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[openttd/fttd.git] / src / newgrf_station.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 newgrf_station.cpp Functions for dealing with station classes and custom stations. */

#include "stdafx.h"
#include "debug.h"
#include "station_base.h"
#include "waypoint_base.h"
#include "roadstop_base.h"
#include "newgrf_cargo.h"
#include "newgrf_station.h"
#include "newgrf_spritegroup.h"
#include "newgrf_sound.h"
#include "newgrf_railtype.h"
#include "town.h"
#include "newgrf_town.h"
#include "company_func.h"
#include "map/slope.h"
#include "newgrf_animation_base.h"
#include "newgrf_class_func.h"
#include "tile_cmd.h"
#include "station_func.h"


template <>
/* static */ void NewGRFClass <StationSpec, StationClassID, STAT_CLASS_MAX>::InsertDefaults()
{
        /* Set up initial data */
        classes[0].global_id = 'DFLT';
        classes[0].name = STR_STATION_CLASS_DFLT;
        classes[0].Insert(NULL);

        classes[1].global_id = 'WAYP';
        classes[1].name = STR_STATION_CLASS_WAYP;
        classes[1].Insert(NULL);
}

template <>
bool NewGRFClass <StationSpec, StationClassID, STAT_CLASS_MAX>::IsUIAvailable (uint index) const
{
        return true;
}

INSTANTIATE_NEWGRF_CLASS_METHODS(StationClass)

static const uint NUM_STATIONSSPECS_PER_STATION = 255; ///< Maximum number of parts per station.

enum TriggerArea {
        TA_TILE,
        TA_PLATFORM,
        TA_WHOLE,
};

struct ETileArea : TileArea {
        ETileArea(const BaseStation *st, TileIndex tile, TriggerArea ta)
        {
                switch (ta) {
                        default: NOT_REACHED();

                        case TA_TILE:
                                this->tile = tile;
                                this->w    = 1;
                                this->h    = 1;
                                break;

                        case TA_PLATFORM: {
                                TileIndex start, end;
                                Axis axis = GetRailStationAxis(tile);
                                TileIndexDiff delta = TileOffsByDiagDir(AxisToDiagDir(axis));

                                for (end = tile; IsRailStationTile(end + delta) && IsCompatibleTrainStationTile(end + delta, tile); end += delta) { /* Nothing */ }
                                for (start = tile; IsRailStationTile(start - delta) && IsCompatibleTrainStationTile(start - delta, tile); start -= delta) { /* Nothing */ }

                                this->tile = start;
                                this->w = TileX(end) - TileX(start) + 1;
                                this->h = TileY(end) - TileY(start) + 1;
                                break;
                        }

                        case TA_WHOLE:
                                st->GetTileArea(this, st->IsWaypoint() ? STATION_WAYPOINT : STATION_RAIL);
                                break;
                }
        }
};


/**
 * Evaluate a tile's position within a station, and return the result in a bit-stuffed format.
 * if not centered: .TNLcCpP, if centered: .TNL..CP
 * - T = Tile layout number (#GetStationGfx)
 * - N = Number of platforms
 * - L = Length of platforms
 * - C = Current platform number from start, c = from end
 * - P = Position along platform from start, p = from end
 * .
 * if centered, C/P start from the centre and c/p are not available.
 * @return Platform information in bit-stuffed format.
 */
uint32 GetPlatformInfo(Axis axis, byte tile, int platforms, int length, int x, int y, bool centred)
{
        uint32 retval = 0;

        if (axis == AXIS_X) {
                Swap(platforms, length);
                Swap(x, y);
        }

        if (centred) {
                x -= platforms / 2;
                y -= length / 2;
                x = Clamp(x, -8, 7);
                y = Clamp(y, -8, 7);
                SB(retval,  0, 4, y & 0xF);
                SB(retval,  4, 4, x & 0xF);
        } else {
                SB(retval,  0, 4, min(15, y));
                SB(retval,  4, 4, min(15, length - y - 1));
                SB(retval,  8, 4, min(15, x));
                SB(retval, 12, 4, min(15, platforms - x - 1));
        }
        SB(retval, 16, 4, min(15, length));
        SB(retval, 20, 4, min(15, platforms));
        SB(retval, 24, 4, tile);

        return retval;
}


/**
 * Find the end of a railway station, from the \a tile, in the direction of \a delta.
 * @param tile Start tile.
 * @param delta Movement direction.
 * @param check_type Stop when the custom station type changes.
 * @param check_axis Stop when the station direction changes.
 * @return Found end of the railway station.
 */
static TileIndex FindRailStationEnd(TileIndex tile, TileIndexDiff delta, bool check_type, bool check_axis)
{
        byte orig_type = 0;
        Axis orig_axis = AXIS_X;
        StationID sid = GetStationIndex(tile);

        if (check_type) orig_type = GetCustomStationSpecIndex(tile);
        if (check_axis) orig_axis = GetRailStationAxis(tile);

        for (;;) {
                TileIndex new_tile = TILE_ADD(tile, delta);

                if (!IsStationTile(new_tile) || GetStationIndex(new_tile) != sid) break;
                if (!HasStationRail(new_tile)) break;
                if (check_type && GetCustomStationSpecIndex(new_tile) != orig_type) break;
                if (check_axis && GetRailStationAxis(new_tile) != orig_axis) break;

                tile = new_tile;
        }
        return tile;
}


static uint32 GetPlatformInfoHelper(TileIndex tile, bool check_type, bool check_axis, bool centred)
{
        int tx = TileX(tile);
        int ty = TileY(tile);
        int sx = TileX(FindRailStationEnd(tile, TileDiffXY(-1,  0), check_type, check_axis));
        int sy = TileY(FindRailStationEnd(tile, TileDiffXY( 0, -1), check_type, check_axis));
        int ex = TileX(FindRailStationEnd(tile, TileDiffXY( 1,  0), check_type, check_axis)) + 1;
        int ey = TileY(FindRailStationEnd(tile, TileDiffXY( 0,  1), check_type, check_axis)) + 1;

        tx -= sx; ex -= sx;
        ty -= sy; ey -= sy;

        return GetPlatformInfo(GetRailStationAxis(tile), GetStationGfx(tile), ex, ey, tx, ty, centred);
}


static uint32 GetRailContinuationInfo(TileIndex tile)
{
        struct DataPair {
                Direction dir;
                DiagDirection exit;
        };

