Remove SIGTYPE_LAST_NOPBS

[openttd/fttd.git] / src / road_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 road_cmd.cpp Commands related to road tiles. */

#include "stdafx.h"
#include "cmd_helper.h"
#include "road_internal.h"
#include "viewport_func.h"
#include "command_func.h"
#include "pathfinder/yapf/yapf.h"
#include "depot_base.h"
#include "newgrf.h"
#include "autoslope.h"
#include "map/zoneheight.h"
#include "map/road.h"
#include "map/bridge.h"
#include "map/tunnelbridge.h"
#include "bridge.h"
#include "strings_func.h"
#include "vehicle_func.h"
#include "sound_func.h"
#include "tunnelbridge.h"
#include "cheat_type.h"
#include "effectvehicle_func.h"
#include "effectvehicle_base.h"
#include "elrail_func.h"
#include "roadveh.h"
#include "town.h"
#include "company_base.h"
#include "core/random_func.hpp"
#include "newgrf_railtype.h"
#include "date_func.h"
#include "genworld.h"
#include "company_gui.h"

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


/**
 * Verify whether a road vehicle is available.
 * @return \c true if at least one road vehicle is available, \c false if not
 */
bool RoadVehiclesAreBuilt()
{
        const RoadVehicle *rv;
        FOR_ALL_ROADVEHICLES(rv) return true;

        return false;
}

/** Invalid RoadBits on a leveled slope. */
static const RoadBits _invalid_leveled_roadbits[15] = {
        ROAD_NONE,         // SLOPE_FLAT
        ROAD_NE | ROAD_SE, // SLOPE_W
        ROAD_NE | ROAD_NW, // SLOPE_S
        ROAD_NE,           // SLOPE_SW
        ROAD_NW | ROAD_SW, // SLOPE_E
        ROAD_NONE,         // SLOPE_EW
        ROAD_NW,           // SLOPE_SE
        ROAD_NONE,         // SLOPE_WSE
        ROAD_SE | ROAD_SW, // SLOPE_N
        ROAD_SE,           // SLOPE_NW
        ROAD_NONE,         // SLOPE_NS
        ROAD_NONE,         // SLOPE_ENW
        ROAD_SW,           // SLOPE_NE
        ROAD_NONE,         // SLOPE_SEN
        ROAD_NONE,         // SLOPE_NWS
};

/** Invalid straight RoadBits on a slope (with and without foundation). */
static const RoadBits _invalid_straight_roadbits[15] = {
        ROAD_NONE, // SLOPE_FLAT
        ROAD_NONE, // SLOPE_W    Foundation
        ROAD_NONE, // SLOPE_S    Foundation
        ROAD_Y,    // SLOPE_SW
        ROAD_NONE, // SLOPE_E    Foundation
        ROAD_ALL,  // SLOPE_EW
        ROAD_X,    // SLOPE_SE
        ROAD_ALL,  // SLOPE_WSE
        ROAD_NONE, // SLOPE_N    Foundation
        ROAD_X,    // SLOPE_NW
        ROAD_ALL,  // SLOPE_NS
        ROAD_ALL,  // SLOPE_ENW
        ROAD_Y,    // SLOPE_NE
        ROAD_ALL,  // SLOPE_SEN
        ROAD_ALL,  // SLOPE_NWS
};

static Foundation GetRoadFoundation(Slope tileh, RoadBits bits);

/**
 * Is it allowed to remove the given road bits from the given tile?
 * @param tile      the tile to remove the road from
 * @param remove    the roadbits that are going to be removed
 * @param owner     the actual owner of the roadbits of the tile
 * @param rt        the road type to remove the bits from
 * @param flags     command flags
 * @param town_check Shall the town rating checked/affected
 * @return A succeeded command when it is allowed to remove the road bits, a failed command otherwise.
 */
CommandCost CheckAllowRemoveRoad(TileIndex tile, RoadBits remove, Owner owner, RoadType rt, DoCommandFlag flags, bool town_check)
{
        if (_game_mode == GM_EDITOR || remove == ROAD_NONE) return CommandCost();

        /* Water can always flood and towns can always remove "normal" road pieces.
         * Towns are not be allowed to remove non "normal" road pieces, like tram
         * tracks as that would result in trams that cannot turn. */
        if (_current_company == OWNER_WATER ||
                        (rt == ROADTYPE_ROAD && !Company::IsValidID(_current_company))) return CommandCost();

        /* Only do the special processing if the road is owned
         * by a town */
        if (owner != OWNER_TOWN) {
                if (owner == OWNER_NONE) return CommandCost();
                CommandCost ret = CheckOwnership(owner);
                return ret;
        }

        if (!town_check) return CommandCost();

        if (_cheats.magic_bulldozer.value) return CommandCost();

        Town *t = ClosestTownFromTile(tile);
        if (t == NULL) return CommandCost();

        /* check if you're allowed to remove the street owned by a town
         * removal allowance depends on difficulty setting */
        CommandCost ret = CheckforTownRating(flags, t, ROAD_REMOVE);
        if (ret.Failed()) return ret;

        /* Get a bitmask of which neighbouring roads has a tile */
        RoadBits n = ROAD_NONE;
        RoadBits present = GetAnyRoadBits(tile, rt);
        if ((present & ROAD_NE) && (GetAnyRoadBits(TILE_ADDXY(tile, -1,  0), rt) & ROAD_SW)) n |= ROAD_NE;
        if ((present & ROAD_SE) && (GetAnyRoadBits(TILE_ADDXY(tile,  0,  1), rt) & ROAD_NW)) n |= ROAD_SE;
        if ((present & ROAD_SW) && (GetAnyRoadBits(TILE_ADDXY(tile,  1,  0), rt) & ROAD_NE)) n |= ROAD_SW;
        if ((present & ROAD_NW) && (GetAnyRoadBits(TILE_ADDXY(tile,  0, -1), rt) & ROAD_SE)) n |= ROAD_NW;

        int rating_decrease = RATING_ROAD_DOWN_STEP_EDGE;
        /* If 0 or 1 bits are set in n, or if no bits that match the bits to remove,
         * then allow it */
        if (KillFirstBit(n) != ROAD_NONE && (n & remove) != ROAD_NONE) {
                /* you can remove all kind of roads with extra dynamite */
                if (!_settings_game.construction.extra_dynamite) {
                        SetDParam(0, t->index);
                        return_cmd_error(STR_ERROR_LOCAL_AUTHORITY_REFUSES_TO_ALLOW_THIS);
                }
                rating_decrease = RATING_ROAD_DOWN_STEP_INNER;
        }
        ChangeTownRating(t, rating_decrease, RATING_ROAD_MINIMUM, flags);

        return CommandCost();
}


/**
 * Clear road bits and type and make necessary adjustments in a road tile
 * @param tile tile to clear road type from
 * @param rt road type to clear
 * @pre IsRoadTile(tile)
 */
static void ClearRoadType(TileIndex tile, RoadType rt)
{
        assert(IsRoadTile(tile));

        RoadTypes rts = GetRoadTypes(tile) & ~RoadTypeToRoadTypes(rt);
        if (rts == ROADTYPES_NONE) {
                DoClearSquare(tile);
                return;
        }

        if (rt == ROADTYPE_ROAD && IsRoadOwner(tile, ROADTYPE_ROAD, OWNER_TOWN)) {
                /* Update nearest-town index */
                SetTownIndex(tile, CalcClosestTownIDFromTile(tile));
        }

        SetRoadBits(tile, ROAD_NONE, rt);
        SetRoadTypes(tile, rts);

        /* If the owner of a roadtype sells all their road, set the ownership
         * of the tile to the owner of the other roadtype. */
        RoadType other_rt = (rt == ROADTYPE_ROAD) ? ROADTYPE_TRAM : ROADTYPE_ROAD;
        Owner other_owner = GetRoadOwner(tile, other_rt);
        if (other_owner != GetTileOwner(tile)) {
                SetTileOwner(tile, other_owner);
        }
}


/**
 * Delete a piece of road from a normal road tile
 * @param tile tile where to remove road from
 * @param flags operation to perform
 * @param pieces roadbits to remove
 * @param rt roadtype to remove
 * @param town_check should we check if the town allows removal?
 */
static CommandCost RemoveRoad_Road(TileIndex tile, DoCommandFlag flags, RoadBits pieces, RoadType rt, bool town_check)
{
        CommandCost ret = EnsureNoVehicleOnGround(tile);
        if (ret.Failed()) return ret;

        ret = CheckAllowRemoveRoad(tile, pieces, GetRoadOwner(tile, rt), rt, flags, town_check);
        if (ret.Failed()) return ret;

        if (HasRoadWorks(tile) && _current_company != OWNER_WATER) return_cmd_error(STR_ERROR_ROAD_WORKS_IN_PROGRESS);

        Slope tileh = GetTileSlope(tile);

        /* Steep slopes behave the same as slopes with one corner raised. */
        if (IsSteepSlope(tileh)) {
                tileh = SlopeWithOneCornerRaised(GetHighestSlopeCorner(tileh));
        }

        RoadBits present = GetRoadBits(tile, rt);
        const RoadBits other = GetOtherRoadBits(tile, rt);
        const Foundation f = GetRoadFoundation(tileh, present);

        /* Autocomplete to a straight road
         * @li if the bits of the other roadtypes result in another foundation
         * @li if build on slopes is disabled */
        if ((IsStraightRoad(other) && (other & _invalid_leveled_roadbits[tileh & SLOPE_ELEVATED]) != ROAD_NONE) ||
                        (tileh != SLOPE_FLAT && !_settings_game.construction.build_on_slopes)) {
                pieces |= MirrorRoadBits(pieces);
        }

        /* limit the bits to delete to the existing bits. */
        pieces &= present;
        if (pieces == ROAD_NONE) return_cmd_error(rt == ROADTYPE_TRAM ? STR_ERROR_THERE_IS_NO_TRAMWAY : STR_ERROR_THERE_IS_NO_ROAD);

        /* Now set present what it will be after the remove */
        present ^= pieces;

        /* Check for invalid RoadBit combinations on slopes */
        if (tileh != SLOPE_FLAT && present != ROAD_NONE &&
                        (present & _invalid_leveled_roadbits[tileh & SLOPE_ELEVATED]) == present) {
                return CMD_ERROR;
        }

        if (flags & DC_EXEC) {
                if (HasRoadWorks(tile)) {
                        /* flooding tile with road works, don't forget to remove the effect vehicle too */
                        assert(_current_company == OWNER_WATER);
                        EffectVehicle *v;
                        FOR_ALL_EFFECTVEHICLES(v) {
                                if (TileVirtXY(v->x_pos, v->y_pos) == tile) {
                                        delete v;
                                }
                        }
                }

                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                if (c != NULL) {
                        c->infrastructure.road[rt] -= CountBits(pieces);
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                if (present == ROAD_NONE) {
                        ClearRoadType(tile, rt);
                } else {
                        /* When bits are removed, you *always* end up with something that
                         * is not a complete straight road tile. However, trams do not have
                         * onewayness, so they cannot remove it either. */
                        if (rt != ROADTYPE_TRAM) SetDisallowedRoadDirections(tile, DRD_NONE);
                        SetRoadBits(tile, present, rt);
                        MarkTileDirtyByTile(tile);
                }
        }

        CommandCost cost(EXPENSES_CONSTRUCTION, CountBits(pieces) * _price[PR_CLEAR_ROAD]);
        /* If we build a foundation we have to pay for it. */
        if (f == FOUNDATION_NONE && GetRoadFoundation(tileh, present) != FOUNDATION_NONE) cost.AddCost(_price[PR_BUILD_FOUNDATION]);
        return cost;
}

/**
 * Delete a piece of road from a bridge
 * @param tile tile where to remove road from
 * @param flags operation to perform
 * @param pieces roadbits to remove
 * @param rt roadtype to remove
 * @param town_check should we check if the town allows removal?
 */
static CommandCost RemoveRoad_Bridge(TileIndex tile, DoCommandFlag flags, RoadBits pieces, RoadType rt, bool town_check)
{
        DiagDirection dir = GetTunnelBridgeDirection(tile);

