Hotfix: Conditional order comparator dropdown list was broken.

[openttd-joker.git] / src / station_cmd.cpp

/* $Id$ */

/*
 * 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/>.
 */

/** @file station_cmd.cpp Handling of station tiles. */

#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 "dock_base.h"
#include "newgrf_railtype.h"
#include "waypoint_base.h"
#include "waypoint_func.h"
#include "pbs.h"
#include "overlay_cmd.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 "zoning.h"

#include "table/strings.h"
#include "newgrf_townname.h"

#include "safeguards.h"

/**
 * Static instance of FlowStat::SharesMap.
 * Note: This instance is created on task start.
 *       Lazy creation on first usage results in a data race between the CDist threads.
 */
/* static */ const FlowStat::SharesMap FlowStat::empty_sharesmap;

/**
 * Check whether the given tile is a hangar.///
 * @param t the tile to of whether it is a hangar.
 * @pre IsTileType(t, MP_STATION)
 * @return true if and only if the tile is a hangar.
 */
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;
}

/**
 * Look for a station around the given tile area.
 * @param ta the area to search over
 * @param closest_station the closest station found so far
 * @param st to 'return' the found station
 * @return Succeeded command (if zero or one station found) or failed command (for two or more stations found).
 */
template <class T>
CommandCost GetStationAround(TileArea ta, StationID closest_station, T **st)
{
        ta.tile -= TileDiffXY(1, 1);
        ta.w    += 2;
        ta.h    += 2;

        /* check around to see if there's any stations there */
        TILE_AREA_LOOP(tile_cur, ta) {
                if (IsTileType(tile_cur, MP_STATION)) {
                        StationID t = GetStationIndex(tile_cur);
                        if (!T::IsValidID(t)) 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();
}

/**
 * Function to check whether the given tile matches some criterion.
 * @param tile the tile to check
 * @return true if it matches, false otherwise
 */
typedef bool (*CMSAMatcher)(TileIndex tile);

/**
 * Counts the numbers of tiles matching a specific type in the area around
 * @param tile the center tile of the 'count area'
 * @param width the x size of area around
 * @param height the y size of area around
 * @param rad the radius to count around area
 * @param cmp the comparator/matcher (@see CMSAMatcher)
 * @return the number of matching tiles around
 */
static int CountMapSquareAround(TileIndex tile, int width, int height, int rad, CMSAMatcher cmp)
{
        int num = 0;

        for (int dx = -rad; dx <= (width-1) + rad; dx++) {
                for (int dy = -rad; dy <= (height-1) + rad; dy++) {
                        TileIndex t = TileAddWrap(tile, dx, dy);
                        if (t != INVALID_TILE && cmp(t)) num++;
                }
        }

        return num;
}

/**
 * Check whether the tile is a mine.
 * @param tile the tile to investigate.
 * @return true if and only if the tile is a mine
 */
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;
}

/**
 * Check whether the tile is water.
 * @param tile the tile to investigate.
 * @return true if and only if the tile is a water tile
 */
static bool CMSAWater(TileIndex tile)
{
        return IsTileType(tile, MP_WATER) && IsWater(tile);
}

/**
 * Check whether the tile is a tree.
 * @param tile the tile to investigate.
 * @return true if and only if the tile is a tree tile
 */
static bool CMSATree(TileIndex tile)
{
        return IsTileType(tile, MP_TREES);
}

static bool CMSAIndustry(TileIndex tile)
{
        return IsTileType(tile, MP_INDUSTRY);
}

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

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

/** Information to handle station action 0 property 24 correctly */
struct StationNameInformation {
        uint32 free_names; ///< Current bitset of free names (we can remove names).
        bool *indtypes;    ///< Array of bools telling whether an industry type has been found.
};

/**
 * Find a station action 0 property 24 station name, or reduce the
 * free_names if needed.
 * @param tile the tile to search
 * @param user_data the StationNameInformation to base the search on
 * @return true if the tile contains an industry that has not given
 *              its name to one of the other stations in town.
 */
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 bool IsUniqueStationName(const char*);

static StringID GenerateStationName(Station *st, TileIndex tile, int width, int height, StationNaming name_class)
{
        static const uint32 _gen_station_name_bits[] = {
                0,                                       // STATIONNAMING_RAIL
                0,                                       // STATIONNAMING_ROAD
                1U << M(STR_SV_STNAME_AIRPORT),          // STATIONNAMING_AIRPORT
                0,         // 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 industry types 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 };

        /* 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 industry >>variable names<< */
        for (int dx = -4; dx <= (width-1) + 4; dx++) {
                for (int dy = -4; dy <= (height-1) + 4; dy++) {
                        if (CMSAIndustry(TILE_MASK(tile + TileDiffXY(dx, dy)))) {
                                char buf[512];

                                // Get town name (code mostly stolen from FormatString)
                                const Industry *ind = Industry::GetByTile(tile + TileDiffXY(dx, dy));
                                const Town *ind_t = ind->town;
                                int64 temp[1];

                                temp[0] = ind_t->townnameparts;
                                StringParameters tmp_params(temp);
                                uint32 grfid = ind_t->townnamegrfid;

                                if (ind_t->name != NULL) {
                                        strecpy(buf, ind_t->name, lastof(buf));
                                } else if (grfid == 0) {
                                        /* Original town name */
                                        GetStringWithArgs(buf, ind_t->townnametype, &tmp_params, lastof(buf));
                                } else {
                                        /* Newgrf town name */
                                        if (GetGRFTownName(grfid) != NULL) {
                                                /* The grf is loaded */
                                                GRFTownNameGenerate(buf, ind_t->townnamegrfid, ind_t->townnametype, ind_t->townnameparts, lastof(buf));
                                        } else {
                                                /* Fallback to english original */
                                                GetStringWithArgs(buf, SPECSTR_TOWNNAME_ENGLISH, &tmp_params, lastof(buf));
                                        }
                                }
                                // End of get town name

                                // Add space :P
                                strecat(buf, " ", lastof(buf));

                                // Add industry name
                                GetString(buf+strlen(buf), (GetIndustrySpec(ind->type))->name, lastof(buf));

                                MakeCamelCase(buf);

                                if (IsUniqueStationName(buf)) {
                                        free(st->name);
                                        st->name = stredup(buf);
                                        return true;
                                }
                        }
                }
        }