        /* Tile offsets and exit dirs for X axis */
        static const DataPair data_x[8] = {
                { DIR_SW, DIAGDIR_SW },
                { DIR_NE, DIAGDIR_NE },
                { DIR_SE, DIAGDIR_SE },
                { DIR_NW, DIAGDIR_NW },
                { DIR_S,  DIAGDIR_SW },
                { DIR_E,  DIAGDIR_NE },
                { DIR_W,  DIAGDIR_SW },
                { DIR_N,  DIAGDIR_NE },
        };

        /* Tile offsets and exit dirs for Y axis */
        static const DataPair data_y[8] = {
                { DIR_SE, DIAGDIR_SE },
                { DIR_NW, DIAGDIR_NW },
                { DIR_SW, DIAGDIR_SW },
                { DIR_NE, DIAGDIR_NE },
                { DIR_S,  DIAGDIR_SE },
                { DIR_W,  DIAGDIR_NW },
                { DIR_E,  DIAGDIR_SE },
                { DIR_N,  DIAGDIR_NW },
        };

        Axis axis = GetRailStationAxis(tile);

        /* Choose appropriate lookup table to use */
        const DataPair *data = (axis == AXIS_X) ? data_x : data_y;

        uint32 res = 0;
        for (uint i = 0; i < lengthof(data_x); i++, data++) {
                TileIndex neighbour_tile = tile + TileOffsByDir (data->dir);
                TrackBits trackbits = TrackStatusToTrackBits(GetTileRailwayStatus(neighbour_tile));
                if (trackbits != TRACK_BIT_NONE) {
                        /* If there is any track on the tile, set the bit in the second byte */
                        SetBit(res, i + 8);

                        /* With tunnels and bridges the tile has tracks, but they are not necessarily connected
                         * with the next tile because the ramp is not going in the right direction. */
                        if (IsTunnelTile (neighbour_tile)) {
                                if (GetTunnelBridgeDirection (neighbour_tile) != data->exit) {
                                        continue;
                                }
                        } else if (IsBridgeHeadTile (neighbour_tile)) {
                                if (GetTunnelBridgeDirection (neighbour_tile) == ReverseDiagDir (data->exit)) {
                                        continue;
                                }
                        }

                        /* If any track reaches our exit direction, set the bit in the lower byte */
                        if (trackbits & DiagdirReachesTracks(data->exit)) SetBit(res, i);
                }
        }

        return res;
}


/* Station Resolver Functions */
/* virtual */ uint32 StationScopeResolver::GetRandomBits() const
{
        return this->st->random_bits | (this->tile == INVALID_TILE ? 0 : GetStationTileRandomBits (this->tile) << 16);
}


/* virtual */ uint32 StationScopeResolver::GetTriggers() const
{
        return this->st->waiting_triggers;
}


/* virtual */ void StationScopeResolver::SetTriggers(int triggers) const
{
        BaseStation *st = const_cast<BaseStation *>(this->st);
        assert(st != NULL);
        st->waiting_triggers = triggers;
}

/**
 * Station variable cache
 * This caches 'expensive' station variable lookups which iterate over
 * several tiles that may be called multiple times per Resolve().
 */
static struct {
        uint32 v40;
        uint32 v41;
        uint32 v45;
        uint32 v46;
        uint32 v47;
        uint32 v49;
        uint8 valid; ///< Bits indicating what variable is valid (for each bit, \c 0 is invalid, \c 1 is valid).
} _svc;

/**
 * Get the town scope associated with a station, if it exists.
 * On the first call, the town scope is created (if possible).
 * @return Town scope, if available.
 */
TownScopeResolver *StationResolverObject::GetTown()
{
        if (this->town_scope == NULL) {
                Town *t = this->station_scope.st->town;
                if (t == NULL) return NULL;
                this->town_scope = new TownScopeResolver (this->grffile, t, false);
        }
        return this->town_scope;
}

/* virtual */ uint32 StationScopeResolver::GetVariable(byte variable, uint32 parameter, bool *available) const
{
        switch (variable) {
                /* Calculated station variables */
                case 0x40:
                        if (!HasBit(_svc.valid, 0)) { _svc.v40 = GetPlatformInfoHelper(this->tile, false, false, false); SetBit(_svc.valid, 0); }
                        return _svc.v40;

                case 0x41:
                        if (!HasBit(_svc.valid, 1)) { _svc.v41 = GetPlatformInfoHelper(this->tile, true,  false, false); SetBit(_svc.valid, 1); }
                        return _svc.v41;

                case 0x42: return GetTerrainType(this->tile) | (GetReverseRailTypeTranslation(GetRailType(this->tile), this->statspec->grf_prop.grffile) << 8);
                case 0x43: return GetCompanyInfo(this->st->owner); // Station owner
                case 0x44: return HasStationReservation(this->tile) ? 7 : 4; // PBS status
                case 0x45:
                        if (!HasBit(_svc.valid, 2)) { _svc.v45 = GetRailContinuationInfo(this->tile); SetBit(_svc.valid, 2); }
                        return _svc.v45;

                case 0x46:
                        if (!HasBit(_svc.valid, 3)) { _svc.v46 = GetPlatformInfoHelper(this->tile, false, false, true); SetBit(_svc.valid, 3); }
                        return _svc.v46;

                case 0x47:
                        if (!HasBit(_svc.valid, 4)) { _svc.v47 = GetPlatformInfoHelper(this->tile, true,  false, true); SetBit(_svc.valid, 4); }
                        return _svc.v47;

                case 0x49:
                        if (!HasBit(_svc.valid, 5)) { _svc.v49 = GetPlatformInfoHelper(this->tile, false, true, false); SetBit(_svc.valid, 5); }
                        return _svc.v49;

                case 0x4A: // Animation frame of tile
                        return GetAnimationFrame(this->tile);