        CommandCost ret = CheckAllowRemoveRoad(tile, pieces, GetRoadOwner(tile, rt), rt, flags, town_check);
        if (ret.Failed()) return ret;

        RoadBits bits = GetRoadBits(tile, rt);

        /* limit the bits to delete to the existing bits. */
        pieces &= bits;
        if (pieces == ROAD_NONE) return_cmd_error(rt == ROADTYPE_TRAM ? STR_ERROR_THERE_IS_NO_TRAMWAY : STR_ERROR_THERE_IS_NO_ROAD);

        if (HasBridgeFlatRamp(GetTileSlope(tile), DiagDirToAxis(dir))) {
                bits &= ~pieces;
        } else {
                assert((pieces & ~AxisToRoadBits(DiagDirToAxis(dir))) == ROAD_NONE);
                pieces = AxisToRoadBits(DiagDirToAxis(dir));
                bits = ROAD_NONE;
        }

        CommandCost cost(EXPENSES_CONSTRUCTION);

        /* Other end and length of the bridge, if we are removing the bridge piece */
        TileIndex other_end;
        uint len;

        /* Roadbits left at the other side */
        RoadBits other_end_bits = ROAD_NONE;

        /* Whether to remove the bridge itself */
        bool remove_bridge = false;

        if ((pieces & DiagDirToRoadBits(dir)) == 0) {
                /* Not removing the bridge piece */
                other_end = INVALID_TILE;

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

                cost.AddCost(CountBits(pieces) * _price[PR_CLEAR_ROAD]);
        } else {
                /* Removing the bridge piece */
                other_end = GetOtherBridgeEnd(tile);
                len = GetTunnelBridgeLength(tile, other_end);

                ret = TunnelBridgeIsFree(tile, other_end);
                if (ret.Failed()) return ret;

                if ((GetOtherRoadBits(tile, rt) & DiagDirToRoadBits(dir)) != 0) {
                        /* The other road type has the bridge piece, so the bridge stays */
                        uint num = CountBits(pieces) + 2 * len;

                        if (!IsExtendedRoadBridge(other_end)) {
                                assert(GetRoadBits(other_end, rt) == AxisToRoadBits(DiagDirToAxis(dir)));
                                assert(GetOtherRoadBits(other_end, rt) == AxisToRoadBits(DiagDirToAxis(dir)));
                                num += 2;
                        } else {
                                other_end_bits = GetRoadBits(other_end, rt) & ~DiagDirToRoadBits(ReverseDiagDir(dir));
                                num++;
                        }

                        cost.AddCost(num * _price[PR_CLEAR_ROAD]);
                } else {
                        /* Removing the last bridge piece and therefore the bridge itself */
                        remove_bridge = true;
                        cost.AddCost((len + 2) * _price[PR_CLEAR_BRIDGE]);

                        if (IsExtendedRoadBridge(other_end)) {
                                other_end_bits = GetRoadBits(other_end, rt) & ~DiagDirToRoadBits(ReverseDiagDir(dir));
                        }
                }
        }

        if (flags & DC_EXEC) {
                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                if (c != NULL) {
                        if (other_end != INVALID_TILE) {
                                c->infrastructure.road[rt] -= (CountBits(bits | pieces) + 2 * len + CountBits(GetRoadBits(other_end, rt))) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                c->infrastructure.road[rt] += CountBits(bits) + CountBits(other_end_bits);
                        } else if ((bits & DiagDirToRoadBits(dir)) != 0) {
                                c->infrastructure.road[rt] -= CountBits(pieces) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                        } else {
                                c->infrastructure.road[rt] -= CountBits(pieces);
                        }
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                if (remove_bridge) RemoveBridgeMiddleTiles(tile, other_end);

                if (bits != ROAD_NONE) {
                        SetRoadBits(tile, bits, rt);
                        if (remove_bridge) MakeNormalRoadFromBridge(tile);
                } else {
                        assert((GetRoadTypes(tile) != RoadTypeToRoadTypes(rt)) || remove_bridge);
                        if (remove_bridge) MakeNormalRoadFromBridge(tile);
                        ClearRoadType(tile, rt);
                }

                MarkTileDirtyByTile(tile);

                if (other_end != INVALID_TILE) {
                        if (other_end_bits != ROAD_NONE) {
                                SetRoadBits(other_end, other_end_bits, rt);
                                if (remove_bridge) MakeNormalRoadFromBridge(other_end);
                        } else {
                                assert((GetRoadTypes(other_end) != RoadTypeToRoadTypes(rt)) || remove_bridge);
                                if (remove_bridge) MakeNormalRoadFromBridge(other_end);
                                ClearRoadType(other_end, rt);
                        }

                        MarkBridgeTilesDirty(tile, other_end, dir, false);
                }
        }

        return cost;
}

/**
 * Delete a piece of road from a crossing
 * @param tile tile where to remove road from
 * @param flags operation to perform
 * @param pieces roadbits to remove
 * @param rt roadtype to remove
 * @param crossing_check should we check if there is a tram track when we are removing road from crossing?
 * @param town_check should we check if the town allows removal?
 */
static CommandCost RemoveRoad_Crossing(TileIndex tile, DoCommandFlag flags, RoadBits pieces, RoadType rt, bool crossing_check, bool town_check)
{
        CommandCost ret = EnsureNoVehicleOnGround(tile);
        if (ret.Failed()) return ret;

        ret = CheckAllowRemoveRoad(tile, pieces, GetRoadOwner(tile, rt), rt, flags, town_check);
        if (ret.Failed()) return ret;

        if (pieces & ComplementRoadBits(GetCrossingRoadBits(tile))) {
                return CMD_ERROR;
        }

        /* Don't allow road to be removed from the crossing when there is tram;
         * we can't draw the crossing without roadbits ;) */
        if (rt == ROADTYPE_ROAD && HasTileRoadType(tile, ROADTYPE_TRAM) && (flags & DC_EXEC || crossing_check)) return CMD_ERROR;

        if (flags & DC_EXEC) {
                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                if (c != NULL) {
                        /* A full diagonal road tile has two road bits. */
                        c->infrastructure.road[rt] -= 2;
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                Track railtrack = GetCrossingRailTrack(tile);
                RoadTypes rts = GetRoadTypes(tile) & ComplementRoadTypes(RoadTypeToRoadTypes(rt));
                if (rts == ROADTYPES_NONE) {
                        TrackBits tracks = GetCrossingRailBits(tile);
                        bool reserved = HasCrossingReservation(tile);
                        MakeRailNormal(tile, GetTileOwner(tile), tracks, GetRailType(tile));
                        if (reserved) SetTrackReservation(tile, tracks);

                        /* Update rail count for level crossings. The plain track should still be accounted
                         * for, so only subtract the difference to the level crossing cost. */
                        c = Company::GetIfValid(GetTileOwner(tile));
                        if (c != NULL) c->infrastructure.rail[GetRailType(tile)] -= LEVELCROSSING_TRACKBIT_FACTOR - 1;
                } else {
                        SetRoadTypes(tile, rts);
                }
                MarkTileDirtyByTile(tile);
                YapfNotifyTrackLayoutChange(tile, railtrack);
        }

        return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_ROAD] * 2);
}

/**
 * Delete a piece of road from a tunnel
 * @param tile tile where to remove road from
 * @param flags operation to perform
 * @param pieces roadbits to remove
 * @param rt roadtype to remove
 * @param town_check should we check if the town allows removal?
 */
static CommandCost RemoveRoad_Tunnel(TileIndex tile, DoCommandFlag flags, RoadBits pieces, RoadType rt, bool town_check)
{
        assert(GetTunnelTransportType(tile) == TRANSPORT_ROAD);

        TileIndex other_end = GetOtherTunnelEnd(tile);
        CommandCost ret = TunnelBridgeIsFree(tile, other_end);
        if (ret.Failed()) return ret;

        ret = CheckAllowRemoveRoad(tile, pieces, GetRoadOwner(tile, rt), rt, flags, town_check);
        if (ret.Failed()) return ret;

        /* If it's the last roadtype, just clear the whole tile */
        if (GetRoadTypes(tile) == RoadTypeToRoadTypes(rt)) return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);

        /* Removing any roadbit in the tunnel axis removes the roadtype (that's the behaviour remove-long-roads needs) */
        if ((AxisToRoadBits(DiagDirToAxis(GetTunnelBridgeDirection(tile))) & pieces) == ROAD_NONE) return_cmd_error(rt == ROADTYPE_TRAM ? STR_ERROR_THERE_IS_NO_TRAMWAY : STR_ERROR_THERE_IS_NO_ROAD);

        CommandCost cost(EXPENSES_CONSTRUCTION);
        /* Pay for *every* tile of the tunnel */
        uint len = GetTunnelBridgeLength(other_end, tile) + 2;
        cost.AddCost(len * _price[PR_CLEAR_ROAD]);

        if (flags & DC_EXEC) {
                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                if (c != NULL) {
                        /* A full diagonal road tile has two road bits. */
                        c->infrastructure.road[rt] -= len * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                SetRoadTypes(other_end, GetRoadTypes(other_end) & ~RoadTypeToRoadTypes(rt));
                SetRoadTypes(tile, GetRoadTypes(tile) & ~RoadTypeToRoadTypes(rt));

                /* If the owner of the bridge sells all its road, also move the ownership
                 * to the owner of the other roadtype. */
                RoadType other_rt = (rt == ROADTYPE_ROAD) ? ROADTYPE_TRAM : ROADTYPE_ROAD;
                Owner other_owner = GetRoadOwner(tile, other_rt);
                if (other_owner != GetTileOwner(tile)) {
                        SetTileOwner(tile, other_owner);
                        SetTileOwner(other_end, other_owner);
                }

                /* Mark tiles dirty that have been repaved */
                MarkTileDirtyByTile(tile);
                MarkTileDirtyByTile(other_end);
        }

        return cost;
}

/**
 * Delete a piece of road from a station
 * @param tile tile where to remove road from
 * @param flags operation to perform
 * @param pieces roadbits to remove
 * @param rt roadtype to remove
 * @param town_check should we check if the town allows removal?
 */
static CommandCost RemoveRoad_Station(TileIndex tile, DoCommandFlag flags, RoadBits pieces, RoadType rt, bool town_check)
{
        if (!IsDriveThroughStopTile(tile)) return CMD_ERROR;

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

        ret = CheckAllowRemoveRoad(tile, pieces, GetRoadOwner(tile, rt), rt, flags, town_check);
        if (ret.Failed()) return ret;

        /* If it's the last roadtype, just clear the whole tile */
        if (GetRoadTypes(tile) == RoadTypeToRoadTypes(rt)) return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);

        if (flags & DC_EXEC) {
                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                if (c != NULL) {
                        /* A full diagonal road tile has two road bits. */
                        c->infrastructure.road[rt] -= 2;
                        DirtyCompanyInfrastructureWindows(c->index);
                }
                SetRoadTypes(tile, GetRoadTypes(tile) & ~RoadTypeToRoadTypes(rt));
                MarkTileDirtyByTile(tile);
        }

        return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_ROAD] * 2);
}

/**
 * Delete a piece of road.
 * @param tile tile where to remove road from
 * @param flags operation to perform
 * @param pieces roadbits to remove
 * @param rt roadtype to remove
 * @param crossing_check should we check if there is a tram track when we are removing road from crossing?
 * @param town_check should we check if the town allows removal?
 */
CommandCost RemoveRoad(TileIndex tile, DoCommandFlag flags, RoadBits pieces, RoadType rt, bool crossing_check, bool town_check = true)
{
        switch (GetTileType(tile)) {
                case TT_ROAD: {
                        if (!HasTileRoadType(tile, rt)) break;

