Fix crash when setting separation mode for vehicles with no orders list.

[openttd-joker.git] / src / tunnelbridge_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 tunnelbridge_cmd.cpp
 * This file deals with tunnels and bridges (non-gui stuff)
 * @todo separate this file into two
 */

#include "stdafx.h"
#include "newgrf_object.h"
#include "viewport_func.h"
#include "cmd_helper.h"
#include "command_func.h"
#include "town.h"
#include "train.h"
#include "ship.h"
#include "roadveh.h"
#include "pathfinder/yapf/yapf_cache.h"
#include "newgrf_sound.h"
#include "autoslope.h"
#include "tunnelbridge_map.h"
#include "bridge_signal_map.h"
#include "tunnel_base.h"
#include "strings_func.h"
#include "date_func.h"
#include "clear_func.h"
#include "vehicle_func.h"
#include "vehicle_gui.h"
#include "sound_func.h"
#include "tunnelbridge.h"
#include "cheat_type.h"
#include "elrail_func.h"
#include "pbs.h"
#include "company_base.h"
#include "newgrf_railtype.h"
#include "object_base.h"
#include "water.h"
#include "company_gui.h"
#include "viewport_func.h"
#include "station_map.h"
#include "industry_map.h"

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

#include "safeguards.h"

BridgeSpec _bridge[MAX_BRIDGES]; ///< The specification of all bridges.
TileIndex _build_tunnel_endtile; ///< The end of a tunnel; as hidden return from the tunnel build command for GUI purposes.

/** Z position of the bridge sprites relative to bridge height (downwards) */
static const int BRIDGE_Z_START = 3;

extern void DrawRoadBits(TileInfo *ti);
extern const RoadBits _invalid_tileh_slopes_road[2][15];


/**
 * Mark bridge tiles dirty.
 * Note: The bridge does not need to exist, everything is passed via parameters.
 * @param begin Start tile.
 * @param end End tile.
 * @param direction Direction from \a begin to \a end.
 * @param bridge_height Bridge height level.
 */
void MarkBridgeDirty(TileIndex begin, TileIndex end, DiagDirection direction, uint bridge_height, const ZoomLevel mark_dirty_if_zoomlevel_is_below)
{
        TileIndexDiff delta = TileOffsByDiagDir(direction);
        for (TileIndex t = begin; t != end; t += delta) {
                MarkTileDirtyByTile(t, mark_dirty_if_zoomlevel_is_below, bridge_height - TileHeight(t));
        }
        MarkTileDirtyByTile(end, mark_dirty_if_zoomlevel_is_below);
}

/**
 * Mark bridge tiles dirty.
 * @param tile Bridge head.
 */
void MarkBridgeDirty(TileIndex tile, const ZoomLevel mark_dirty_if_zoomlevel_is_below)
{
        MarkBridgeDirty(tile, GetOtherTunnelBridgeEnd(tile), GetTunnelBridgeDirection(tile), GetBridgeHeight(tile), mark_dirty_if_zoomlevel_is_below);
}

/**
 * Mark bridge or tunnel tiles dirty.
 * @param tile Bridge head or tunnel entrance.
 */
void MarkBridgeOrTunnelDirty(TileIndex tile, const ZoomLevel mark_dirty_if_zoomlevel_is_below)
{
        if (IsBridge(tile)) {
                MarkBridgeDirty(tile, mark_dirty_if_zoomlevel_is_below);
        } else {
                MarkTileDirtyByTile(tile);
                MarkTileDirtyByTile(GetOtherTunnelBridgeEnd(tile));
        }
}
 
/**
 * Get number of signals on bridge or tunnel with signal simulation.
 * @param length Length of bridge/tunnel middle
 * @return Number of signals on signalled bridge/tunnel of this length
 */
uint GetTunnelBridgeSignalSimulationSignalCount(uint length)
{
        return 2 + (length / _settings_game.construction.simulated_wormhole_signals);
}

/** Reset the data been eventually changed by the grf loaded. */
void ResetBridges()
{
        /* First, free sprite table data */
        for (BridgeType i = 0; i < MAX_BRIDGES; i++) {
                if (_bridge[i].sprite_table != nullptr) {
                        for (BridgePieces j = BRIDGE_PIECE_NORTH; j < BRIDGE_PIECE_INVALID; j++) free(_bridge[i].sprite_table[j]);
                        free(_bridge[i].sprite_table);
                }
        }

        /* Then, wipe out current bridges */
        memset(&_bridge, 0, sizeof(_bridge));
        /* And finally, reinstall default data */
        memcpy(&_bridge, &_orig_bridge, sizeof(_orig_bridge));
}

/**
 * Calculate the price factor for building a long bridge.
 * Basically the cost delta is 1,1, 1, 2,2, 3,3,3, 4,4,4,4, 5,5,5,5,5, 6,6,6,6,6,6,  7,7,7,7,7,7,7,  8,8,8,8,8,8,8,8,
 * @param length Length of the bridge.
 * @return Price factor for the bridge.
 */
int CalcBridgeLenCostFactor(int length)
{
        if (length < 2) return length;

        length -= 2;
        int sum = 2;
        for (int delta = 1;; delta++) {
                for (int count = 0; count < delta; count++) {
                        if (length == 0) return sum;
                        sum += delta;
                        length--;
                }
        }
}

/**
 * Get the foundation for a bridge.
 * @param tileh The slope to build the bridge on.
 * @param axis The axis of the bridge entrance.
 * @return The foundation required.
 */
Foundation GetBridgeFoundation(Slope tileh, Axis axis)
{
        if (tileh == SLOPE_FLAT ||
                        ((tileh == SLOPE_NE || tileh == SLOPE_SW) && axis == AXIS_X) ||
                        ((tileh == SLOPE_NW || tileh == SLOPE_SE) && axis == AXIS_Y)) return FOUNDATION_NONE;

        return (HasSlopeHighestCorner(tileh) ? InclinedFoundation(axis) : FlatteningFoundation(tileh));
}

/**
 * Determines if the track on a bridge ramp is flat or goes up/down.
 *
 * @param tileh Slope of the tile under the bridge head
 * @param axis Orientation of bridge
 * @return true iff the track is flat.
 */
bool HasBridgeFlatRamp(Slope tileh, Axis axis)
{
        ApplyFoundationToSlope(GetBridgeFoundation(tileh, axis), &tileh);
        /* If the foundation slope is flat the bridge has a non-flat ramp and vice versa. */
        return (tileh != SLOPE_FLAT);
}

static inline const PalSpriteID *GetBridgeSpriteTable(int index, BridgePieces table)
{
        const BridgeSpec *bridge = GetBridgeSpec(index);
        assert(table < BRIDGE_PIECE_INVALID);
        if (bridge->sprite_table == nullptr || bridge->sprite_table[table] == nullptr) {
                return _bridge_sprite_table[index][table];
        } else {
                return bridge->sprite_table[table];
        }
}


/**
 * Determines the foundation for the north bridge head, and tests if the resulting slope is valid.
 *
 * @param axis Axis of the bridge
 * @param tileh Slope of the tile under the north bridge head; returns slope on top of foundation
 * @param z TileZ corresponding to tileh, gets modified as well
 * @return Error or cost for bridge foundation
 */
static CommandCost CheckBridgeSlopeNorth(Axis axis, Slope *tileh, int *z)
{
        Foundation f = GetBridgeFoundation(*tileh, axis);
        *z += ApplyFoundationToSlope(f, tileh);

        Slope valid_inclined = (axis == AXIS_X ? SLOPE_NE : SLOPE_NW);
        if ((*tileh != SLOPE_FLAT) && (*tileh != valid_inclined)) return CommandError();

        if (f == FOUNDATION_NONE) return CommandCost();

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

/**
 * Determines the foundation for the south bridge head, and tests if the resulting slope is valid.
 *
 * @param axis Axis of the bridge
 * @param tileh Slope of the tile under the south bridge head; returns slope on top of foundation
 * @param z TileZ corresponding to tileh, gets modified as well
 * @return Error or cost for bridge foundation
 */
static CommandCost CheckBridgeSlopeSouth(Axis axis, Slope *tileh, int *z)
{
        Foundation f = GetBridgeFoundation(*tileh, axis);
        *z += ApplyFoundationToSlope(f, tileh);

        Slope valid_inclined = (axis == AXIS_X ? SLOPE_SW : SLOPE_SE);
        if ((*tileh != SLOPE_FLAT) && (*tileh != valid_inclined)) return CommandError();

        if (f == FOUNDATION_NONE) return CommandCost();

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

/**
 * Is a bridge of the specified type and length available?
 * @param bridge_type Wanted type of bridge.
 * @param bridge_len  Wanted length of the bridge.
 * @return A succeeded (the requested bridge is available) or failed (it cannot be built) command.
 */
CommandCost CheckBridgeAvailability(BridgeType bridge_type, uint bridge_len, DoCommandFlag flags)
{
        if (flags & DC_QUERY_COST) {
                if (bridge_len <= _settings_game.construction.max_bridge_length) return CommandCost();
                return CommandError(STR_ERROR_BRIDGE_TOO_LONG);
        }

        if (bridge_type >= MAX_BRIDGES) return CommandError();

        const BridgeSpec *b = GetBridgeSpec(bridge_type);
        if (b->avail_year > _cur_year) return CommandError();

        uint max = min(b->max_length, _settings_game.construction.max_bridge_length);

        if (b->min_length > bridge_len) return CommandError();
        if (bridge_len <= max) return CommandCost();
        return CommandError(STR_ERROR_BRIDGE_TOO_LONG);
}

/**
 * Build a Bridge
 * @param end_tile end tile
 * @param flags type of operation
 * @param p1 packed start tile coords (~ dx)
 * @param p2 various bitstuffed elements
 * - p2 = (bit  0- 7) - bridge type (hi bh)
 * - p2 = (bit  8-12) - rail type or road types.
 * - p2 = (bit 15-16) - transport type.
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        CompanyID company = _current_company;

        RailType railtype = INVALID_RAILTYPE;
        RoadTypes roadtypes = ROADTYPES_NONE;

        /* unpack parameters */
        BridgeType bridge_type = GB(p2, 0, 8);

        if (!IsValidTile(p1)) return CommandError(STR_ERROR_BRIDGE_THROUGH_MAP_BORDER);

        TransportType transport_type = Extract<TransportType, 15, 2>(p2);

        /* type of bridge */
        switch (transport_type) {
                case TRANSPORT_ROAD:
                        roadtypes = Extract<RoadTypes, 8, 2>(p2);
                        if (!HasExactlyOneBit(roadtypes) || !HasRoadTypesAvail(company, roadtypes)) return CommandError();
                        break;

                case TRANSPORT_RAIL:
                        railtype = Extract<RailType, 8, 5>(p2);
                        if (!ValParamRailtype(railtype)) return CommandError();
                        break;

                case TRANSPORT_WATER:
                        break;

                default:
                        /* Airports don't have bridges. */
                        return CommandError();
        }
        TileIndex tile_start = p1;
        TileIndex tile_end = end_tile;

        if (company == OWNER_DEITY) {
                if (transport_type != TRANSPORT_ROAD) return CommandError();
                const Town *town = CalcClosestTownFromTile(tile_start);

                company = OWNER_TOWN;

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

        if (tile_start == tile_end) {
                return CommandError(STR_ERROR_CAN_T_START_AND_END_ON);
        }

        Axis direction;
        if (TileX(tile_start) == TileX(tile_end)) {
                direction = AXIS_Y;
        } else if (TileY(tile_start) == TileY(tile_end)) {
                direction = AXIS_X;
        } else {
                return CommandError(STR_ERROR_START_AND_END_MUST_BE_IN);
        }

        if (tile_end < tile_start) Swap(tile_start, tile_end);

        uint bridge_len = GetTunnelBridgeLength(tile_start, tile_end);
        if (transport_type != TRANSPORT_WATER) {
                /* set and test bridge length, availability */
                CommandCost ret = CheckBridgeAvailability(bridge_type, bridge_len, flags);
                if (ret.Failed()) return ret;
        } else {
                if (bridge_len > _settings_game.construction.max_bridge_length) return CommandError(STR_ERROR_BRIDGE_TOO_LONG);
        }

        int z_start;
        int z_end;
        Slope tileh_start = GetTileSlope(tile_start, &z_start);
        Slope tileh_end = GetTileSlope(tile_end, &z_end);
        bool pbs_reservation = false;

