STR_LAI_STATION_DESCRIPTION_WAYPOINT; break;
  }
  td->str = str;
}


static TrackStatus GetTileTrackStatus_Station(TileIndex tile, TransportType mode, uint sub_mode, DiagDirection side)
{
  TrackBits trackbits = TRACK_BIT_NONE;

  switch (mode) {
    case TRANSPORT_RAIL:
      if (HasStationRail(tile) && !IsStationTileBlocked(tile)) {
        trackbits = TrackToTrackBits(GetRailStationTrack(tile));
      }
      break;

    case TRANSPORT_WATER:
      /* buoy is coded as a station, it is always on open water */
      if (IsBuoy(tile)) {
        trackbits = TRACK_BIT_ALL;
        /* remove tracks that connect NE map edge */
        if (TileX(tile) == 0) trackbits &= ~(TRACK_BIT_X | TRACK_BIT_UPPER | TRACK_BIT_RIGHT);
        /* remove tracks that connect NW map edge */
        if (TileY(tile) == 0) trackbits &= ~(TRACK_BIT_Y | TRACK_BIT_LEFT | TRACK_BIT_UPPER);
      }
      break;

    case TRANSPORT_ROAD:
      if ((GetRoadTypes(tile) & sub_mode) != 0 && IsRoadStop(tile)) {
        DiagDirection dir = GetRoadStopDir(tile);
        Axis axis = DiagDirToAxis(dir);

        if (side != INVALID_DIAGDIR) {
          if (axis != DiagDirToAxis(side) || (IsStandardRoadStopTile(tile) && dir != side)) break;
        }

        trackbits = AxisToTrackBits(axis);
      }
      break;

    default:
      break;
  }

  return CombineTrackStatus(TrackBitsToTrackdirBits(trackbits), TRACKDIR_BIT_NONE);
}


static void TileLoop_Station(TileIndex tile)
{
  /* FIXME -- GetTileTrackStatus_Station -> animated stationtiles
   * hardcoded.....not good */
  switch (GetStationType(tile)) {
    case STATION_AIRPORT:
      AirportTileAnimationTrigger(Station::GetByTile(tile), tile, AAT_TILELOOP);
      break;

    case STATION_DOCK:
      if (!IsTileFlat(tile)) break; // only handle water part
      FALLTHROUGH;

    case STATION_OILRIG: //(station part)
    case STATION_BUOY:
      TileLoop_Water(tile);
      break;

    default: break;
  }
}


static void AnimateTile_Station(TileIndex tile)
{
  if (HasStationRail(tile)) {
    AnimateStationTile(tile);
    return;
  }

  if (IsAirport(tile)) {
    AnimateAirportTile(tile);
  }
}


static bool ClickTile_Station(TileIndex tile)
{
  const BaseStation *bst = BaseStation::GetByTile(tile);

  if (bst->facilities & FACIL_WAYPOINT) {
    ShowWaypointWindow(Waypoint::From(bst));
  } else if (IsHangar(tile)) {
    const Station *st = Station::From(bst);
    ShowDepotWindow(st->airport.GetHangarTile(st->airport.GetHangarNum(tile)), VEH_AIRCRAFT);
  } else {
    ShowStationViewWindow(bst->index);
  }
  return true;
}

static VehicleEnterTileStatus VehicleEnter_Station(Vehicle *v, TileIndex tile, int x, int y)
{
  if (v->type == VEH_TRAIN) {
    StationID station_id = GetStationIndex(tile);
    if (!v->current_order.ShouldStopAtStation(v, station_id)) return VETSB_CONTINUE;
    if (!IsRailStation(tile) || !v->IsFrontEngine()) return VETSB_CONTINUE;

    int station_ahead;
    int station_length;
    int stop = GetTrainStopLocation(station_id, tile, Train::From(v), &station_ahead, &station_length);

    /* Stop whenever that amount of station ahead + the distance from the
     * begin of the platform to the stop location is longer than the length
     * of the platform. Station ahead 'includes' the current tile where the
     * vehicle is on, so we need to subtract that. */
    if (stop + station_ahead - (int)TILE_SIZE >= station_length) return VETSB_CONTINUE;

    DiagDirection dir = DirToDiagDir(v->direction);

    x &= 0xF;
    y &= 0xF;

    if (DiagDirToAxis(dir) != AXIS_X) Swap(x, y);
    if (y == TILE_SIZE / 2) {
      if (dir != DIAGDIR_SE && dir != DIAGDIR_SW) x = TILE_SIZE - 1 - x;
      stop &= TILE_SIZE - 1;

      if (x == stop) {
        return VETSB_ENTERED_STATION | (VehicleEnterTileStatus)(station_id << VETS_STATION_ID_OFFSET); // enter station
      } else if (x < stop) {
        v->vehstatus |= VS_TRAIN_SLOWING;
        uint16 spd = max(0, (stop - x) * 20 - 15);
        if (spd < v->cur_speed) v->cur_speed = spd;
      }
    }
  } else if (v->type == VEH_ROAD) {
    RoadVehicle *rv = RoadVehicle::From(v);
    if (rv->state < RVSB_IN_ROAD_STOP && !IsReversingRoadTrackdir((Trackdir)rv->state) && rv->frame == 0) {
      if (IsRoadStop(tile) && rv->IsFrontEngine()) {
        /* Attempt to allocate a parking bay in a road stop */
        return RoadStop::GetByTile(tile, GetRoadStopType(tile))->Enter(rv) ? VETSB_CONTINUE : VETSB_CANNOT_ENTER;
      }
    }
  }

  return VETSB_CONTINUE;
}

void TriggerWatchedCargoCallbacks(Station *st)
{
  /* Collect cargoes accepted since the last big tick. */
  CargoTypes cargoes = 0;
  for (CargoID cid = 0; cid < NUM_CARGO; cid++) {
    if (HasBit(st->goods[cid].status, GoodsEntry::GES_ACCEPTED_BIGTICK)) SetBit(cargoes, cid);
  }

  /* Anything to do? */
  if (cargoes == 0) return;