                        if (IsTileSubtype(tile, TT_TRACK)) {
                                return RemoveRoad_Road(tile, flags, pieces, rt, town_check);
                        } else {
                                return RemoveRoad_Bridge(tile, flags, pieces, rt, town_check);
                        }
                }

                case TT_MISC:
                        switch (GetTileSubtype(tile)) {
                                case TT_MISC_CROSSING:
                                        if (!HasTileRoadType(tile, rt)) break;
                                        return RemoveRoad_Crossing(tile, flags, pieces, rt, crossing_check, town_check);

                                case TT_MISC_TUNNEL:
                                        if (!HasTileRoadType(tile, rt)) break;
                                        if (GetTunnelTransportType(tile) != TRANSPORT_ROAD) break;
                                        return RemoveRoad_Tunnel(tile, flags, pieces, rt, town_check);

                                default:
                                        break;
                        }

                        break;

                case TT_STATION:
                        if (!HasTileRoadType(tile, rt)) break;

                        return RemoveRoad_Station(tile, flags, pieces, rt, town_check);

                default:
                        break;
        }

        /* The tile doesn't have the given road type */
        return_cmd_error(rt == ROADTYPE_TRAM ? STR_ERROR_THERE_IS_NO_TRAMWAY : STR_ERROR_THERE_IS_NO_ROAD);
}


/**
 * Calculate the costs for roads on slopes
 * Also compute the road bits that have to be built to fit the slope
 *
 * @param tileh The current slope
 * @param pieces The RoadBits we want to add
 * @param existing The existent RoadBits of the current type
 * @param other The existent RoadBits for the other type
 * @param build The actual RoadBits to build
 * @return The costs for these RoadBits on this slope
 */
static CommandCost CheckRoadSlope(Slope tileh, RoadBits pieces, RoadBits existing, RoadBits other, RoadBits *build)
{
        /* Remove already build pieces */
        CLRBITS(pieces, existing);

        /* If we can't build anything stop here */
        if (pieces == ROAD_NONE) return CMD_ERROR;

        /* All RoadBit combos are valid on flat land */
        if (tileh == SLOPE_FLAT) {
                if (build != NULL) *build = pieces;
                return CommandCost();
        }

        /* Steep slopes behave the same as slopes with one corner raised. */
        if (IsSteepSlope(tileh)) {
                tileh = SlopeWithOneCornerRaised(GetHighestSlopeCorner(tileh));
        }

        /* Roads on slopes */
        if (_settings_game.construction.build_on_slopes && (_invalid_leveled_roadbits[tileh] & (other | existing | pieces)) == ROAD_NONE) {
                if (build != NULL) *build = pieces;

                /* If we add leveling we've got to pay for it */
                if ((other | existing) == ROAD_NONE) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);

                return CommandCost();
        }

        /* Autocomplete uphill roads */
        pieces |= MirrorRoadBits(pieces);
        RoadBits type_bits = existing | pieces;

        /* Uphill roads */
        if (IsStraightRoad(type_bits) && (other == type_bits || other == ROAD_NONE) &&
                        (_invalid_straight_roadbits[tileh] & type_bits) == ROAD_NONE) {
                /* Slopes without foundation */
                if (!IsSlopeWithOneCornerRaised(tileh)) {
                        if (build != NULL) *build = pieces;
                        if (HasExactlyOneBit(existing) && GetRoadFoundation(tileh, existing) == FOUNDATION_NONE) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
                        return CommandCost();
                }

                /* Prevent build on slopes if it isn't allowed */
                if (_settings_game.construction.build_on_slopes) {
                        if (build != NULL) *build = pieces;

                        /* If we add foundation we've got to pay for it */
                        if ((other | existing) == ROAD_NONE) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);

                        return CommandCost();
                }
        }
        return CMD_ERROR;
}

/**
 * Check if a given roadbits set is valid for a road bridge head
 * @param tileh The slope
 * @param dir The bridge direction
 * @param bits The roadbits
 * @return Whether the given combination is valid
 */
bool IsValidRoadBridgeBits(Slope tileh, DiagDirection dir, RoadBits bits)
{
        DiagDirDiff diff = CheckExtendedBridgeHead(tileh, dir);

        switch (diff) {
                case DIAGDIRDIFF_SAME: return true;
                case DIAGDIRDIFF_REVERSE: return false;
                default: return (bits & DiagDirToRoadBits(ChangeDiagDir(dir, diff))) == 0;
        }
}

/**
 * Build a piece of road, clearing the land if necessary
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param rt roadtype to build
 * @param pieces roadbits to build
 * @param company company building the road
 * @param town owner/closest town
 * @param drd directions to disallow
 * @return the cost of this operation or an error
 */
static CommandCost BuildRoad_Clear(TileIndex tile, DoCommandFlag flags, RoadType rt, RoadBits pieces, CompanyID company, TownID town, DisallowedRoadDirections drd)
{
        CommandCost cost(EXPENSES_CONSTRUCTION);

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

        Slope tileh = GetTileSlope(tile);

        /* Check the foundation/slopes when adding road/tram bits */
        ret = CheckRoadSlope(tileh, pieces, ROAD_NONE, ROAD_NONE, &pieces);
        /* Return an error if we need to build a foundation (ret != 0) but the
         * current setting is turned off */
        if (ret.Failed() || (ret.GetCost() != 0 && !_settings_game.construction.build_on_slopes)) {
                return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
        }
        cost.AddCost(ret);

        uint num_pieces = CountBits(pieces);
        cost.AddCost(num_pieces * _price[PR_BUILD_ROAD]);

        if (flags & DC_EXEC) {
                MakeRoadNormal(tile, pieces, RoadTypeToRoadTypes(rt), town, company, company);

                /* Update company infrastructure count. */
                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                if (c != NULL) {
                        c->infrastructure.road[rt] += num_pieces;
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                if (rt != ROADTYPE_TRAM && IsStraightRoad(pieces)) {
                        SetDisallowedRoadDirections(tile, drd);
                }

                MarkTileDirtyByTile(tile);
        }

        return cost;
}

/**
 * Build a piece of road on a road tile
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param rt roadtype to build
 * @param pieces roadbits to build
 * @param company company building the road
 * @param town owner/closest town
 * @param toggle_drd directions to toggle disallow
 * @return the cost of this operation or an error
 */
static CommandCost BuildRoad_Road(TileIndex tile, DoCommandFlag flags, RoadType rt, RoadBits pieces, CompanyID company, TownID town, DisallowedRoadDirections toggle_drd)
{
        if (HasRoadWorks(tile)) return_cmd_error(STR_ERROR_ROAD_WORKS_IN_PROGRESS);

        RoadBits existing = ROAD_NONE;

        if (HasTileRoadType(tile, rt)) {
                existing = GetRoadBits(tile, rt);
                bool crossing = !IsStraightRoad(existing | pieces);

                if (rt != ROADTYPE_TRAM && (GetDisallowedRoadDirections(tile) != DRD_NONE || toggle_drd != DRD_NONE) && crossing) {
                        /* Junctions cannot be one-way */
                        return_cmd_error(STR_ERROR_ONEWAY_ROADS_CAN_T_HAVE_JUNCTION);
                }

                if ((existing & pieces) == pieces) {
                        /* We only want to set the (dis)allowed road directions */
                        if (toggle_drd == DRD_NONE || rt == ROADTYPE_TRAM) {
                                return_cmd_error(STR_ERROR_ALREADY_BUILT);
                        }

                        if (crossing) return_cmd_error(STR_ERROR_ONEWAY_ROADS_CAN_T_HAVE_JUNCTION);

                        Owner owner = GetRoadOwner(tile, ROADTYPE_ROAD);
                        if (owner != OWNER_NONE) {
                                CommandCost ret = CheckOwnership(owner, tile);
                                if (ret.Failed()) return ret;
                        }

                        DisallowedRoadDirections dis_existing = GetDisallowedRoadDirections(tile);
                        DisallowedRoadDirections dis_new      = dis_existing ^ toggle_drd;

                        /* We allow removing disallowed directions to break up
                         * deadlocks, but adding them can break articulated
                         * vehicles. As such, only when less is disallowed,
                         * i.e. bits are removed, we skip the vehicle check. */
                        if (CountBits(dis_existing) <= CountBits(dis_new)) {
                                CommandCost ret = EnsureNoVehicleOnGround(tile);
                                if (ret.Failed()) return ret;
                        }

                        /* Ignore half built tiles */
                        if ((flags & DC_EXEC) && rt != ROADTYPE_TRAM && IsStraightRoad(existing)) {
                                SetDisallowedRoadDirections(tile, dis_new);
                                MarkTileDirtyByTile(tile);
                        }

                        return CommandCost();
                }
        }

        CommandCost cost(EXPENSES_CONSTRUCTION);

        RoadBits other_bits = GetOtherRoadBits(tile, rt);

        Slope tileh = GetTileSlope(tile);

        if (other_bits != pieces) {
                /* Check the foundation/slopes when adding road/tram bits */
                CommandCost ret = CheckRoadSlope(tileh, pieces, existing, other_bits, &pieces);
                /* Return an error if we need to build a foundation (ret != 0) but the
                 * current setting is turned off */
                if (ret.Failed() || (ret.GetCost() != 0 && !_settings_game.construction.build_on_slopes)) {
                        return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
                }
                cost.AddCost(ret);
        }

        /* Don't put the pieces that already exist */
        pieces &= ComplementRoadBits(existing);

        /* Check if new road bits will have the same foundation as other existing road types */
        Foundation found_new = GetRoadFoundation(tileh, pieces | existing);

        /* Test if all other roadtypes can be built at that foundation */
        for (RoadType rtest = ROADTYPE_ROAD; rtest < ROADTYPE_END; rtest++) {
                if (rtest != rt) { // check only other road types
                        RoadBits bits = GetRoadBits(tile, rtest);
                        /* do not check if there are not road bits of given type */
                        if (bits != ROAD_NONE && GetRoadFoundation(tileh, bits) != found_new) {
                                return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
                        }
                }
        }

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

        uint num_pieces = CountBits(pieces);
        cost.AddCost(num_pieces * _price[PR_BUILD_ROAD]);

        if (flags & DC_EXEC) {
                if (existing == ROAD_NONE) {
                        SetRoadTypes(tile, GetRoadTypes(tile) | RoadTypeToRoadTypes(rt));
                        SetRoadOwner(tile, rt, company);
                        if (rt == ROADTYPE_ROAD) SetTownIndex(tile, town);
                }

                SetRoadBits(tile, existing | pieces, rt);

                /* Update company infrastructure count. */
                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                if (c != NULL) {
                        c->infrastructure.road[rt] += num_pieces;
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                if (rt != ROADTYPE_TRAM) {
                        SetDisallowedRoadDirections(tile, IsStraightRoad(existing | pieces) ?
                                        GetDisallowedRoadDirections(tile) ^ toggle_drd : DRD_NONE);
                }

                MarkTileDirtyByTile(tile);
        }

        return cost;
}

/**
 * Build a piece of road on a bridge tile
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param rt roadtype to build
 * @param pieces roadbits to build
 * @param company company building the road
 * @param town owner/closest town
 * @param drd directions to disallow
 * @return the cost of this operation or an error
 */
static CommandCost BuildRoad_Bridge(TileIndex tile, DoCommandFlag flags, RoadType rt, RoadBits pieces, CompanyID company, TownID town, DisallowedRoadDirections drd)
{
        DiagDirection dir = GetTunnelBridgeDirection(tile);
        Slope tileh = GetTileSlope(tile);
        uint num;
        bool other_end;

        if (HasBridgeFlatRamp(tileh, DiagDirToAxis(dir))) {
                RoadBits existing = GetRoadBits(tile, rt);
                pieces &= ~existing;
                if (pieces == ROAD_NONE) return_cmd_error(STR_ERROR_ALREADY_BUILT);

                if (!IsValidRoadBridgeBits(tileh, dir, existing | pieces)) {
                        return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
                }

                num = CountBits(pieces);
                other_end = (pieces & DiagDirToRoadBits(dir)) != 0;
                pieces |= existing;
        } else {
                /* Only allow building the outern roadbit, so building long roads stops at existing bridges */
                if (pieces != DiagDirToRoadBits(ReverseDiagDir(dir))) {
                        return BuildRoad_Clear(tile, flags, rt, pieces, company, town, drd);
                }

                if (HasTileRoadType(tile, rt)) return_cmd_error(STR_ERROR_ALREADY_BUILT);

                pieces = AxisToRoadBits(DiagDirToAxis(dir));
                num = 2;
                other_end = true;
        }