        /* 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, width, height, 3, CMSAWater) >= 5) {
                return STR_SV_STNAME_LAKESIDE;
        }

        /* Check woods */
        if (HasBit(free_names, M(STR_SV_STNAME_WOODS)) && (
                                CountMapSquareAround(tile, width, height, 3, CMSATree) >= 8 ||
                                CountMapSquareAround(tile, width, height, 3, 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

/**
 * Find the closest deleted station of the current company
 * @param tile the tile to search from.
 * @return the closest station or NULL if too far.
 */
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 = this->dock_station;
                        break;

                default: NOT_REACHED();
        }

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

void Station::UpdateCargoHistory()
{
        CargoSpec* cs;
        FOR_ALL_CARGOSPECS(cs) {
                auto amount = this->goods[cs->Index()].cargo.AvailableCount();

                std::rotate(std::begin(this->station_cargo_history) + cs->Index() * MAX_STATION_CARGO_HISTORY_DAYS,
                                        std::begin(this->station_cargo_history) + cs->Index() * MAX_STATION_CARGO_HISTORY_DAYS + 1,
                                        std::begin(this->station_cargo_history) + (cs->Index() + 1) * MAX_STATION_CARGO_HISTORY_DAYS);

                this->station_cargo_history[(cs->Index() + 1) * MAX_STATION_CARGO_HISTORY_DAYS - 1] = std::clamp(amount / STATION_CARGO_HISTORY_FACTOR, (uint)0, (uint)UINT8_MAX);
        }
}

/**
 * Update the virtual coords needed to draw the station sign.
 */
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);
}

/** Update the virtual coords needed to draw the station sign for all stations. */
void UpdateAllStationVirtCoords()
{
        BaseStation *st;

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

/**
 * Get a mask of the cargo types that the station accepts.
 * @param st Station to query
 * @return the expected mask
 */
static uint GetAcceptanceMask(const Station *st)
{
        uint mask = 0;

        for (CargoID i = 0; i < NUM_CARGO; i++) {
                if (HasBit(st->goods[i].status, GoodsEntry::GES_ACCEPTANCE)) mask |= 1 << i;
        }
        return mask;
}

/**
 * Items contains the two cargo names that are to be accepted or rejected.
 * msg is the string id of the message to display.
 */
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);
}

/**
 * Get the cargo types being produced around the tile (in a rectangle).
 * @param tile Northtile of area
 * @param w X extent of the area
 * @param h Y extent of the area
 * @param rad Search radius in addition to the given area
 */
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;
}

/**
 * Get the acceptance of cargoes around the tile in 1/8.
 * @param tile Center of the search area
 * @param w X extent of area
 * @param h Y extent of area
 * @param rad Search radius in addition to given area
 * @param always_accepted bitmask of cargo accepted by houses and headquarters; can be NULL
 */
CargoArray GetAcceptanceAroundTiles(TileIndex tile, int w, int h, int rad, uint32 *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;
}

/**
 * Update the acceptance for a station.
 * @param st Station to update
 * @param show_msg controls whether to display a message that acceptance was changed.
 */
void UpdateStationAcceptance(Station *st, bool show_msg)
{
        /* old accepted goods types */
        uint 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. */
        uint 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);
        if (Overlays::Instance()->HasStation(st)) st->MarkAcceptanceTilesDirty();
}

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);
        }
}

/**
 * Common part of building various station parts and possibly attaching them to an existing one.
 * @param [in,out] st Station to attach to
 * @param flags Command flags
 * @param reuse Whether to try to reuse a deleted station (gray sign) if possible
 * @param area Area occupied by the new part
 * @param name_class Station naming class to use to generate the new station's name
 * @return Command error that occurred, if any
 */
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(STR_ERROR_TOO_CLOSE_TO_ANOTHER_STATION);
                }

                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, area.w, area.h, name_class);

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

/**
 * This is called right after a station was deleted.
 * It checks if the whole station is free of substations, and if so, the station will be
 * deleted after a little while.
 * @param st Station
 */
static void DeleteStationIfEmpty(BaseStation *st)
{
        if (!st->IsInUse()) {
                if (Station::IsExpected(st)) Overlays::Instance()->RemoveStation((Station *)st);
                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);

        if (Station::IsExpected(st)) {
                MarkWholeScreenDirty();
        }
}

CommandCost ClearTile_Station(TileIndex tile, DoCommandFlag flags);

/**
 * Checks if the given tile is buildable, flat and has a certain height.
 * @param tile TileIndex to check.
 * @param invalid_dirs Prohibited directions for slopes (set of #DiagDirection).
 * @param allowed_z Height allowed for the tile. If allowed_z is negative, it will be set to the height of this tile.
 * @param allow_steep Whether steep slopes are allowed.
 * @param check_bridge Check for the existence of a bridge.
 * @return The cost in case of success, or an error code if it failed.
 */
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;
}

/**
 * Tries to clear the given area.
 * @param tile_area Area to check.
 * @param flags Operation to perform.
 * @return The cost in case of success, or an error code if it failed.
 */
CommandCost CheckFlatLand(TileArea tile_area, DoCommandFlag flags)
{
        CommandCost cost(EXPENSES_CONSTRUCTION);
        int allowed_z = -1;

        TILE_AREA_LOOP(tile_cur, tile_area) {
                CommandCost ret = CheckBuildableTile(tile_cur, 0, allowed_z, true);
                if (ret.Failed()) return ret;
                cost.AddCost(ret);

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

        return cost;
}
 
 /**
 * Checks given water area for obstacles.
 * @param tile_area Area to check.
 * @param flags Operation to perform.
 * @return The cost in case of success, or an error code if it failed.
 */
CommandCost CheckClearWater(TileArea tile_area, DoCommandFlag flags)
{
        CommandCost cost(EXPENSES_CONSTRUCTION);

        TILE_AREA_LOOP(tile_cur, tile_area) {
                if (!IsWaterTile(tile_cur) || GetTileSlope(tile_cur) != SLOPE_FLAT) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
                if (IsBridgeAbove(tile_cur)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
                CommandCost ret = EnsureNoVehicleOnGround(tile_cur);
                if (ret.Failed()) return ret;
        }

        return cost;
}

/**
 * Checks if a rail station can be built at the given area.
 * @param tile_area Area to check.
 * @param flags Operation to perform.
 * @param axis Rail station axis.
 * @param station StationID to be queried and returned if available.
 * @param rt The rail type to check for (overbuilding rail stations over rail).
 * @param affected_vehicles List of trains with PBS reservations on the tiles
 * @param spec_class Station class.
 * @param spec_index Index into the station class.
 * @param plat_len Platform length.
 * @param numtracks Number of platforms.
 * @return The cost in case of success, or an error code if it failed.
 */
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;
}