        CommandCost terraform_cost_north = CheckBridgeSlopeNorth(direction, &tileh_start, &z_start);
        CommandCost terraform_cost_south = CheckBridgeSlopeSouth(direction, &tileh_end,   &z_end);

        /* Aqueducts can't be built of flat land. */
        if (transport_type == TRANSPORT_WATER && (tileh_start == SLOPE_FLAT || tileh_end == SLOPE_FLAT)) return CommandError(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
        if (z_start != z_end) return CommandError(STR_ERROR_BRIDGEHEADS_NOT_SAME_HEIGHT);

        CommandCost cost(EXPENSES_CONSTRUCTION);
        Owner owner;
        bool is_new_owner;
        bool is_upgrade = false;
        if (IsBridgeTile(tile_start) && IsBridgeTile(tile_end) &&
                        GetOtherBridgeEnd(tile_start) == tile_end &&
                        GetTunnelBridgeTransportType(tile_start) == transport_type) {
                /* Replace a current bridge. */

                /* If this is a railway bridge, make sure the railtypes match. */
                if (transport_type == TRANSPORT_RAIL && GetRailType(tile_start) != railtype) {
                        return CommandError(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
                }

                /* Do not replace town bridges with lower speed bridges, unless in scenario editor. */
                if (!(flags & DC_QUERY_COST) && IsTileOwner(tile_start, OWNER_TOWN) &&
                                GetBridgeSpec(bridge_type)->speed < GetBridgeSpec(GetBridgeType(tile_start))->speed &&
                                _game_mode != GM_EDITOR) {
                        Town *t = ClosestTownFromTile(tile_start, UINT_MAX);

                        if (t == nullptr) {
                                return CommandError();
                        } else {
                                SetDParam(0, t->index);
                                return CommandError(STR_ERROR_LOCAL_AUTHORITY_REFUSES_TO_ALLOW_THIS);
                        }
                }

                /* Do not replace the bridge with the same bridge type. */
                if (!(flags & DC_QUERY_COST) && (bridge_type == GetBridgeType(tile_start)) && (transport_type != TRANSPORT_ROAD || (roadtypes & ~GetRoadTypes(tile_start)) == 0)) {
                        return CommandError(STR_ERROR_ALREADY_BUILT);
                }

                /* Do not allow replacing another company's bridges. */
                if (!IsTileOwner(tile_start, company) && !IsTileOwner(tile_start, OWNER_TOWN) && !IsTileOwner(tile_start, OWNER_NONE)) {
                        return CommandError(STR_ERROR_AREA_IS_OWNED_BY_ANOTHER);
                }

                cost.AddCost((bridge_len + 1) * _price[PR_CLEAR_BRIDGE]); // The cost of clearing the current bridge.
                owner = GetTileOwner(tile_start);

                /* If bridge belonged to bankrupt company, it has a new owner now */
                is_new_owner = (owner == OWNER_NONE);
                if (is_new_owner) owner = company;

                switch (transport_type) {
                        case TRANSPORT_RAIL:
                                /* Keep the reservation, the path stays valid. */
                                pbs_reservation = HasTunnelBridgeReservation(tile_start);
                                break;

                        case TRANSPORT_ROAD:
                                /* Do not remove road types when upgrading a bridge */
                                roadtypes |= GetRoadTypes(tile_start);
                                break;

                        default: break;
                }

                is_upgrade = true;
        } else {
                /* Build a new bridge. */

                bool allow_on_slopes = (_settings_game.construction.build_on_slopes && transport_type != TRANSPORT_WATER);

                /* Try and clear the start landscape */
                CommandCost ret = DoCommand(tile_start, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
                if (ret.Failed()) return ret;
                cost = ret;

                if (terraform_cost_north.Failed() || (terraform_cost_north.GetCost() != 0 && !allow_on_slopes)) return CommandError(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
                cost.AddCost(terraform_cost_north);

                /* Try and clear the end landscape */
                ret = DoCommand(tile_end, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
                if (ret.Failed()) return ret;
                cost.AddCost(ret);

                /* false - end tile slope check */
                if (terraform_cost_south.Failed() || (terraform_cost_south.GetCost() != 0 && !allow_on_slopes)) return CommandError(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
                cost.AddCost(terraform_cost_south);

                const TileIndex heads[] = {tile_start, tile_end};
                for (int i = 0; i < 2; i++) {
                        if (IsBridgeAbove(heads[i])) {
                                TileIndex north_head = GetNorthernBridgeEnd(heads[i]);

                                if (direction == GetBridgeAxis(heads[i])) return CommandError(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

                                if (z_start + 1 == GetBridgeHeight(north_head)) {
                                        return CommandError(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
                                }
                        }
                }

                TileIndexDiff delta = (direction == AXIS_X ? TileDiffXY(1, 0) : TileDiffXY(0, 1));
                for (TileIndex tile = tile_start + delta; tile != tile_end; tile += delta) {
                        if (GetTileMaxZ(tile) > z_start) return CommandError(STR_ERROR_BRIDGE_TOO_LOW_FOR_TERRAIN);

                        if (z_start >= (GetTileZ(tile) + _settings_game.construction.max_bridge_height)) {
                                /*
                                 * Disallow too high bridges.
                                 * Properly rendering a map where very high bridges (might) exist is expensive.
                                 * See http://www.tt-forums.net/viewtopic.php?f=33&t=40844&start=980#p1131762
                                 * for a detailed discussion. z_start here is one heightlevel below the bridge level.
                                 */
                                return CommandError(STR_ERROR_BRIDGE_TOO_HIGH_FOR_TERRAIN);
                        }

                        if (IsBridgeAbove(tile)) {
                                /* Disallow crossing bridges for the time being */
                                return CommandError(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
                        }

                        switch (GetTileType(tile)) {
                                case MP_WATER:
                                        if (!IsWater(tile) && !IsCoast(tile)) goto not_valid_below;
                                        break;

                                case MP_RAILWAY:
                                        if (!IsPlainRail(tile)) goto not_valid_below;
                                        break;

                                case MP_ROAD:
                                        if (IsRoadDepot(tile)) goto not_valid_below;
                                        break;

                                case MP_TUNNELBRIDGE:
                                        if (IsTunnel(tile)) break;
                                        if (direction == DiagDirToAxis(GetTunnelBridgeDirection(tile))) goto not_valid_below;
                                        if (z_start < GetBridgeHeight(tile)) goto not_valid_below;
                                        break;

                                case MP_OBJECT: {
                                        const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
                                        if ((spec->flags & OBJECT_FLAG_ALLOW_UNDER_BRIDGE) == 0) goto not_valid_below;
                                        if (GetTileMaxZ(tile) + spec->height > z_start) goto not_valid_below;
                                        break;
                                }

                                case MP_CLEAR:
                                        break;

                                default:
        not_valid_below:;
                                        /* try and clear the middle landscape */
                                        ret = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
                                        if (ret.Failed()) return ret;
                                        cost.AddCost(ret);
                                        break;
                        }

                        if (flags & DC_EXEC) {
                                /* We do this here because when replacing a bridge with another
                                 * type calling SetBridgeMiddle isn't needed. After all, the
                                 * tile already has the has_bridge_above bits set. */
                                SetBridgeMiddle(tile, direction);
                        }
                }

                owner = company;
                is_new_owner = true;
        }

        /* do the drill? */
        if (flags & DC_EXEC) {
                DiagDirection dir = AxisToDiagDir(direction);

                Company *c = Company::GetIfValid(company);
                switch (transport_type) {
                        case TRANSPORT_RAIL:
                                /* Add to company infrastructure count if required. */
                                if (is_new_owner && c != nullptr) c->infrastructure.rail[railtype] += (bridge_len + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                MakeRailBridgeRamp(tile_start, owner, bridge_type, dir,                 railtype, is_upgrade);
                                MakeRailBridgeRamp(tile_end,   owner, bridge_type, ReverseDiagDir(dir), railtype, is_upgrade);
                                SetTunnelBridgeReservation(tile_start, pbs_reservation);
                                SetTunnelBridgeReservation(tile_end,   pbs_reservation);
                                break;

                        case TRANSPORT_ROAD: {
                                RoadTypes prev_roadtypes = IsBridgeTile(tile_start) ? GetRoadTypes(tile_start) : ROADTYPES_NONE;
                                if (is_new_owner) {
                                        /* Also give unowned present roadtypes to new owner */
                                        if (HasBit(prev_roadtypes, ROADTYPE_ROAD) && GetRoadOwner(tile_start, ROADTYPE_ROAD) == OWNER_NONE) ClrBit(prev_roadtypes, ROADTYPE_ROAD);
                                        if (HasBit(prev_roadtypes, ROADTYPE_TRAM) && GetRoadOwner(tile_start, ROADTYPE_TRAM) == OWNER_NONE) ClrBit(prev_roadtypes, ROADTYPE_TRAM);
                                }
                                if (c != nullptr) {
                                        /* Add all new road types to the company infrastructure counter. */
                                        RoadType new_rt;
                                        FOR_EACH_SET_ROADTYPE(new_rt, roadtypes ^ prev_roadtypes) {
                                                /* A full diagonal road tile has two road bits. */
                                                c->infrastructure.road[new_rt] += (bridge_len + 2) * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                        }
                                }
                                Owner owner_road = HasBit(prev_roadtypes, ROADTYPE_ROAD) ? GetRoadOwner(tile_start, ROADTYPE_ROAD) : company;
                                Owner owner_tram = HasBit(prev_roadtypes, ROADTYPE_TRAM) ? GetRoadOwner(tile_start, ROADTYPE_TRAM) : company;
                                MakeRoadBridgeRamp(tile_start, owner, owner_road, owner_tram, bridge_type, dir,                 roadtypes, is_upgrade);
                                MakeRoadBridgeRamp(tile_end,   owner, owner_road, owner_tram, bridge_type, ReverseDiagDir(dir), roadtypes, is_upgrade);
                                break;
                        }

                        case TRANSPORT_WATER:
                                if (is_new_owner && c != nullptr) c->infrastructure.water += (bridge_len + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                MakeAqueductBridgeRamp(tile_start, owner, dir);
                                MakeAqueductBridgeRamp(tile_end,   owner, ReverseDiagDir(dir));
                                break;

                        default:
                                NOT_REACHED();
                }

                /* Mark all tiles dirty */
                MarkBridgeDirty(tile_start, tile_end, AxisToDiagDir(direction), z_start);
                DirtyCompanyInfrastructureWindows(company);
        }

        if ((flags & DC_EXEC) && transport_type == TRANSPORT_RAIL) {
                Track track = AxisToTrack(direction);
                AddSideToSignalBuffer(tile_start, INVALID_DIAGDIR, company);
                YapfNotifyTrackLayoutChange(tile_start, track);
        }

        /* for human player that builds the bridge he gets a selection to choose from bridges (DC_QUERY_COST)
         * It's unnecessary to execute this command every time for every bridge. So it is done only
         * and cost is computed in "bridge_gui.c". For AI, Towns this has to be of course calculated
         */
        Company *c = Company::GetIfValid(company);
        if (!(flags & DC_QUERY_COST) || (c != nullptr && c->is_ai)) {
                bridge_len += 2; // begin and end tiles/ramps

                switch (transport_type) {
                        case TRANSPORT_ROAD: cost.AddCost(bridge_len * _price[PR_BUILD_ROAD] * 2 * CountBits(roadtypes)); break;
                        case TRANSPORT_RAIL: cost.AddCost(bridge_len * RailBuildCost(railtype)); break;
                        default: break;
                }

                if (c != nullptr) bridge_len = CalcBridgeLenCostFactor(bridge_len);

                if (transport_type != TRANSPORT_WATER) {
                        cost.AddCost((int64)bridge_len * _price[PR_BUILD_BRIDGE] * GetBridgeSpec(bridge_type)->price >> 8);
                } else {
                        /* Aqueducts use a separate base cost. */
                        cost.AddCost((int64)bridge_len * _price[PR_BUILD_AQUEDUCT]);
                }