        TileIndex other_tile;
        RoadBits other_pieces;

        if (other_end) {
                other_tile = GetOtherBridgeEnd(tile);

                /* Don't allow adding roadtype to the bridge when vehicles are already driving on it */
                CommandCost ret = TunnelBridgeIsFree(tile, other_tile);
                if (ret.Failed()) return ret;

                /* Don't allow to mix owners */
                CompanyID new_owner   = HasTileRoadType(tile, rt) ? GetRoadOwner(tile, rt) : company;
                CompanyID other_owner = HasTileRoadType(other_tile, rt) ? GetRoadOwner(other_tile, rt) : company;
                if (new_owner != other_owner) return CMD_ERROR;

                num += 2 * GetTunnelBridgeLength(tile, other_tile);

                if (IsExtendedRoadBridge(other_tile)) {
                        other_pieces = GetRoadBits(other_tile, rt) | DiagDirToRoadBits(ReverseDiagDir(dir));
                        num++;
                } else {
                        assert(GetRoadBits(other_tile, rt) == ROAD_NONE);
                        other_pieces = AxisToRoadBits(DiagDirToAxis(dir));
                        num += 2;
                }
        } else {
                CommandCost ret = EnsureNoVehicleOnGround(tile);
                if (ret.Failed()) return ret;
        }

        if (flags & DC_EXEC) {
                if (other_end) {
                        /* Update company infrastructure count. */
                        Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                        if (c != NULL) {
                                uint existing = CountBits(GetRoadBits(tile, rt)) + CountBits(GetRoadBits(other_tile, rt));
                                c->infrastructure.road[rt] -= existing;
                                c->infrastructure.road[rt] += (existing + num) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                DirtyCompanyInfrastructureWindows(c->index);
                        }

                        if (!HasTileRoadType(other_tile, rt)) {
                                SetRoadTypes(other_tile, GetRoadTypes(other_tile) | RoadTypeToRoadTypes(rt));
                                SetRoadOwner(other_tile, rt, company);
                        }
                        SetRoadBits(other_tile, other_pieces, rt);

                        MarkBridgeTilesDirty(tile, other_tile, dir, false);
                } else {
                        /* Update company infrastructure count. */
                        Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                        if (c != NULL) {
                                c->infrastructure.road[rt] += (pieces & DiagDirToRoadBits(dir)) != 0 ? num * TUNNELBRIDGE_TRACKBIT_FACTOR : num;
                                DirtyCompanyInfrastructureWindows(c->index);
                        }
                }

                if (!HasTileRoadType(tile, rt)) {
                        SetRoadTypes(tile, GetRoadTypes(tile) | RoadTypeToRoadTypes(rt));
                        SetRoadOwner(tile, rt, company);
                }
                SetRoadBits(tile, pieces, rt);
                MarkTileDirtyByTile(tile);
        }

        return CommandCost(EXPENSES_CONSTRUCTION, num * _price[PR_BUILD_ROAD]);
}

/**
 * Build a piece of road on a crossing tile
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param rt roadtype to build
 * @param pieces roadbits to build
 * @param company company building the road
 * @param town owner/closest town
 * @param drd directions to disallow
 * @return the cost of this operation or an error
 */
static CommandCost BuildRoad_Crossing(TileIndex tile, DoCommandFlag flags, RoadType rt, RoadBits pieces, CompanyID company, TownID town, DisallowedRoadDirections drd)
{
        if (pieces & ComplementRoadBits(GetCrossingRoadBits(tile))) {
                return BuildRoad_Clear(tile, flags, rt, pieces, company, town, drd);
        }

        if (HasTileRoadType(tile, rt)) return_cmd_error(STR_ERROR_ALREADY_BUILT);

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

        if (flags & DC_EXEC) {
                SetRoadTypes(tile, GetRoadTypes(tile) | RoadTypeToRoadTypes(rt));
                SetRoadOwner(tile, rt, company);
                if (rt == ROADTYPE_ROAD) SetTownIndex(tile, town);

                /* Update company infrastructure count. */
                Company *c = Company::GetIfValid(company);
                if (c != NULL) {
                        c->infrastructure.road[rt] += 2;
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                MarkTileDirtyByTile(tile);
        }

        return CommandCost(EXPENSES_CONSTRUCTION, 2 * _price[PR_BUILD_ROAD]);
}

/**
 * Build a piece of road on a railway tile
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param rt roadtype to build
 * @param pieces roadbits to build
 * @param company company building the road
 * @param town owner/closest town
 * @param drd directions to disallow
 * @return the cost of this operation or an error
 */
static CommandCost BuildRoad_Railway(TileIndex tile, DoCommandFlag flags, RoadType rt, RoadBits pieces, CompanyID company, TownID town, DisallowedRoadDirections drd)
{
        Slope tileh = GetTileSlope(tile);

        if (!IsTileSubtype(tile, TT_TRACK)) goto do_clear;

        /* Level crossings may only be built on these slopes */
        if (IsSteepSlope(tileh) || !HasBit(VALID_LEVEL_CROSSING_SLOPES, tileh)) {
                return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
        }

        if (RailNoLevelCrossings(GetRailType(tile))) {
                return_cmd_error(STR_ERROR_CROSSING_DISALLOWED);
        }

        if (HasSignalOnTrack(tile, TRACK_UPPER)) goto do_clear;

        Axis roaddir;
        switch (GetTrackBits(tile)) {
                case TRACK_BIT_X:
                        if (pieces & ROAD_X) goto do_clear;
                        roaddir = AXIS_Y;
                        break;

                case TRACK_BIT_Y:
                        if (pieces & ROAD_Y) goto do_clear;
                        roaddir = AXIS_X;
                        break;

                default:
                do_clear:
                        return BuildRoad_Clear(tile, flags, rt, pieces, company, town, drd);
        }

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

        if (flags & DC_EXEC) {
                Track railtrack = AxisToTrack(OtherAxis(roaddir));
                YapfNotifyTrackLayoutChange(tile, railtrack);
                /* Update company infrastructure counts. A level crossing has two road bits. */
                Company *c = Company::GetIfValid(company);
                if (c != NULL) {
                        c->infrastructure.road[rt] += 2;
                        if (rt != ROADTYPE_ROAD) c->infrastructure.road[ROADTYPE_ROAD] += 2;
                        DirtyCompanyInfrastructureWindows(company);
                }
                /* Update rail count for level crossings. The plain track is already
                 * counted, so only add the difference to the level crossing cost. */
                c = Company::GetIfValid(GetTileOwner(tile));
                if (c != NULL) c->infrastructure.rail[GetRailType(tile)] += LEVELCROSSING_TRACKBIT_FACTOR - 1;

                /* Always add road to the roadtypes (can't draw without it) */
                bool reserved = HasBit(GetRailReservationTrackBits(tile), railtrack);
                MakeRoadCrossing(tile, company, company, GetTileOwner(tile), roaddir, GetRailType(tile), RoadTypeToRoadTypes(rt) | ROADTYPES_ROAD, town);
                SetCrossingReservation(tile, reserved);
                UpdateLevelCrossing(tile, false);
                MarkTileDirtyByTile(tile);
        }

        return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_ROAD] * (rt == ROADTYPE_ROAD ? 2 : 4));
}

/**
 * Build a piece of road on a tunnel tile
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param rt roadtype to build
 * @param pieces roadbits to build
 * @param company company building the road
 * @param town owner/closest town
 * @param drd directions to disallow
 * @return the cost of this operation or an error
 */
static CommandCost BuildRoad_Tunnel(TileIndex tile, DoCommandFlag flags, RoadType rt, RoadBits pieces, CompanyID company, TownID town, DisallowedRoadDirections drd)
{
        /* Only allow building the outern roadbit, so building long roads stops at existing bridges */
        if (GetTunnelTransportType(tile) != TRANSPORT_ROAD || pieces != DiagDirToRoadBits(ReverseDiagDir(GetTunnelBridgeDirection(tile)))) {
                return BuildRoad_Clear(tile, flags, rt, pieces, company, town, drd);
        }

        if (HasTileRoadType(tile, rt)) return_cmd_error(STR_ERROR_ALREADY_BUILT);

        TileIndex other_end = GetOtherTunnelEnd(tile);

        /* Don't allow adding roadtype to the tunnel when vehicles are already driving on it */
        CommandCost ret = TunnelBridgeIsFree(tile, other_end);
        if (ret.Failed()) return ret;

        /* There are 2 pieces on *every* tile of the tunnel */
        uint num_pieces = 2 * (GetTunnelBridgeLength(tile, other_end) + 2);

        if (flags & DC_EXEC) {
                SetRoadTypes(other_end, GetRoadTypes(other_end) | RoadTypeToRoadTypes(rt));
                SetRoadTypes(tile, GetRoadTypes(tile) | RoadTypeToRoadTypes(rt));
                SetRoadOwner(other_end, rt, company);
                SetRoadOwner(tile, rt, company);

                /* Mark tiles dirty that have been repaved */
                MarkTileDirtyByTile(other_end);
                MarkTileDirtyByTile(tile);

                /* Update company infrastructure count. */
                Company *c = Company::GetIfValid(company);
                if (c != NULL) {
                        c->infrastructure.road[rt] += num_pieces * TUNNELBRIDGE_TRACKBIT_FACTOR;
                        DirtyCompanyInfrastructureWindows(c->index);
                }
        }

        return CommandCost(EXPENSES_CONSTRUCTION, num_pieces * _price[PR_BUILD_ROAD]);
}

/**
 * Build a piece of road on a station tile
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param rt roadtype to build
 * @param pieces roadbits to build
 * @param company company building the road
 * @param town owner/closest town
 * @param drd directions to disallow
 * @return the cost of this operation or an error
 */
static CommandCost BuildRoad_Station(TileIndex tile, DoCommandFlag flags, RoadType rt, RoadBits pieces, CompanyID company, TownID town, DisallowedRoadDirections drd)
{
        if ((GetAnyRoadBits(tile, rt) & pieces) == pieces) return_cmd_error(STR_ERROR_ALREADY_BUILT);

        if (!IsDriveThroughStopTile(tile) || (pieces & ~AxisToRoadBits(GetRoadStopAxis(tile)))) {
                return BuildRoad_Clear(tile, flags, rt, pieces, company, town, drd);
        }

        if (HasTileRoadType(tile, rt)) return_cmd_error(STR_ERROR_ALREADY_BUILT);

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

        if (flags & DC_EXEC) {
                SetRoadTypes(tile, GetRoadTypes(tile) | RoadTypeToRoadTypes(rt));
                SetRoadOwner(tile, rt, company);

                /* Update company infrastructure count. */
                Company *c = Company::GetIfValid(company);
                if (c != NULL) {
                        c->infrastructure.road[rt] += 2;
                        DirtyCompanyInfrastructureWindows(c->index);
                }

                MarkTileDirtyByTile(tile);
        }

        return CommandCost(EXPENSES_CONSTRUCTION, 2 * _price[PR_BUILD_ROAD]);
}

/**
 * Build a piece of road.
 * @param tile tile where to build road
 * @param flags operation to perform
 * @param p1 bit 0..3 road pieces to build (RoadBits)
 *           bit 4..5 road type
 *           bit 6..7 disallowed directions to toggle
 * @param p2 the town that is building the road (0 if not applicable)
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        CompanyID company = _current_company;

        /* Road pieces are max 4 bitset values (NE, NW, SE, SW) and town can only be non-zero
         * if a non-company is building the road */
        if (company == OWNER_TOWN) {
                if (!Town::IsValidID(p2)) return CMD_ERROR;
        } else {
                if (p2 != 0) return CMD_ERROR;

                const Town *town = CalcClosestTownFromTile(tile);
                p2 = (town != NULL) ? town->index : (TownID)INVALID_TOWN;

                if (company == OWNER_DEITY) {
                        company = OWNER_TOWN;