/**
 * Checks if a road stop can be built at the given tile.
 * @param tile_area Area to check.
 * @param flags Operation to perform.
 * @param invalid_dirs Prohibited directions (set of DiagDirections).
 * @param is_drive_through True if trying to build a drive-through station.
 * @param is_truck_stop True when building a truck stop, false otherwise.
 * @param axis Axis of a drive-through road stop.
 * @param station StationID to be queried and returned if available.
 * @param rts Road types to build.
 * @return The cost in case of success, or an error code if it failed.
 */
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));
                                }

                                /* 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;
}

/** /// Checks if an airport can be built at the given area.
 * @param tile_area Area to check.
 * @param flags Operation to perform.
 * @param station StationID of airport allowed in search area.
 * @return The cost in case of success, or an error code if it failed.
 */
static CommandCost CheckFlatLandAirport(TileArea tile_area, DoCommandFlag flags, StationID *station)
{
        CommandCost cost(EXPENSES_CONSTRUCTION);
        int allowed_z = -1;

        TILE_AREA_LOOP(tile_cur, tile_area) {
                CommandCost ret = CheckBuildableTile(tile_cur, 0, allowed_z, true);
                if (ret.Failed()) return ret;
                cost.AddCost(ret);

                /* if station is set, then allow building on top of an already
                 * existing airport, either the one in *station if it is not
                 * INVALID_STATION, or anyone otherwise and store which one
                 * in *station */
                if (station != NULL && IsTileType(tile_cur, MP_STATION)) {
                        if (!IsAirport(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 {
                        ret = DoCommand(tile_cur, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
                        if (ret.Failed()) return ret;
                        cost.AddCost(ret);
                }
        }

        return cost;
}

/**
 * Check whether we can expand the rail part of the given station.
 * @param st the station to expand
 * @param new_ta the current (and if all is fine new) tile area of the rail part of the station
 * @param axis the axis of the newly build rail
 * @return Succeeded or failed command.
 */
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;
}

/**
 * Create the station layout for the given number of tracks and platform length.
 * @param layout    The layout to write to.
 * @param numtracks The number of tracks to write.
 * @param plat_len  The length of the platforms.
 * @param statspec  The specification of the station to (possibly) get the layout from.
 */
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);
                }
        }
}

/**
 * Find a nearby station that joins this station.
 * /// @tparam T the class to find a station for
 * @param existing_station an existing station we build over
 * @param station_to_join the station to join to
 * @param adjacent whether adjacent stations are allowed
 * @param ta the area of the newly build station
 * @param st 'return' pointer for the found station
 * @param error_message the error message when building a station on top of others
 * @return command cost with the error or 'okay'
 */
template <class T>
CommandCost FindJoiningBaseStation(StationID existing_station, StationID station_to_join, bool adjacent, TileArea ta, T **st, StringID error_message)
{
        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 are no similar stations around us. */
                CommandCost ret = GetStationAround(ta, existing_station, st);
                if (ret.Failed()) return ret;
        }

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

        return CommandCost();
}

/**
 * Find a nearby station that joins this station.
 * @param existing_station an existing station we build over
 * @param station_to_join the station to join to
 * @param adjacent whether adjacent stations are allowed
 * @param ta the area of the newly build station
 * @param st 'return' pointer for the found station
 * @param error_message the error message when building a station on top of others
 * @return command cost with the error or 'okay'
 */
static CommandCost FindJoiningStation(StationID existing_station, StationID station_to_join, bool adjacent, TileArea ta, Station **st, StringID error_message = STR_ERROR_MUST_REMOVE_RAILWAY_STATION_FIRST)
{
        return FindJoiningBaseStation<Station>(existing_station, station_to_join, adjacent, ta, st, error_message);
}

/**
 * Find a nearby waypoint that joins this waypoint.
 * @param existing_waypoint an existing waypoint we build over
 * @param waypoint_to_join the waypoint to join to
 * @param adjacent whether adjacent waypoints are allowed
 * @param ta the area of the newly build waypoint
 * @param wp 'return' pointer for the found waypoint
 * @return command cost with the error or 'okay'
 */
CommandCost FindJoiningWaypoint(StationID existing_waypoint, StationID waypoint_to_join, bool adjacent, TileArea ta, Waypoint **wp)
{
        return FindJoiningBaseStation<Waypoint>(existing_waypoint, waypoint_to_join, adjacent, ta, wp, STR_ERROR_MUST_REMOVE_RAILWAYPOINT_FIRST);
}

/**
 * Clear platform reservation during station building/removing.
 * @param v vehicle which holds reservation
 */
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);
}

/**
 * Restore platform reservation during station building/removing.
 * @param v vehicle which held reservation
 */
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);
}

/**
 * Build rail station
 * @param tile_org northern most position of station dragging/placement
 * @param flags operation to perform
 * @param p1 various bitstuffed elements
 * - p1 = (bit  0- 4) - railtype
 * - p1 = (bit  5)    - orientation (Axis)
 * - p1 = (bit  8-15) - number of tracks
 * - p1 = (bit 16-23) - platform length
 * - p1 = (bit 24)    - allow stations directly adjacent to other stations.
 * @param p2 various bitstuffed elements
 * - p2 = (bit  0- 7) - custom station class
 * - p2 = (bit  8-15) - custom station id
 * - p2 = (bit 16-31) - station ID to join (NEW_STATION if build new one)
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdBuildRailStation(TileIndex tile_org, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        /* Unpack parameters */
        RailType rt    = Extract<RailType, 0, 5>(p1);
        Axis axis      = Extract<Axis, 5, 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);
                st->catchment.BeforeAddRect(tile_org, w_org, h_org, CA_TRAIN);