        }

        return cost;
}
 
/**
 * Check if the amount of tiles of the chunnel ramp is between allowed limits.
 * @param tile the actual tile.
 * @param ramp ramp_start tile.
 * @param delta the tile offset.
 * @return an empty string if between limits or a formatted string for the error message.
 */
static inline StringID IsRampBetweenLimits(TileIndex ramp_start, TileIndex tile, TileIndexDiff delta)
{
        uint min_length = 4;
        uint max_length = 7;
        if (Delta(ramp_start, tile) < (uint)abs(delta) * min_length || (uint)abs(delta) * max_length < Delta(ramp_start, tile)) {
                /* Add 1 in message to have consistency with cursor count in game. */
                SetDParam(0, max_length + 1);
                return STR_ERROR_CHUNNEL_RAMP;
        }

        return STR_NULL;
}

/**
 * See if chunnel building is possible.
 * All chunnel related issues are tucked away in one procedure
 * @pre   only on z level 0.
 * @param tile start tile of tunnel.
 * @param direction the direction we want to build.
 * @param is_chunnel pointer to set if chunnel is allowed or not.
 * @param sea_tiles pointer for the amount of tiles used to cross a sea.
 * @return an error message or if success the is_chunnel flag is set to true and the amount of tiles needed to cross the water is returned.
 */
static inline CommandCost CanBuildChunnel(TileIndex tile, DiagDirection direction, bool &is_chunnel, int &sea_tiles)
{
        const int start_z = 0;
        bool crossed_sea = false;
        TileIndex ramp_start = tile;

        if (GetTileZ(tile) > 0) return CommandError(STR_ERROR_CHUNNEL_ONLY_OVER_SEA);

        const TileIndexDiff delta = TileOffsByDiagDir(direction);
        for (;;) {
                tile += delta;
                if (!IsValidTile(tile)) return CommandError(STR_ERROR_CHUNNEL_THROUGH_MAP_BORDER);
                _build_tunnel_endtile = tile;
                int end_z;
                Slope end_tileh = GetTileSlope(tile, &end_z);

                if (start_z == end_z) {
                        /* Handle chunnels only on sea level and only one time crossing. */
                        if (!crossed_sea &&
                                        (IsCoastTile(tile) ||
                                        (IsValidTile(tile + delta) && HasTileWaterGround(tile + delta)) ||
                                        (IsValidTile(tile + delta * 2) && HasTileWaterGround(tile + delta * 2)))) {

                                /* A shore was found, check if start ramp was too short or too long. */
                                StringID err_msg = IsRampBetweenLimits(ramp_start, tile, delta);
                                if (err_msg > STR_NULL) return CommandError(err_msg);

                                /* Pass the water and find a proper shore tile that potentially
                                 * could have a tunnel portal behind. */
                                for (;;) {
                                        end_tileh = GetTileSlope(tile);
                                        if (direction == DIAGDIR_NE && (end_tileh & SLOPE_NE) == SLOPE_NE) break;
                                        if (direction == DIAGDIR_SE && (end_tileh & SLOPE_SE) == SLOPE_SE) break;
                                        if (direction == DIAGDIR_SW && (end_tileh & SLOPE_SW) == SLOPE_SW) break;
                                        if (direction == DIAGDIR_NW && (end_tileh & SLOPE_NW) == SLOPE_NW) break;

                                        /* No drilling under oil rigs.*/
                                        if ((IsTileType(tile, MP_STATION) && IsOilRig(tile)) ||
                                                        (IsTileType(tile, MP_INDUSTRY)               &&
                                                        GetIndustryGfx(tile) >= GFX_OILRIG_1         &&
                                                        GetIndustryGfx(tile) <= GFX_OILRIG_5)) return CommandError(STR_ERROR_NO_DRILLING_ABOVE_CHUNNEL);

                                        if (IsTileType(tile, MP_WATER) && IsSea(tile)) crossed_sea = true;
                                        if (!_cheats.crossing_tunnels.value && IsTunnelInWay(tile, start_z)) return CommandError(STR_ERROR_ANOTHER_TUNNEL_IN_THE_WAY);
                                        tile += delta;
                                        if (!IsValidTile(tile)) return CommandError(STR_ERROR_CHUNNEL_THROUGH_MAP_BORDER);
                                        _build_tunnel_endtile = tile;
                                        sea_tiles++;
                                }
                                if (!crossed_sea) return CommandError(STR_ERROR_CHUNNEL_ONLY_OVER_SEA);
                                ramp_start = tile;
                        } else {
                                /* Check if end ramp was too short or too long after crossing the sea. */
                                if (crossed_sea) {
                                        StringID err_msg = IsRampBetweenLimits(ramp_start, tile, delta);
                                        if (err_msg > STR_NULL) return CommandError(err_msg);
                                }
                                break;
                        }
                }
        }
        is_chunnel = crossed_sea;

        return CommandCost();
}


/**
 * Build Tunnel.
 * @param start_tile start tile of tunnel
 * @param flags type of operation
 * @param p1 bit 0-4 railtype or roadtypes
 *           bit 8-9 transport type
 * @param p2 unused
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdBuildTunnel(TileIndex start_tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        CompanyID company = _current_company;

        TransportType transport_type = Extract<TransportType, 8, 2>(p1);

        RailType railtype = INVALID_RAILTYPE;
        RoadTypes rts = ROADTYPES_NONE;
        _build_tunnel_endtile = 0;
        switch (transport_type) {
                case TRANSPORT_RAIL:
                        railtype = Extract<RailType, 0, 5>(p1);
                        if (!ValParamRailtype(railtype)) return CommandError();
                        break;

                case TRANSPORT_ROAD:
                        rts = Extract<RoadTypes, 0, 2>(p1);
                        if (!HasExactlyOneBit(rts) || !HasRoadTypesAvail(company, rts)) return CommandError();
                        break;

                default: return CommandError();
        }

        if (company == OWNER_DEITY) {
                if (transport_type != TRANSPORT_ROAD) return CommandError();
                const Town *town = CalcClosestTownFromTile(start_tile);

                company = OWNER_TOWN;

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

        int start_z;
        int end_z;
        Slope start_tileh = GetTileSlope(start_tile, &start_z);
        DiagDirection direction = GetInclinedSlopeDirection(start_tileh);
        if (direction == INVALID_DIAGDIR) return CommandError(STR_ERROR_SITE_UNSUITABLE_FOR_TUNNEL);

        if (HasTileWaterGround(start_tile)) return CommandError(STR_ERROR_CAN_T_BUILD_ON_WATER);

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

        /* XXX - do NOT change 'ret' in the loop, as it is used as the price
         * for the clearing of the entrance of the tunnel. Assigning it to
         * cost before the loop will yield different costs depending on start-
         * position, because of increased-cost-by-length: 'cost += cost >> 3' */

        TileIndexDiff delta = TileOffsByDiagDir(direction);

        TileIndex end_tile = start_tile;

        /* Tile shift coefficient. Will decrease for very long tunnels to avoid exponential growth of price*/
        int tiles_coef = 3;
        /* Number of tiles from start of tunnel */
        int tiles = 0;
        /* Number of tiles at which the cost increase coefficient per tile is halved */
        int tiles_bump = 25;
        /* flags for chunnels. */
        bool is_chunnel = false;
        bool crossed_sea = false;
        /* Number of tiles counted for crossing sea */
        int sea_tiles = 0;

        if (start_z == 0 && _settings_game.construction.chunnel) {
                CommandCost chunnel_test = CanBuildChunnel(start_tile, direction, is_chunnel, sea_tiles);
                if (chunnel_test.Failed()) return chunnel_test;
        }

        Slope end_tileh;
        for (;;) {
                end_tile += delta;
                if (!IsValidTile(end_tile)) return CommandError(STR_ERROR_TUNNEL_THROUGH_MAP_BORDER);
                end_tileh = GetTileSlope(end_tile, &end_z);

                if (start_z == end_z) {
                        if (is_chunnel && !crossed_sea) {
                                end_tile += sea_tiles * delta;
                                tiles += sea_tiles;
                                crossed_sea = true;
                        }
                        else {
                                break;
                        }
                }
                tiles++;
        }

        /* The cost of the digging. */
        CommandCost cost(EXPENSES_CONSTRUCTION);
        for (int i = 1; i <= tiles; i++) {
                if (i == tiles_bump) {
                        tiles_coef++;
                        tiles_bump *= 2;
                }

                cost.AddCost(_price[PR_BUILD_TUNNEL]);
                cost.AddCost(cost.GetCost() >> tiles_coef); // add a multiplier for longer tunnels
        }

        /* Add the cost of the entrance */
        cost.AddCost(_price[PR_BUILD_TUNNEL]);
        cost.AddCost(ret);

        /* if the command fails from here on we want the end tile to be highlighted */
        _build_tunnel_endtile = end_tile;

        if (tiles > _settings_game.construction.max_tunnel_length) return CommandError(STR_ERROR_TUNNEL_TOO_LONG);

        if (HasTileWaterGround(end_tile)) return CommandError(STR_ERROR_CAN_T_BUILD_ON_WATER);

        /* Clear the tile in any case */
        ret = DoCommand(end_tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
        if (ret.Failed()) return CommandError(STR_ERROR_UNABLE_TO_EXCAVATE_LAND);
        cost.AddCost(ret);

        /* slope of end tile must be complementary to the slope of the start tile */
        if (end_tileh != ComplementSlope(start_tileh)) {
                /* Mark the tile as already cleared for the terraform command.
                 * Do this for all tiles (like trees), not only objects. */
                ClearedObjectArea *coa = FindClearedObject(end_tile);
                if (coa == nullptr) {
                        coa = _cleared_object_areas.Append();
                        coa->first_tile = end_tile;
                        coa->area = TileArea(end_tile, 1, 1);
                }

                /* Hide the tile from the terraforming command */
                TileIndex old_first_tile = coa->first_tile;
                coa->first_tile = INVALID_TILE;
                ret = DoCommand(end_tile, end_tileh & start_tileh, 0, flags, CMD_TERRAFORM_LAND);
                coa->first_tile = old_first_tile;
                if (ret.Failed()) return CommandError(STR_ERROR_UNABLE_TO_EXCAVATE_LAND);
                cost.AddCost(ret);
        }
        cost.AddCost(_price[PR_BUILD_TUNNEL]);

        /* Pay for the rail/road in the tunnel including entrances */
        switch (transport_type) {
                case TRANSPORT_ROAD: cost.AddCost((tiles + 2) * _price[PR_BUILD_ROAD] * 2); break;
                case TRANSPORT_RAIL: cost.AddCost((tiles + 2) * RailBuildCost(railtype)); break;
                default: NOT_REACHED();
        }

        if (is_chunnel) cost.MultiplyCost(2);

        if (flags & DC_EXEC) {
                Company *c = Company::GetIfValid(company);
                uint num_pieces = (tiles + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;

                /* The most northern tile first. */
                TileIndex tn = start_tile;
                TileIndex ts = end_tile;
                if(start_tile > end_tile) Swap(tn, ts);

                if (!Tunnel::CanAllocateItem()) return CommandError(STR_ERROR_TUNNEL_TOO_MANY);
                const Tunnel *t = new Tunnel(tn, ts, TileHeight(tn), is_chunnel);

                if (transport_type == TRANSPORT_RAIL) {
                        if (!IsTunnelTile(start_tile) && c != nullptr) c->infrastructure.rail[railtype] += num_pieces;
                        MakeRailTunnel(start_tile, company, t->index, direction, railtype);
                        MakeRailTunnel(end_tile, company, t->index, ReverseDiagDir(direction), railtype);
                        AddSideToSignalBuffer(start_tile, INVALID_DIAGDIR, company);
                        YapfNotifyTrackLayoutChange(start_tile, DiagDirToDiagTrack(direction));
                } else {
                        if (c != nullptr) {
                                RoadType rt;
                                FOR_EACH_SET_ROADTYPE(rt, rts ^ (IsTunnelTile(start_tile) ? GetRoadTypes(start_tile) : ROADTYPES_NONE)) {
                                        c->infrastructure.road[rt] += num_pieces * 2; // A full diagonal road has two road bits.
                                }
                        }
                        MakeRoadTunnel(start_tile, company, t->index, direction, rts);
                        MakeRoadTunnel(end_tile, company, t->index, ReverseDiagDir(direction), rts);
                }
                DirtyCompanyInfrastructureWindows(company);
        }

        return cost;
}


/**
 * Are we allowed to remove the tunnel or bridge at \a tile?
 * @param tile End point of the tunnel or bridge.
 * @return A succeeded command if the tunnel or bridge may be removed, a failed command otherwise.
 */
static inline CommandCost CheckAllowRemoveTunnelBridge(TileIndex tile)
{
        /* Floods can remove anything as well as the scenario editor */
        if (_current_company == OWNER_WATER || _game_mode == GM_EDITOR) return CommandCost();

        switch (GetTunnelBridgeTransportType(tile)) {
                case TRANSPORT_ROAD: {
                        RoadTypes rts = GetRoadTypes(tile);
                        Owner road_owner = _current_company;
                        Owner tram_owner = _current_company;