                        /* If we are not within a town, we are not owned by the town */
                        if (town == NULL || DistanceSquare(tile, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
                                company = OWNER_NONE;
                        }
                }
        }

        RoadBits pieces = Extract<RoadBits, 0, 4>(p1);

        /* do not allow building 'zero' road bits, code wouldn't handle it */
        if (pieces == ROAD_NONE) return CMD_ERROR;

        RoadType rt = Extract<RoadType, 4, 2>(p1);
        if (!IsValidRoadType(rt) || !ValParamRoadType(rt)) return CMD_ERROR;

        DisallowedRoadDirections toggle_drd = Extract<DisallowedRoadDirections, 6, 2>(p1);

        switch (GetTileType(tile)) {
                case TT_ROAD:
                        if (IsTileSubtype(tile, TT_BRIDGE)) {
                                return BuildRoad_Bridge(tile, flags, rt, pieces, company, p2, toggle_drd);
                        } else {
                                return BuildRoad_Road(tile, flags, rt, pieces, company, p2, toggle_drd);
                        }

                case TT_RAILWAY:
                        return BuildRoad_Railway(tile, flags, rt, pieces, company, p2, toggle_drd);

                case TT_STATION:
                        return BuildRoad_Station(tile, flags, rt, pieces, company, p2, toggle_drd);

                case TT_MISC:
                        switch (GetTileSubtype(tile)) {
                                case TT_MISC_CROSSING:
                                        return BuildRoad_Crossing(tile, flags, rt, pieces, company, p2, toggle_drd);

                                case TT_MISC_TUNNEL:
                                        return BuildRoad_Tunnel(tile, flags, rt, pieces, company, p2, toggle_drd);

                                case TT_MISC_DEPOT:
                                        if (IsRoadDepot(tile) && (GetAnyRoadBits(tile, rt) & pieces) == pieces) return_cmd_error(STR_ERROR_ALREADY_BUILT);
                                        /* fall through */
                                default:
                                        break;
                        }
                        /* fall through */
                default:
                        return BuildRoad_Clear(tile, flags, rt, pieces, company, p2, toggle_drd);
        }
}

/**
 * Checks whether a road or tram connection can be found when building a new road or tram.
 * @param tile Tile at which the road being built will end.
 * @param rt Roadtype of the road being built.
 * @param dir Direction that the road is following.
 * @return True if the next tile at dir direction is suitable for being connected directly by a second roadbit at the end of the road being built.
 */
static bool CanConnectToRoad(TileIndex tile, RoadType rt, DiagDirection dir)
{
        RoadBits bits = GetAnyRoadBits(tile + TileOffsByDiagDir(dir), rt, false);
        return (bits & DiagDirToRoadBits(ReverseDiagDir(dir))) != 0;
}

/**
 * Build a long piece of road.
 * @param start_tile start tile of drag (the building cost will appear over this tile)
 * @param flags operation to perform
 * @param p1 end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit 0) - start tile starts in the 2nd half of tile (p2 & 1). Only used if bit 6 is set or if we are building a single tile
 * - p2 = (bit 1) - end tile starts in the 2nd half of tile (p2 & 2). Only used if bit 6 is set or if we are building a single tile
 * - p2 = (bit 2) - direction: 0 = along x-axis, 1 = along y-axis (p2 & 4)
 * - p2 = (bit 3 + 4) - road type
 * - p2 = (bit 5) - set road direction
 * - p2 = (bit 6) - defines two different behaviors for this command:
 *      - 0 = Build up to an obstacle. Do not build the first and last roadbits unless they can be connected to something, or if we are building a single tile
 *      - 1 = Fail if an obstacle is found. Always take into account bit 0 and 1. This behavior is used for scripts
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdBuildLongRoad(TileIndex start_tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        DisallowedRoadDirections drd = DRD_NORTHBOUND;

        if (p1 >= MapSize()) return CMD_ERROR;

        TileIndex end_tile = p1;
        RoadType rt = Extract<RoadType, 3, 2>(p2);
        if (!IsValidRoadType(rt) || !ValParamRoadType(rt)) return CMD_ERROR;

        Axis axis = Extract<Axis, 2, 1>(p2);
        /* Only drag in X or Y direction dictated by the direction variable */
        if (axis == AXIS_X && TileY(start_tile) != TileY(end_tile)) return CMD_ERROR; // x-axis
        if (axis == AXIS_Y && TileX(start_tile) != TileX(end_tile)) return CMD_ERROR; // y-axis

        DiagDirection dir = AxisToDiagDir(axis);

        /* Swap direction, also the half-tile drag var (bit 0 and 1) */
        if (start_tile > end_tile || (start_tile == end_tile && HasBit(p2, 0))) {
                dir = ReverseDiagDir(dir);
                p2 ^= 3;
                drd = DRD_SOUTHBOUND;
        }

        /* On the X-axis, we have to swap the initial bits, so they
         * will be interpreted correctly in the GTTS. Furthermore
         * when you just 'click' on one tile to build them. */
        if ((axis == AXIS_Y) == (start_tile == end_tile && HasBit(p2, 0) == HasBit(p2, 1))) drd ^= DRD_BOTH;
        /* No disallowed direction bits have to be toggled */
        if (!HasBit(p2, 5)) drd = DRD_NONE;

        CommandCost cost(EXPENSES_CONSTRUCTION);
        CommandCost last_error = CMD_ERROR;
        TileIndex tile = start_tile;
        bool had_bridge = false;
        bool had_tunnel = false;
        bool had_success = false;
        bool is_ai = HasBit(p2, 6);

        /* Start tile is the first tile clicked by the user. */
        for (;;) {
                RoadBits bits = AxisToRoadBits(axis);

                /* Determine which road parts should be built. */
                if (!is_ai && start_tile != end_tile) {
                        /* Only build the first and last roadbit if they can connect to something. */
                        if (tile == end_tile && !CanConnectToRoad(tile, rt, dir)) {
                                bits = DiagDirToRoadBits(ReverseDiagDir(dir));
                        } else if (tile == start_tile && !CanConnectToRoad(tile, rt, ReverseDiagDir(dir))) {
                                bits = DiagDirToRoadBits(dir);
                        }
                } else {
                        /* Road parts only have to be built at the start tile or at the end tile. */
                        if (tile == end_tile && !HasBit(p2, 1)) bits &= DiagDirToRoadBits(ReverseDiagDir(dir));
                        if (tile == start_tile && HasBit(p2, 0)) bits &= DiagDirToRoadBits(dir);
                }

                CommandCost ret = DoCommand(tile, drd << 6 | rt << 4 | bits, 0, flags, CMD_BUILD_ROAD);
                if (ret.Failed()) {
                        last_error = ret;
                        if (last_error.GetErrorMessage() != STR_ERROR_ALREADY_BUILT) {
                                if (is_ai) return last_error;
                                break;
                        }
                } else {
                        had_success = true;
                        /* Only pay for the upgrade on one side of the bridges and tunnels */
                        if (IsTunnelTile(tile)) {
                                if (!had_tunnel || GetTunnelBridgeDirection(tile) == dir) {
                                        cost.AddCost(ret);
                                }
                                had_tunnel = true;
                        } else if (IsRoadBridgeTile(tile)) {
                                if (!had_bridge || GetTunnelBridgeDirection(tile) == dir) {
                                        cost.AddCost(ret);
                                }
                                had_bridge = true;
                        } else {
                                cost.AddCost(ret);
                        }
                }

                if (tile == end_tile) break;

                tile += TileOffsByDiagDir(dir);
        }

        return had_success ? cost : last_error;
}

/**
 * Remove a long piece of road.
 * @param start_tile start tile of drag
 * @param flags operation to perform
 * @param p1 end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit 0) - start tile starts in the 2nd half of tile (p2 & 1)
 * - p2 = (bit 1) - end tile starts in the 2nd half of tile (p2 & 2)
 * - p2 = (bit 2) - direction: 0 = along x-axis, 1 = along y-axis (p2 & 4)
 * - p2 = (bit 3 + 4) - road type
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdRemoveLongRoad(TileIndex start_tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        CommandCost cost(EXPENSES_CONSTRUCTION);

        if (p1 >= MapSize()) return CMD_ERROR;

        TileIndex end_tile = p1;
        RoadType rt = Extract<RoadType, 3, 2>(p2);
        if (!IsValidRoadType(rt)) return CMD_ERROR;

        Axis axis = Extract<Axis, 2, 1>(p2);
        /* Only drag in X or Y direction dictated by the direction variable */
        if (axis == AXIS_X && TileY(start_tile) != TileY(end_tile)) return CMD_ERROR; // x-axis
        if (axis == AXIS_Y && TileX(start_tile) != TileX(end_tile)) return CMD_ERROR; // y-axis

        /* Swap start and ending tile, also the half-tile drag var (bit 0 and 1) */
        if (start_tile > end_tile || (start_tile == end_tile && HasBit(p2, 0))) {
                TileIndex t = start_tile;
                start_tile = end_tile;
                end_tile = t;
                p2 ^= IsInsideMM(p2 & 3, 1, 3) ? 3 : 0;
        }

        Money money = GetAvailableMoneyForCommand();
        TileIndex tile = start_tile;
        CommandCost last_error = CMD_ERROR;
        bool had_success = false;
        /* Start tile is the small number. */
        for (;;) {
                RoadBits bits = AxisToRoadBits(axis);

                if (tile == end_tile && !HasBit(p2, 1)) bits &= ROAD_NW | ROAD_NE;
                if (tile == start_tile && HasBit(p2, 0)) bits &= ROAD_SE | ROAD_SW;

                /* try to remove the halves. */
                if (bits != 0) {
                        CommandCost ret = RemoveRoad(tile, flags & ~DC_EXEC, bits, rt, true);
                        if (ret.Succeeded()) {
                                if (flags & DC_EXEC) {
                                        money -= ret.GetCost();
                                        if (money < 0) {
                                                _additional_cash_required = DoCommand(start_tile, end_tile, p2, flags & ~DC_EXEC, CMD_REMOVE_LONG_ROAD).GetCost();
                                                return cost;
                                        }
                                        RemoveRoad(tile, flags, bits, rt, true, false);
                                }
                                cost.AddCost(ret);
                                had_success = true;
                        } else {
                                /* Ownership errors are more important. */
                                if (last_error.GetErrorMessage() != STR_ERROR_OWNED_BY) last_error = ret;
                        }
                }

                if (tile == end_tile) break;

                tile += (axis == AXIS_Y) ? TileDiffXY(0, 1) : TileDiffXY(1, 0);
        }

        return had_success ? cost : last_error;
}

/**
 * Build a road depot.
 * @param tile tile where to build the depot
 * @param flags operation to perform
 * @param p1 bit 0..1 entrance direction (DiagDirection)
 *           bit 2..3 road type
 * @param p2 unused
 * @param text unused
 * @return the cost of this operation or an error
 *
 * @todo When checking for the tile slope,
 * distinguish between "Flat land required" and "land sloped in wrong direction"
 */
CommandCost CmdBuildRoadDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        DiagDirection dir = Extract<DiagDirection, 0, 2>(p1);
        RoadType rt = Extract<RoadType, 2, 2>(p1);

        if (!IsValidRoadType(rt) || !ValParamRoadType(rt)) return CMD_ERROR;

        Slope tileh = GetTileSlope(tile);
        if (tileh != SLOPE_FLAT && (
                                !_settings_game.construction.build_on_slopes ||
                                !CanBuildDepotByTileh(dir, tileh)
                        )) {
                return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
        }

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

        if (HasBridgeAbove(tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

        if (!Depot::CanAllocateItem()) return CMD_ERROR;

        if (flags & DC_EXEC) {
                Depot *dep = new Depot(tile);
                dep->build_date = _date;

                /* A road depot has two road bits. */
                Company::Get(_current_company)->infrastructure.road[rt] += 2;
                DirtyCompanyInfrastructureWindows(_current_company);