  /* Loop over all houses in the catchment. */
  Rect r = st->GetCatchmentRect();
  TileArea ta(TileXY(r.left, r.top), TileXY(r.right, r.bottom));
  TILE_AREA_LOOP(tile, ta) {
    if (IsTileType(tile, MP_HOUSE)) {
      WatchedCargoCallback(tile, cargoes);
    }
  }
}

static bool StationHandleBigTick(BaseStation *st)
{
  if (!st->IsInUse()) {
    if (++st->delete_ctr >= 8) delete st;
    return false;
  }

  if (Station::IsExpected(st)) {
    TriggerWatchedCargoCallbacks(Station::From(st));

    for (CargoID i = 0; i < NUM_CARGO; i++) {
      ClrBit(Station::From(st)->goods[i].status, GoodsEntry::GES_ACCEPTED_BIGTICK);
    }
  }


  if ((st->facilities & FACIL_WAYPOINT) == 0) UpdateStationAcceptance(Station::From(st), true);

  return true;
}

static inline void byte_inc_sat(byte *p)
{
  byte b = *p + 1;
  if (b != 0) *p = b;
}

static void TruncateCargo(const CargoSpec *cs, GoodsEntry *ge, uint amount = UINT_MAX)
{
  /* If truncating also punish the source stations' ratings to
   * decrease the flow of incoming cargo. */

  StationCargoAmountMap waiting_per_source;
  ge->cargo.Truncate(amount, &waiting_per_source);
  for (StationCargoAmountMap::iterator i(waiting_per_source.begin()); i != waiting_per_source.end(); ++i) {
    Station *source_station = Station::GetIfValid(i->first);
    if (source_station == NULL) continue;

    GoodsEntry &source_ge = source_station->goods[cs->Index()];
    source_ge.max_waiting_cargo = max(source_ge.max_waiting_cargo, i->second);
  }
}

static void UpdateStationRating(Station *st)
{
  bool waiting_changed = false;

  byte_inc_sat(&st->time_since_load);
  byte_inc_sat(&st->time_since_unload);

  const CargoSpec *cs;
  FOR_ALL_CARGOSPECS(cs) {
    GoodsEntry *ge = &st->goods[cs->Index()];
    /* Slowly increase the rating back to his original level in the case we
     *  didn't deliver cargo yet to this station. This happens when a bribe
     *  failed while you didn't moved that cargo yet to a station. */
    if (!ge->HasRating() && ge->rating < INITIAL_STATION_RATING) {
      ge->rating++;
    }

    /* Only change the rating if we are moving this cargo */
    if (ge->HasRating()) {
      byte_inc_sat(&ge->time_since_pickup);
      if (ge->time_since_pickup == 255 && _settings_game.order.selectgoods) {
        ClrBit(ge->status, GoodsEntry::GES_RATING);
        ge->last_speed = 0;
        TruncateCargo(cs, ge);
        waiting_changed = true;
        continue;
      }

      bool skip = false;
      int rating = 0;
      uint waiting = ge->cargo.AvailableCount();

      /* num_dests is at least 1 if there is any cargo as
       * INVALID_STATION is also a destination.
       */
      uint num_dests = (uint)ge->cargo.Packets()->MapSize();

      /* Average amount of cargo per next hop, but prefer solitary stations
       * with only one or two next hops. They are allowed to have more
       * cargo waiting per next hop.
       * With manual cargo distribution waiting_avg = waiting / 2 as then
       * INVALID_STATION is the only destination.
       */
      uint waiting_avg = waiting / (num_dests + 1);

      if (HasBit(cs->callback_mask, CBM_CARGO_STATION_RATING_CALC)) {
        /* Perform custom station rating. If it succeeds the speed, days in transit and
         * waiting cargo ratings must not be executed. */

        /* NewGRFs expect last speed to be 0xFF when no vehicle has arrived yet. */
        uint last_speed = ge->HasVehicleEverTriedLoading() ? ge->last_speed : 0xFF;

        uint32 var18 = min(ge->time_since_pickup, 0xFF) | (min(ge->max_waiting_cargo, 0xFFFF) << 8) | (min(last_speed, 0xFF) << 24);
        /* Convert to the 'old' vehicle types */
        uint32 var10 = (st->last_vehicle_type == VEH_INVALID) ? 0x0 : (st->last_vehicle_type + 0x10);
        uint16 callback = GetCargoCallback(CBID_CARGO_STATION_RATING_CALC, var10, var18, cs);
        if (callback != CALLBACK_FAILED) {
          skip = true;
          rating = GB(callback, 0, 14);

          /* Simulate a 15 bit signed value */
          if (HasBit(callback, 14)) rating -= 0x4000;
        }
      }

      if (!skip) {
        int b = ge->last_speed - 85;
        if (b >= 0) rating += b >> 2;

        byte waittime = ge->time_since_pickup;
        if (st->last_vehicle_type == VEH_SHIP) waittime >>= 2;
        (waittime > 21) ||
        (rating += 25, waittime > 12) ||
        (rating += 25, waittime > 6) ||
        (rating += 45, waittime > 3) ||
        (rating += 35, true);

        (rating -= 90, ge->max_waiting_cargo > 1500) ||
        (rating += 55, ge->max_waiting_cargo > 1000) ||
        (rating += 35, ge->max_waiting_cargo > 600) ||
        (rating += 10, ge->max_waiting_cargo > 300) ||
        (rating += 20, ge->max_waiting_cargo > 100) ||
        (rating += 10, true);
      }

      if (Company::IsValidID(st->owner) && HasBit(st->town->statues, st->owner)) rating += 26;

      byte age = ge->last_age;
      (age >= 3) ||
      (rating += 10, age >= 2) ||
      (rating += 10, age >= 1) ||
      (rating += 13, true);

      {
        int or_ = ge->rating; // old rating

        /* only modify rating in steps of -2, -1, 0, 1 or 2 */
        ge->rating = rating = or_ + Clamp(Clamp(rating, 0, 255) - or_, -2, 2);

        /* if rating is <= 64 and more than 100 items waiting on average per destination,
         * remove some random amount of goods from the station */
        if (rating <= 64 && waiting_avg >= 100) {
          int dec = Random() & 0x1F;
          if (waiting_avg < 200) dec &= 7;
          waiting -= (dec + 1) * num_dests;
          waiting_changed = true;
        }

        /* if rating is <= 127 and there are any items waiting, maybe remove some goods. */
        if (rating <= 127 && waiting != 0) {
          uint32 r = Random();
          if (rating <= (int)GB(r, 0, 7)) {
            /* Need to have int, otherwise it will just overflow etc. */
            waiting = max((int)waiting - (int)((GB(r, 8, 2) - 1) * num_dests), 0);
            waiting_changed = true;
          }
        }