                        if (HasBit(rts, ROADTYPE_ROAD)) road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);
                        if (HasBit(rts, ROADTYPE_TRAM)) tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);

                        /* 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 */
                                return CheckTileOwnership(tile);
                        }
                        if (road_owner == OWNER_NONE || road_owner == OWNER_TOWN) road_owner = _current_company;
                        if (tram_owner == OWNER_NONE) tram_owner = _current_company;

                        CommandCost ret = CheckOwnership(road_owner, tile);
                        if (ret.Succeeded()) ret = CheckOwnership(tram_owner, tile);
                        return ret;
                }

                case TRANSPORT_RAIL:
                        return CheckOwnership(GetTileOwner(tile));

                case TRANSPORT_WATER: {
                        /* Always allow to remove aqueducts without owner. */
                        Owner aqueduct_owner = GetTileOwner(tile);
                        if (aqueduct_owner == OWNER_NONE) aqueduct_owner = _current_company;
                        return CheckOwnership(aqueduct_owner);
                }

                default: NOT_REACHED();
        }
}

/**
 * Remove a tunnel from the game, update town rating, etc.
 * @param tile Tile containing one of the endpoints of the tunnel.
 * @param flags Command flags.
 * @return Succeeded or failed command.
 */
static CommandCost DoClearTunnel(TileIndex tile, DoCommandFlag flags)
{
        CommandCost ret = CheckAllowRemoveTunnelBridge(tile);
        if (ret.Failed()) return ret;

        TileIndex endtile = GetOtherTunnelEnd(tile);

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

        _build_tunnel_endtile = endtile;

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

                /* Check if you are allowed to remove the tunnel 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 */
        if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
                ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM, flags);
        }

        const bool is_chunnel = Tunnel::GetByTile(tile)->is_chunnel;

        uint len = GetTunnelBridgeLength(tile, endtile) + 2; // Don't forget the end tiles.

        if (flags & DC_EXEC) {
                if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) {
                        /* We first need to request values before calling DoClearSquare */
                        DiagDirection dir = GetTunnelBridgeDirection(tile);
                        Track track = DiagDirToDiagTrack(dir);
                        Owner owner = GetTileOwner(tile);

                        Train *v = nullptr;
                        if (HasTunnelBridgeReservation(tile)) {
                                v = GetTrainForReservation(tile, track);
                                if (v != nullptr) FreeTrainTrackReservation(v);
                        }

                        if (Company::IsValidID(owner)) {
                                Company::Get(owner)->infrastructure.rail[GetRailType(tile)] -= len * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                if (IsTunnelBridgeWithSignalSimulation(tile)) { // handle tunnel/bridge signals.
                                        Company::Get(GetTileOwner(tile))->infrastructure.signal -= GetTunnelBridgeSignalSimulationSignalCount(tile, endtile);
                                }
                                DirtyCompanyInfrastructureWindows(owner);
                        }

                        delete Tunnel::GetByTile(tile);

                        DoClearSquare(tile);
                        DoClearSquare(endtile);

                        /* cannot use INVALID_DIAGDIR for signal update because the tunnel doesn't exist anymore */
                        AddSideToSignalBuffer(tile,    ReverseDiagDir(dir), owner);
                        AddSideToSignalBuffer(endtile, dir,                 owner);

                        YapfNotifyTrackLayoutChange(tile,    track);
                        YapfNotifyTrackLayoutChange(endtile, track);

                        if (v != nullptr) TryPathReserve(v);
                } else {
                        RoadType rt;
                        FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
                                /* A full diagonal road tile has two road bits. */
                                Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
                                if (c != nullptr) {
                                        c->infrastructure.road[rt] -= len * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                        DirtyCompanyInfrastructureWindows(c->index);
                                }
                        }

                        delete Tunnel::GetByTile(tile);

                        DoClearSquare(tile);
                        DoClearSquare(endtile);
                }
                ViewportMapInvalidateTunnelCacheByTile(tile);
                ViewportMapInvalidateTunnelCacheByTile(endtile);
        }
        return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_TUNNEL] * len * (is_chunnel ? 2 : 1));
}


/**
 * Remove a bridge from the game, update town rating, etc.
 * @param tile Tile containing one of the endpoints of the bridge.
 * @param flags Command flags.
 * @return Succeeded or failed command.
 */
static CommandCost DoClearBridge(TileIndex tile, DoCommandFlag flags)
{
        CommandCost ret = CheckAllowRemoveTunnelBridge(tile);
        if (ret.Failed()) return ret;

        TileIndex endtile = GetOtherBridgeEnd(tile);

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

        DiagDirection direction = GetTunnelBridgeDirection(tile);
        TileIndexDiff delta = TileOffsByDiagDir(direction);

        Town *t = nullptr;
        if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
                t = ClosestTownFromTile(tile, UINT_MAX); // 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 */
        if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
                ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM, flags);
        }

        Money base_cost = (GetTunnelBridgeTransportType(tile) != TRANSPORT_WATER) ? _price[PR_CLEAR_BRIDGE] : _price[PR_CLEAR_AQUEDUCT];
        uint len = GetTunnelBridgeLength(tile, endtile) + 2; // Don't forget the end tiles.

        if (flags & DC_EXEC) {
                /* read this value before actual removal of bridge */
                bool rail = GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL;
                Owner owner = GetTileOwner(tile);
                int height = GetBridgeHeight(tile);
                Train *v = nullptr;

                if (rail && HasTunnelBridgeReservation(tile)) {
                        v = GetTrainForReservation(tile, DiagDirToDiagTrack(direction));
                        if (v != nullptr) FreeTrainTrackReservation(v);
                }

                /* Update company infrastructure counts. */
                if (rail) {
                        if (Company::IsValidID(owner)) {
                                Company::Get(owner)->infrastructure.rail[GetRailType(tile)] -= len * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                if (IsTunnelBridgeWithSignalSimulation(tile)) { // handle tunnel/bridge signals.
                                        Company::Get(GetTileOwner(tile))->infrastructure.signal -= GetTunnelBridgeSignalSimulationSignalCount(tile, endtile);
                                }
                        }
                } else if (GetTunnelBridgeTransportType(tile) == TRANSPORT_ROAD) {
                        SubtractRoadTunnelBridgeInfrastructure(tile, endtile);
                } else { // Aqueduct
                        if (Company::IsValidID(owner)) Company::Get(owner)->infrastructure.water -= len * TUNNELBRIDGE_TRACKBIT_FACTOR;
                }
                DirtyAllCompanyInfrastructureWindows();

                if (IsTunnelBridgeSignalSimulationEntrance(tile)) ClearBridgeEntranceSimulatedSignals(tile);
                if (IsTunnelBridgeSignalSimulationEntrance(endtile)) ClearBridgeEntranceSimulatedSignals(endtile);

                DoClearSquare(tile);
                DoClearSquare(endtile);
                for (TileIndex c = tile + delta; c != endtile; c += delta) {
                        /* do not let trees appear from 'nowhere' after removing bridge */
                        if (IsNormalRoadTile(c) && GetRoadside(c) == ROADSIDE_TREES) {
                                int minz = GetTileMaxZ(c) + 3;
                                if (height < minz) SetRoadside(c, ROADSIDE_PAVED);
                        }
                        ClearBridgeMiddle(c);
                        MarkTileDirtyByTile(c, ZOOM_LVL_DRAW_MAP, height - TileHeight(c));
                }

                if (rail) {
                        /* cannot use INVALID_DIAGDIR for signal update because the bridge doesn't exist anymore */
                        AddSideToSignalBuffer(tile,    ReverseDiagDir(direction), owner);
                        AddSideToSignalBuffer(endtile, direction,                 owner);

                        Track track = DiagDirToDiagTrack(direction);
                        YapfNotifyTrackLayoutChange(tile,    track);
                        YapfNotifyTrackLayoutChange(endtile, track);

                        if (v != nullptr) TryPathReserve(v, true);
                }
        }

        return CommandCost(EXPENSES_CONSTRUCTION, len * base_cost);
}

/**
 * Remove a tunnel or a bridge from the game.
 * @param tile Tile containing one of the endpoints.
 * @param flags Command flags.
 * @return Succeeded or failed command.
 */
static CommandCost ClearTile_TunnelBridge(TileIndex tile, DoCommandFlag flags)
{
        if (IsTunnel(tile)) {
                if (flags & DC_AUTO) return CommandError(STR_ERROR_MUST_DEMOLISH_TUNNEL_FIRST);
                return DoClearTunnel(tile, flags);
        } else { // IsBridge(tile)
                if (flags & DC_AUTO) return CommandError(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
                return DoClearBridge(tile, flags);
        }
}

/**
 * Draw a single pillar sprite.
 * @param psid      Pillarsprite
 * @param x         Pillar X
 * @param y         Pillar Y
 * @param z         Pillar Z
 * @param w         Bounding box size in X direction
 * @param h         Bounding box size in Y direction
 * @param subsprite Optional subsprite for drawing halfpillars
 */
static inline void DrawPillar(const PalSpriteID *psid, int x, int y, int z, int w, int h, const SubSprite *subsprite)
{
        static const int PILLAR_Z_OFFSET = TILE_HEIGHT - BRIDGE_Z_START; ///< Start offset of pillar wrt. bridge (downwards)
        AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, w, h, BB_HEIGHT_UNDER_BRIDGE - PILLAR_Z_OFFSET, z, IsTransparencySet(TO_BRIDGES), 0, 0, -PILLAR_Z_OFFSET, subsprite);
}

/**
 * Draw two bridge pillars (north and south).
 * @param z_bottom Bottom Z
 * @param z_top    Top Z
 * @param psid     Pillarsprite
 * @param x        Pillar X
 * @param y        Pillar Y
 * @param w        Bounding box size in X direction
 * @param h        Bounding box size in Y direction
 * @return Reached Z at the bottom
 */
static int DrawPillarColumn(int z_bottom, int z_top, const PalSpriteID *psid, int x, int y, int w, int h)
{
        int cur_z;
        for (cur_z = z_top; cur_z >= z_bottom; cur_z -= TILE_HEIGHT) {
                DrawPillar(psid, x, y, cur_z, w, h, nullptr);
        }
        return cur_z;
}

/**
 * Draws the pillars under high bridges.
 *
 * @param psid Image and palette of a bridge pillar.
 * @param ti #TileInfo of current bridge-middle-tile.
 * @param axis Orientation of bridge.
 * @param drawfarpillar Whether to draw the pillar at the back
 * @param x Sprite X position of front pillar.
 * @param y Sprite Y position of front pillar.
 * @param z_bridge Absolute height of bridge bottom.
 */
static void DrawBridgePillars(const PalSpriteID *psid, const TileInfo *ti, Axis axis, bool drawfarpillar, int x, int y, int z_bridge)
{
        static const int bounding_box_size[2]  = {16, 2}; ///< bounding box size of pillars along bridge direction
        static const int back_pillar_offset[2] = { 0, 9}; ///< sprite position offset of back facing pillar

        static const int INF = 1000; ///< big number compared to sprite size
        static const SubSprite half_pillar_sub_sprite[2][2] = {
                { {  -14, -INF, INF, INF }, { -INF, -INF, -15, INF } }, // X axis, north and south
                { { -INF, -INF,  15, INF }, {   16, -INF, INF, INF } }, // Y axis, north and south
        };

        if (psid->sprite == 0) return;

        /* Determine ground height under pillars */
        DiagDirection south_dir = AxisToDiagDir(axis);
        int z_front_north = ti->z;
        int z_back_north = ti->z;
        int z_front_south = ti->z;
        int z_back_south = ti->z;
        GetSlopePixelZOnEdge(ti->tileh, south_dir, &z_front_south, &z_back_south);
        GetSlopePixelZOnEdge(ti->tileh, ReverseDiagDir(south_dir), &z_front_north, &z_back_north);

        /* Shared height of pillars */
        int z_front = max(z_front_north, z_front_south);
        int z_back = max(z_back_north, z_back_south);

        /* x and y size of bounding-box of pillars */
        int w = bounding_box_size[axis];
        int h = bounding_box_size[OtherAxis(axis)];
        /* sprite position of back facing pillar */
        int x_back = x - back_pillar_offset[axis];
        int y_back = y - back_pillar_offset[OtherAxis(axis)];

        /* Draw front pillars */
        int bottom_z = DrawPillarColumn(z_front, z_bridge, psid, x, y, w, h);
        if (z_front_north < z_front) DrawPillar(psid, x, y, bottom_z, w, h, &half_pillar_sub_sprite[axis][0]);
        if (z_front_south < z_front) DrawPillar(psid, x, y, bottom_z, w, h, &half_pillar_sub_sprite[axis][1]);