                MakeRoadDepot(tile, _current_company, dep->index, dir, rt);
                MarkTileDirtyByTile(tile);
                MakeDefaultName(dep);
        }
        cost.AddCost(_price[PR_BUILD_DEPOT_ROAD]);
        return cost;
}

static CommandCost ClearTile_Road(TileIndex tile, DoCommandFlag flags)
{
        if (IsTileSubtype(tile, TT_TRACK)) {
                RoadBits b = GetAllRoadBits(tile);

                /* Clear the road if only one piece is on the tile OR we are not using the DC_AUTO flag */
                if ((HasExactlyOneBit(b) && GetRoadBits(tile, ROADTYPE_TRAM) == ROAD_NONE) || !(flags & DC_AUTO)) {
                        CommandCost ret(EXPENSES_CONSTRUCTION);
                        RoadType rt;
                        FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
                                CommandCost tmp_ret = RemoveRoad(tile, flags, GetRoadBits(tile, rt), rt, true);
                                if (tmp_ret.Failed()) return tmp_ret;
                                ret.AddCost(tmp_ret);
                        }
                        return ret;
                }

                return_cmd_error(STR_ERROR_MUST_REMOVE_ROAD_FIRST);
        } else {
                if (flags & DC_AUTO) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

                /* Floods can remove anything as well as the scenario editor */

                if (_current_company != OWNER_WATER && _game_mode != GM_EDITOR) {
                        RoadTypes rts = GetRoadTypes(tile);
                        Owner road_owner = _current_company;
                        if (HasBit(rts, ROADTYPE_ROAD)) road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);

                        /* We can remove unowned road and if the town allows it */
                        if (road_owner == OWNER_TOWN && _current_company != OWNER_TOWN && !(_settings_game.construction.extra_dynamite || _cheats.magic_bulldozer.value)) {
                                /* Town does not allow */
                                CommandCost ret = CheckTileOwnership(tile);
                                if (ret.Failed()) return ret;
                        } else {
                                if (road_owner != OWNER_NONE && road_owner != OWNER_TOWN) {
                                        CommandCost ret = CheckOwnership(road_owner, tile);
                                        if (ret.Failed()) return ret;
                                }

                                if (HasBit(rts, ROADTYPE_TRAM)) {
                                        Owner tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);
                                        if (tram_owner != OWNER_NONE) {
                                                CommandCost ret = CheckOwnership(tram_owner, tile);
                                                if (ret.Failed()) return ret;
                                        }
                                }
                        }
                }

                TileIndex endtile = GetOtherBridgeEnd(tile);

                CommandCost ret = TunnelBridgeIsFree(tile, endtile);
                if (ret.Failed()) return ret;

                if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
                        Town *t = ClosestTownFromTile(tile); // town penalty rating

                        /* Check if you are allowed to remove the bridge owned by a town
                         * Removal depends on difficulty settings */
                        CommandCost ret = CheckforTownRating(flags, t, TUNNELBRIDGE_REMOVE);
                        if (ret.Failed()) return ret;

                        /* checks if the owner is town then decrease town rating by RATING_TUNNEL_BRIDGE_DOWN_STEP until
                         * you have a "Poor" (0) town rating */
                        ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM, flags);
                }

                uint len = GetTunnelBridgeLength(tile, endtile);

                if (flags & DC_EXEC) {
                        RemoveBridgeMiddleTiles(tile, endtile);

                        DiagDirection dir = GetTunnelBridgeDirection(tile);
                        RoadBits bridge_piece = DiagDirToRoadBits(dir);
                        RoadBits other_nonbridge_pieces = ComplementRoadBits(DiagDirToRoadBits(ReverseDiagDir(dir)));
                        bool other_extended = IsExtendedRoadBridge(endtile);

                        MakeNormalRoadFromBridge(endtile);

                        RoadType rt;
                        FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
                                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                                RoadBits pieces = GetRoadBits(tile, rt);

                                if ((pieces & bridge_piece) == 0) {
                                        /* This roadtype does not connect to the bridge */
                                        if (c != NULL) {
                                                c->infrastructure.road[rt] -= CountBits(pieces);
                                                DirtyCompanyInfrastructureWindows(c->index);
                                        }
                                } else {
                                        /* This roadtype connects to the bridge */
                                        RoadBits other_pieces = GetRoadBits(endtile, rt);

                                        if (c != NULL) {
                                                /* A full diagonal road tile has two road bits. */
                                                c->infrastructure.road[rt] -= (CountBits(pieces) + 2 * len + CountBits(other_pieces)) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                                DirtyCompanyInfrastructureWindows(c->index);
                                        }

                                        if (other_extended && ((other_pieces &= other_nonbridge_pieces) != 0)) {
                                                SetRoadBits(endtile, other_pieces, rt);
                                                if (c != NULL) c->infrastructure.road[rt] += CountBits(other_pieces);
                                        } else {
                                                ClearRoadType(endtile, rt);
                                        }
                                }

                        }

                        DoClearSquare(tile);
                        MarkTileDirtyByTile(endtile);
                }

                return CommandCost(EXPENSES_CONSTRUCTION, (len + 2) * _price[PR_CLEAR_BRIDGE]);
        }
}


/**
 * Get the foundationtype of a RoadBits Slope combination
 *
 * @param tileh The Slope part
 * @param bits The RoadBits part
 * @return The resulting Foundation
 */
static Foundation GetRoadFoundation(Slope tileh, RoadBits bits)
{
        /* Flat land and land without a road doesn't require a foundation */
        if (tileh == SLOPE_FLAT || bits == ROAD_NONE) return FOUNDATION_NONE;

        /* Steep slopes behave the same as slopes with one corner raised. */
        if (IsSteepSlope(tileh)) {
                tileh = SlopeWithOneCornerRaised(GetHighestSlopeCorner(tileh));
        }

        /* Leveled RoadBits on a slope */
        if ((_invalid_leveled_roadbits[tileh] & bits) == ROAD_NONE) return FOUNDATION_LEVELED;

        /* Straight roads without foundation on a slope */
        if (!IsSlopeWithOneCornerRaised(tileh) &&
                        (_invalid_straight_roadbits[tileh] & bits) == ROAD_NONE)
                return FOUNDATION_NONE;

        /* Roads on steep Slopes or on Slopes with one corner raised */
        return (bits == ROAD_X ? FOUNDATION_INCLINED_X : FOUNDATION_INCLINED_Y);
}

const byte _road_sloped_sprites[14] = {
        0,  0,  2,  0,
        0,  1,  0,  0,
        3,  0,  0,  0,
        0,  0
};

/**
 * Draw the ground sprite for a road tile
 * @param tile The tile to draw
 * @param roadside The roadside of the tile
 * @param image The sprite to draw
 * @param paved_offset The offset to add to the sprite if the road is paved
 * @param unpaved_offset The offset to add to the sprite if the tile is on snow or in the desert
 * @return The palette to use for further drawing
 */
static PaletteID DrawRoadGroundSprite(TileIndex tile, Roadside roadside, SpriteID image, int paved_offset, int unpaved_offset)
{
        PaletteID pal = PAL_NONE;

        switch (roadside) {
                case ROADSIDE_BARREN:
                        if (IsOnSnow(tile)) {
                                image += unpaved_offset;
                        } else {
                                pal = PALETTE_TO_BARE_LAND;
                        }
                        break;

                case ROADSIDE_GRASS:
                        if (IsOnSnow(tile)) image += unpaved_offset;
                        break;

                default:
                        if (IsOnSnow(tile) && !(_settings_game.game_creation.landscape == LT_TROPIC && HasGrfMiscBit(GMB_DESERT_PAVED_ROADS))) {
                                image += unpaved_offset;
                        } else {
                                image += paved_offset;
                        }
                        break;
        }

        DrawGroundSprite(image, pal);

        return pal;
}

/**
 * Draws the catenary for the given tile
 * @param ti   information about the tile (slopes, height etc)
 * @param tram the roadbits for the tram
 */
void DrawTramCatenary(const TileInfo *ti, RoadBits tram)
{
        /* Do not draw catenary if it is invisible */
        if (IsInvisibilitySet(TO_CATENARY)) return;

        /* Don't draw the catenary under a low bridge */
        if (HasBridgeAbove(ti->tile) && !IsTransparencySet(TO_CATENARY)) {
                int height = GetBridgeHeight(GetNorthernBridgeEnd(ti->tile));

                if (height <= GetTileMaxZ(ti->tile) + 1) return;
        }

        SpriteID front;
        SpriteID back;

        if (ti->tileh != SLOPE_FLAT) {
                back  = SPR_TRAMWAY_BACK_WIRES_SLOPED  + _road_sloped_sprites[ti->tileh - 1];
                front = SPR_TRAMWAY_FRONT_WIRES_SLOPED + _road_sloped_sprites[ti->tileh - 1];
        } else {
                back  = SPR_TRAMWAY_BASE + _road_backpole_sprites_1[tram];
                front = SPR_TRAMWAY_BASE + _road_frontwire_sprites_1[tram];
        }

        AddSortableSpriteToDraw(back,  PAL_NONE, ti->x, ti->y, 16, 16, TILE_HEIGHT + BB_HEIGHT_UNDER_BRIDGE, ti->z, IsTransparencySet(TO_CATENARY));
        AddSortableSpriteToDraw(front, PAL_NONE, ti->x, ti->y, 16, 16, TILE_HEIGHT + BB_HEIGHT_UNDER_BRIDGE, ti->z, IsTransparencySet(TO_CATENARY));
}

/**
 * Draws details on/around the road
 * @param img the sprite to draw
 * @param ti  the tile to draw on
 * @param dx  the offset from the top of the BB of the tile
 * @param dy  the offset from the top of the BB of the tile
 * @param h   the height of the sprite to draw
 */
static void DrawRoadDetail(SpriteID img, const TileInfo *ti, int dx, int dy, int h)
{
        int x = ti->x | dx;
        int y = ti->y | dy;
        int z = ti->z;
        if (ti->tileh != SLOPE_FLAT) z = GetSlopePixelZ(x, y);
        AddSortableSpriteToDraw(img, PAL_NONE, x, y, 2, 2, h, z);
}

/**
 * Draw ground sprite and road pieces
 * @param ti TileInfo
 */
static void DrawRoadBits(TileInfo *ti)
{
        RoadBits road = GetRoadBits(ti->tile, ROADTYPE_ROAD);
        RoadBits tram = GetRoadBits(ti->tile, ROADTYPE_TRAM);

        SpriteID image = 0;

        if (IsTileSubtype(ti->tile, TT_BRIDGE)) {
                assert(ti->tileh != SLOPE_FLAT);
                DrawFoundation(ti, FOUNDATION_LEVELED, GetTunnelBridgeDirection(ti->tile));
        } else if (ti->tileh != SLOPE_FLAT) {
                Foundation f = GetRoadFoundation(ti->tileh, road | tram);

                DrawFoundation(ti, f);

                /* DrawFoundation() modifies ti.
                 * Default sloped sprites.. */
                if (ti->tileh != SLOPE_FLAT) image = _road_sloped_sprites[ti->tileh - 1] + SPR_ROAD_SLOPE_START;
        }

        if (image == 0) image = _road_tile_sprites_1[road != ROAD_NONE ? road : tram];

        Roadside roadside = IsTileSubtype(ti->tile, TT_TRACK) ? GetRoadside(ti->tile) : ROADSIDE_GRASS;

        PaletteID pal = DrawRoadGroundSprite(ti->tile, roadside, image, -19, 19);