                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->UpdateVirtCoord();
                UpdateStationAcceptance(st, false);
                st->RecomputeIndustriesNear();
                ZoningMarkDirtyStationCoverageArea(st);
                InvalidateWindowData(WC_SELECT_STATION, 0, 0);
                InvalidateWindowData(WC_STATION_LIST, st->owner, 0);
                SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_TRAINS);
                DirtyCompanyInfrastructureWindows(st->owner);
        }

        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;
}

/**
 * Remove a number of tiles from any rail station within the area.
 * @param ta the area to clear station tile from.
 * @param affected_stations the stations affected.
 * @param flags the command flags.
 * @param removal_cost the cost for removing the tile, including the rail.
 * @param keep_rail whether to keep the rail of the station.
 * @tparam T the type of station to remove.
 * @return the number of cleared tiles or an error.
 */
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) {
                        bool already_affected = affected_stations.Include(st);
                        if (!already_affected) ZoningMarkDirtyStationCoverageArea(st);

                        /* read variables before the station tile is removed */
                        uint specindex = GetCustomStationSpecIndex(tile);
                        Track track = GetRailStationTrack(tile);
                        Owner owner = GetTileOwner(tile);
                        RailType rt = GetRailType(tile);
                        if (Station::IsExpected(st)) ((Station *)st)->catchment.AfterRemoveTile(tile, CA_TRAIN);
                        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 (Station::IsExpected(st) && Overlays::Instance()->HasStation((Station *)st)) ((Station *)st)->MarkAcceptanceTilesDirty();
                        if (build_rail) MakeRailNormal(tile, owner, TrackToTrackBits(track), rt);
                        if (Station::IsExpected(st) && Overlays::Instance()->HasStation((Station *)st)) ((Station *)st)->MarkAcceptanceTilesDirty();
                        Company::Get(owner)->infrastructure.station--;
                        DirtyCompanyInfrastructureWindows(owner);

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

                        DeallocateSpecFromStation(st, specindex);

                        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;
}

/**
 * Remove a single tile from a rail station.
 * This allows for custom-built station with holes and weird layouts
 * @param start tile of station piece to remove
 * @param flags operation to perform
 * @param p1 start_tile
 * @param p2 various bitstuffed elements
 * - p2 = bit 0 - if set keep the rail
 * @param text unused
 * @return the cost of this operation or an error
 */
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);
                if (Overlays::Instance()->HasStation(st)) st->MarkAcceptanceTilesDirty();
                st->MarkTilesDirty(false);
                st->RecomputeIndustriesNear();
        }

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

/**
 * Remove a single tile from a waypoint.
 * This allows for custom-built waypoint with holes and weird layouts
 * @param start tile of waypoint piece to remove
 * @param flags operation to perform
 * @param p1 start_tile
 * @param p2 various bitstuffed elements
 * - p2 = bit 0 - if set keep the rail
 * @param text unused
 * @return the cost of this operation or an error
 */
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));
}


/**
 * Remove a rail station/waypoint
 * @param st The station/waypoint to remove the rail part from
 * @param flags operation to perform
 * @param removal_cost the cost for removing a tile
 * @tparam T the type of station to remove
 * @return cost or failure of operation
 */
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;
}

/**
 * Remove a rail station
 * @param tile Tile of the station.
 * @param flags operation to perform
 * @return cost or failure of operation
 */
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);

        if (flags & DC_EXEC) ZoningMarkDirtyStationCoverageArea(st);

        CommandCost cost = RemoveRailStation(st, flags, _price[PR_CLEAR_STATION_RAIL]);

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

        return cost;
}

/**
 * Remove a rail waypoint
 * @param tile Tile of the waypoint.
 * @param flags operation to perform
 * @return cost or failure of operation
 */
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]);
}


/**
 * @param truck_station Determines whether a stop is #ROADSTOP_BUS or #ROADSTOP_TRUCK
 * @param st The Station to do the whole procedure for
 * @return a pointer to where to link a new RoadStop*
 */
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);

/**
 * Find a nearby station that joins this road stop.
 * @param existing_stop an existing road stop we build over
 * @param station_to_join the station to join to
 * @param adjacent whether adjacent stations are allowed
 * @param ta the area of the newly build station
 * @param st 'return' pointer for the found station
 * @return command cost with the error or 'okay'
 */
static CommandCost FindJoiningRoadStop(StationID existing_stop, StationID station_to_join, bool adjacent, TileArea ta, Station **st)
{
        return FindJoiningBaseStation<Station>(existing_stop, station_to_join, adjacent, ta, st, STR_ERROR_MUST_REMOVE_ROAD_STOP_FIRST);
}

/**
 * Build a bus or truck stop.
 * @param tile Northernmost tile of the stop.
 * @param flags Operation to perform.
 * @param p1 bit 0..7: Width of the road stop.
 *           bit 8..15: Length of the road stop.
 * @param p2 bit 0: 0 For bus stops, 1 for truck stops.
 *           bit 1: 0 For normal stops, 1 for drive-through.
 *           bit 2..3: The roadtypes.
 *           bit 5: Allow stations directly adjacent to other stations.
 *           bit 6..7: Entrance direction (#DiagDirection) for normal stops.
 *           bit 6: #Axis of the road for drive-through stops.
 *           bit 16..31: Station ID to join (NEW_STATION if build new one).
 * @param text Unused.
 * @return The cost of this operation or an error.
 */
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 lenght = (uint8)GB(p1, 8, 8);

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

        TileArea roadstop_area(tile, width, lenght);

        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);
                        st->catchment.BeforeAddTile(cur_tile, type ? CA_TRUCK : CA_BUS);

                        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++;
                        DirtyCompanyInfrastructureWindows(st->owner);

                        MarkTileDirtyByTile(cur_tile);
                }
                ZoningMarkDirtyStationCoverageArea(st);
        }

        if (st != NULL) {
                st->UpdateVirtCoord();
                UpdateStationAcceptance(st, false);
                st->RecomputeIndustriesNear();
                InvalidateWindowData(WC_SELECT_STATION, 0, 0);
                InvalidateWindowData(WC_STATION_LIST, st->owner, 0);
                SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_ROADVEHS);
        }
        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;
}