        /* Draw back pillars, skip top two parts, which are hidden by the bridge */
        int z_bridge_back = z_bridge - 2 * (int)TILE_HEIGHT;
        if (drawfarpillar && (z_back_north <= z_bridge_back || z_back_south <= z_bridge_back)) {
                bottom_z = DrawPillarColumn(z_back, z_bridge_back, psid, x_back, y_back, w, h);
                if (z_back_north < z_back) DrawPillar(psid, x_back, y_back, bottom_z, w, h, &half_pillar_sub_sprite[axis][0]);
                if (z_back_south < z_back) DrawPillar(psid, x_back, y_back, bottom_z, w, h, &half_pillar_sub_sprite[axis][1]);
        }
}

/**
 * Draws the trambits over an already drawn (lower end) of a bridge.
 * @param x       the x of the bridge
 * @param y       the y of the bridge
 * @param z       the z of the bridge
 * @param offset  number representing whether to level or sloped and the direction
 * @param overlay do we want to still see the road?
 * @param head    are we drawing bridge head?
 */
static void DrawBridgeTramBits(int x, int y, int z, int offset, bool overlay, bool head)
{
        static const SpriteID tram_offsets[2][6] = { { 107, 108, 109, 110, 111, 112 }, { 4, 5, 15, 16, 17, 18 } };
        static const SpriteID back_offsets[6]    =   {  95,  96,  99, 102, 100, 101 };
        static const SpriteID front_offsets[6]   =   {  97,  98, 103, 106, 104, 105 };

        static const uint size_x[6] = {  1, 16, 16,  1, 16,  1 };
        static const uint size_y[6] = { 16,  1,  1, 16,  1, 16 };
        static const uint front_bb_offset_x[6] = { 15,  0,  0, 15,  0, 15 };
        static const uint front_bb_offset_y[6] = {  0, 15, 15,  0, 15,  0 };

        /* The sprites under the vehicles are drawn as SpriteCombine. StartSpriteCombine() has already been called
         * The bounding boxes here are the same as for bridge front/roof */
        if (head || !IsInvisibilitySet(TO_BRIDGES)) {
                AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + tram_offsets[overlay][offset], PAL_NONE,
                        x, y, size_x[offset], size_y[offset], 0x28, z,
                        !head && IsTransparencySet(TO_BRIDGES));
        }

        /* Do not draw catenary if it is set invisible */
        if (!IsInvisibilitySet(TO_CATENARY)) {
                AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + back_offsets[offset], PAL_NONE,
                        x, y, size_x[offset], size_y[offset], 0x28, z,
                        IsTransparencySet(TO_CATENARY));
        }

        /* Start a new SpriteCombine for the front part */
        EndSpriteCombine();
        StartSpriteCombine();

        /* For sloped sprites the bounding box needs to be higher, as the pylons stop on a higher point */
        if (!IsInvisibilitySet(TO_CATENARY)) {
                AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + front_offsets[offset], PAL_NONE,
                        x, y, size_x[offset] + front_bb_offset_x[offset], size_y[offset] + front_bb_offset_y[offset], 0x28, z,
                        IsTransparencySet(TO_CATENARY), front_bb_offset_x[offset], front_bb_offset_y[offset]);
        }
}

/* Draws a signal on tunnel / bridge entrance tile. */
static void DrawTunnelBridgeRampSignal(const TileInfo *ti)
{
        bool side = (_settings_game.vehicle.road_side != 0) &&_settings_game.construction.train_signal_side;

        static const Point SignalPositions[2][4] = {
                {   /*  X         X         Y         Y     Signals on the left side */
                        {13,  3}, { 2, 13}, { 3,  4}, {13, 14}
                }, {/*  X         X         Y         Y     Signals on the right side */
                        {14, 13}, { 3,  3}, {13,  2}, { 3, 13}
                }
        };

        uint position;
        DiagDirection dir = GetTunnelBridgeDirection(ti->tile);

        switch (dir) {
                default: NOT_REACHED();
                case DIAGDIR_NE: position = 0; break;
                case DIAGDIR_SE: position = 2; break;
                case DIAGDIR_SW: position = 1; break;
                case DIAGDIR_NW: position = 3; break;
        }

        SignalType type = SIGTYPE_NORMAL;

        bool is_green = (GetTunnelBridgeSignalState(ti->tile) == SIGNAL_STATE_GREEN);
        bool show_exit;
        if (IsTunnelBridgeSignalSimulationExit(ti->tile)) {
                show_exit = true;
                position ^= 1;
                if (IsTunnelBridgePBS(ti->tile)) type = SIGTYPE_PBS_ONEWAY;
        } else {
                show_exit = false;
        }

        uint x = TileX(ti->tile) * TILE_SIZE + SignalPositions[side != show_exit][position ^ (show_exit ? 1 : 0)].x;
        uint y = TileY(ti->tile) * TILE_SIZE + SignalPositions[side != show_exit][position ^ (show_exit ? 1 : 0)].y;
        uint z = ti->z;

        if (ti->tileh == SLOPE_FLAT && side == show_exit && dir == DIAGDIR_SE) z += 2;
        if (ti->tileh == SLOPE_FLAT && side != show_exit && dir == DIAGDIR_SW) z += 2;

        if (ti->tileh != SLOPE_FLAT && IsBridge(ti->tile)) z += 8; // sloped bridge head
        SignalVariant variant = IsTunnelBridgeSemaphore(ti->tile) ? SIG_SEMAPHORE : SIG_ELECTRIC;
        const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));

        SpriteID sprite = GetCustomSignalSprite(rti, ti->tile, type, variant, is_green ? SIGNAL_STATE_GREEN : SIGNAL_STATE_RED);
        bool is_custom_sprite = (sprite != 0);

        if (is_custom_sprite) {
                sprite += position;
        }
        else {
                if (variant == SIG_ELECTRIC && type == SIGTYPE_NORMAL) {
                        /* Normal electric signals are picked from original sprites. */
                        sprite = SPR_ORIGINAL_SIGNALS_BASE + ((position << 1) + is_green);
                }
                else {
                        /* All other signals are picked from add on sprites. */
                        sprite = SPR_SIGNALS_BASE + ((type - 1) * 16 + variant * 64 + (position << 1) + is_green) + (type > SIGTYPE_LAST_NOPBS ? 64 : 0);
                }
        }

        AddSortableSpriteToDraw(sprite, PAL_NONE, x, y, 1, 1, TILE_HEIGHT, z, false, 0, 0, BB_Z_SEPARATOR);
}

/**
 * Draws a tunnel of bridge tile.
 * For tunnels, this is rather simple, as you only need to draw the entrance.
 * Bridges are a bit more complex. base_offset is where the sprite selection comes into play
 * and it works a bit like a bitmask.<p> For bridge heads:
 * @param ti TileInfo of the structure to draw
 * <ul><li>Bit 0: direction</li>
 * <li>Bit 1: northern or southern heads</li>
 * <li>Bit 2: Set if the bridge head is sloped</li>
 * <li>Bit 3 and more: Railtype Specific subset</li>
 * </ul>
 * Please note that in this code, "roads" are treated as railtype 1, whilst the real railtypes are 0, 2 and 3
 */
static void DrawTile_TunnelBridge(TileInfo *ti)
{
        TransportType transport_type = GetTunnelBridgeTransportType(ti->tile);
        DiagDirection tunnelbridge_direction = GetTunnelBridgeDirection(ti->tile);

        if (IsTunnel(ti->tile)) {
                /* Front view of tunnel bounding boxes:
                 *
                 *   122223  <- BB_Z_SEPARATOR
                 *   1    3
                 *   1    3                1,3 = empty helper BB
                 *   1    3                  2 = SpriteCombine of tunnel-roof and catenary (tram & elrail)
                 *
                 */

                static const int _tunnel_BB[4][12] = {
                        /*  tunnnel-roof  |  Z-separator  | tram-catenary
                         * w  h  bb_x bb_y| x   y   w   h |bb_x bb_y w h */
                        {  1,  0, -15, -14,  0, 15, 16,  1, 0, 1, 16, 15 }, // NE
                        {  0,  1, -14, -15, 15,  0,  1, 16, 1, 0, 15, 16 }, // SE
                        {  1,  0, -15, -14,  0, 15, 16,  1, 0, 1, 16, 15 }, // SW
                        {  0,  1, -14, -15, 15,  0,  1, 16, 1, 0, 15, 16 }, // NW
                };
                const int *BB_data = _tunnel_BB[tunnelbridge_direction];

                bool catenary = false;

                SpriteID image;
                SpriteID railtype_overlay = 0;
                if (transport_type == TRANSPORT_RAIL) {
                        const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
                        image = rti->base_sprites.tunnel;
                        if (rti->UsesOverlay()) {
                                /* Check if the railtype has custom tunnel portals. */
                                railtype_overlay = GetCustomRailSprite(rti, ti->tile, RTSG_TUNNEL_PORTAL);
                                if (railtype_overlay != 0) image = SPR_RAILTYPE_TUNNEL_BASE; // Draw blank grass tunnel base.
                        }
                } else {
                        image = SPR_TUNNEL_ENTRY_REAR_ROAD;
                }

                if (HasTunnelBridgeSnowOrDesert(ti->tile)) image += railtype_overlay != 0 ? 8 : 32;

                image += tunnelbridge_direction * 2;
                DrawGroundSprite(image, PAL_NONE);

                if (transport_type == TRANSPORT_ROAD) {
                        RoadTypes rts = GetRoadTypes(ti->tile);

                        if (HasBit(rts, ROADTYPE_TRAM)) {
                                static const SpriteID tunnel_sprites[2][4] = { { 28, 78, 79, 27 }, {  5, 76, 77,  4 } };

                                DrawGroundSprite(SPR_TRAMWAY_BASE + tunnel_sprites[rts - ROADTYPES_TRAM][tunnelbridge_direction], PAL_NONE);

                                /* Do not draw wires if they are invisible */
                                if (!IsInvisibilitySet(TO_CATENARY)) {
                                        catenary = true;
                                        StartSpriteCombine();
                                        AddSortableSpriteToDraw(SPR_TRAMWAY_TUNNEL_WIRES + tunnelbridge_direction, PAL_NONE, ti->x, ti->y, BB_data[10], BB_data[11], TILE_HEIGHT, ti->z, IsTransparencySet(TO_CATENARY), BB_data[8], BB_data[9], BB_Z_SEPARATOR);
                                }
                        }
                } else {
                        const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
                        if (rti->UsesOverlay()) {
                                SpriteID surface = GetCustomRailSprite(rti, ti->tile, RTSG_TUNNEL);
                                if (surface != 0) DrawGroundSprite(surface + tunnelbridge_direction, PAL_NONE);
                        }

                        DrawOverlay(ti, MP_TUNNELBRIDGE);

                        /* PBS debugging, draw reserved tracks darker */
                        if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasTunnelBridgeReservation(ti->tile)) {
                                if (rti->UsesOverlay()) {
                                        SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
                                        DrawGroundSprite(overlay + RTO_X + DiagDirToAxis(tunnelbridge_direction), PALETTE_CRASH);
                                } else {
                                        DrawGroundSprite(DiagDirToAxis(tunnelbridge_direction) == AXIS_X ? rti->base_sprites.single_x : rti->base_sprites.single_y, PALETTE_CRASH);
                                }
                        }

                        if (HasRailCatenaryDrawn(GetRailType(ti->tile))) {
                                /* Maybe draw pylons on the entry side */
                                DrawRailCatenary(ti);

                                catenary = true;
                                StartSpriteCombine();
                                /* Draw wire above the ramp */
                                DrawRailCatenaryOnTunnel(ti);
                        }
                }

                if (railtype_overlay != 0 && !catenary) StartSpriteCombine();

                AddSortableSpriteToDraw(image + 1, PAL_NONE, ti->x + TILE_SIZE - 1, ti->y + TILE_SIZE - 1, BB_data[0], BB_data[1], TILE_HEIGHT, ti->z, false, BB_data[2], BB_data[3], BB_Z_SEPARATOR);
                /* Draw railtype tunnel portal overlay if defined. */
                if (railtype_overlay != 0) AddSortableSpriteToDraw(railtype_overlay + tunnelbridge_direction, PAL_NONE, ti->x + TILE_SIZE - 1, ti->y + TILE_SIZE - 1, BB_data[0], BB_data[1], TILE_HEIGHT, ti->z, false, BB_data[2], BB_data[3], BB_Z_SEPARATOR);

                if (catenary || railtype_overlay != 0) EndSpriteCombine();