        /* At some point we really must cap the cargo. Previously this
         * was a strict 4095, but now we'll have a less strict, but
         * increasingly aggressive truncation of the amount of cargo. */
        static const uint WAITING_CARGO_THRESHOLD  = 1 << 12;
        static const uint WAITING_CARGO_CUT_FACTOR = 1 <<  6;
        static const uint MAX_WAITING_CARGO        = 1 << 15;

        if (waiting > WAITING_CARGO_THRESHOLD) {
          uint difference = waiting - WAITING_CARGO_THRESHOLD;
          waiting -= (difference / WAITING_CARGO_CUT_FACTOR);

          waiting = min(waiting, MAX_WAITING_CARGO);
          waiting_changed = true;
        }

        /* We can't truncate cargo that's already reserved for loading.
         * Thus StoredCount() here. */
        if (waiting_changed && waiting < ge->cargo.AvailableCount()) {
          /* Feed back the exact own waiting cargo at this station for the
           * next rating calculation. */
          ge->max_waiting_cargo = 0;

          TruncateCargo(cs, ge, ge->cargo.AvailableCount() - waiting);
        } else {
          /* If the average number per next hop is low, be more forgiving. */
          ge->max_waiting_cargo = waiting_avg;
        }
      }
    }
  }

  StationID index = st->index;
  if (waiting_changed) {
    SetWindowDirty(WC_STATION_VIEW, index); // update whole window
  } else {
    SetWindowWidgetDirty(WC_STATION_VIEW, index, WID_SV_ACCEPT_RATING_LIST); // update only ratings list
  }
}

void RerouteCargo(Station *st, CargoID c, StationID avoid, StationID avoid2)
{
  GoodsEntry &ge = st->goods[c];

  /* Reroute cargo in station. */
  ge.cargo.Reroute(UINT_MAX, &ge.cargo, avoid, avoid2, &ge);

  /* Reroute cargo staged to be transferred. */
  for (std::list<Vehicle *>::iterator it(st->loading_vehicles.begin()); it != st->loading_vehicles.end(); ++it) {
    for (Vehicle *v = *it; v != NULL; v = v->Next()) {
      if (v->cargo_type != c) continue;
      v->cargo.Reroute(UINT_MAX, &v->cargo, avoid, avoid2, &ge);
    }
  }
}

void DeleteStaleLinks(Station *from)
{
  for (CargoID c = 0; c < NUM_CARGO; ++c) {
    const bool auto_distributed = (_settings_game.linkgraph.GetDistributionType(c) != DT_MANUAL);
    GoodsEntry &ge = from->goods[c];
    LinkGraph *lg = LinkGraph::GetIfValid(ge.link_graph);
    if (lg == NULL) continue;
    Node node = (*lg)[ge.node];
    for (EdgeIterator it(node.Begin()); it != node.End();) {
      Edge edge = it->second;
      Station *to = Station::Get((*lg)[it->first].Station());
      assert(to->goods[c].node == it->first);
      ++it; // Do that before removing the edge. Anything else may crash.
      assert(_date >= edge.LastUpdate());
      uint timeout = LinkGraph::MIN_TIMEOUT_DISTANCE + (DistanceManhattan(from->xy, to->xy) >> 3);
      if ((uint)(_date - edge.LastUpdate()) > timeout) {
        bool updated = false;

        if (auto_distributed) {
          /* Have all vehicles refresh their next hops before deciding to
           * remove the node. */
          OrderList *l;
          SmallVector<Vehicle *, 32> vehicles;
          FOR_ALL_ORDER_LISTS(l) {
            bool found_from = false;
            bool found_to = false;
            for (Order *order = l->GetFirstOrder(); order != NULL; order = order->next) {
              if (!order->IsType(OT_GOTO_STATION) && !order->IsType(OT_IMPLICIT)) continue;
              if (order->GetDestination() == from->index) {
                found_from = true;
                if (found_to) break;
              } else if (order->GetDestination() == to->index) {
                found_to = true;
                if (found_from) break;
              }
            }
            if (!found_to || !found_from) continue;
            *(vehicles.Append()) = l->GetFirstSharedVehicle();
          }

          Vehicle **iter = vehicles.Begin();
          while (iter != vehicles.End()) {
            Vehicle *v = *iter;

            LinkRefresher::Run(v, false); // Don't allow merging. Otherwise lg might get deleted.
            if (edge.LastUpdate() == _date) {
              updated = true;
              break;
            }

            Vehicle *next_shared = v->NextShared();
            if (next_shared) {
              *iter = next_shared;
              ++iter;
            } else {
              vehicles.Erase(iter);
            }

            if (iter == vehicles.End()) iter = vehicles.Begin();
          }
        }

        if (!updated) {
          /* If it's still considered dead remove it. */
          node.RemoveEdge(to->goods[c].node);
          ge.flows.DeleteFlows(to->index);
          RerouteCargo(from, c, to->index, from->index);
        }
      } else if (edge.LastUnrestrictedUpdate() != INVALID_DATE && (uint)(_date - edge.LastUnrestrictedUpdate()) > timeout) {
        edge.Restrict();
        ge.flows.RestrictFlows(to->index);
        RerouteCargo(from, c, to->index, from->index);
      } else if (edge.LastRestrictedUpdate() != INVALID_DATE && (uint)(_date - edge.LastRestrictedUpdate()) > timeout) {
        edge.Release();
      }
    }
    assert(_date >= lg->LastCompression());
    if ((uint)(_date - lg->LastCompression()) > LinkGraph::COMPRESSION_INTERVAL) {
      lg->Compress();
    }
  }
}

void IncreaseStats(Station *st, CargoID cargo, StationID next_station_id, uint capacity, uint usage, EdgeUpdateMode mode)
{
  GoodsEntry &ge1 = st->goods[cargo];
  Station *st2 = Station::Get(next_station_id);
  GoodsEntry &ge2 = st2->goods[cargo];
  LinkGraph *lg = NULL;
  if (ge1.link_graph == INVALID_LINK_GRAPH) {
    if (ge2.link_graph == INVALID_LINK_GRAPH) {
      if (LinkGraph::CanAllocateItem()) {
        lg = new LinkGraph(cargo);
        LinkGraphSchedule::instance.Queue(lg);
        ge2.link_graph = lg->index;
        ge2.node = lg->AddNode(st2);
      } else {
        DEBUG(misc, 0, "Can't allocate link graph");
      }
    } else {
      lg = LinkGraph::Get(ge2.link_graph);
    }
    if (lg) {
      ge1.link_graph = lg->index;
      ge1.node = lg->AddNode(st);
    }
  } else if (ge2.link_graph == INVALID_LINK_GRAPH) {
    lg = LinkGraph::Get(ge1.link_graph);
    ge2.link_graph = lg->index;
    ge2.node = lg->AddNode(st2);
  } else {
    lg = LinkGraph::Get(ge1.link_graph);
    if (ge1.link_graph != ge2.link_graph) {
      LinkGraph *lg2 = LinkGraph::Get(ge2.link_graph);
      if (lg->Size() < lg2->Size()) {
        LinkGraphSchedule::instance.Unqueue(lg);
        lg2->Merge(lg); // Updates GoodsEntries of lg
        lg = lg2;
      } else {
        LinkGraphSchedule::instance.Unqueue(lg2);
        lg->Merge(lg2); // Updates GoodsEntries of lg2
      }
    }
  }
  if (lg != NULL) {
    (*lg)[ge1.node].UpdateEdge(ge2.node, capacity, usage, mode);
  }
}

