Function CmdBuildBridge

src/tunnelbridge_cmd.cpp:310–636

* Build a Bridge * @param flags type of operation * @param tile_end end tile * @param tile_start start tile * @param transport_type transport type. * @param bridge_type bridge type (hi bh) * @param road_rail_type rail type or road types. * @return the cost of this operation or an error */

 * @return the cost of this operation or an error
 */
CommandCost CmdBuildBridge(DoCommandFlags flags, TileIndex tile_end, TileIndex tile_start, TransportType transport_type, BridgeType bridge_type, uint8_t road_rail_type)
{
	CompanyID company = _current_company;

	RailType railtype = INVALID_RAILTYPE;
	RoadType roadtype = INVALID_ROADTYPE;

	for (TileIndex t : {tile_start, tile_end}) {
		if (!IsValidTile(t)) return CommandCost(STR_ERROR_BRIDGE_THROUGH_MAP_BORDER);
		/* User cannot modify height of tiles with one coordinate equal to zero, they are always at the sea level, and you can't build bridge in the sea.
		 * Furthermore, they are void tiles unless map is infinite water. If we don't return for them here, we will still fail as their slope is invalid. */
		if (TileX(t) == 0 || TileY(t) == 0) return CommandCost(transport_type == TRANSPORT_WATER ? STR_ERROR_BRIDGE_THROUGH_MAP_BORDER : STR_ERROR_TOO_CLOSE_TO_EDGE_OF_MAP);
	}

	/* type of bridge */
	switch (transport_type) {
		case TRANSPORT_ROAD:
			roadtype = (RoadType)road_rail_type;
			if (!ValParamRoadType(roadtype)) return CMD_ERROR;
			break;

		case TRANSPORT_RAIL:
			railtype = (RailType)road_rail_type;
			if (!ValParamRailType(railtype)) return CMD_ERROR;
			break;

		case TRANSPORT_WATER:
			break;

		default:
			/* Airports don't have bridges. */
			return CMD_ERROR;
	}

	if (company == OWNER_DEITY) {
		if (transport_type != TRANSPORT_ROAD) return CMD_ERROR;
		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[to_underlying(HouseZone::TownEdge)]) {
			company = OWNER_NONE;
		}
	}

	if (tile_start == tile_end) {
		return CommandCost(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 CommandCost(STR_ERROR_START_AND_END_MUST_BE_IN);
	}