                /* Add helper BB for sprite sorting that separates the tunnel from things beside of it. */
                AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, ti->x,              ti->y,              BB_data[6], BB_data[7], TILE_HEIGHT, ti->z);
                AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, ti->x + BB_data[4], ti->y + BB_data[5], BB_data[6], BB_data[7], TILE_HEIGHT, ti->z);

                /* Draw signals for tunnel. */
                if (IsTunnelBridgeWithSignalSimulation(ti->tile)) DrawTunnelBridgeRampSignal(ti);

                DrawBridgeMiddle(ti);
        } else { // IsBridge(ti->tile)
                if (transport_type == TRANSPORT_ROAD && IsRoadCustomBridgeHead(ti->tile)) {
                        DrawRoadBits(ti);
                        DrawBridgeMiddle(ti);
                        return;
                }

                const PalSpriteID *psid;
                int base_offset;
                bool ice = HasTunnelBridgeSnowOrDesert(ti->tile);

                if (transport_type == TRANSPORT_RAIL) {
                        base_offset = GetRailTypeInfo(GetRailType(ti->tile))->bridge_offset;
                        assert(base_offset != 8); // This one is used for roads
                } else {
                        base_offset = 8;
                }

                /* as the lower 3 bits are used for other stuff, make sure they are clear */
                assert( (base_offset & 0x07) == 0x00);

                DrawFoundation(ti, GetBridgeFoundation(ti->tileh, DiagDirToAxis(tunnelbridge_direction)));

                /* HACK Wizardry to convert the bridge ramp direction into a sprite offset */
                base_offset += (6 - tunnelbridge_direction) % 4;

                /* Table number BRIDGE_PIECE_HEAD always refers to the bridge heads for any bridge type */
                if (transport_type != TRANSPORT_WATER) {
                        if (ti->tileh == SLOPE_FLAT) base_offset += 4; // sloped bridge head
                        psid = &GetBridgeSpriteTable(GetBridgeType(ti->tile), BRIDGE_PIECE_HEAD)[base_offset];
                } else {
                        psid = _aqueduct_sprites + base_offset;
                }

                if (!ice) {
                        TileIndex next = ti->tile + TileOffsByDiagDir(tunnelbridge_direction);
                        if (ti->tileh != SLOPE_FLAT && ti->z == 0 && HasTileWaterClass(next) && GetWaterClass(next) == WATER_CLASS_SEA) {
                                DrawShoreTile(ti->tileh);
                        } else {
                                DrawClearLandTile(ti, 3);
                        }
                } else {
                        DrawGroundSprite(SPR_FLAT_SNOW_DESERT_TILE + SlopeToSpriteOffset(ti->tileh), PAL_NONE);
                }

                /* draw ramp */

                /* Draw Trambits and PBS Reservation as SpriteCombine */
                if (transport_type == TRANSPORT_ROAD || transport_type == TRANSPORT_RAIL) 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);

                if (transport_type == TRANSPORT_ROAD) {
                        RoadTypes rts = GetRoadTypes(ti->tile);

                        if (HasBit(rts, ROADTYPE_TRAM)) {
                                uint offset = tunnelbridge_direction;
                                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();
                } else if (transport_type == TRANSPORT_RAIL) {
                        const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
                        if (rti->UsesOverlay()) {
                                SpriteID surface = GetCustomRailSprite(rti, ti->tile, RTSG_BRIDGE);
                                if (surface != 0) {
                                        if (HasBridgeFlatRamp(ti->tileh, DiagDirToAxis(tunnelbridge_direction))) {
                                                AddSortableSpriteToDraw(surface + ((DiagDirToAxis(tunnelbridge_direction) == AXIS_X) ? RTBO_X : RTBO_Y), PAL_NONE, ti->x, ti->y, 16, 16, 0, ti->z + 8);
                                        } else {
                                                AddSortableSpriteToDraw(surface + RTBO_SLOPE + tunnelbridge_direction, PAL_NONE, ti->x, ti->y, 16, 16, 8, ti->z);
                                        }
                                }
                                /* Don't fallback to non-overlay sprite -- the spec states that
                                 * if an overlay is present then the bridge surface must be
                                 * present. */
                        }

                        /* PBS debugging, draw reserved tracks darker */
                        if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasTunnelBridgeReservation(ti->tile)) {
                                if (rti->UsesOverlay()) {
                                        SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
                                        if (HasBridgeFlatRamp(ti->tileh, DiagDirToAxis(tunnelbridge_direction))) {
                                                AddSortableSpriteToDraw(overlay + RTO_X + DiagDirToAxis(tunnelbridge_direction), PALETTE_CRASH, ti->x, ti->y, 16, 16, 0, ti->z + 8);
                                        } else {
                                                AddSortableSpriteToDraw(overlay + RTO_SLOPE_NE + tunnelbridge_direction, PALETTE_CRASH, ti->x, ti->y, 16, 16, 8, ti->z);
                                        }
                                } else {
                                        if (HasBridgeFlatRamp(ti->tileh, DiagDirToAxis(tunnelbridge_direction))) {
                                                AddSortableSpriteToDraw(DiagDirToAxis(tunnelbridge_direction) == AXIS_X ? rti->base_sprites.single_x : rti->base_sprites.single_y, PALETTE_CRASH, ti->x, ti->y, 16, 16, 0, ti->z + 8);
                                        } else {
                                                AddSortableSpriteToDraw(rti->base_sprites.single_sloped + tunnelbridge_direction, PALETTE_CRASH, ti->x, ti->y, 16, 16, 8, ti->z);
                                        }
                                }
                        }

                        EndSpriteCombine();
                        if (HasRailCatenaryDrawn(GetRailType(ti->tile))) {
                                DrawRailCatenary(ti);
                        }
                }

                /* Draw signals for bridge. */
                if (IsTunnelBridgeWithSignalSimulation(ti->tile)) DrawTunnelBridgeRampSignal(ti);

                DrawBridgeMiddle(ti);
        }
}


/**
 * Compute bridge piece. Computes the bridge piece to display depending on the position inside the bridge.
 * bridges pieces sequence (middle parts).
 * Note that it is not covering the bridge heads, which are always referenced by the same sprite table.
 * bridge len 1: BRIDGE_PIECE_NORTH
 * bridge len 2: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_SOUTH
 * bridge len 3: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_MIDDLE_ODD   BRIDGE_PIECE_SOUTH
 * bridge len 4: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * bridge len 5: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_MIDDLE_EVEN  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * bridge len 6: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * bridge len 7: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_MIDDLE_ODD   BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * #0 - always as first, #1 - always as last (if len>1)
 * #2,#3 are to pair in order
 * for odd bridges: #5 is going in the bridge middle if on even position, #4 on odd (counting from 0)
 * @param north Northernmost tile of bridge
 * @param south Southernmost tile of bridge
 * @return Index of bridge piece
 */
static BridgePieces CalcBridgePiece(uint north, uint south)
{
        if (north == 1) {
                return BRIDGE_PIECE_NORTH;
        } else if (south == 1) {
                return BRIDGE_PIECE_SOUTH;
        } else if (north < south) {
                return north & 1 ? BRIDGE_PIECE_INNER_SOUTH : BRIDGE_PIECE_INNER_NORTH;
        } else if (north > south) {
                return south & 1 ? BRIDGE_PIECE_INNER_NORTH : BRIDGE_PIECE_INNER_SOUTH;
        } else {
                return north & 1 ? BRIDGE_PIECE_MIDDLE_EVEN : BRIDGE_PIECE_MIDDLE_ODD;
        }
}

/**
 * Draw the middle bits of a bridge.
 * @param ti Tile information of the tile to draw it on.
 */
void DrawBridgeMiddle(const TileInfo *ti)
{
        /* Sectional view of bridge bounding boxes:
         *
         *  1           2                                1,2 = SpriteCombine of Bridge front/(back&floor) and RoadCatenary
         *  1           2                                  3 = empty helper BB
         *  1     7     2                                4,5 = pillars under higher bridges
         *  1 6 88888 6 2                                  6 = elrail-pylons
         *  1 6 88888 6 2                                  7 = elrail-wire
         *  1 6 88888 6 2  <- TILE_HEIGHT                  8 = rail-vehicle on bridge
         *  3333333333333  <- BB_Z_SEPARATOR
         *                 <- unused
         *    4       5    <- BB_HEIGHT_UNDER_BRIDGE
         *    4       5
         *    4       5
         *
         */

        if (!IsBridgeAbove(ti->tile)) return;

        TileIndex rampnorth = GetNorthernBridgeEnd(ti->tile);
        TileIndex rampsouth = GetSouthernBridgeEnd(ti->tile);
        TransportType transport_type = GetTunnelBridgeTransportType(rampsouth);

        Axis axis = GetBridgeAxis(ti->tile);
        BridgePieces piece = CalcBridgePiece(
                GetTunnelBridgeLength(ti->tile, rampnorth) + 1,
                GetTunnelBridgeLength(ti->tile, rampsouth) + 1
        );

        const PalSpriteID *psid;
        bool drawfarpillar;
        if (transport_type != TRANSPORT_WATER) {
                BridgeType type =  GetBridgeType(rampsouth);
                drawfarpillar = !HasBit(GetBridgeSpec(type)->flags, 0);

                uint base_offset;
                if (transport_type == TRANSPORT_RAIL) {
                        base_offset = GetRailTypeInfo(GetRailType(rampsouth))->bridge_offset;
                } else {
                        base_offset = 8;
                }

                psid = base_offset + GetBridgeSpriteTable(type, piece);
        } else {
                drawfarpillar = true;
                psid = _aqueduct_sprites;
        }

        if (axis != AXIS_X) psid += 4;

        int x = ti->x;
        int y = ti->y;
        uint bridge_z = GetBridgePixelHeight(rampsouth);
        int z = bridge_z - BRIDGE_Z_START;

        /* Add a bounding box that separates the bridge from things below it. */
        AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, x, y, 16, 16, 1, bridge_z - TILE_HEIGHT + BB_Z_SEPARATOR);

        /* Draw Trambits as SpriteCombine */
        if (transport_type == TRANSPORT_ROAD || transport_type == TRANSPORT_RAIL) StartSpriteCombine();

        /* Draw floor and far part of bridge*/
        if (!IsInvisibilitySet(TO_BRIDGES)) {
                if (axis == AXIS_X) {
                        AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 16, 1, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 0, BRIDGE_Z_START);
                } else {
                        AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 1, 16, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 0, BRIDGE_Z_START);
                }
        }

        psid++;

        if (transport_type == TRANSPORT_ROAD) {
                const RoadTypes rts = GetRoadTypes(rampsouth);

                bool has_tram = HasBit(rts, ROADTYPE_TRAM);
                bool has_road = HasBit(rts, ROADTYPE_ROAD);
                if (IsRoadCustomBridgeHeadTile(rampsouth)) {
                        RoadBits entrance_bit = DiagDirToRoadBits(GetTunnelBridgeDirection(rampsouth));
                        has_tram = has_tram && (GetCustomBridgeHeadRoadBits(rampsouth, ROADTYPE_TRAM) & entrance_bit);
                        has_road = has_road && (GetCustomBridgeHeadRoadBits(rampsouth, ROADTYPE_ROAD) & entrance_bit);
                }

                if (has_tram) {
                        /* DrawBridgeTramBits() calls EndSpriteCombine() and StartSpriteCombine() */
                        DrawBridgeTramBits(x, y, bridge_z, axis ^ 1, has_road, false);
                } else {
                        EndSpriteCombine();
                        StartSpriteCombine();
                }
        } else if (transport_type == TRANSPORT_RAIL) {
                const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(rampsouth));
                if (rti->UsesOverlay() && !IsInvisibilitySet(TO_BRIDGES)) {
                        SpriteID surface = GetCustomRailSprite(rti, rampsouth, RTSG_BRIDGE, TCX_ON_BRIDGE);
                        if (surface != 0) {
                                AddSortableSpriteToDraw(surface + axis, PAL_NONE, x, y, 16, 16, 0, bridge_z, IsTransparencySet(TO_BRIDGES));
                        }
                }

                if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && !IsInvisibilitySet(TO_BRIDGES) && HasTunnelBridgeReservation(rampnorth)
                        && !IsTunnelBridgeWithSignalSimulation(rampnorth)) {
                        if (rti->UsesOverlay()) {
                                SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
                                AddSortableSpriteToDraw(overlay + RTO_X + axis, PALETTE_CRASH, ti->x, ti->y, 16, 16, 0, bridge_z, IsTransparencySet(TO_BRIDGES));
                        } else {
                                AddSortableSpriteToDraw(axis == AXIS_X ? rti->base_sprites.single_x : rti->base_sprites.single_y, PALETTE_CRASH, ti->x, ti->y, 16, 16, 0, bridge_z, IsTransparencySet(TO_BRIDGES));
                        }
                }