void IncreaseStats(Station *st, const Vehicle *front, StationID next_station_id)
{
  for (const Vehicle *v = front; v != NULL; v = v->Next()) {
    if (v->refit_cap > 0) {
      /* The cargo count can indeed be higher than the refit_cap if
       * wagons have been auto-replaced and subsequently auto-
       * refitted to a higher capacity. The cargo gets redistributed
       * among the wagons in that case.
       * As usage is not such an important figure anyway we just
       * ignore the additional cargo then.*/
      IncreaseStats(st, v->cargo_type, next_station_id, v->refit_cap,
        min(v->refit_cap, v->cargo.StoredCount()), EUM_INCREASE);
    }
  }
}

/* called for every station each tick */
static void StationHandleSmallTick(BaseStation *st)
{
  if ((st->facilities & FACIL_WAYPOINT) != 0 || !st->IsInUse()) return;

  byte b = st->delete_ctr + 1;
  if (b >= STATION_RATING_TICKS) b = 0;
  st->delete_ctr = b;

  if (b == 0) UpdateStationRating(Station::From(st));
}

void OnTick_Station()
{
  if (_game_mode == GM_EDITOR) return;

  BaseStation *st;
  FOR_ALL_BASE_STATIONS(st) {
    StationHandleSmallTick(st);

    /* Clean up the link graph about once a week. */
    if (Station::IsExpected(st) && (_tick_counter + st->index) % STATION_LINKGRAPH_TICKS == 0) {
      DeleteStaleLinks(Station::From(st));
    };

    /* Run STATION_ACCEPTANCE_TICKS = 250 tick interval trigger for station animation.
     * Station index is included so that triggers are not all done
     * at the same time. */
    if ((_tick_counter + st->index) % STATION_ACCEPTANCE_TICKS == 0) {
      /* Stop processing this station if it was deleted */
      if (!StationHandleBigTick(st)) continue;
      TriggerStationAnimation(st, st->xy, SAT_250_TICKS);
      if (Station::IsExpected(st)) AirportAnimationTrigger(Station::From(st), AAT_STATION_250_TICKS);
    }
  }
}

void StationMonthlyLoop()
{
  Station *st;

  FOR_ALL_STATIONS(st) {
    for (CargoID i = 0; i < NUM_CARGO; i++) {
      GoodsEntry *ge = &st->goods[i];
      SB(ge->status, GoodsEntry::GES_LAST_MONTH, 1, GB(ge->status, GoodsEntry::GES_CURRENT_MONTH, 1));
      ClrBit(ge->status, GoodsEntry::GES_CURRENT_MONTH);
    }
  }
}


void ModifyStationRatingAround(TileIndex tile, Owner owner, int amount, uint radius)
{
  Station *st;

  FOR_ALL_STATIONS(st) {
    if (st->owner == owner &&
        DistanceManhattan(tile, st->xy) <= radius) {
      for (CargoID i = 0; i < NUM_CARGO; i++) {
        GoodsEntry *ge = &st->goods[i];

        if (ge->status != 0) {
          ge->rating = Clamp(ge->rating + amount, 0, 255);
        }
      }
    }
  }
}

static uint UpdateStationWaiting(Station *st, CargoID type, uint amount, SourceType source_type, SourceID source_id)
{
  /* We can't allocate a CargoPacket? Then don't do anything
   * at all; i.e. just discard the incoming cargo. */
  if (!CargoPacket::CanAllocateItem()) return 0;

  GoodsEntry &ge = st->goods[type];
  amount += ge.amount_fract;
  ge.amount_fract = GB(amount, 0, 8);

  amount >>= 8;
  /* No new "real" cargo item yet. */
  if (amount == 0) return 0;

  StationID next = ge.GetVia(st->index);
  ge.cargo.Append(new CargoPacket(st->index, st->xy, amount, source_type, source_id), next);
  LinkGraph *lg = NULL;
  if (ge.link_graph == INVALID_LINK_GRAPH) {
    if (LinkGraph::CanAllocateItem()) {
      lg = new LinkGraph(type);
      LinkGraphSchedule::instance.Queue(lg);
      ge.link_graph = lg->index;
      ge.node = lg->AddNode(st);
    } else {
      DEBUG(misc, 0, "Can't allocate link graph");
    }
  } else {
    lg = LinkGraph::Get(ge.link_graph);
  }
  if (lg != NULL) (*lg)[ge.node].UpdateSupply(amount);

  if (!ge.HasRating()) {
    InvalidateWindowData(WC_STATION_LIST, st->index);
    SetBit(ge.status, GoodsEntry::GES_RATING);
  }

  TriggerStationRandomisation(st, st->xy, SRT_NEW_CARGO, type);
  TriggerStationAnimation(st, st->xy, SAT_NEW_CARGO, type);
  AirportAnimationTrigger(st, AAT_STATION_NEW_CARGO, type);

  SetWindowDirty(WC_STATION_VIEW, st->index);
  st->MarkTilesDirty(true);
  return amount;
}

static bool IsUniqueStationName(const char *name)
{
  const Station *st;

  FOR_ALL_STATIONS(st) {
    if (st->name != NULL && strcmp(st->name, name) == 0) return false;
  }

  return true;
}

CommandCost CmdRenameStation(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
  Station *st = Station::GetIfValid(p1);
  if (st == NULL) return CMD_ERROR;