/**
 * Remove a bus station/truck stop
 * @param tile TileIndex been queried
 * @param flags operation to perform
 * @return cost or failure of operation
 */
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) {
                ZoningMarkDirtyStationCoverageArea(st);
                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);
                }

                if (Overlays::Instance()->HasStation(st)) st->MarkAcceptanceTilesDirty();
                SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_ROADVEHS);
                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->dest_tile = v->GetOrderStationLocation(st->index);
                        }
                }

                st->rect.AfterRemoveTile(st, tile);
                st->catchment.AfterRemoveTile(tile, is_truck ? CA_TRUCK : CA_BUS);

                st->UpdateVirtCoord();
                st->RecomputeIndustriesNear();
                DeleteStationIfEmpty(st);

                /* 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]);
}

/**
 * Remove bus or truck stops.
 * @param tile Northernmost tile of the removal area.
 * @param flags Operation to perform.
 * @param p1 bit 0..7: Width of the removal area.
 *           bit 8..15: Height of the removal area.
 * @param p2 bit 0: 0 For bus stops, 1 for truck stops.
 * @param p2 bit 1: 0 to keep roads of all drive-through stops, 1 to remove them.
 * @param text Unused.
 * @return The cost of this operation or an error.
 */
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;
}

/**
 * Computes the minimal distance from town's xy to any airport's tile.
 * @param it An iterator over all airport tiles.
 * @param town_tile town's tile (t->xy)
 * @return minimal manhattan distance from town_tile to any airport's tile
 */
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;
}

/**
 * Get a possible noise reduction factor based on distance from town center.
 * The further you get, the less noise you generate.
 * So all those folks at city council can now happily slee...  work in their offices
 * @param as airport information
 * @param it An iterator over all airport tiles.
 * @param town_tile TileIndex of town's center, the one who will receive the airport's candidature
 * @return the noise that will be generated, according to distance
 */
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;
}

/**
 * Finds the town nearest to given airport. Based on minimal manhattan distance to any airport's tile.
 * If two towns have the same distance, town with lower index is returned.
 * @param as airport's description
 * @param it An iterator over all airport tiles
 * @return nearest town to airport
 */
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;
}


/** Recalculate the noise generated by the airports of each town */
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);
                }
        }
}


/**
 * /// Checks if an airport can be removed (no aircraft on it or landing)
 * @param st Station whose airport is to be removed
 * @param flags Operation to perform
 * @return Cost or failure of operation
 */
static CommandCost CanRemoveAirport(Station *st, DoCommandFlag flags)
{
        const Aircraft *a;
        FOR_ALL_AIRCRAFT(a) {
                if (!a->IsNormalAircraft()) continue;
                if (a->targetairport == st->index && a->state != FLYING)
                        return_cmd_error(STR_ERROR_AIRCRAFT_IN_THE_WAY);
        }

        CommandCost cost(EXPENSES_CONSTRUCTION);

        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]);
        }

        return cost;
}


/**
 * Place an Airport.
 * @param tile tile where airport will be built
 * @param flags operation to perform
 * @param p1
 * - p1 = (bit  0- 7) - airport type, @see airport.h
 * - p1 = (bit  8-15) - airport layout
 * @param p2 various bitstuffed elements
 * - p2 = (bit     0) - allow airports directly adjacent to other airports.
 * - p2 = (bit 16-31) - station ID to join (NEW_STATION if build new one)
 * @param text unused
 * @return the cost of this operation or an error
 */
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);
        }

        StationID est = INVALID_STATION;
        CommandCost cost = CheckFlatLandAirport(airport_area, flags, &est);
        if (cost.Failed()) return cost;

        Station *st = NULL;
        ret = FindJoiningStation(est, station_to_join, HasBit(p2, 0), airport_area, &st, STR_ERROR_MUST_DEMOLISH_AIRPORT_FIRST);
        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;

        /* action to be performed */
        enum {
                AIRPORT_NEW,      // airport is a new station
                AIRPORT_ADD,      // add an airport to an existing station
                AIRPORT_UPGRADE,  // upgrade the airport in a station
        } action =
                (est != INVALID_STATION) ? AIRPORT_UPGRADE :
                (st != NULL) ? AIRPORT_ADD : AIRPORT_NEW;

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

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

        if (action == AIRPORT_UPGRADE) {
                const AirportSpec *old_as = st->airport.GetSpec();
                AirportTileTableIterator old_iter(old_as->table[st->airport.layout], st->airport.tile);
                Town *old_nearest = AirportGetNearestTown(old_as, old_iter);
                if (old_nearest == nearest) {
                        newnoise_level -= GetAirportNoiseLevelForTown(old_as, old_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 (newnoise_level > nearest->MaxTownNoise()) {
                        authority_refuse_message = STR_ERROR_LOCAL_AUTHORITY_REFUSES_NOISE;
                        authority_refuse_town = nearest;
                }
        } else if (action != AIRPORT_UPGRADE) {
                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);
        }

        if (action == AIRPORT_UPGRADE) {
                /* check that the old airport can be removed */
                CommandCost r = CanRemoveAirport(st, flags);
                if (r.Failed()) return r;
                cost.AddCost(r);
        }

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

        if (flags & DC_EXEC) {
                if (action == AIRPORT_UPGRADE) {
                        /* delete old airport if upgrading */
                        const AirportSpec *old_as = st->airport.GetSpec();
                        AirportTileTableIterator old_iter(old_as->table[st->airport.layout], st->airport.tile);
                        Town *old_nearest = AirportGetNearestTown(old_as, old_iter);

                        if (old_nearest != nearest) {
                                old_nearest->noise_reached -= GetAirportNoiseLevelForTown(old_as, old_iter, old_nearest->xy);
                                if (_settings_game.economy.station_noise_level) {
                                        SetWindowDirty(WC_TOWN_VIEW, st->town->index);
                                }
                        }

                        TILE_AREA_LOOP(tile_cur, st->airport) {
                                if (IsHangarTile(tile_cur)) OrderBackup::Reset(tile_cur, false);
                                DeleteAnimatedTile(tile_cur);
                                DoClearSquare(tile_cur);
                                DeleteNewGRFInspectWindow(GSF_AIRPORTTILES, tile_cur);
                        }

                        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();
                }

                /* 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);
                        st->catchment.BeforeAddTile(iter, as->catchment);

                        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);
                }

                if (action != AIRPORT_NEW) UpdateAirplanesOnNewStation(st);

                if (action == AIRPORT_UPGRADE) {
                        UpdateStationSignCoord(st);
                } else {
                        Company::Get(st->owner)->infrastructure.airport++;
                        DirtyCompanyInfrastructureWindows(st->owner);
                        st->UpdateVirtCoord();
                }