                /* Variables which use the parameter */
                /* Variables 0x60 to 0x65 and 0x69 are handled separately below */
                case 0x66: { // Animation frame of nearby tile
                        TileIndex tile = this->tile;
                        if (parameter != 0) tile = GetNearbyTile(parameter, tile);
                        return this->st->TileBelongsToRailStation(tile) ? GetAnimationFrame(tile) : UINT_MAX;
                }

                case 0x67: { // Land info of nearby tile
                        Axis axis = GetRailStationAxis(this->tile);
                        TileIndex tile = this->tile;
                        if (parameter != 0) tile = GetNearbyTile(parameter, tile); // only perform if it is required

                        Slope tileh = GetTileSlope(tile);
                        bool swap = (axis == AXIS_Y && HasBit(tileh, CORNER_W) != HasBit(tileh, CORNER_E));

                        return GetNearbyTileInformation (tile, this->grffile->grf_version >= 8) ^ (swap ? SLOPE_EW : 0);
                }

                case 0x68: { // Station info of nearby tiles
                        TileIndex nearby_tile = GetNearbyTile(parameter, this->tile);

                        if (!HasStationTileRail(nearby_tile)) return 0xFFFFFFFF;

                        uint32 grfid = this->st->speclist[GetCustomStationSpecIndex(this->tile)].grfid;
                        bool perpendicular = GetRailStationAxis(this->tile) != GetRailStationAxis(nearby_tile);
                        bool same_station = this->st->TileBelongsToRailStation(nearby_tile);
                        uint32 res = GB(GetStationGfx(nearby_tile), 1, 2) << 12 | !!perpendicular << 11 | !!same_station << 10;

                        uint spec_index = GetCustomStationSpecIndex (nearby_tile);
                        if (spec_index != 0) {
                                const StationSpecList ssl = BaseStation::GetByTile(nearby_tile)->speclist[spec_index];
                                res |= 1 << (ssl.grfid != grfid ? 9 : 8) | ssl.localidx;
                        }
                        return res;
                }

                /* General station variables */
                case 0x82: return 50;
                case 0x84: return this->st->string_id;
                case 0x86: return 0;
                case 0xF0: return this->st->facilities;
                case 0xFA: return Clamp(this->st->build_date - DAYS_TILL_ORIGINAL_BASE_YEAR, 0, 65535);
        }

        return this->st->GetNewGRFVariable (this->grffile, variable, parameter, available);
}

uint32 Station::GetNewGRFVariable (const GRFFile *grffile, byte variable, byte parameter, bool *available) const
{
        switch (variable) {
                case 0x48: { // Accepted cargo types
                        CargoID cargo_type;
                        uint32 value = 0;

                        for (cargo_type = 0; cargo_type < NUM_CARGO; cargo_type++) {
                                if (HasBit(this->goods[cargo_type].status, GoodsEntry::GES_ACCEPTANCE)) SetBit(value, cargo_type);
                        }
                        return value;
                }

                case 0x8A: return this->had_vehicle_of_type;
                case 0xF1: return (this->airport.tile != INVALID_TILE) ? this->airport.GetSpec()->ttd_airport_type : ATP_TTDP_LARGE;
                case 0xF2: return (this->truck_stops != NULL) ? this->truck_stops->status : 0;
                case 0xF3: return (this->bus_stops != NULL)   ? this->bus_stops->status   : 0;
                case 0xF6: return this->airport.flags;
                case 0xF7: return GB(this->airport.flags, 8, 8);
        }

        /* Handle cargo variables with parameter, 0x60 to 0x65 and 0x69 */
        if ((variable >= 0x60 && variable <= 0x65) || variable == 0x69) {
                CargoID c = GetCargoTranslation (parameter, grffile);

                if (c == CT_INVALID) {
                        switch (variable) {
                                case 0x62: return 0xFFFFFFFF;
                                case 0x64: return 0xFF00;
                                default:   return 0;
                        }
                }
                const GoodsEntry *ge = &this->goods[c];

                switch (variable) {
                        case 0x60: return min(ge->cargo.TotalCount(), 4095);
                        case 0x61: return ge->HasVehicleEverTriedLoading() ? ge->time_since_pickup : 0;
                        case 0x62: return ge->HasRating() ? ge->rating : 0xFFFFFFFF;
                        case 0x63: return ge->cargo.DaysInTransit();
                        case 0x64: return ge->HasVehicleEverTriedLoading() ? ge->last_speed | (ge->last_age << 8) : 0xFF00;
                        case 0x65: return GB(ge->status, GoodsEntry::GES_ACCEPTANCE, 1) << 3;
                        case 0x69: {
                                assert_compile((int)GoodsEntry::GES_EVER_ACCEPTED + 1 == (int)GoodsEntry::GES_LAST_MONTH);
                                assert_compile((int)GoodsEntry::GES_EVER_ACCEPTED + 2 == (int)GoodsEntry::GES_CURRENT_MONTH);
                                assert_compile((int)GoodsEntry::GES_EVER_ACCEPTED + 3 == (int)GoodsEntry::GES_ACCEPTED_BIGTICK);
                                return GB(ge->status, GoodsEntry::GES_EVER_ACCEPTED, 4);
                        }
                }
        }

        /* Handle cargo variables (deprecated) */
        if (variable >= 0x8C && variable <= 0xEC) {
                const GoodsEntry *g = &this->goods[GB(variable - 0x8C, 3, 4)];
                switch (GB(variable - 0x8C, 0, 3)) {
                        case 0: return g->cargo.TotalCount();
                        case 1: return GB(min(g->cargo.TotalCount(), 4095), 0, 4) | (GB(g->status, GoodsEntry::GES_ACCEPTANCE, 1) << 7);
                        case 2: return g->time_since_pickup;
                        case 3: return g->rating;
                        case 4: return g->cargo.Source();
                        case 5: return g->cargo.DaysInTransit();
                        case 6: return g->last_speed;
                        case 7: return g->last_age;
                }
        }

        DEBUG(grf, 1, "Unhandled station variable 0x%X", variable);