        /* For tram we overlay the road graphics with either tram tracks only
         * (when there is actual road beneath the trams) or with tram tracks
         * and some dirts which hides the road graphics */
        if (tram != ROAD_NONE) {
                if (ti->tileh != SLOPE_FLAT) {
                        image = _road_sloped_sprites[ti->tileh - 1] + SPR_TRAMWAY_SLOPED_OFFSET;
                } else {
                        image = _road_tile_sprites_1[tram] - SPR_ROAD_Y;
                }
                image += (road == ROAD_NONE) ? SPR_TRAMWAY_TRAM : SPR_TRAMWAY_OVERLAY;
                DrawGroundSprite(image, pal);
        }

        if (IsTileSubtype(ti->tile, TT_TRACK) && road != ROAD_NONE) {
                DisallowedRoadDirections drd = GetDisallowedRoadDirections(ti->tile);
                if (drd != DRD_NONE) {
                        DrawGroundSpriteAt(SPR_ONEWAY_BASE + drd - 1 + ((road == ROAD_X) ? 0 : 3), PAL_NONE, 8, 8, GetPartialPixelZ(8, 8, ti->tileh));
                }
        }

        if (IsTileSubtype(ti->tile, TT_TRACK) && HasRoadWorks(ti->tile)) {
                /* Road works */
                DrawGroundSprite((road | tram) & ROAD_X ? SPR_EXCAVATION_X : SPR_EXCAVATION_Y, PAL_NONE);
                return;
        }

        if (tram != ROAD_NONE) DrawTramCatenary(ti, tram);

        if (!IsTileSubtype(ti->tile, TT_TRACK)) return;

        /* Return if full detail is disabled, or we are zoomed fully out. */
        if (!HasBit(_display_opt, DO_FULL_DETAIL) || _cur_dpi->zoom > ZOOM_LVL_DETAIL) return;

        /* Do not draw details (street lights, trees) under low bridge */
        if (HasBridgeAbove(ti->tile) && (roadside == ROADSIDE_TREES || roadside == ROADSIDE_STREET_LIGHTS)) {
                int height = GetBridgeHeight(GetNorthernBridgeEnd(ti->tile));
                int minz = GetTileMaxZ(ti->tile) + 2;

                if (roadside == ROADSIDE_TREES) minz++;

                if (height < minz) return;
        }

        /* If there are no road bits, return, as there is nothing left to do */
        if (HasAtMostOneBit(road)) return;

        /* Draw extra details. */
        for (const DrawRoadTileStruct *drts = _road_display_table[roadside][road | tram]; drts->image != 0; drts++) {
                DrawRoadDetail(drts->image, ti, drts->subcoord_x, drts->subcoord_y, 0x10);
        }
}

/** Tile callback function for rendering a road tile to the screen */
static void DrawTile_Road(TileInfo *ti)
{
        if (IsTileSubtype(ti->tile, TT_TRACK) || IsExtendedRoadBridge(ti->tile)) {
                DrawRoadBits(ti);
        } else {
                DrawBridgeGround(ti);

                /* draw ramp */

                DiagDirection dir = GetTunnelBridgeDirection(ti->tile);

                const PalSpriteID *psid = GetBridgeRampSprite(GetRoadBridgeType(ti->tile), 8, ti->tileh, dir);

                /* Draw Trambits as SpriteCombine */
                StartSpriteCombine();

                /* HACK set the height of the BB of a sloped ramp to 1 so a vehicle on
                 * it doesn't disappear behind it
                 */
                /* Bridge heads are drawn solid no matter how invisibility/transparency is set */
                AddSortableSpriteToDraw(psid->sprite, psid->pal, ti->x, ti->y, 16, 16, ti->tileh == SLOPE_FLAT ? 0 : 8, ti->z);

                RoadTypes rts = GetRoadTypes(ti->tile);

                if (HasBit(rts, ROADTYPE_TRAM)) {
                        uint offset = dir;
                        int z = ti->z;
                        if (ti->tileh != SLOPE_FLAT) {
                                offset = (offset + 1) & 1;
                                z += TILE_HEIGHT;
                        } else {
                                offset += 2;
                        }
                        /* DrawBridgeTramBits() calls EndSpriteCombine() and StartSpriteCombine() */
                        DrawBridgeTramBits(ti->x, ti->y, z, offset, HasBit(rts, ROADTYPE_ROAD), true);
                }

                EndSpriteCombine();
        }

        DrawBridgeMiddle(ti);
}

void DrawLevelCrossing(TileInfo *ti)
{
        if (ti->tileh != SLOPE_FLAT) DrawFoundation(ti, FOUNDATION_LEVELED);

        PaletteID pal = PAL_NONE;
        const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));

        if (rti->UsesOverlay()) {
                Axis axis = GetCrossingRailAxis(ti->tile);

                DrawRoadGroundSprite(ti->tile, GetRoadside(ti->tile), SPR_ROAD_Y + axis, -19, 19);

                SpriteID rail = GetCustomRailSprite(rti, ti->tile, RTSG_CROSSING) + axis;
                /* Draw tracks, but draw PBS reserved tracks darker. */
                pal = (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasCrossingReservation(ti->tile)) ? PALETTE_CRASH : PAL_NONE;
                DrawGroundSprite(rail, pal);

                DrawRailTileSeq(ti, &_crossing_layout, TO_CATENARY, rail, 0, PAL_NONE);
        } else {
                SpriteID image = rti->base_sprites.crossing;

                if (GetCrossingRoadAxis(ti->tile) == AXIS_X) image++;
                if (IsCrossingBarred(ti->tile)) image += 2;

                pal = DrawRoadGroundSprite(ti->tile, GetRoadside(ti->tile), image, 4, 8);

                /* PBS debugging, draw reserved tracks darker */
                if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasCrossingReservation(ti->tile)) {
                        DrawGroundSprite(GetCrossingRoadAxis(ti->tile) == AXIS_Y ? GetRailTypeInfo(GetRailType(ti->tile))->base_sprites.single_x : GetRailTypeInfo(GetRailType(ti->tile))->base_sprites.single_y, PALETTE_CRASH);
                }
        }

        if (HasTileRoadType(ti->tile, ROADTYPE_TRAM)) {
                DrawGroundSprite(SPR_TRAMWAY_OVERLAY + (GetCrossingRoadAxis(ti->tile) ^ 1), pal);
                DrawTramCatenary(ti, GetCrossingRoadBits(ti->tile));
        }

        if (HasCatenaryDrawn(GetRailType(ti->tile))) DrawCatenary(ti);

        DrawBridgeMiddle(ti);
}

/**
 * Updates cached nearest town for all road tiles
 * @param invalidate are we just invalidating cached data?
 * @pre invalidate == true implies _generating_world == true
 */
void UpdateNearestTownForRoadTiles(bool invalidate)
{
        assert(!invalidate || _generating_world);

        for (TileIndex t = 0; t < MapSize(); t++) {
                if ((IsRoadTile(t) || IsLevelCrossingTile(t)) && !HasTownOwnedRoad(t)) {
                        TownID tid = (TownID)INVALID_TOWN;
                        if (!invalidate) {
                                const Town *town = CalcClosestTownFromTile(t);
                                if (town != NULL) tid = town->index;
                        }
                        SetTownIndex(t, tid);
                }
        }
}

static int GetSlopePixelZ_Road(TileIndex tile, uint x, uint y)
{
        int z;
        Slope tileh = GetTilePixelSlope(tile, &z);

        if (IsTileSubtype(tile, TT_TRACK)) {
                if (tileh == SLOPE_FLAT) return z;
                z += ApplyPixelFoundationToSlope(GetRoadFoundation(tileh, GetAllRoadBits(tile)), &tileh);
                return z + GetPartialPixelZ(x & 0xF, y & 0xF, tileh);
        } else if (IsExtendedRoadBridge(tile)) {
                return z + TILE_HEIGHT;
        } else {
                x &= 0xF;
                y &= 0xF;

                DiagDirection dir = GetTunnelBridgeDirection(tile);

                z += ApplyPixelFoundationToSlope(GetBridgeFoundation(tileh, DiagDirToAxis(dir)), &tileh);

                /* On the bridge ramp? */
                uint pos = (DiagDirToAxis(dir) == AXIS_X ? y : x);
                if (5 <= pos && pos <= 10) {
                        return z + ((tileh == SLOPE_FLAT) ? GetBridgePartialPixelZ(dir, x, y) : TILE_HEIGHT);
                }

                return z + GetPartialPixelZ(x, y, tileh);
        }
}

static Foundation GetFoundation_Road(TileIndex tile, Slope tileh)
{
        return IsTileSubtype(tile, TT_TRACK) ? GetRoadFoundation(tileh, GetAllRoadBits(tile)) :
                IsExtendedRoadBridge(tile) ? FOUNDATION_LEVELED :
                GetBridgeFoundation(tileh, DiagDirToAxis(GetTunnelBridgeDirection(tile)));
}

static const Roadside _town_road_types[][2] = {
        { ROADSIDE_GRASS,         ROADSIDE_GRASS },
        { ROADSIDE_PAVED,         ROADSIDE_PAVED },
        { ROADSIDE_PAVED,         ROADSIDE_PAVED },
        { ROADSIDE_TREES,         ROADSIDE_TREES },
        { ROADSIDE_STREET_LIGHTS, ROADSIDE_PAVED }
};

static const Roadside _town_road_types_2[][2] = {
        { ROADSIDE_GRASS,         ROADSIDE_GRASS },
        { ROADSIDE_PAVED,         ROADSIDE_PAVED },
        { ROADSIDE_STREET_LIGHTS, ROADSIDE_PAVED },
        { ROADSIDE_STREET_LIGHTS, ROADSIDE_PAVED },
        { ROADSIDE_STREET_LIGHTS, ROADSIDE_PAVED }
};

void UpdateRoadSide(TileIndex tile, HouseZonesBits grp)
{
        /* Adjust road ground type depending on 'grp' (grp is the distance to the center) */
        const Roadside *new_rs = (_settings_game.game_creation.landscape == LT_TOYLAND) ? _town_road_types_2[grp] : _town_road_types[grp];
        Roadside cur_rs = GetRoadside(tile);

        /* We have our desired type, do nothing */
        if (cur_rs == new_rs[0]) return;

        /* We have the pre-type of the desired type, switch to the desired type */
        if (cur_rs == new_rs[1]) {
                cur_rs = new_rs[0];
        /* We have barren land, install the pre-type */
        } else if (cur_rs == ROADSIDE_BARREN) {
                cur_rs = new_rs[1];
        /* We're totally off limits, remove any installation and make barren land */
        } else {
                cur_rs = ROADSIDE_BARREN;
        }

        SetRoadside(tile, cur_rs);
        MarkTileDirtyByTile(tile);
}

static void TileLoop_Road(TileIndex tile)
{
        switch (_settings_game.game_creation.landscape) {
                case LT_ARCTIC: {
                        int z = IsTileSubtype(tile, TT_TRACK) ? GetTileZ(tile) : GetTileMaxZ(tile);
                        if (IsOnSnow(tile) != (z > GetSnowLine())) {
                                ToggleSnow(tile);
                                MarkTileDirtyByTile(tile);
                        }
                        break;
                }

                case LT_TROPIC:
                        if (GetTropicZone(tile) == TROPICZONE_DESERT && !IsOnDesert(tile)) {
                                ToggleDesert(tile);
                                MarkTileDirtyByTile(tile);
                        }
                        break;
        }

        if (!IsTileSubtype(tile, TT_TRACK)) return;

        const Town *t = ClosestTownFromTile(tile);
        if (!HasRoadWorks(tile)) {
                HouseZonesBits grp = HZB_TOWN_EDGE;

                if (t != NULL) {
                        grp = GetTownRadiusGroup(t, tile);

                        /* Show an animation to indicate road work */
                        if (t->road_build_months != 0 &&
                                        (DistanceManhattan(t->xy, tile) < 8 || grp != HZB_TOWN_EDGE) &&
                                        !HasAtMostOneBit(GetAllRoadBits(tile)) &&
                                        GetFoundationSlope(tile) == SLOPE_FLAT &&
                                        EnsureNoVehicleOnGround(tile).Succeeded() &&
                                        Chance16(1, 40)) {
                                StartRoadWorks(tile);
                                /* Remove any trees or lamps in case or roadwork */
                                switch (GetRoadside(tile)) {
                                        case ROADSIDE_BARREN:
                                        case ROADSIDE_GRASS:  SetRoadside(tile, ROADSIDE_GRASS); break;
                                        default:              SetRoadside(tile, ROADSIDE_PAVED); break;
                                }