                EndSpriteCombine();

                if (HasRailCatenaryDrawn(GetRailType(rampsouth))) {
                        DrawRailCatenaryOnBridge(ti);
                }
        }

        /* draw roof, the component of the bridge which is logically between the vehicle and the camera */
        if (!IsInvisibilitySet(TO_BRIDGES)) {
                if (axis == AXIS_X) {
                        y += 12;
                        if (psid->sprite & SPRITE_MASK) AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 16, 4, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 3, BRIDGE_Z_START);
                } else {
                        x += 12;
                        if (psid->sprite & SPRITE_MASK) AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 4, 16, 0x28, z, IsTransparencySet(TO_BRIDGES), 3, 0, BRIDGE_Z_START);
                }
        }

        /* Draw TramFront as SpriteCombine */
        if (transport_type == TRANSPORT_ROAD) EndSpriteCombine();

        /* Do not draw anything more if bridges are invisible */
        if (IsInvisibilitySet(TO_BRIDGES)) return;

        psid++;
        if (ti->z + 5 == z) {
                /* draw poles below for small bridges */
                if (psid->sprite != 0) {
                        SpriteID image = psid->sprite;
                        SpriteID pal   = psid->pal;
                        if (IsTransparencySet(TO_BRIDGES)) {
                                SetBit(image, PALETTE_MODIFIER_TRANSPARENT);
                                pal = PALETTE_TO_TRANSPARENT;
                        }

                        DrawGroundSpriteAt(image, pal, x - ti->x, y - ti->y, z - ti->z);
                }
        } else {
                /* draw pillars below for high bridges */
                DrawBridgePillars(psid, ti, axis, drawfarpillar, x, y, z);
        }
}


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

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

        if (IsTunnel(tile)) {
                uint pos = (DiagDirToAxis(GetTunnelBridgeDirection(tile)) == AXIS_X ? y : x);

                /* In the tunnel entrance? */
                if (5 <= pos && pos <= 10) return z;
        } else { // IsBridge(tile)
                if (IsRoadCustomBridgeHeadTile(tile)) {
                        return z + TILE_HEIGHT + (IsSteepSlope(tileh) ? TILE_HEIGHT : 0);
                }

                DiagDirection dir = GetTunnelBridgeDirection(tile);
                uint pos = (DiagDirToAxis(dir) == AXIS_X ? y : x);

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

                /* On the bridge ramp? */
                if (5 <= pos && pos <= 10) {
                        int delta;

                        if (tileh != SLOPE_FLAT) return z + TILE_HEIGHT;

                        switch (dir) {
                                default: NOT_REACHED();
                                case DIAGDIR_NE: delta = (TILE_SIZE - 1 - x) / 2; break;
                                case DIAGDIR_SE: delta = y / 2; break;
                                case DIAGDIR_SW: delta = x / 2; break;
                                case DIAGDIR_NW: delta = (TILE_SIZE - 1 - y) / 2; break;
                        }
                        return z + 1 + delta;
                }
        }

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

static Foundation GetFoundation_TunnelBridge(TileIndex tile, Slope tileh)
{
        if (IsRoadCustomBridgeHeadTile(tile)) return FOUNDATION_LEVELED;
        return IsTunnel(tile) ? FOUNDATION_NONE : GetBridgeFoundation(tileh, DiagDirToAxis(GetTunnelBridgeDirection(tile)));
}

static void GetTileDesc_TunnelBridge(TileIndex tile, TileDesc *td)
{
        TransportType tt = GetTunnelBridgeTransportType(tile);

        if (IsTunnel(tile)) {
                if (Tunnel::GetByTile(tile)->is_chunnel) {
                        td->str = (tt == TRANSPORT_RAIL) ? IsTunnelBridgeWithSignalSimulation(tile) ? STR_LAI_TUNNEL_DESCRIPTION_RAILROAD_SIGNAL_CHUNNEL : STR_LAI_TUNNEL_DESCRIPTION_RAILROAD_CHUNNEL : STR_LAI_TUNNEL_DESCRIPTION_ROAD_CHUNNEL;
                } else {
                        td->str = (tt == TRANSPORT_RAIL) ? IsTunnelBridgeWithSignalSimulation(tile) ? STR_LAI_TUNNEL_DESCRIPTION_RAILROAD_SIGNAL : STR_LAI_TUNNEL_DESCRIPTION_RAILROAD : STR_LAI_TUNNEL_DESCRIPTION_ROAD;
                }
        } else { // IsBridge(tile)
                td->str = (tt == TRANSPORT_WATER) ? STR_LAI_BRIDGE_DESCRIPTION_AQUEDUCT : IsTunnelBridgeWithSignalSimulation(tile) ? STR_LAI_BRIDGE_DESCRIPTION_RAILROAD_SIGNAL : GetBridgeSpec(GetBridgeType(tile))->transport_name[tt];
        }
        td->owner[0] = GetTileOwner(tile);

        Owner road_owner = INVALID_OWNER;
        Owner tram_owner = INVALID_OWNER;
        RoadTypes rts = GetRoadTypes(tile);
        if (HasBit(rts, ROADTYPE_ROAD)) road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);
        if (HasBit(rts, ROADTYPE_TRAM)) tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);

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

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

                if (!IsTunnel(tile)) {
                        uint16 spd = GetBridgeSpec(GetBridgeType(tile))->speed;
                        if (td->rail_speed == 0 || spd < td->rail_speed) {
                                td->rail_speed = spd;
                        }
                }
        } else if (tt == TRANSPORT_ROAD && !IsTunnel(tile)) {
                td->road_speed = GetBridgeSpec(GetBridgeType(tile))->speed;
        }
}


static void TileLoop_TunnelBridge(TileIndex tile)
{
        bool snow_or_desert = HasTunnelBridgeSnowOrDesert(tile);
        switch (_settings_game.game_creation.landscape) {
                case LT_ARCTIC: {
                        /* As long as we do not have a snow density, we want to use the density
                         * from the entry edge.  */
                        int z = GetTileMaxZ(tile);
                        if (snow_or_desert != (z > GetSnowLine())) {
                                SetTunnelBridgeSnowOrDesert(tile, !snow_or_desert);
                                MarkTileDirtyByTile(tile);
                        }
                        break;
                }

                case LT_TROPIC:
                        if (GetTropicZone(tile) == TROPICZONE_DESERT && !snow_or_desert) {
                                SetTunnelBridgeSnowOrDesert(tile, true);
                                MarkTileDirtyByTile(tile);
                        }
                        break;

                default:
                        break;
        }
}

static bool ClickTile_TunnelBridge(TileIndex tile)
{
        /* Show vehicles found in tunnel. */
        if (IsTunnelTile(tile)) {
                int count = 0;
                const Train *t;
                TileIndex tile_end = GetOtherTunnelBridgeEnd(tile);
                FOR_ALL_TRAINS(t) {
                        if (!t->IsFrontEngine()) continue;
                        if (tile == t->tile || tile_end == t->tile) {
                                ShowVehicleViewWindow(t);
                                count++;
                        }
                        if (count > 19) break;  // no more than 20 windows open
                }
                if (count > 0) return true;
        }
        return false;
}

extern const TrackBits _road_trackbits[16];

static TrackStatus GetTileTrackStatus_TunnelBridge(TileIndex tile, TransportType mode, uint sub_mode, DiagDirection side)
{
        TransportType transport_type = GetTunnelBridgeTransportType(tile);
        
        if (transport_type != mode || (transport_type == TRANSPORT_ROAD && (GetRoadTypes(tile) & sub_mode) == 0)) return 0;

        DiagDirection dir = GetTunnelBridgeDirection(tile);

        if (mode == TRANSPORT_ROAD && IsRoadCustomBridgeHeadTile(tile)) {
                if (side != INVALID_DIAGDIR && side == dir) return 0;
                TrackBits bits = TRACK_BIT_NONE;
                if (sub_mode & ROADTYPES_TRAM) bits |= _road_trackbits[GetCustomBridgeHeadRoadBits(tile, ROADTYPE_TRAM)];
                if (sub_mode & ROADTYPES_ROAD) bits |= _road_trackbits[GetCustomBridgeHeadRoadBits(tile, ROADTYPE_ROAD)];
                return CombineTrackStatus(TrackBitsToTrackdirBits(bits), TRACKDIR_BIT_NONE);
        }

        if (side != INVALID_DIAGDIR && side != ReverseDiagDir(dir)) return 0;

        return CombineTrackStatus(TrackBitsToTrackdirBits(DiagDirToDiagTrackBits(dir)), TRACKDIR_BIT_NONE);
}
 
static void UpdateRoadTunnelBridgeInfrastructure(TileIndex begin, TileIndex end, bool add) {
        /* A full diagonal road has two road bits. */
        const uint middle_len = 2 * GetTunnelBridgeLength(begin, end) * TUNNELBRIDGE_TRACKBIT_FACTOR;
        const uint len = middle_len + (4 * TUNNELBRIDGE_TRACKBIT_FACTOR);

        /* Iterate all present road types as each can have a different owner. */
        RoadType rt;
        FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(begin)) {
                Company * const c = Company::GetIfValid(GetRoadOwner(begin, rt));
                if (c != nullptr) {
                        uint infra = 0;
                        if (IsBridge(begin)) {
                                const RoadBits bits = GetCustomBridgeHeadRoadBits(begin, rt);
                                infra += CountBits(bits) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                                if (bits & DiagDirToRoadBits(GetTunnelBridgeDirection(begin))) {
                                        infra += middle_len;
                                }
                        } else {
                                infra += len;
                        }
                        if (add) {
                                c->infrastructure.road[rt] += infra;
                        } else {
                                c->infrastructure.road[rt] -= infra;
                        }
                }
        }
        FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(end)) {
                Company * const c = Company::GetIfValid(GetRoadOwner(end, rt));
                if (c != nullptr) {
                        uint infra = 0;
                        if (IsBridge(end)) {
                                const RoadBits bits = GetCustomBridgeHeadRoadBits(end, rt);
                                infra += CountBits(bits) * TUNNELBRIDGE_TRACKBIT_FACTOR;
                        }
                        if (add) {
                                c->infrastructure.road[rt] += infra;
                        } else {
                                c->infrastructure.road[rt] -= infra;
                        }
                }
        }
}

void AddRoadTunnelBridgeInfrastructure(TileIndex begin, TileIndex end) {
        UpdateRoadTunnelBridgeInfrastructure(begin, end, true);
}

void SubtractRoadTunnelBridgeInfrastructure(TileIndex begin, TileIndex end) {
        UpdateRoadTunnelBridgeInfrastructure(begin, end, false);
}

static void ChangeTileOwner_TunnelBridge(TileIndex tile, Owner old_owner, Owner new_owner)
{
        const TileIndex other_end = GetOtherTunnelBridgeEnd(tile);
        /* Set number of pieces to zero if it's the southern tile as we
         * don't want to update the infrastructure counts twice. */
        const uint num_pieces = tile < other_end ? (GetTunnelBridgeLength(tile, other_end) + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR : 0;
        const TransportType tt = GetTunnelBridgeTransportType(tile);

        if (tt == TRANSPORT_ROAD) SubtractRoadTunnelBridgeInfrastructure(tile, other_end);

        for (RoadType rt = ROADTYPE_ROAD; rt < ROADTYPE_END; rt++) {
                /* Update all roadtypes, no matter if they are present */
                if (GetRoadOwner(tile, rt) == old_owner) {
                        SetRoadOwner(tile, rt, new_owner == INVALID_OWNER ? OWNER_NONE : new_owner);
                }
        }

        if (tt == TRANSPORT_ROAD) AddRoadTunnelBridgeInfrastructure(tile, other_end);