        *available = false;
        return UINT_MAX;
}

uint32 Waypoint::GetNewGRFVariable (const GRFFile *grffile, byte variable, byte parameter, bool *available) const
{
        switch (variable) {
                case 0x48: return 0; // Accepted cargo types
                case 0x8A: return HVOT_WAYPOINT;
                case 0xF1: return 0; // airport type
                case 0xF2: return 0; // truck stop status
                case 0xF3: return 0; // bus stop status
                case 0xF6: return 0; // airport flags
                case 0xF7: return 0; // airport flags cont.
        }

        /* Handle cargo variables with parameter, 0x60 to 0x65 */
        if (variable >= 0x60 && variable <= 0x65) {
                return 0;
        }

        /* Handle cargo variables (deprecated) */
        if (variable >= 0x8C && variable <= 0xEC) {
                switch (GB(variable - 0x8C, 0, 3)) {
                        case 3: return INITIAL_STATION_RATING;
                        case 4: return INVALID_STATION;
                        default: return 0;
                }
        }

        DEBUG(grf, 1, "Unhandled station variable 0x%X", variable);

        *available = false;
        return UINT_MAX;
}

/* virtual */ const SpriteGroup *StationResolverObject::ResolveReal(const RealSpriteGroup *group) const
{
        if (this->station_scope.statspec->cls_id == STAT_CLASS_WAYP) {
                return group->get_first (true);
        }

        uint cargo = 0;
        const Station *st = Station::From(this->station_scope.st);

        switch (this->station_scope.cargo_type) {
                case CT_INVALID:
                case CT_DEFAULT_NA:
                case CT_PURCHASE:
                        cargo = 0;
                        break;

                case CT_DEFAULT:
                        for (CargoID cargo_type = 0; cargo_type < NUM_CARGO; cargo_type++) {
                                cargo += st->goods[cargo_type].cargo.TotalCount();
                        }
                        break;

                default:
                        cargo = st->goods[this->station_scope.cargo_type].cargo.TotalCount();
                        break;
        }

        if (HasBit(this->station_scope.statspec->flags, SSF_DIV_BY_STATION_SIZE)) cargo /= (st->train_station.w + st->train_station.h);
        cargo = min(0xfff, cargo);

        uint threshold = this->station_scope.statspec->cargo_threshold;
        if (cargo > threshold) {
                uint count = group->get_count (true);
                if (count > 0) {
                        uint set = ((cargo - threshold) * count) / (4096 - threshold);
                        return group->get_group (true, set);
                }
        } else {
                uint count = group->get_count (false);
                if (count > 0) {
                        uint set = (cargo * count) / (threshold + 1);
                        return group->get_group (false, set);
                }
        }

        return group->get_first (false);
}

/**
 * Resolver for stations.
 * @param statspec Station (type) specification.
 * @param st Instance of the station.
 * @param tile %Tile of the station.
 * @param callback Callback ID.
 * @param callback_param1 First parameter (var 10) of the callback.
 * @param callback_param2 Second parameter (var 18) of the callback.
 */
StationResolverObject::StationResolverObject(const StationSpec *statspec, BaseStation *st, TileIndex tile,
                CallbackID callback, uint32 callback_param1, uint32 callback_param2)
        : ResolverObject(statspec->grf_prop.grffile, callback, callback_param1, callback_param2),
          station_scope (this->grffile, statspec, st, tile), town_scope(NULL)
{
        assert (st != NULL);

        /* Invalidate all cached vars */
        _svc.valid = 0;

        CargoID ctype = CT_DEFAULT_NA;

        if (!this->station_scope.st->IsWaypoint()) {
                const Station *st = Station::From(this->station_scope.st);
                /* Pick the first cargo that we have waiting */
                const CargoSpec *cs;
                FOR_ALL_CARGOSPECS(cs) {
                        if (this->station_scope.statspec->grf_prop.spritegroup[cs->Index()] != NULL &&
                                        st->goods[cs->Index()].cargo.TotalCount() > 0) {
                                ctype = cs->Index();
                                break;
                        }
                }
        }

        if (this->station_scope.statspec->grf_prop.spritegroup[ctype] == NULL) {
                ctype = CT_DEFAULT;
        }

        /* Remember the cargo type we've picked */
        this->station_scope.cargo_type = ctype;
        this->root_spritegroup = this->station_scope.statspec->grf_prop.spritegroup[this->station_scope.cargo_type];
}

StationResolverObject::~StationResolverObject()
{
        delete this->town_scope;
}

/**
 * Constructor for station scopes.
 * @param grffile GRFFile the resolved SpriteGroup belongs to.
 * @param statspec Station (type) specification.
 * @param st Instance of the station.
 * @param tile %Tile of the station.
 */
StationScopeResolver::StationScopeResolver (const GRFFile *grffile, const StationSpec *statspec, BaseStation *st, TileIndex tile)
        : ScopeResolver(), grffile(grffile)
{
        assert (st != NULL);

        this->tile = tile;
        this->st = st;
        this->statspec = statspec;
        this->cargo_type = CT_INVALID;
}


/** Scope resolver for stations not yet built. */
struct FakeStationScopeResolver : public ScopeResolver {
        const GRFFile *const grffile;       ///< GRFFile the resolved SpriteGroup belongs to.
        TileIndex tile;                     ///< %Tile of the station.
        const struct StationSpec *statspec; ///< Station (type) specification.
        RailType railtype;                  ///< Rail type.
        Axis axis;                          ///< Station axis, used only for the slope check callback.

        FakeStationScopeResolver (const GRFFile *grffile, const StationSpec *statspec,
                        TileIndex tile, RailType rt, Axis axis = INVALID_AXIS)
                : ScopeResolver(), grffile(grffile), tile(tile),
                  statspec(statspec), railtype(rt), axis(axis)
        {
        }

        uint32 GetVariable (byte variable, uint32 parameter, bool *available) const OVERRIDE;
};

uint32 FakeStationScopeResolver::GetVariable (byte variable, uint32 parameter, bool *available) const
{
        /* Station does not exist, so we're in a purchase list or the land slope check callback. */
        switch (variable) {
                case 0x40:
                case 0x41:
                case 0x46:
                case 0x47:
                case 0x49: return 0x2110000;        // Platforms, tracks & position
                case 0x42: return GetReverseRailTypeTranslation (this->railtype, this->statspec->grf_prop.grffile) << 8;
                case 0x43: return GetCompanyInfo (_current_company); // Station owner
                case 0x44: return 2;                // PBS status
                case 0x67: // Land info of nearby tile
                        if (this->axis != INVALID_AXIS && this->tile != INVALID_TILE) {
                                TileIndex tile = this->tile;
                                if (parameter != 0) tile = GetNearbyTile (parameter, tile, true, this->axis); // only perform if it is required