  CommandCost ret = CheckOwnership(st->owner);
  if (ret.Failed()) return ret;

  bool reset = StrEmpty(text);

  if (!reset) {
    if (Utf8StringLength(text) >= MAX_LENGTH_STATION_NAME_CHARS) return CMD_ERROR;
    if (!IsUniqueStationName(text)) return_cmd_error(STR_ERROR_NAME_MUST_BE_UNIQUE);
  }

  if (flags & DC_EXEC) {
    free(st->name);
    st->name = reset ? NULL : stredup(text);

    st->UpdateVirtCoord();
    InvalidateWindowData(WC_STATION_LIST, st->owner, 1);
  }

  return CommandCost();
}

void FindStationsAroundTiles(const TileArea &location, StationList *stations)
{
  /* area to search = producer plus station catchment radius */
  uint max_rad = (_settings_game.station.modified_catchment ? MAX_CATCHMENT : CA_UNMODIFIED);

  uint x = TileX(location.tile);
  uint y = TileY(location.tile);

  uint min_x = (x > max_rad) ? x - max_rad : 0;
  uint max_x = x + location.w + max_rad;
  uint min_y = (y > max_rad) ? y - max_rad : 0;
  uint max_y = y + location.h + max_rad;

  if (min_x == 0 && _settings_game.construction.freeform_edges) min_x = 1;
  if (min_y == 0 && _settings_game.construction.freeform_edges) min_y = 1;
  if (max_x >= MapSizeX()) max_x = MapSizeX() - 1;
  if (max_y >= MapSizeY()) max_y = MapSizeY() - 1;

  for (uint cy = min_y; cy < max_y; cy++) {
    for (uint cx = min_x; cx < max_x; cx++) {
      TileIndex cur_tile = TileXY(cx, cy);
      if (!IsTileType(cur_tile, MP_STATION)) continue;

      Station *st = Station::GetByTile(cur_tile);
      /* st can be NULL in case of waypoints */
      if (st == NULL) continue;

      if (_settings_game.station.modified_catchment) {
        int rad = st->GetCatchmentRadius();
        int rad_x = cx - x;
        int rad_y = cy - y;

        if (rad_x < -rad || rad_x >= rad + location.w) continue;
        if (rad_y < -rad || rad_y >= rad + location.h) continue;
      }

      /* Insert the station in the set. This will fail if it has
       * already been added.
       */
      stations->Include(st);
    }
  }
}

const StationList *StationFinder::GetStations()
{
  if (this->tile != INVALID_TILE) {
    FindStationsAroundTiles(*this, &this->stations);
    this->tile = INVALID_TILE;
  }
  return &this->stations;
}

uint MoveGoodsToStation(CargoID type, uint amount, SourceType source_type, SourceID source_id, const StationList *all_stations)
{
  /* Return if nothing to do. Also the rounding below fails for 0. */
  if (amount == 0) return 0;

  Station *st1 = NULL;   // Station with best rating
  Station *st2 = NULL;   // Second best station
  uint best_rating1 = 0; // rating of st1
  uint best_rating2 = 0; // rating of st2

  for (Station * const *st_iter = all_stations->Begin(); st_iter != all_stations->End(); ++st_iter) {
    Station *st = *st_iter;

    /* Is the station reserved exclusively for somebody else? */
    if (st->owner != OWNER_NONE && st->town->exclusive_counter > 0 && st->town->exclusivity != st->owner) continue;

    if (st->goods[type].rating == 0) continue; // Lowest possible rating, better not to give cargo anymore

    if (_settings_game.order.selectgoods && !st->goods[type].HasVehicleEverTriedLoading()) continue; // Selectively servicing stations, and not this one

    if (IsCargoInClass(type, CC_PASSENGERS)) {
      if (st->facilities == FACIL_TRUCK_STOP) continue; // passengers are never served by just a truck stop
    } else {
      if (st->facilities == FACIL_BUS_STOP) continue; // non-passengers are never served by just a bus stop
    }

    /* This station can be used, add it to st1/st2 */
    if (st1 == NULL || st->goods[type].rating >= best_rating1) {
      st2 = st1; best_rating2 = best_rating1; st1 = st; best_rating1 = st->goods[type].rating;
    } else if (st2 == NULL || st->goods[type].rating >= best_rating2) {
      st2 = st; best_rating2 = st->goods[type].rating;
    }
  }

  /* no stations around at all? */
  if (st1 == NULL) return 0;

  /* From now we'll calculate with fractal cargo amounts.
   * First determine how much cargo we really have. */
  amount *= best_rating1 + 1;

  if (st2 == NULL) {
    /* only one station around */
    return UpdateStationWaiting(st1, type, amount, source_type, source_id);
  }

  /* several stations around, the best two (highest rating) are in st1 and st2 */
  assert(st1 != NULL);
  assert(st2 != NULL);
  assert(best_rating1 != 0 || best_rating2 != 0);

  /* Then determine the amount the worst station gets. We do it this way as the
   * best should get a bonus, which in this case is the rounding difference from
   * this calculation. In reality that will mean the bonus will be pretty low.
   * Nevertheless, the best station should always get the most cargo regardless
   * of rounding issues. */
  uint worst_cargo = amount * best_rating2 / (best_rating1 + best_rating2);
  assert(worst_cargo <= (amount - worst_cargo));

  /* And then send the cargo to the stations! */
  uint moved = UpdateStationWaiting(st1, type, amount - worst_cargo, source_type, source_id);
  /* These two UpdateStationWaiting's can't be in the statement as then the order
   * of execution would be undefined and that could cause desyncs with callbacks. */
  return moved + UpdateStationWaiting(st2, type, worst_cargo, source_type, source_id);
}

void BuildOilRig(TileIndex tile)
{
  if (!Station::CanAllocateItem()) {
    DEBUG(misc, 0, "Can't allocate station for oilrig at 0x%X, reverting to oilrig only", tile);
    return;
  }

  Station *st = new Station(tile);
  st->town = ClosestTownFromTile(tile, UINT_MAX);

  st->string_id = GenerateStationName(st, tile, STATIONNAMING_OILRIG);

  assert(IsTileType(tile, MP_INDUSTRY));
  DeleteAnimatedTile(tile);
  MakeOilrig(tile, st->index, GetWaterClass(tile));

  st->owner = OWNER_NONE;
  st->airport.type = AT_OILRIG;
  st->airport.Add(tile);
  st->dock_tile = tile;
  st->facilities = FACIL_AIRPORT | FACIL_DOCK;
  st->build_date = _date;

  st->rect.BeforeAddTile(tile, StationRect::ADD_FORCE);

  st->UpdateVirtCoord();
  UpdateStationAcceptance(st, false);
  st->RecomputeIndustriesNear();
}

void DeleteOilRig(TileIndex tile)
{
  Station *st = Station::GetByTile(tile);