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

        /* Update company infrastructure counts for rail and water as well.
         * No need to dirty windows here, we'll redraw the whole screen anyway. */
        Company *old = Company::Get(old_owner);
        if (tt == TRANSPORT_RAIL) {
                old->infrastructure.rail[GetRailType(tile)] -= num_pieces;
                if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.rail[GetRailType(tile)] += num_pieces;
        } else if (tt == TRANSPORT_WATER) {
                old->infrastructure.water -= num_pieces;
                if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.water += num_pieces;
        }

        if (IsTunnelBridgeWithSignalSimulation(tile) && IsTunnelBridgeSignalSimulationEntrance(tile)) {
                uint num_sigs = GetTunnelBridgeSignalSimulationSignalCount(tile, other_end);
                Company::Get(old_owner)->infrastructure.signal -= num_sigs;
                if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.signal += num_sigs;
        }

        if (new_owner != INVALID_OWNER) {
                SetTileOwner(tile, new_owner);
        } else {
                if (tt == TRANSPORT_RAIL) {
                        /* Since all of our vehicles have been removed, it is safe to remove the rail
                         * bridge / tunnel. */
                        CommandCost ret = DoCommand(tile, 0, 0, DC_EXEC | DC_BANKRUPT, CMD_LANDSCAPE_CLEAR);
                        assert(ret.Succeeded());
                } else {
                        /* In any other case, we can safely reassign the ownership to OWNER_NONE. */
                        SetTileOwner(tile, OWNER_NONE);
                }
        }
}

/**
 * Frame when the 'enter tunnel' sound should be played. This is the second
 * frame on a tile, so the sound is played shortly after entering the tunnel
 * tile, while the vehicle is still visible.
 */
static const byte TUNNEL_SOUND_FRAME = 1;

/**
 * Frame when a vehicle should be hidden in a tunnel with a certain direction.
 * This differs per direction, because of visibility / bounding box issues.
 * Note that direction, in this case, is the direction leading into the tunnel.
 * When entering a tunnel, hide the vehicle when it reaches the given frame.
 * When leaving a tunnel, show the vehicle when it is one frame further
 * to the 'outside', i.e. at (TILE_SIZE-1) - (frame) + 1
 */
extern const byte _tunnel_visibility_frame[DIAGDIR_END] = {12, 8, 8, 12};

extern const byte _tunnel_turnaround_pre_visibility_frame[DIAGDIR_END] = { 31, 27, 27, 31 };

static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex tile, int x, int y)
{
        int z = GetSlopePixelZ(x, y) - v->z_pos;

        if (abs(z) > 2) return VETSB_CANNOT_ENTER;
        /* Direction into the wormhole */
        const DiagDirection dir = GetTunnelBridgeDirection(tile);
        /* Direction of the vehicle */
        const DiagDirection vdir = DirToDiagDir(v->direction);
        /* New position of the vehicle on the tile */
        byte pos = (DiagDirToAxis(vdir) == AXIS_X ? x : y) & TILE_UNIT_MASK;
        /* Number of units moved by the vehicle since entering the tile */
        byte frame = (vdir == DIAGDIR_NE || vdir == DIAGDIR_NW) ? TILE_SIZE - 1 - pos : pos;

        if (IsTunnel(tile)) {
                if (v->type == VEH_TRAIN) {
                        Train *t = Train::From(v);

                        if (t->track != TRACK_BIT_WORMHOLE && dir == vdir) {
                                if (t->IsFrontEngine() && frame == TUNNEL_SOUND_FRAME) {
                                        if (!PlayVehicleSound(t, VSE_TUNNEL) && RailVehInfo(t->engine_type)->engclass == 0) {
                                                SndPlayVehicleFx(SND_05_TRAIN_THROUGH_TUNNEL, v);
                                        }
                                        return VETSB_CONTINUE;
                                }
                                if (frame == _tunnel_visibility_frame[dir]) {
                                        t->tile = tile;
                                        t->track = TRACK_BIT_WORMHOLE;
                                        if (Tunnel::GetByTile(tile)->is_chunnel) SetBit(t->gv_flags, GVF_CHUNNEL_BIT);
                                        t->vehstatus |= VS_HIDDEN;
                                        return VETSB_ENTERED_WORMHOLE;
                                }
                        }

                        if (dir == ReverseDiagDir(vdir) && frame == TILE_SIZE - _tunnel_visibility_frame[dir] && z == 0) {
                                /* We're at the tunnel exit ?? */
                                if (t->tile != tile && GetOtherTunnelEnd(t->tile) != tile) return VETSB_CONTINUE; // In chunnel
                                t->tile = tile;
                                t->track = DiagDirToDiagTrackBits(vdir);
                                assert(t->track);
                                t->vehstatus &= ~VS_HIDDEN;
                                return VETSB_ENTERED_WORMHOLE;
                        }
                } else if (v->type == VEH_ROAD) {
                        RoadVehicle *rv = RoadVehicle::From(v);

                        /* Enter tunnel? */
                        if (rv->state != RVSB_WORMHOLE && dir == vdir) {
                                if (frame == _tunnel_visibility_frame[dir]) {
                                        /* Frame should be equal to the next frame number in the RV's movement */
                                        assert_msg(frame == rv->frame + 1 || rv->frame == _tunnel_turnaround_pre_visibility_frame[dir],
                                                +"frame: %u, rv->frame: %u, dir: %u, _tunnel_turnaround_pre_visibility_frame[dir]: %u", frame, rv->frame, dir, _tunnel_turnaround_pre_visibility_frame[dir]);
                                        rv->tile = tile;
                                        rv->state = RVSB_WORMHOLE;
                                        if (Tunnel::GetByTile(tile)->is_chunnel) SetBit(rv->gv_flags, GVF_CHUNNEL_BIT);
                                        rv->vehstatus |= VS_HIDDEN;
                                        return VETSB_ENTERED_WORMHOLE;
                                } else {
                                        return VETSB_CONTINUE;
                                }
                        }

                        /* We're at the tunnel exit ?? */
                        if (dir == ReverseDiagDir(vdir) && frame == TILE_SIZE - _tunnel_visibility_frame[dir] && z == 0) {
                                if (rv->tile != tile && GetOtherTunnelEnd(rv->tile) != tile) return VETSB_CONTINUE; // In chunnel
                                rv->tile = tile;
                                rv->state = DiagDirToDiagTrackdir(vdir);
                                rv->frame = frame;
                                rv->vehstatus &= ~VS_HIDDEN;
                                return VETSB_ENTERED_WORMHOLE;
                        }
                }
        } else { // IsBridge(tile)
                if (v->vehstatus & VS_HIDDEN) return VETSB_CONTINUE; // Building bridges between chunnel portals allowed.
                if (v->type != VEH_SHIP) {
                        /* modify speed of vehicle */
                        uint16 spd = GetBridgeSpec(GetBridgeType(tile))->speed;

                        if (v->type == VEH_ROAD) spd *= 2;
                        Vehicle *first = v->First();
                        first->cur_speed = min(first->cur_speed, spd);
                }

                if (vdir == dir) {
                        /* Vehicle enters bridge at the last frame inside this tile. */
                        if (frame != TILE_SIZE - 1) return VETSB_CONTINUE;
                        switch (v->type) {
                                case VEH_TRAIN: {
                                        Train *t = Train::From(v);
                                        t->track = TRACK_BIT_WORMHOLE;
                                        ClrBit(t->gv_flags, GVF_GOINGUP_BIT);
                                        ClrBit(t->gv_flags, GVF_GOINGDOWN_BIT);
                                        break;
                                }

                                case VEH_ROAD: {
                                        RoadVehicle *rv = RoadVehicle::From(v);
                                        if (IsRoadCustomBridgeHeadTile(tile)) {
                                                RoadBits bits = ROAD_NONE;
                                                if (rv->compatible_roadtypes & ROADTYPES_TRAM) bits |= GetCustomBridgeHeadRoadBits(tile, ROADTYPE_TRAM);
                                                if (rv->compatible_roadtypes & ROADTYPES_ROAD) bits |= GetCustomBridgeHeadRoadBits(tile, ROADTYPE_ROAD);
                                                if (!(bits & DiagDirToRoadBits(GetTunnelBridgeDirection(tile)))) return VETSB_CONTINUE;
                                        }
                                        rv->state = RVSB_WORMHOLE;
                                        /* There are no slopes inside bridges / tunnels. */
                                        ClrBit(rv->gv_flags, GVF_GOINGUP_BIT);
                                        ClrBit(rv->gv_flags, GVF_GOINGDOWN_BIT);
                                        break;
                                }

                                case VEH_SHIP:
                                        Ship::From(v)->state = TRACK_BIT_WORMHOLE;
                                        break;

                                default: NOT_REACHED();
                        }
                        return VETSB_ENTERED_WORMHOLE;
                } else if (vdir == ReverseDiagDir(dir)) {
                        v->tile = tile;
                        switch (v->type) {
                                case VEH_TRAIN: {
                                        Train *t = Train::From(v);
                                        if (t->track == TRACK_BIT_WORMHOLE) {
                                                t->track = DiagDirToDiagTrackBits(vdir);
                                                return VETSB_ENTERED_WORMHOLE;
                                        }
                                        break;
                                }

                                case VEH_ROAD: {
                                        RoadVehicle *rv = RoadVehicle::From(v);
                                        if (rv->state == RVSB_WORMHOLE) {
                                                rv->state = DiagDirToDiagTrackdir(vdir);
                                                rv->frame = 0;
                                                return VETSB_ENTERED_WORMHOLE;
                                        }
                                        break;
                                }

                                case VEH_SHIP: {
                                        Ship *ship = Ship::From(v);
                                        if (ship->state == TRACK_BIT_WORMHOLE) {
                                                ship->state = DiagDirToDiagTrackBits(vdir);
                                                return VETSB_ENTERED_WORMHOLE;
                                        }
                                        break;
                                }

                                default: NOT_REACHED();
                        }
                }
        }
        return VETSB_CONTINUE;
}

static CommandCost TerraformTile_TunnelBridge(TileIndex tile, DoCommandFlag flags, int z_new, Slope tileh_new)
{
        if (_settings_game.construction.build_on_slopes && AutoslopeEnabled() && IsBridge(tile) && GetTunnelBridgeTransportType(tile) != TRANSPORT_WATER) {
                DiagDirection direction = GetTunnelBridgeDirection(tile);
                Axis axis = DiagDirToAxis(direction);
                CommandCost res;
                int z_old;
                Slope tileh_old = GetTileSlope(tile, &z_old);
 
                if (IsRoadCustomBridgeHeadTile(tile)) {
                        const RoadBits pieces = GetCustomBridgeHeadAllRoadBits(tile);
                        const RoadBits entrance_piece = DiagDirToRoadBits(direction);

                        /* Steep slopes behave the same as slopes with one corner raised. */
                        const Slope normalised_tileh_new = IsSteepSlope(tileh_new) ? SlopeWithOneCornerRaised(GetHighestSlopeCorner(tileh_new)) : tileh_new;

                        if ((_invalid_tileh_slopes_road[0][normalised_tileh_new & SLOPE_ELEVATED] & (pieces & ~entrance_piece)) != ROAD_NONE) {
                                return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
                        }
                }

                /* Check if new slope is valid for bridges in general (so we can safely call GetBridgeFoundation()) */
                if ((direction == DIAGDIR_NW) || (direction == DIAGDIR_NE)) {
                        CheckBridgeSlopeSouth(axis, &tileh_old, &z_old);
                        res = CheckBridgeSlopeSouth(axis, &tileh_new, &z_new);
                } else {
                        CheckBridgeSlopeNorth(axis, &tileh_old, &z_old);
                        res = CheckBridgeSlopeNorth(axis, &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);
}

extern const TileTypeProcs _tile_type_tunnelbridge_procs = {
        DrawTile_TunnelBridge,           // draw_tile_proc
        GetSlopePixelZ_TunnelBridge,     // get_slope_z_proc
        ClearTile_TunnelBridge,          // clear_tile_proc
        nullptr,                            // add_accepted_cargo_proc
        GetTileDesc_TunnelBridge,        // get_tile_desc_proc
        GetTileTrackStatus_TunnelBridge, // get_tile_track_status_proc
        ClickTile_TunnelBridge,          // click_tile_proc
        nullptr,                            // animate_tile_proc
        TileLoop_TunnelBridge,           // tile_loop_proc
        ChangeTileOwner_TunnelBridge,    // change_tile_owner_proc
        nullptr,                            // add_produced_cargo_proc
        VehicleEnter_TunnelBridge,       // vehicle_enter_tile_proc
        GetFoundation_TunnelBridge,      // get_foundation_proc
        TerraformTile_TunnelBridge,      // terraform_tile_proc
};