                                Slope tileh = GetTileSlope(tile);
                                bool swap = (this->axis == AXIS_Y && HasBit(tileh, CORNER_W) != HasBit(tileh, CORNER_E));

                                return GetNearbyTileInformation (tile, this->grffile->grf_version >= 8) ^ (swap ? SLOPE_EW : 0);
                        }
                        break;

                case 0xFA: return Clamp (_date - DAYS_TILL_ORIGINAL_BASE_YEAR, 0, 65535); // Build date, clamped to a 16 bit value
        }

        *available = false;
        return UINT_MAX;
}

/** Resolver for stations not yet built. */
struct FakeStationResolverObject : public ResolverObject {
        FakeStationScopeResolver station_scope; ///< The station scope resolver.
        TownScopeResolver *town_scope;      ///< The town scope resolver (created on the first call).

        const SpriteGroup *root_spritegroup; ///< Root SpriteGroup to use for resolving

        /**
         * Resolver for stations not yet built.
         * @param statspec Station (type) specification.
         * @param tile %Tile of the station.
         * @param rt Rail type.
         * @param callback Callback ID.
         * @param callback_param1 First parameter (var 10) of the callback.
         * @param callback_param2 Second parameter (var 18) of the callback.
         * @param axis Axis of the station tile to build, if any.
         */
        FakeStationResolverObject (const StationSpec *statspec, TileIndex tile,
                        RailType rt, CallbackID callback = CBID_NO_CALLBACK,
                        uint32 callback_param1 = 0, uint32 callback_param2 = 0,
                        Axis axis = INVALID_AXIS)
                : ResolverObject (statspec->grf_prop.grffile,
                        callback, callback_param1, callback_param2),
                  station_scope (this->grffile, statspec, tile, rt, axis),
                  town_scope (NULL)
        {
                /* Invalidate all cached vars */
                _svc.valid = 0;

                /* No station, so we are in a purchase list */
                const SpriteGroup *const *groups = statspec->grf_prop.spritegroup;
                const SpriteGroup *root = groups[CT_PURCHASE];

                if (root == NULL) {
                        root = groups[CT_DEFAULT];
                }

                this->root_spritegroup = root;
        }

        ~FakeStationResolverObject();

        TownScopeResolver *GetTown (void);

        ScopeResolver *GetScope (VarSpriteGroupScope scope = VSG_SCOPE_SELF, byte relative = 0) OVERRIDE
        {
                switch (scope) {
                        case VSG_SCOPE_SELF:
                                return &this->station_scope;

                        case VSG_SCOPE_PARENT: {
                                TownScopeResolver *tsr = this->GetTown();
                                if (tsr != NULL) return tsr;
                                /* FALL-THROUGH */
                        }

                        default:
                                return ResolverObject::GetScope (scope, relative);
                }
        }

        const SpriteGroup *ResolveReal (const RealSpriteGroup *group) const OVERRIDE
        {
                return group->get_first (true);
        }

        /**
         * Resolve SpriteGroup.
         * @return Result spritegroup.
         */
        const SpriteGroup *Resolve (void)
        {
                return SpriteGroup::Resolve (this->root_spritegroup, *this);
        }
};

FakeStationResolverObject::~FakeStationResolverObject()
{
        delete this->town_scope;
}

/**
 * Get the town scope associated with a station, if it exists.
 * On the first call, the town scope is created (if possible).
 * @return Town scope, if available.
 */
TownScopeResolver *FakeStationResolverObject::GetTown (void)
{
        if (this->town_scope == NULL) {
                Town *t = NULL;
                if (this->station_scope.tile != INVALID_TILE) {
                        t = ClosestTownFromTile(this->station_scope.tile);
                }
                if (t == NULL) return NULL;
                this->town_scope = new TownScopeResolver (this->grffile, t, true);
        }
        return this->town_scope;
}


/**
 * Resolve sprites for drawing a station tile.
 * @param statspec Station spec
 * @param st Station
 * @param tile Station tile being drawn
 * @param var10 Value to put in variable 10; normally 0; 1 when resolving the groundsprite and SSF_SEPARATE_GROUND is set.
 * @return First sprite of the Action 1 spriteset to use, minus an offset of 0x42D to accommodate for weird NewGRF specs.
 */
SpriteID GetCustomStationRelocation(const StationSpec *statspec, BaseStation *st, TileIndex tile, uint32 var10)
{
        assert (st != NULL);
        StationResolverObject object(statspec, st, tile, CBID_NO_CALLBACK, var10);
        const SpriteGroup *group = object.Resolve();
        if (group == NULL || !group->IsType (SGT_RESULT)) return 0;
        return group->GetResult() - 0x42D;
}

/**
 * Resolve sprites for drawing a station tile in the GUI.
 * @param statspec Station spec
 * @param rt Rail type.
 * @param var10 Value to put in variable 10; normally 0; 1 when resolving the groundsprite and SSF_SEPARATE_GROUND is set.
 * @return First sprite of the Action 1 spriteset to use, minus an offset of 0x42D to accommodate for weird NewGRF specs.
 */
static SpriteID GetCustomStationRelocation (const StationSpec *statspec,
        RailType rt, uint32 var10)
{
        FakeStationResolverObject object (statspec, INVALID_TILE, rt, CBID_NO_CALLBACK, var10);
        const SpriteGroup *group = object.Resolve();
        if (group == NULL || !group->IsType (SGT_RESULT)) return 0;
        return group->GetResult() - 0x42D;
}