  MakeWaterKeepingClass(tile, OWNER_NONE);

  st->dock_tile = INVALID_TILE;
  st->airport.Clear();
  st->facilities &= ~(FACIL_AIRPORT | FACIL_DOCK);
  st->airport.flags = 0;

  st->rect.AfterRemoveTile(st, tile);

  st->UpdateVirtCoord();
  st->RecomputeIndustriesNear();
  if (!st->IsInUse()) delete st;
}

static void ChangeTileOwner_Station(TileIndex tile, Owner old_owner, Owner new_owner)
{
  if (IsRoadStopTile(tile)) {
    for (RoadType rt = ROADTYPE_ROAD; rt < ROADTYPE_END; rt++) {
      /* Update all roadtypes, no matter if they are present */
      if (GetRoadOwner(tile, rt) == old_owner) {
        if (HasTileRoadType(tile, rt)) {
          /* A drive-through road-stop has always two road bits. No need to dirty windows here, we'll redraw the whole screen anyway. */
          Company::Get(old_owner)->infrastructure.road[rt] -= 2;
          if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.road[rt] += 2;
        }
        SetRoadOwner(tile, rt, new_owner == INVALID_OWNER ? OWNER_NONE : new_owner);
      }
    }
  }

  if (!IsTileOwner(tile, old_owner)) return;

  if (new_owner != INVALID_OWNER) {
    /* Update company infrastructure counts. Only do it here
     * if the new owner is valid as otherwise the clear
     * command will do it for us. No need to dirty windows
     * here, we'll redraw the whole screen anyway.*/
    Company *old_company = Company::Get(old_owner);
    Company *new_company = Company::Get(new_owner);

    /* Update counts for underlying infrastructure. */
    switch (GetStationType(tile)) {
      case STATION_RAIL:
      case STATION_WAYPOINT:
        if (!IsStationTileBlocked(tile)) {
          old_company->infrastructure.rail[GetRailType(tile)]--;
          new_company->infrastructure.rail[GetRailType(tile)]++;
        }
        break;

      case STATION_BUS:
      case STATION_TRUCK:
        /* Road stops were already handled above. */
        break;

      case STATION_BUOY:
      case STATION_DOCK:
        if (GetWaterClass(tile) == WATER_CLASS_CANAL) {
          old_company->infrastructure.water--;
          new_company->infrastructure.water++;
        }
        break;

      default:
        break;
    }

    /* Update station tile count. */
    if (!IsBuoy(tile) && !IsAirport(tile)) {
      old_company->infrastructure.station--;
      new_company->infrastructure.station++;
    }

    /* for buoys, owner of tile is owner of water, st->owner == OWNER_NONE */
    SetTileOwner(tile, new_owner);
    InvalidateWindowClassesData(WC_STATION_LIST, 0);
  } else {
    if (IsDriveThroughStopTile(tile)) {
      /* Remove the drive-through road stop */
      DoCommand(tile, 1 | 1 << 8, (GetStationType(tile) == STATION_TRUCK) ? ROADSTOP_TRUCK : ROADSTOP_BUS, DC_EXEC | DC_BANKRUPT, CMD_REMOVE_ROAD_STOP);
      assert(IsTileType(tile, MP_ROAD));
      /* Change owner of tile and all roadtypes */
      ChangeTileOwner(tile, old_owner, new_owner);
    } else {
      DoCommand(tile, 0, 0, DC_EXEC | DC_BANKRUPT, CMD_LANDSCAPE_CLEAR);
      /* Set tile owner of water under (now removed) buoy and dock to OWNER_NONE.
       * Update owner of buoy if it was not removed (was in orders).
       * Do not update when owned by OWNER_WATER (sea and rivers). */
      if ((IsTileType(tile, MP_WATER) || IsBuoyTile(tile)) && IsTileOwner(tile, old_owner)) SetTileOwner(tile, OWNER_NONE);
    }
  }
}

static bool CanRemoveRoadWithStop(TileIndex tile, DoCommandFlag flags)
{
  /* Yeah... water can always remove stops, right? */
  if (_current_company == OWNER_WATER) return true;

  RoadTypes rts = GetRoadTypes(tile);
  if (HasBit(rts, ROADTYPE_TRAM)) {
    Owner tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);
    if (tram_owner != OWNER_NONE && CheckOwnership(tram_owner).Failed()) return false;
  }
  if (HasBit(rts, ROADTYPE_ROAD)) {
    Owner road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);
    if (road_owner != OWNER_TOWN) {
      if (road_owner != OWNER_NONE && CheckOwnership(road_owner).Failed()) return false;
    } else {
      if (CheckAllowRemoveRoad(tile, GetAnyRoadBits(tile, ROADTYPE_ROAD), OWNER_TOWN, ROADTYPE_ROAD, flags).Failed()) return false;
    }
  }

  return true;
}

CommandCost ClearTile_Station(TileIndex tile, DoCommandFlag flags)
{
  if (flags & DC_AUTO) {
    switch (GetStationType(tile)) {
      default: break;
      case STATION_RAIL:     return_cmd_error(STR_ERROR_MUST_DEMOLISH_RAILROAD);
      case STATION_WAYPOINT: return_cmd_error(STR_ERROR_BUILDING_MUST_BE_DEMOLISHED);
      case STATION_AIRPORT:  return_cmd_error(STR_ERROR_MUST_DEMOLISH_AIRPORT_FIRST);
      case STATION_TRUCK:    return_cmd_error(HasTileRoadType(tile, ROADTYPE_TRAM) ? STR_ERROR_MUST_DEMOLISH_CARGO_TRAM_STATION_FIRST : STR_ERROR_MUST_DEMOLISH_TRUCK_STATION_FIRST);
      case STATION_BUS:      return_cmd_error(HasTileRoadType(tile, ROADTYPE_TRAM) ? STR_ERROR_MUST_DEMOLISH_PASSENGER_TRAM_STATION_FIRST : STR_ERROR_MUST_DEMOLISH_BUS_STATION_FIRST);
      case STATION_BUOY:     return_cmd_error(STR_ERROR_BUOY_IN_THE_WAY);
      case STATION_DOCK:     return_cmd_error(STR_ERROR_MUST_DEMOLISH_DOCK_FIRST);
      case STATION_OILRIG:
        SetDParam(1, STR_INDUSTRY_NAME_OIL_RIG);
        return_cmd_error(STR_ERROR_GENERIC_OBJECT_IN_THE_WAY);
    }
  }