                UpdateStationAcceptance(st, false);
                st->RecomputeIndustriesNear();
                ZoningMarkDirtyStationCoverageArea(st);
                InvalidateWindowData(WC_SELECT_STATION, 0, 0);
                InvalidateWindowData(WC_STATION_LIST, st->owner, 0);
                InvalidateWindowData(WC_STATION_VIEW, st->index, -1);

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

        return cost;
}
 
 /**
 * Place a Seaplane Airport.
 * @param tile tile where airport will be built
 * @param flags operation to perform
 * @param p1
 * - p1 = (bit  0- 7) - airport type, @see airport.h
 * - p1 = (bit  8-15) - airport layout
 * @param p2 various bitstuffed elements
 * - p2 = (bit     0) - allow airports directly adjacent to other airports.
 * - p2 = (bit 16-31) - station ID to join (NEW_STATION if build new one)
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdBuildSeaplaneAirport(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);
        }

        CommandCost cost = CheckClearWater(airport_area, 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. */
        AirportTileTableIterator iter(as->table[layout], tile);
        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, STATIONNAMING_AIRPORT);
        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(), GetWaterClass(iter));
                        SetStationTileRandomBits(iter, GB(Random(), 0, 4));
                        st->airport.Add(iter);
                        st->catchment.BeforeAddTile(iter, as->catchment);

                        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++;
                DirtyCompanyInfrastructureWindows(st->owner);

                st->UpdateVirtCoord();
                UpdateStationAcceptance(st, false);
                st->RecomputeIndustriesNear();
                InvalidateWindowData(WC_SELECT_STATION, 0, 0);
                InvalidateWindowData(WC_STATION_LIST, st->owner, 0);
                InvalidateWindowData(WC_STATION_VIEW, st->index, -1);

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

        return cost;
}

/**
 * Remove an airport
 * @param tile TileIndex been queried
 * @param flags operation to perform
 * @return cost or failure of operation
 */
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;
        }

        CommandCost cost = CanRemoveAirport(st, flags);
        if (cost.Failed()) return cost;

        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) {
                        ZoningMarkDirtyStationCoverageArea(st);
                        const AirportSpec *as = st->airport.GetSpec();
                        if (IsHangarTile(tile_cur)) OrderBackup::Reset(tile_cur, false);
                        DeleteAnimatedTile(tile_cur);
                        st->catchment.AfterRemoveTile(tile_cur, as->catchment);
                        WaterClass wc = GetWaterClass(tile_cur);
                        DoClearSquare(tile_cur);

                        if (wc != WATER_CLASS_INVALID){
                                SetTileType(tile_cur, MP_WATER);
                                SetWaterClass(tile_cur, wc);
                                if (wc == WATER_CLASS_CANAL) {
                                        SetTileOwner(tile_cur, st->owner);
                                }
                        }

                        DeleteNewGRFInspectWindow(GSF_AIRPORTTILES, tile_cur);
                }

                /* 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--;
                DirtyCompanyInfrastructureWindows(st->owner);

                st->UpdateVirtCoord();
                st->RecomputeIndustriesNear();
                DeleteStationIfEmpty(st);
                DeleteNewGRFInspectWindow(GSF_AIRPORTS, st->index);
        }

        return cost;
}

/**
 * Open/close an airport to incoming aircraft.
 * @param tile Unused.
 * @param flags Operation to perform.
 * @param p1 Station ID of the airport.
 * @param p2 Unused.
 * @param text unused
 * @return the cost of this operation or an error
 */
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();
}

/**
 * Tests whether the company's vehicles have this station in orders
 * @param station station ID
 * @param include_company If true only check vehicles of \a company, if false only check vehicles of other companies
 * @param company company ID
 */
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 };

/**
 * Build a dock/haven.
 * @param tile tile where dock will be built
 * @param flags operation to perform
 * @param p1 (bit 0) - allow docks directly adjacent to other docks.
 * @param p2 bit 16-31: station ID to join (NEW_STATION if build new one)
 * @param text unused
 * @return the cost of this operation or an error
 */
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;

        TileIndex slope_tile = tile;

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

        TileIndex flat_tile = slope_tile + TileOffsByDiagDir(direction);

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

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

        if (IsBridgeAbove(slope_tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

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

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

        if (IsBridgeAbove(flat_tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

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

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

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

        TileArea dock_area = TileArea(slope_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);

        if (!Dock::CanAllocateItem()) return_cmd_error(STR_ERROR_TOO_MANY_DOCKS);

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

        if (flags & DC_EXEC) {
                /* Create the dock and insert it into the list of docks. */
                Dock *dock = new Dock(slope_tile, flat_tile);
                dock->next = st->docks;
                st->docks = dock;

                st->dock_station.Add(slope_tile);
                st->dock_station.Add(flat_tile);
                st->AddFacility(FACIL_DOCK, slope_tile);

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

                /* 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;
                DirtyCompanyInfrastructureWindows(st->owner);

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

                st->UpdateVirtCoord();
                UpdateStationAcceptance(st, false);
                st->RecomputeIndustriesNear();
                ZoningMarkDirtyStationCoverageArea(st);
                InvalidateWindowData(WC_SELECT_STATION, 0, 0);
                InvalidateWindowData(WC_STATION_LIST, st->owner, 0);
                SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_SHIPS);
        }

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

/**
 * Remove a dock
 * @param tile TileIndex been queried
 * @param flags operation to perform
 * @return cost or failure of operation
 */
static CommandCost RemoveDock(TileIndex tile, DoCommandFlag flags)
{
        Station *st = Station::GetByTile(tile);
        CommandCost ret = CheckOwnership(st->owner);
        if (ret.Failed()) return ret;

        Dock *removing_dock = Dock::GetByTile(tile);
        assert(removing_dock != NULL);

        TileIndex tile1 = removing_dock->sloped;
        TileIndex tile2 = removing_dock->flat;

        DiagDirection direction = DiagdirBetweenTiles(removing_dock->sloped, removing_dock->flat);
        TileIndex docking_location = removing_dock->flat + TileOffsByDiagDir(direction);