/**
 * Resolve the sprites for custom station foundations.
 * @param statspec Station spec
 * @param st Station
 * @param tile Station tile being drawn
 * @param layout Spritelayout as returned by previous callback
 * @param edge_info Information about northern tile edges; whether they need foundations or merge into adjacent tile's foundations.
 * @return First sprite of a set of foundation sprites for various slopes, or 0 if default foundations shall be drawn.
 */
SpriteID GetCustomStationFoundationRelocation(const StationSpec *statspec, BaseStation *st, TileIndex tile, uint layout, uint edge_info)
{
        /* callback_param1 == 2 means  we are resolving the foundation sprites. */
        StationResolverObject object(statspec, st, tile, CBID_NO_CALLBACK, 2, layout | (edge_info << 16));

        const SpriteGroup *group = object.Resolve();
        if (group == NULL || !group->IsType (SGT_RESULT)) return 0;

        /* Note: SpriteGroup::Resolve zeroes all registers, so register 0x100 is initialised to 0. (compatibility) */
        return group->GetResult() + GetRegister(0x100);
}


uint16 GetStationCallback(CallbackID callback, uint32 param1, uint32 param2, const StationSpec *statspec, BaseStation *st, TileIndex tile)
{
        assert (st != NULL);
        StationResolverObject object(statspec, st, tile, callback, param1, param2);
        return SpriteGroup::CallbackResult (object.Resolve());
}

uint16 GetStationCallback (CallbackID callback, uint32 param1, uint32 param2,
        const StationSpec *statspec, RailType rt, TileIndex tile)
{
        FakeStationResolverObject object (statspec, tile, rt, callback, param1, param2);
        return SpriteGroup::CallbackResult (object.Resolve());
}

/**
 * Check the slope of a tile of a new station.
 * @param north_tile Norther tile of the station rect.
 * @param cur_tile Tile to check.
 * @param statspec Station spec.
 * @param rt Rail type.
 * @param axis Axis of the new station.
 * @param plat_len Platform length.
 * @param numtracks Number of platforms.
 * @return Succeeded or failed command.
 */
CommandCost PerformStationTileSlopeCheck (TileIndex north_tile,
        TileIndex cur_tile, const StationSpec *statspec, RailType rt,
        Axis axis, byte plat_len, byte numtracks)
{
        TileIndexDiff diff = cur_tile - north_tile;
        Slope slope = GetTileSlope(cur_tile);

        FakeStationResolverObject object (statspec, cur_tile, rt, CBID_STATION_LAND_SLOPE_CHECK,
                        (slope << 4) | (slope ^ (axis == AXIS_Y && HasBit(slope, CORNER_W) != HasBit(slope, CORNER_E) ? SLOPE_EW : 0)),
                        (numtracks << 24) | (plat_len << 16) | (axis == AXIS_Y ? TileX(diff) << 8 | TileY(diff) : TileY(diff) << 8 | TileX(diff)),
                        axis);

        uint16 cb_res = SpriteGroup::CallbackResult (object.Resolve());

        /* Failed callback means success. */
        if (cb_res == CALLBACK_FAILED) return CommandCost();

        /* The meaning of bit 10 is inverted for a grf version < 8. */
        if (statspec->grf_prop.grffile->grf_version < 8) ToggleBit(cb_res, 10);
        return GetErrorMessageFromLocationCallbackResult(cb_res, statspec->grf_prop.grffile, STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
}


/**
 * Allocate a StationSpec to a Station. This is called once per build operation.
 * @param statspec StationSpec to allocate.
 * @param st Station to allocate it to.
 * @param exec Whether to actually allocate the spec.
 * @return Index within the Station's spec list, or -1 if the allocation failed.
 */
int AllocateSpecToStation(const StationSpec *statspec, BaseStation *st, bool exec)
{
        uint i;

        if (statspec == NULL || st == NULL) return 0;

        for (i = 1; i < st->num_specs && i < NUM_STATIONSSPECS_PER_STATION; i++) {
                if (st->speclist[i].spec == NULL && st->speclist[i].grfid == 0) break;
        }

        if (i == NUM_STATIONSSPECS_PER_STATION) {
                /* As final effort when the spec list is already full...
                 * try to find the same spec and return that one. This might
                 * result in slightly "wrong" (as per specs) looking stations,
                 * but it's fairly unlikely that one reaches the limit anyways.
                 */
                for (i = 1; i < st->num_specs && i < NUM_STATIONSSPECS_PER_STATION; i++) {
                        if (st->speclist[i].spec == statspec) return i;
                }

                return -1;
        }

        if (exec) {
                if (i >= st->num_specs) {
                        st->num_specs = i + 1;
                        st->speclist = xrealloct (st->speclist, st->num_specs);

                        if (st->num_specs == 2) {
                                /* Initial allocation */
                                st->speclist[0].spec     = NULL;
                                st->speclist[0].grfid    = 0;
                                st->speclist[0].localidx = 0;
                        }
                }

                st->speclist[i].spec     = statspec;
                st->speclist[i].grfid    = statspec->grf_prop.grffile->grfid;
                st->speclist[i].localidx = statspec->grf_prop.local_id;

                StationUpdateCachedTriggers(st);
        }

        return i;
}


/**
 * Deallocate a StationSpec from a Station. Called when removing a single station tile.
 * @param st Station to work with.
 * @param specindex Index of the custom station within the Station's spec list.
 * @return Indicates whether the StationSpec was deallocated.
 */
void DeallocateSpecFromStation(BaseStation *st, byte specindex)
{
        /* specindex of 0 (default) is never freeable */
        if (specindex == 0) return;

        ETileArea area = ETileArea(st, INVALID_TILE, TA_WHOLE);
        /* Check all tiles over the station to check if the specindex is still in use */
        TILE_AREA_LOOP(tile, area) {
                if (st->TileBelongsToRailStation(tile) && GetCustomStationSpecIndex(tile) == specindex) {
                        return;
                }
        }

        /* This specindex is no longer in use, so deallocate it */
        st->speclist[specindex].spec     = NULL;
        st->speclist[specindex].grfid    = 0;
        st->speclist[specindex].localidx = 0;

        /* If this was the highest spec index, reallocate */
        if (specindex == st->num_specs - 1) {
                for (; st->speclist[st->num_specs - 1].grfid == 0 && st->num_specs > 1; st->num_specs--) {}

                if (st->num_specs > 1) {
                        st->speclist = xrealloct (st->speclist, st->num_specs);
                } else {
                        free(st->speclist);
                        st->num_specs = 0;
                        st->speclist  = NULL;
                        st->cached_anim_triggers = 0;
                        st->cached_cargo_triggers = 0;
                        return;
                }
        }