  switch (GetStationType(tile)) {
    case STATION_RAIL:     return RemoveRailStation(tile, flags);
    case STATION_WAYPOINT: return RemoveRailWaypoint(tile, flags);
    case STATION_AIRPORT:  return RemoveAirport(tile, flags);
    case STATION_TRUCK:
      if (IsDriveThroughStopTile(tile) && !CanRemoveRoadWithStop(tile, flags)) {
        return_cmd_error(STR_ERROR_MUST_DEMOLISH_TRUCK_STATION_FIRST);
      }
      return RemoveRoadStop(tile, flags);
    case STATION_BUS:
      if (IsDriveThroughStopTile(tile) && !CanRemoveRoadWithStop(tile, flags)) {
        return_cmd_error(STR_ERROR_MUST_DEMOLISH_BUS_STATION_FIRST);
      }
      return RemoveRoadStop(tile, flags);
    case STATION_BUOY:     return RemoveBuoy(tile, flags);
    case STATION_DOCK:     return RemoveDock(tile, flags);
    default: break;
  }

  return CMD_ERROR;
}

static CommandCost TerraformTile_Station(TileIndex tile, DoCommandFlag flags, int z_new, Slope tileh_new)
{
  if (_settings_game.construction.build_on_slopes && AutoslopeEnabled()) {
    /* TODO: If you implement newgrf callback 149 'land slope check', you have to decide what to do with it here.
     *       TTDP does not call it.
     */
    if (GetTileMaxZ(tile) == z_new + GetSlopeMaxZ(tileh_new)) {
      switch (GetStationType(tile)) {
        case STATION_WAYPOINT:
        case STATION_RAIL: {
          DiagDirection direction = AxisToDiagDir(GetRailStationAxis(tile));
          if (!AutoslopeCheckForEntranceEdge(tile, z_new, tileh_new, direction)) break;
          if (!AutoslopeCheckForEntranceEdge(tile, z_new, tileh_new, ReverseDiagDir(direction))) break;
          return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
        }

        case STATION_AIRPORT:
          return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);

        case STATION_TRUCK:
        case STATION_BUS: {
          DiagDirection direction = GetRoadStopDir(tile);
          if (!AutoslopeCheckForEntranceEdge(tile, z_new, tileh_new, direction)) break;
          if (IsDriveThroughStopTile(tile)) {
            if (!AutoslopeCheckForEntranceEdge(tile, z_new, tileh_new, ReverseDiagDir(direction))) break;
          }
          return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
        }

        default: break;
      }
    }
  }
  return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
}

uint FlowStat::GetShare(StationID st) const
{
  uint32 prev = 0;
  for (SharesMap::const_iterator it = this->shares.begin(); it != this->shares.end(); ++it) {
    if (it->second == st) {
      return it->first - prev;
    } else {
      prev = it->first;
    }
  }
  return 0;
}

StationID FlowStat::GetVia(StationID excluded, StationID excluded2) const
{
  if (this->unrestricted == 0) return INVALID_STATION;
  assert(!this->shares.empty());
  SharesMap::const_iterator it = this->shares.upper_bound(RandomRange(this->unrestricted));
  assert(it != this->shares.end() && it->first <= this->unrestricted);
  if (it->second != excluded && it->second != excluded2) return it->second;

  /* We've hit one of the excluded stations.
   * Draw another share, from outside its range. */

  uint end = it->first;
  uint begin = (it == this->shares.begin() ? 0 : (--it)->first);
  uint interval = end - begin;
  if (interval >= this->unrestricted) return INVALID_STATION; // Only one station in the map.
  uint new_max = this->unrestricted - interval;
  uint rand = RandomRange(new_max);
  SharesMap::const_iterator it2 = (rand < begin) ? this->shares.upper_bound(rand) :
      this->shares.upper_bound(rand + interval);
  assert(it2 != this->shares.end() && it2->first <= this->unrestricted);
  if (it2->second != excluded && it2->second != excluded2) return it2->second;

  /* We've hit the second excluded station.
   * Same as before, only a bit more complicated. */

  uint end2 = it2->first;
  uint begin2 = (it2 == this->shares.begin() ? 0 : (--it2)->first);
  uint interval2 = end2 - begin2;
  if (interval2 >= new_max) return INVALID_STATION; // Only the two excluded stations in the map.
  new_max -= interval2;
  if (begin > begin2) {
    Swap(begin, begin2);
    Swap(end, end2);
    Swap(interval, interval2);
  }
  rand = RandomRange(new_max);
  SharesMap::const_iterator it3 = this->shares.upper_bound(this->unrestricted);
  if (rand < begin) {
    it3 = this->shares.upper_bound(rand);
  } else if (rand < begin2 - interval) {
    it3 = this->shares.upper_bound(rand + interval);
  } else {
    it3 = this->shares.upper_bound(rand + interval + interval2);
  }
  assert(it3 != this->shares.end() && it3->first <= this->unrestricted);
  return it3->second;
}

void FlowStat::Invalidate()
{
  assert(!this->shares.empty());
  SharesMap new_shares;
  uint i = 0;
  for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
    new_shares[++i] = it->second;
    if (it->first == this->unrestricted) this->unrestricted = i;
  }
  this->shares.swap(new_shares);
  assert(!this->shares.empty() && this->unrestricted <= (--this->shares.end())->first);
}

void FlowStat::ChangeShare(StationID st, int flow)
{
  /* We assert only before changing as afterwards the shares can actually
   * be empty. In that case the whole flow stat must be deleted then. */
  assert(!this->shares.empty());

  uint removed_shares = 0;
  uint added_shares = 0;
  uint last_share = 0;
  SharesMap new_shares;
  for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
    if (it->second == st) {
      if (flow < 0) {
        uint share = it->first - last_share;
        if (flow == INT_MIN || (uint)(-flow) >= share) {
          removed_shares += share;
          if (it->first <= this->unrestricted) this->unrestricted -= share;
          if (flow != INT_MIN) flow += share;
          last_share = it->first;
          continue; // remove the whole share
        }
        removed_shares += (uint)(-flow);
      } else {
        added_shares += (uint)(flow);
      }
      if (it->first <= this->unrestricted) this->unrestricted += flow;