                                if (_settings_client.sound.ambient) SndPlayTileFx(SND_21_JACKHAMMER, tile);
                                CreateEffectVehicleAbove(
                                        TileX(tile) * TILE_SIZE + 7,
                                        TileY(tile) * TILE_SIZE + 7,
                                        0,
                                        EV_BULLDOZER);
                                MarkTileDirtyByTile(tile);
                                return;
                        }
                }

                UpdateRoadSide(tile, grp);
        } else if (DecreaseRoadWorksCounter(tile)) {
                if (_settings_game.economy.mod_road_rebuild) {
                        /* Generate a nicer town surface */
                        const RoadBits old_rb = GetAnyRoadBits(tile, ROADTYPE_ROAD);
                        const RoadBits new_rb = CleanUpRoadBits(tile, old_rb);

                        if (old_rb != new_rb) {
                                RemoveRoad(tile, DC_EXEC | DC_AUTO | DC_NO_WATER, (old_rb ^ new_rb), ROADTYPE_ROAD, true);
                        }
                }

                MarkTileDirtyByTile(tile);
        }
}

static bool ClickTile_Road(TileIndex tile)
{
        return false;
}

static TrackStatus GetTileRoadStatus_Road(TileIndex tile, uint sub_mode, DiagDirection side)
{
        /* Converts RoadBits to TrackdirBits */
        static const TrackdirBits road_trackdirbits[16] = {
                TRACKDIR_BIT_NONE,                           // ROAD_NONE
                TRACKDIR_BIT_NONE,                           // ROAD_NW
                TRACKDIR_BIT_NONE,                           // ROAD_SW
                TRACKDIR_BIT_LEFT_S | TRACKDIR_BIT_LEFT_N,   // ROAD_W
                TRACKDIR_BIT_NONE,                           // ROAD_SE
                TRACKDIR_BIT_Y_SE | TRACKDIR_BIT_Y_NW,       // ROAD_Y
                TRACKDIR_BIT_LOWER_E | TRACKDIR_BIT_LOWER_W, // ROAD_S
                TRACKDIR_BIT_LEFT_S | TRACKDIR_BIT_LOWER_E | TRACKDIR_BIT_Y_SE
                        | TRACKDIR_BIT_LEFT_N | TRACKDIR_BIT_LOWER_W | TRACKDIR_BIT_Y_NW,  // ROAD_Y | ROAD_SW
                TRACKDIR_BIT_NONE,                           // ROAD_NE
                TRACKDIR_BIT_UPPER_E | TRACKDIR_BIT_UPPER_W, // ROAD_N
                TRACKDIR_BIT_X_NE | TRACKDIR_BIT_X_SW,       // ROAD_X
                TRACKDIR_BIT_LEFT_S | TRACKDIR_BIT_UPPER_E | TRACKDIR_BIT_X_NE
                        | TRACKDIR_BIT_LEFT_N | TRACKDIR_BIT_UPPER_W | TRACKDIR_BIT_X_SW,  // ROAD_X | ROAD_NW
                TRACKDIR_BIT_RIGHT_S | TRACKDIR_BIT_RIGHT_N, // ROAD_E
                TRACKDIR_BIT_RIGHT_S | TRACKDIR_BIT_UPPER_E | TRACKDIR_BIT_Y_SE
                        | TRACKDIR_BIT_RIGHT_N | TRACKDIR_BIT_UPPER_W | TRACKDIR_BIT_Y_NW, // ROAD_Y | ROAD_NE
                TRACKDIR_BIT_RIGHT_S | TRACKDIR_BIT_LOWER_E | TRACKDIR_BIT_X_NE
                        | TRACKDIR_BIT_RIGHT_N | TRACKDIR_BIT_LOWER_W | TRACKDIR_BIT_X_SW, // ROAD_X | ROAD_SE
                TRACKDIR_BIT_MASK,                           // ROAD_ALL
        };

        static const uint drd_mask[DRD_END] = { 0xFFFF, 0xFF00, 0xFF, 0x0 };

        if ((GetRoadTypes(tile) & sub_mode) == 0) return 0;

        if (IsTileSubtype(tile, TT_TRACK)) {
                if (HasRoadWorks(tile)) return 0;
        } else {
                if (side == GetTunnelBridgeDirection(tile)) return 0;
        }

        RoadType rt = (RoadType)FindFirstBit(sub_mode);
        RoadBits bits = GetRoadBits(tile, rt);

        /* no roadbit at this side of tile, return 0 */
        if (side != INVALID_DIAGDIR && (DiagDirToRoadBits(side) & bits) == 0) return 0;

        TrackdirBits trackdirbits = road_trackdirbits[bits];
        if (IsTileSubtype(tile, TT_TRACK) && rt == ROADTYPE_ROAD) trackdirbits &= (TrackdirBits)drd_mask[GetDisallowedRoadDirections(tile)];

        return CombineTrackStatus(trackdirbits, TRACKDIR_BIT_NONE);
}

static const StringID _road_tile_strings[] = {
        STR_LAI_ROAD_DESCRIPTION_ROAD,
        STR_LAI_ROAD_DESCRIPTION_ROAD,
        STR_LAI_ROAD_DESCRIPTION_ROAD,
        STR_LAI_ROAD_DESCRIPTION_ROAD_WITH_STREETLIGHTS,
        STR_LAI_ROAD_DESCRIPTION_ROAD,
        STR_LAI_ROAD_DESCRIPTION_TREE_LINED_ROAD,
        STR_LAI_ROAD_DESCRIPTION_ROAD,
        STR_LAI_ROAD_DESCRIPTION_ROAD,
};

static void GetTileDesc_Road(TileIndex tile, TileDesc *td)
{
        RoadTypes rts = GetRoadTypes(tile);

        Owner tram_owner = INVALID_OWNER;
        if (HasBit(rts, ROADTYPE_TRAM)) tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);

        if (IsTileSubtype(tile, TT_TRACK)) {
                if (!HasBit(rts, ROADTYPE_ROAD)) {
                        td->str = STR_LAI_ROAD_DESCRIPTION_TRAMWAY;
                        td->owner[0] = tram_owner;
                        return;
                }
                td->str = _road_tile_strings[GetRoadside(tile)];
        } else {
                const BridgeSpec *spec = GetBridgeSpec(GetRoadBridgeType(tile));
                td->str = spec->transport_name[TRANSPORT_ROAD];
                td->road_speed = spec->speed;
                if (!HasBit(rts, ROADTYPE_ROAD)) {
                        td->owner[0] = tram_owner;
                        return;
                }
        }

        /* So the tile at least has a road; check if it has both road and tram */
        Owner road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);

        if (HasBit(rts, ROADTYPE_TRAM)) {
                td->owner_type[0] = STR_LAND_AREA_INFORMATION_ROAD_OWNER;
                td->owner[0] = road_owner;
                td->owner_type[1] = STR_LAND_AREA_INFORMATION_TRAM_OWNER;
                td->owner[1] = tram_owner;
        } else {
                /* One to rule them all */
                td->owner[0] = road_owner;
        }
}


static void ChangeTileOwner_Road(TileIndex tile, Owner old_owner, Owner new_owner)
{
        Company *oldc = Company::Get(old_owner);

        Company *newc;
        if (new_owner != INVALID_OWNER) {
                newc = Company::Get(new_owner);
        } else {
                new_owner = OWNER_NONE;
                newc = NULL;
        }

        if (IsTileSubtype(tile, TT_TRACK)) {
                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)) {
                                        /* No need to dirty windows here, we'll redraw the whole screen anyway. */
                                        uint num_bits = CountBits(GetRoadBits(tile, rt));
                                        oldc->infrastructure.road[rt] -= num_bits;
                                        if (newc != NULL) newc->infrastructure.road[rt] += num_bits;
                                }

                                SetRoadOwner(tile, rt, new_owner);
                        }
                }
        } else {
                TileIndex other_end = GetOtherBridgeEnd(tile);
                /* Set number of pieces to zero if it's the southern tile as we
                 * don't want to update the infrastructure counts twice. */
                uint len = tile < other_end ? GetTunnelBridgeLength(tile, other_end) * 2 : 0;
                RoadBits bridge_piece = DiagDirToRoadBits(GetTunnelBridgeDirection(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 (HasBit(GetRoadTypes(tile), rt)) {
                                        /* Update company infrastructure counts.
                                         * No need to dirty windows here, we'll redraw the whole screen anyway. */
                                        RoadBits pieces = GetRoadBits(tile, rt);
                                        uint num_pieces = CountBits(pieces);
                                        if ((pieces & bridge_piece) != 0) {
                                                num_pieces = (num_pieces + len) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                        }
                                        oldc->infrastructure.road[rt] -= num_pieces;
                                        if (newc != NULL) newc->infrastructure.road[rt] += num_pieces;
                                }

                                SetRoadOwner(tile, rt, new_owner);
                        }
                }

                if (IsTileOwner(tile, old_owner)) SetTileOwner(tile, new_owner);
        }
}

static CommandCost TerraformTile_Road(TileIndex tile, DoCommandFlag flags, int z_new, Slope tileh_new)
{
        if (_settings_game.construction.build_on_slopes && AutoslopeEnabled()) {
                if (IsTileSubtype(tile, TT_TRACK)) {
                        RoadBits bits = GetAllRoadBits(tile);
                        RoadBits bits_new;
                        /* Check if the slope-road_bits combination is valid at all, i.e. it is safe to call GetRoadFoundation(). */
                        if (CheckRoadSlope(tileh_new, bits, ROAD_NONE, ROAD_NONE, &bits_new).Succeeded()) {
                                if (bits == bits_new) {
                                        int z_old;
                                        Slope tileh_old = GetTileSlope(tile, &z_old);

                                        /* Get the slope on top of the foundation */
                                        z_old += ApplyFoundationToSlope(GetRoadFoundation(tileh_old, bits), &tileh_old);
                                        z_new += ApplyFoundationToSlope(GetRoadFoundation(tileh_new, bits), &tileh_new);

                                        /* The surface slope must not be changed */
                                        if ((z_old == z_new) && (tileh_old == tileh_new)) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
                                }
                        }
                } else if (IsExtendedRoadBridge(tile)) {
                        if (IsValidRoadBridgeBits(tileh_new, GetTunnelBridgeDirection(tile), GetAllRoadBits(tile))) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
                } else {
                        int z_old;
                        Slope tileh_old = GetTileSlope(tile, &z_old);

                        DiagDirection direction = GetTunnelBridgeDirection(tile);

                        /* Check if new slope is valid for bridges in general (so we can safely call GetBridgeFoundation()) */
                        CheckBridgeSlope(direction, &tileh_old, &z_old);
                        CommandCost res = CheckBridgeSlope(direction, &tileh_new, &z_new);

                        /* Surface slope is valid and remains unchanged? */
                        if (res.Succeeded() && (z_old == z_new) && (tileh_old == tileh_new)) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
                }
        }

        return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
}

/** Tile callback functions for road tiles */
extern const TileTypeProcs _tile_type_road_procs = {
        DrawTile_Road,           // draw_tile_proc
        GetSlopePixelZ_Road,     // get_slope_z_proc
        ClearTile_Road,          // clear_tile_proc
        NULL,                    // add_accepted_cargo_proc
        GetTileDesc_Road,        // get_tile_desc_proc
        NULL,                    // get_tile_railway_status_proc
        GetTileRoadStatus_Road,  // get_tile_road_status_proc
        NULL,                    // get_tile_waterway_status_proc
        ClickTile_Road,          // click_tile_proc
        NULL,                    // animate_tile_proc
        TileLoop_Road,           // tile_loop_proc
        ChangeTileOwner_Road,    // change_tile_owner_proc
        NULL,                    // add_produced_cargo_proc
        GetFoundation_Road,      // get_foundation_proc
        TerraformTile_Road,      // terraform_tile_proc
};