        StationUpdateCachedTriggers(st);
}

/**
 * Draw representation of a station tile for GUI purposes.
 * @param dpi The area to draw on.
 * @param x Position x of image.
 * @param y Position y of image.
 * @param axis Axis.
 * @param railtype Rail type.
 * @param sclass, station Type of station.
 * @param station station ID
 * @return True if the tile was drawn (allows for fallback to default graphic)
 */
bool DrawStationTile (BlitArea *dpi, int x, int y, RailType railtype,
        Axis axis, StationClassID sclass, uint station)
{
        const DrawTileSprites *sprites = NULL;
        const RailtypeInfo *rti = GetRailTypeInfo(railtype);
        PaletteID palette = COMPANY_SPRITE_COLOUR(_local_company);
        uint tile = 2;

        const StationSpec *statspec = StationClass::Get(sclass)->GetSpec(station);
        if (statspec == NULL) return false;

        if (HasBit(statspec->callback_mask, CBM_STATION_SPRITE_LAYOUT)) {
                uint16 callback = GetStationCallback (CBID_STATION_SPRITE_LAYOUT, 0x2110000, 0, statspec, railtype);
                if (callback != CALLBACK_FAILED) tile = callback;
        }

        uint32 total_offset = rti->GetRailtypeSpriteOffset();
        uint32 relocation = 0;
        uint32 ground_relocation = 0;
        const NewGRFSpriteLayout *layout = NULL;

        if (statspec->renderdata.empty()) {
                sprites = GetDefaultStationTileLayout() + (tile + axis);
        } else {
                uint t = (tile < statspec->renderdata.size()) ? tile : 0;
                layout = statspec->renderdata[t + axis].get();
                if (!layout->NeedsPreprocessing()) {
                        sprites = layout;
                        layout = NULL;
                }
        }

        NewGRFSpriteLayout::Result result;
        PalSpriteID ground;
        const DrawTileSeqStruct *seq;
        if (layout != NULL) {
                /* Sprite layout which needs preprocessing */
                bool separate_ground = HasBit(statspec->flags, SSF_SEPARATE_GROUND);
                uint32 var10_values = result.prepare (layout, 0, total_offset, rti->fallback_railtype, separate_ground);
                uint8 var10;
                FOR_EACH_SET_BIT(var10, var10_values) {
                        uint32 var10_relocation = GetCustomStationRelocation (statspec, railtype, var10);
                        result.process (layout, var10, var10_relocation, separate_ground);
                }
                ground = result.get_ground();
                seq = result.get_seq();
                total_offset = 0;
        } else {
                /* Simple sprite layout */
                ground = sprites->ground;
                seq = sprites->seq;
                ground_relocation = relocation = GetCustomStationRelocation (statspec, railtype, 0);
                if (HasBit(ground.sprite, SPRITE_MODIFIER_CUSTOM_SPRITE)) {
                        ground_relocation = GetCustomStationRelocation (statspec, railtype, 1);
                }
                ground_relocation += rti->fallback_railtype;
        }

        SpriteID image = ground.sprite;
        PaletteID pal = ground.pal;
        RailTrackOffset overlay_offset;
        if (rti->UsesOverlay() && SplitGroundSpriteForOverlay (&image, &overlay_offset)) {
                SpriteID ground = GetCustomRailSprite(rti, INVALID_TILE, RTSG_GROUND);
                DrawSprite (dpi, image, PAL_NONE, x, y);
                DrawSprite (dpi, ground + overlay_offset, PAL_NONE, x, y);
        } else {
                image += HasBit(image, SPRITE_MODIFIER_CUSTOM_SPRITE) ? ground_relocation : total_offset;
                if (HasBit(pal, SPRITE_MODIFIER_CUSTOM_SPRITE)) pal += ground_relocation;
                DrawSprite (dpi, image, GroundSpritePaletteTransform (image, pal, palette), x, y);
        }

        DrawRailTileSeqInGUI (dpi, x, y, seq, total_offset, relocation, palette);

        return true;
}


const StationSpec *GetStationSpec(TileIndex t)
{
        uint specindex = GetCustomStationSpecIndex(t);
        if (specindex == 0) return NULL;

        const BaseStation *st = BaseStation::GetByTile(t);
        return specindex < st->num_specs ? st->speclist[specindex].spec : NULL;
}


/**
 * Check whether a rail station tile is NOT traversable.
 * @param tile %Tile to test.
 * @return Station tile is blocked.
 * @note This could be cached (during build) in the map array to save on all the dereferencing.
 */
bool IsStationTileBlocked(TileIndex tile)
{
        const StationSpec *statspec = GetStationSpec(tile);

        return statspec != NULL && HasBit(statspec->blocked, GetStationGfx(tile));
}

/**
 * Check if a rail station tile shall have pylons when electrified.
 * @param tile %Tile to test.
 * @return Tile shall have pylons.
 * @note This could be cached (during build) in the map array to save on all the dereferencing.
 */
bool CanStationTileHavePylons(TileIndex tile)
{
        const StationSpec *statspec = GetStationSpec(tile);
        uint gfx = GetStationGfx(tile);
        /* Default stations do not draw pylons under roofs (gfx >= 4) */
        return statspec != NULL ? HasBit(statspec->pylons, gfx) : gfx < 4;
}

/**
 * Check if a rail station tile shall have wires when electrified.
 * @param tile %Tile to test.
 * @return Tile shall have wires.
 * @note This could be cached (during build) in the map array to save on all the dereferencing.
 */
bool CanStationTileHaveWires(TileIndex tile)
{
        const StationSpec *statspec = GetStationSpec(tile);
        return statspec == NULL || !HasBit(statspec->wires, GetStationGfx(tile));
}

/** Helper class for animation control. */
struct StationAnimationBase {
        static const CallbackID cb_animation_speed      = CBID_STATION_ANIMATION_SPEED;
        static const CallbackID cb_animation_next_frame = CBID_STATION_ANIM_NEXT_FRAME;

        static const StationCallbackMask cbm_animation_speed      = CBM_STATION_ANIMATION_SPEED;
        static const StationCallbackMask cbm_animation_next_frame = CBM_STATION_ANIMATION_NEXT_FRAME;

