Function CmdBuildRoad

src/road_cmd.cpp:599–928

* Build a piece of road. * @param flags operation to perform * @param tile tile where to build road * @param pieces road pieces to build (RoadBits) * @param rt road type * @param toggle_drd disallowed directions to toggle * @param town_id the town that is building the road (TownID::Invalid() if not applicable) * @return the cost of this operation or an error */

 * @return the cost of this operation or an error
 */
CommandCost CmdBuildRoad(DoCommandFlags flags, TileIndex tile, RoadBits pieces, RoadType rt, DisallowedRoadDirections toggle_drd, TownID town_id)
{
	CompanyID company = _current_company;
	CommandCost cost(EXPENSES_CONSTRUCTION);

	RoadBits existing = ROAD_NONE;
	RoadBits other_bits = ROAD_NONE;

	/* Road pieces are max 4 bitset values (NE, NW, SE, SW) and town can only be non-zero
	 * if a non-company is building the road */
	if ((Company::IsValidID(company) && town_id != TownID::Invalid()) || (company == OWNER_TOWN && !Town::IsValidID(town_id)) || (company == OWNER_DEITY && town_id != TownID::Invalid())) return CMD_ERROR;
	if (company != OWNER_TOWN) {
		const Town *town = CalcClosestTownFromTile(tile);
		town_id = (town != nullptr) ? town->index : TownID::Invalid();

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

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

	/* do not allow building 'zero' road bits, code wouldn't handle it */
	if (pieces == ROAD_NONE || !IsValidRoadBits(pieces) || !IsValidDisallowedRoadDirections(toggle_drd)) return CMD_ERROR;
	if (!ValParamRoadType(rt)) return CMD_ERROR;

	Slope tileh = GetTileSlope(tile);
	RoadTramType rtt = GetRoadTramType(rt);

	bool need_to_clear = false;
	switch (GetTileType(tile)) {
		case MP_ROAD:
			switch (GetRoadTileType(tile)) {
				case RoadTileType::Normal: {
					if (HasRoadWorks(tile)) return CommandCost(STR_ERROR_ROAD_WORKS_IN_PROGRESS);

					other_bits = GetRoadBits(tile, OtherRoadTramType(rtt));
					if (!HasTileRoadType(tile, rtt)) break;

					existing = GetRoadBits(tile, rtt);
					bool crossing = !IsStraightRoad(existing | pieces);
					if (rtt == RTT_ROAD && (GetDisallowedRoadDirections(tile) != DRD_NONE || toggle_drd != DRD_NONE) && crossing) {
						/* Junctions cannot be one-way */
						return CommandCost(STR_ERROR_ONEWAY_ROADS_CAN_T_HAVE_JUNCTION);
					}
					if ((existing & pieces) == pieces) {
						/* We only want to set the (dis)allowed road directions */
						if (toggle_drd != DRD_NONE && rtt == RTT_ROAD) {
							Owner owner = GetRoadOwner(tile, rtt);
							if (owner != OWNER_NONE) {
								CommandCost ret = CheckOwnership(owner, tile);
								if (ret.Failed()) return ret;
							}

							DisallowedRoadDirections dis_existing = GetDisallowedRoadDirections(tile);