      /* If we don't continue above the whole flow has been added or
       * removed. */
      flow = 0;
    }
    new_shares[it->first + added_shares - removed_shares] = it->second;
    last_share = it->first;
  }
  if (flow > 0) {
    new_shares[last_share + (uint)flow] = st;
    if (this->unrestricted < last_share) {
      this->ReleaseShare(st);
    } else {
      this->unrestricted += flow;
    }
  }
  this->shares.swap(new_shares);
}

void FlowStat::RestrictShare(StationID st)
{
  assert(!this->shares.empty());
  uint flow = 0;
  uint last_share = 0;
  SharesMap new_shares;
  for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
    if (flow == 0) {
      if (it->first > this->unrestricted) return; // Not present or already restricted.
      if (it->second == st) {
        flow = it->first - last_share;
        this->unrestricted -= flow;
      } else {
        new_shares[it->first] = it->second;
      }
    } else {
      new_shares[it->first - flow] = it->second;
    }
    last_share = it->first;
  }
  if (flow == 0) return;
  new_shares[last_share + flow] = st;
  this->shares.swap(new_shares);
  assert(!this->shares.empty());
}

void FlowStat::ReleaseShare(StationID st)
{
  assert(!this->shares.empty());
  uint flow = 0;
  uint next_share = 0;
  bool found = false;
  for (SharesMap::reverse_iterator it(this->shares.rbegin()); it != this->shares.rend(); ++it) {
    if (it->first < this->unrestricted) return; // Note: not <= as the share may hit the limit.
    if (found) {
      flow = next_share - it->first;
      this->unrestricted += flow;
      break;
    } else {
      if (it->first == this->unrestricted) return; // !found -> Limit not hit.
      if (it->second == st) found = true;
    }
    next_share = it->first;
  }
  if (flow == 0) return;
  SharesMap new_shares;
  new_shares[flow] = st;
  for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
    if (it->second != st) {
      new_shares[flow + it->first] = it->second;
    } else {
      flow = 0;
    }
  }
  this->shares.swap(new_shares);
  assert(!this->shares.empty());
}

void FlowStat::ScaleToMonthly(uint runtime)
{
  assert(runtime > 0);
  SharesMap new_shares;
  uint share = 0;
  for (SharesMap::iterator i = this->shares.begin(); i != this->shares.end(); ++i) {
    share = max(share + 1, i->first * 30 / runtime);
    new_shares[share] = i->second;
    if (this->unrestricted == i->first) this->unrestricted = share;
  }
  this->shares.swap(new_shares);
}

void FlowStatMap::AddFlow(StationID origin, StationID via, uint flow)
{
  FlowStatMap::iterator origin_it = this->find(origin);
  if (origin_it == this->end()) {
    this->insert(std::make_pair(origin, FlowStat(via, flow)));
  } else {
    origin_it->second.ChangeShare(via, flow);
    assert(!origin_it->second.GetShares()->empty());
  }
}

void FlowStatMap::PassOnFlow(StationID origin, StationID via, uint flow)
{
  FlowStatMap::iterator prev_it = this->find(origin);
  if (prev_it == this->end()) {
    FlowStat fs(via, flow);
    fs.AppendShare(INVALID_STATION, flow);
    this->insert(std::make_pair(origin, fs));
  } else {
    prev_it->second.ChangeShare(via, flow);
    prev_it->second.ChangeShare(INVALID_STATION, flow);
    assert(!prev_it->second.GetShares()->empty());
  }
}

void FlowStatMap::FinalizeLocalConsumption(StationID self)
{
  for (FlowStatMap::iterator i = this->begin(); i != this->end(); ++i) {
    FlowStat &fs = i->second;
    uint local = fs.GetShare(INVALID_STATION);
    if (local > INT_MAX) { // make sure it fits in an int
      fs.ChangeShare(self, -INT_MAX);
      fs.ChangeShare(INVALID_STATION, -INT_MAX);
      local -= INT_MAX;
    }
    fs.ChangeShare(self, -(int)local);
    fs.ChangeShare(INVALID_STATION, -(int)local);

    /* If the local share is used up there must be a share for some
     * remote station. */
    assert(!fs.GetShares()->empty());
  }
}

StationIDStack FlowStatMap::DeleteFlows(StationID via)
{
  StationIDStack ret;
  for (FlowStatMap::iterator f_it = this->begin(); f_it != this->end();) {
    FlowStat &s_flows = f_it->second;
    s_flows.ChangeShare(via, INT_MIN);
    if (s_flows.GetShares()->empty()) {
      ret.Push(f_it->first);
      this->erase(f_it++);
    } else {
      ++f_it;
    }
  }
  return ret;
}

void FlowStatMap::RestrictFlows(StationID via)
{
  for (FlowStatMap::iterator it = this->begin(); it != this->end(); ++it) {
    it->second.RestrictShare(via);
  }
}

void FlowStatMap::ReleaseFlows(StationID via)
{
  for (FlowStatMap::iterator it = this->begin(); it != this->end(); ++it) {
    it->second.ReleaseShare(via);
  }
}

uint FlowStatMap::GetFlow() const
{
  uint ret = 0;
  for (FlowStatMap::const_iterator i = this->begin(); i != this->end(); ++i) {
    ret += (--(i->second.GetShares()->end()))->first;
  }
  return ret;
}

uint FlowStatMap::GetFlowVia(StationID via) const
{
  uint ret = 0;
  for (FlowStatMap::const_iterator i = this->begin(); i != this->end(); ++i) {
    ret += i->second.GetShare(via);
  }
  return ret;
}

uint FlowStatMap::GetFlowFrom(StationID from) const
{
  FlowStatMap::const_iterator i = this->find(from);
  if (i == this->end()) return 0;
  return (--(i->second.GetShares()->end()))->first;
}

uint FlowStatMap::GetFlowFromVia(StationID from, StationID via) const
{
  FlowStatMap::const_iterator i = this->find(from);
  if (i == this->end()) return 0;
  return i->second.GetShare(via);
}

extern const TileTypeProcs _tile_type_station_procs = {
  DrawTile_Station,           // draw_tile_proc
  GetSlopePixelZ_Station,     // get_slope_z_proc
  ClearTile_Station,          // clear_tile_proc
  NULL,                       // add_accepted_cargo_proc
  GetTileDesc_Station,        // get_tile_desc_proc
  GetTileTrackStatus_Station, // get_tile_track_status_proc
  ClickTile_Station,          // click_tile_proc
  AnimateTile_Station,        // animate_tile_proc
  TileLoop_Station,           // tile_loop_proc
  ChangeTileOwner_Station,    // change_tile_owner_proc
  NULL,                       // add_produced_cargo_proc
  VehicleEnter_Station,       // vehicle_enter_tile_proc
  GetFoundation_Station,      // get_foundation_proc
  TerraformTile_Station,      // terraform_tile_proc
};