        /** Callback wrapper for animation control. */
        static uint16 get_callback (CallbackID callback, uint32 param1, uint32 param2, const StationSpec *statspec, BaseStation *st, TileIndex tile)
        {
                return GetStationCallback (callback, param1, param2, statspec, st, tile);
        }
};

void AnimateStationTile(TileIndex tile)
{
        const StationSpec *ss = GetStationSpec(tile);
        if (ss == NULL) return;

        AnimationBase::AnimateTile <StationAnimationBase> (ss, BaseStation::GetByTile(tile), tile, HasBit(ss->flags, SSF_CB141_RANDOM_BITS));
}

void TriggerStationAnimation(BaseStation *st, TileIndex tile, StationAnimationTrigger trigger, CargoID cargo_type)
{
        /* List of coverage areas for each animation trigger */
        static const TriggerArea tas[] = {
                TA_TILE, TA_WHOLE, TA_WHOLE, TA_PLATFORM, TA_PLATFORM, TA_PLATFORM, TA_WHOLE
        };

        /* Get Station if it wasn't supplied */
        if (st == NULL) st = BaseStation::GetByTile(tile);

        /* Check the cached animation trigger bitmask to see if we need
         * to bother with any further processing. */
        if (!HasBit(st->cached_anim_triggers, trigger)) return;

        uint16 random_bits = Random();
        ETileArea area = ETileArea(st, tile, tas[trigger]);

        /* Check all tiles over the station to check if the specindex is still in use */
        TILE_AREA_LOOP(tile, area) {
                if (st->TileBelongsToRailStation(tile)) {
                        const StationSpec *ss = GetStationSpec(tile);
                        if (ss != NULL && HasBit(ss->animation.triggers, trigger)) {
                                CargoID cargo;
                                if (cargo_type == CT_INVALID) {
                                        cargo = CT_INVALID;
                                } else {
                                        cargo = ss->grf_prop.grffile->cargo_map[cargo_type];
                                }
                                uint16 callback = GetStationCallback (CBID_STATION_ANIM_START_STOP,
                                                (random_bits << 16) | Random(),
                                                (uint8)trigger | (cargo << 8),
                                                ss, st, tile);
                                AnimationBase::ChangeAnimationFrame (ss, tile, callback);
                        }
                }
        }
}

/**
 * Trigger station randomisation
 * @param st station being triggered
 * @param tile specific tile of platform to trigger
 * @param trigger trigger type
 * @param cargo_type cargo type causing trigger
 */
void TriggerStationRandomisation(Station *st, TileIndex tile, StationRandomTrigger trigger, CargoID cargo_type)
{
        /* List of coverage areas for each animation trigger */
        static const TriggerArea tas[] = {
                TA_WHOLE, TA_WHOLE, TA_PLATFORM, TA_PLATFORM, TA_PLATFORM, TA_PLATFORM
        };

        /* Get Station if it wasn't supplied */
        if (st == NULL) st = Station::GetByTile(tile);

        /* Check the cached cargo trigger bitmask to see if we need
         * to bother with any further processing. */
        if (st->cached_cargo_triggers == 0) return;
        if (cargo_type != CT_INVALID && !HasBit(st->cached_cargo_triggers, cargo_type)) return;

        uint32 whole_reseed = 0;
        ETileArea area = ETileArea(st, tile, tas[trigger]);

        uint32 empty_mask = 0;
        if (trigger == SRT_CARGO_TAKEN) {
                /* Create a bitmask of completely empty cargo types to be matched */
                for (CargoID i = 0; i < NUM_CARGO; i++) {
                        if (st->goods[i].cargo.TotalCount() == 0) {
                                SetBit(empty_mask, i);
                        }
                }
        }

        /* Convert trigger to bit */
        uint8 trigger_bit = 1 << trigger;

        /* Check all tiles over the station to check if the specindex is still in use */
        TILE_AREA_LOOP(tile, area) {
                if (st->TileBelongsToRailStation(tile)) {
                        const StationSpec *ss = GetStationSpec(tile);
                        if (ss == NULL) continue;

                        /* Cargo taken "will only be triggered if all of those
                         * cargo types have no more cargo waiting." */
                        if (trigger == SRT_CARGO_TAKEN) {
                                if ((ss->cargo_triggers & ~empty_mask) != 0) continue;
                        }

                        if (cargo_type == CT_INVALID || HasBit(ss->cargo_triggers, cargo_type)) {
                                StationResolverObject object(ss, st, tile, CBID_RANDOM_TRIGGER, 0);
                                object.trigger = trigger_bit;

                                const SpriteGroup *group = object.Resolve();
                                if (group == NULL) continue;

                                uint32 reseed = object.GetReseedSum();
                                if (reseed != 0) {
                                        whole_reseed |= reseed;
                                        reseed >>= 16;

                                        /* Set individual tile random bits */
                                        uint8 random_bits = GetStationTileRandomBits(tile);
                                        random_bits &= ~reseed;
                                        random_bits |= Random() & reseed;
                                        SetStationTileRandomBits(tile, random_bits);

                                        MarkTileDirtyByTile(tile);
                                }
                        }
                }
        }

        /* Update whole station random bits */
        if ((whole_reseed & 0xFFFF) != 0) {
                st->random_bits &= ~whole_reseed;
                st->random_bits |= Random() & whole_reseed;
        }
}

/**
 * Update the cached animation trigger bitmask for a station.
 * @param st Station to update.
 */
void StationUpdateCachedTriggers(BaseStation *st)
{
        st->cached_anim_triggers = 0;
        st->cached_cargo_triggers = 0;

        /* Combine animation trigger bitmask for all station specs
         * of this station. */
        for (uint i = 0; i < st->num_specs; i++) {
                const StationSpec *ss = st->speclist[i].spec;
                if (ss != NULL) {
                        st->cached_anim_triggers |= ss->animation.triggers;
                        st->cached_cargo_triggers |= ss->cargo_triggers;
                }
        }
}