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

        if (flags & DC_EXEC) {
                st->catchment.AfterRemoveTile(tile1, CA_DOCK);
                st->catchment.AfterRemoveTile(tile2, CA_DOCK);
                ZoningMarkDirtyStationCoverageArea(st);

                if (st->docks == removing_dock) {
                        /* The first dock in the list is removed. */
                        st->docks = removing_dock->next;
                        /* Last dock is removed. */
                        if (st->docks == NULL) {
                                st->facilities &= ~FACIL_DOCK;
                        }
                } else {
                        /* Tell the predecessor in the list to skip this dock. */
                        Dock *pred = st->docks;
                        while (pred->next != removing_dock) pred = pred->next;
                        pred->next = removing_dock->next;
                }

                delete removing_dock;

                DoClearSquare(tile1);
                MarkTileDirtyByTile(tile1);
                MakeWaterKeepingClass(tile2, st->owner);

                if (Overlays::Instance()->HasStation(st)) st->MarkAcceptanceTilesDirty();
                st->rect.AfterRemoveTile(st, tile1);
                st->rect.AfterRemoveTile(st, tile2);

                st->dock_station.Clear();
                for (Dock *dock = st->docks; dock != NULL; dock = dock->next) {
                        st->dock_station.Add(dock->flat);
                        st->dock_station.Add(dock->sloped);
                }

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

                SetWindowWidgetDirty(WC_STATION_VIEW, st->index, WID_SV_SHIPS);
                st->UpdateVirtCoord();
                st->RecomputeIndustriesNear();
                DeleteStationIfEmpty(st);

                /* 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->dest_tile = 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];
}

/**
 * Check whether a sprite is a track sprite, which can be replaced by a non-track ground sprite and a rail overlay.
 * If the ground sprite is suitable, \a ground is replaced with the new non-track ground sprite, and \a overlay_offset
 * is set to the overlay to draw.
 * @param          ti             Positional info for the tile to decide snowyness etc. May be NULL.
 * @param [in,out] ground         Groundsprite to draw.
 * @param [out]    overlay_offset Overlay to draw.
 * @return true if overlay can be drawn.
 */
bool SplitGroundSpriteForOverlay(const TileInfo *ti, SpriteID *ground, RailTrackOffset *overlay_offset)
{
        bool snow_desert;
        switch (*ground) {
                case SPR_RAIL_TRACK_X:
                        snow_desert = false;
                        *overlay_offset = RTO_X;
                        break;

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

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

                case SPR_RAIL_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);
                        }
                }
        }

        DrawOverlay(ti, MP_STATION);

        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.IsType(OT_GOTO_WAYPOINT) && v->current_order.GetDestination() == station_id && v->current_order.GetWaypointFlags() & OWF_REVERSE) {
                        Train *t = Train::From(v);
                        // reverse at waypoint
                        if (t->reverse_distance == 0) t->reverse_distance = t->gcache.cached_total_length;
                }
                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;
}

/**
 * Run the watched cargo callback for all houses in the catchment area.
 * @param st Station.
 */
void TriggerWatchedCargoCallbacks(Station *st)
{
        /* Collect cargoes accepted since the last big tick. */
        uint 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);
                }
        }
}

/**
 * This function is called for each station once every 250 ticks.
 * Not all stations will get the tick at the same time.
 * @param st the station receiving the tick.
 * @return true if the station is still valid (wasn't deleted)
 */
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;
}

/**
 * Truncate the cargo by a specific amount.
 * @param cs The type of cargo to perform the truncation for.
 * @param ge The goods entry, of the station, to truncate.
 * @param amount The amount to truncate the cargo by.
 */
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()];
                uint source_avg_waiting = source_ge.cargo.AvailableCount() / max(1u, (uint)source_ge.cargo.Packets()->MapSize());

                if (i->second > source_avg_waiting) {
                        source_ge.max_waiting_cargo = i->second;
                        source_ge.punishment_triggered = true;
                }
        }
}

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 = max(1u, (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 / 1 as then
                         * INVALID_STATION is the only destination.
                         */
                        uint waiting_avg = waiting / num_dests;

                        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 - 15;
                                if (b >= 0) rating += b >> 2;

                                (rating -= 90, ge->max_waiting_cargo > 2000) ||
                                (rating += 52, ge->max_waiting_cargo > 1000) ||
                                (rating += 52, ge->max_waiting_cargo > 500) ||
                                (rating += 52, ge->max_waiting_cargo > 250) ||
                                (rating += 52, ge->max_waiting_cargo > 125) ||
                                (rating += 52, true);
                        }

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

                        byte age = ge->last_age;
                        (age >= 30) ||
                        (rating += 10, age >= 20) ||
                        (rating += 10, age >= 10) ||
                        (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. */
                                        TruncateCargo(cs, ge, ge->cargo.AvailableCount() - waiting);
                                }
                                
                                if (ge->punishment_triggered) {
                                        // We were punished by another station. Delay the update of waiting cargo until next rating.
                                        ge->punishment_in_effect = true;
                                        ge->punishment_triggered = false;
                                }
                                else
                                {
                                        ge->punishment_in_effect = false;
                                        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
        }
}

/**
 * Reroute cargo of type c at station st or in any vehicles unloading there.
 * Make sure the cargo's new next hop is neither "avoid" nor "avoid2".
 * @param st Station to be rerouted at.
 * @param c Type of cargo.
 * @param avoid Original next hop of cargo, avoid this.
 * @param avoid2 Another station to be avoided when rerouting.
 */
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 transfered. */
        for (Vehicle *v : st->loading_vehicles) {
                for (; v != NULL; v = v->Next()) {
                        if (v->cargo_type != c) continue;
                        v->cargo.Reroute(UINT_MAX, &v->cargo, avoid, avoid2, &ge);
                }
        }
}

/**
 * Check all next hops of cargo packets in this station for existance of a
 * a valid link they may use to travel on. Reroute any cargo not having a valid
 * link and remove timed out links found like this from the linkgraph. We're
 * not all links here as that is expensive and useless. A link no one is using
 * doesn't hurt either.
 * @param from Station to check.
 */
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 = max<uint>((LinkGraph::MIN_TIMEOUT_DISTANCE + (DistanceManhattan(from->xy, to->xy) >> 3)) / std::max<uint8>(_settings_game.economy.daylength, 1), 1);
                        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()) > max<uint>(LinkGraph::COMPRESSION_INTERVAL / std::max<uint>(_settings_game.economy.daylength, 1), 1)) {
                        lg->Compress();
                }
        }
}

/**
 * Increase capacity for a link stat given by station cargo and next hop.
 * @param st Station to get the link stats from.
 * @param cargo Cargo to increase stat for.
 * @param next_station_id Station the consist will be travelling to next.
 * @param capacity Capacity to add to link stat.
 * @param usage Usage to add to link stat.
 * @param mode Update mode to be applied.
 */
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);
        }
}

/* 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);
                }
        }
}

/** Daily loop for stations. */
void StationDailyLoop()
{
        // Only record cargo history every second day.
        if (_date % 2 != 0) {
                Station *st;

                FOR_ALL_STATIONS(st) {
                        st->UpdateCargoHistory();
                }
        }
}

/** Monthly loop for stations. */
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;
}

/**
 * Rename a station
 * @param tile unused
 * @param flags operation to perform
 * @param p1 station ID that is to be renamed
 * @param p2 unused
 * @param text the new name or an empty string when resetting to the default
 * @return the cost of this operation or an error
 */
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();
}

/**
 * Find all stations around a rectangular producer (industry, house, headquarter, ...)
 *
 * @param location The location/area of the producer
 * @param stations The list to store the stations in
 */
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);
                }
        }
}

/**
 * Run a tile loop to find stations around a tile, on demand. Cache the result for further requests
 * @return pointer to a StationList containing all stations found
 */
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->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, 1, 1, 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_station.tile = tile;
        st->facilities = FACIL_AIRPORT;

        if (!Dock::CanAllocateItem()) {
                DEBUG(misc, 0, "Can't allocate dock for oilrig at 0x%X, reverting to oilrig with airport only", tile);
        } else {
                st->docks = new Dock(tile, tile + ToTileIndexDiff({1, 0}));
                st->dock_station.tile = tile;
                st->facilities |= FACIL_DOCK;
        }

        st->build_date = _date;

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

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

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

        st->catchment.AfterRemoveTile(tile, st->GetCatchmentRadius());
        MakeWaterKeepingClass(tile, OWNER_NONE);

        st->dock_station.tile = INVALID_TILE;
        if (st->docks != NULL) {
                delete st->docks;
                st->docks = NULL;
        }
        st->airport.Clear();
        st->facilities &= ~(FACIL_AIRPORT | FACIL_DOCK);
        st->airport.flags = 0;

        if (Overlays::Instance()->HasStation(st)) st->MarkAcceptanceTilesDirty();
        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);
                }
        }
}

/**
 * Check if a drive-through road stop tile can be cleared.
 * Road stops built on town-owned roads check the conditions
 * that would allow clearing of the original road.
 * @param tile road stop tile to check
 * @param flags command flags
 * @return true if the road can be cleared
 */
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;
}

/**
 * Clear a single tile of a station.
 * @param tile The tile to clear.
 * @param flags The DoCommand flags related to the "command".
 * @return The cost, or error of clearing.
 */
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);
}

/**
 * Get flow for a station.
 * @param st Station to get flow for.
 * @return Flow for st.
 */
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;
}

/**
 * Get a station a package can be routed to, but exclude the given ones.
 * @param excluded StationID not to be selected.
 * @param excluded2 Another StationID not to be selected.
 * @return A station ID from the shares map.
 */
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;
}

/**
 * Reduce all flows to minimum capacity so that they don't get in the way of
 * link usage statistics too much. Keep them around, though, to continue
 * routing any remaining cargo.
 */
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);
}

/**
 * Change share for specified station. By specifing INT_MIN as parameter you
 * can erase a share. Newly added flows will be unrestricted.
 * @param st Next Hop to be removed.
 * @param flow Share to be added or removed.
 */
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);
}

/**
 * Restrict a flow by moving it to the end of the map and decreasing the amount
 * of unrestricted flow.
 * @param st Station of flow to be restricted.
 */
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());
}

/**
 * Release ("unrestrict") a flow by moving it to the begin of the map and
 * increasing the amount of unrestricted flow.
 * @param st Station of flow to be released.
 */
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());
}

/**
 * Scale all shares from link graph's runtime to monthly values.
 * @param runtime Time the link graph has been running without compression.
 * @pre runtime must be greater than 0 as we don't want infinite flow values.
 */
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);
}

/**
 * Add some flow from "origin", going via "via".
 * @param origin Origin of the flow.
 * @param via Next hop.
 * @param flow Amount of flow to be added.
 */
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());
        }
}

/**
 * Pass on some flow, remembering it as invalid, for later subtraction from
 * locally consumed flow. This is necessary because we can't have negative
 * flows and we don't want to sort the flows before adding them up.
 * @param origin Origin of the flow.
 * @param via Next hop.
 * @param flow Amount of flow to be passed.
 */
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());
        }
}

/**
 * Subtract invalid flows from locally consumed flow.
 * @param self ID of own station.
 */
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());
        }
}

/**
 * Delete all flows at a station for specific cargo and destination.
 * @param via Remote station of flows to be deleted.
 * @return IDs of source stations for which the complete FlowStat, not only a
 *         share, has been erased.
 */
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;
}

/**
 * Restrict all flows at a station for specific cargo and destination.
 * @param via Remote station of flows to be restricted.
 */
void FlowStatMap::RestrictFlows(StationID via)
{
        for (FlowStatMap::iterator it = this->begin(); it != this->end(); ++it) {
                it->second.RestrictShare(via);
        }
}

/**
 * Release all flows at a station for specific cargo and destination.
 * @param via Remote station of flows to be released.
 */
void FlowStatMap::ReleaseFlows(StationID via)
{
        for (FlowStatMap::iterator it = this->begin(); it != this->end(); ++it) {
                it->second.ReleaseShare(via);
        }
}

/**
 * Get the sum of all flows from this FlowStatMap.
 * @return sum of all flows.
 */
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;
}

/**
 * Get the sum of flows via a specific station from this FlowStatMap.
 * @param via Remote station to look for.
 * @return all flows for 'via' added up.
 */
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;
}

/**
 * Get the sum of flows from a specific station from this FlowStatMap.
 * @param from Origin station to look for.
 * @return all flows from 'from' added up.
 */
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;
}

/**
 * Get the flow from a specific station via a specific other station.
 * @param from Origin station to look for.
 * @param via Remote station to look for.
 * @return flow share originating at 'from' and going to 'via'.
 */
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
};