Function CmdBuildLongRoad

src/road_cmd.cpp:966–1050

* Build a long piece of road. * @param flags operation to perform * @param end_tile end tile of drag * @param start_tile start tile of drag * @param rt road type * @param axis direction * @param drd set road direction * @param start_half start tile starts in the 2nd half of tile (p2 & 1). Only used if \c is_ai is set or if we are building a single tile * @param end_half end tile starts in

 * @return the cost of this operation or an error
 */
CommandCost CmdBuildLongRoad(DoCommandFlags flags, TileIndex end_tile, TileIndex start_tile, RoadType rt, Axis axis, DisallowedRoadDirections drd, bool start_half, bool end_half, bool is_ai)
{
	if (start_tile >= Map::Size()) return CMD_ERROR;

	if (!ValParamRoadType(rt) || !IsValidAxis(axis) || !IsValidDisallowedRoadDirections(drd)) return CMD_ERROR;

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

	DiagDirection dir = AxisToDiagDir(axis);

	/* Swap direction, also the half-tile drag vars. */
	if (start_tile > end_tile || (start_tile == end_tile && start_half)) {
		dir = ReverseDiagDir(dir);
		start_half = !start_half;
		end_half = !end_half;
		if (drd == DRD_NORTHBOUND || drd == DRD_SOUTHBOUND) drd ^= DRD_BOTH;
	}

	/* On the X-axis, we have to swap the initial bits, so they
	 * will be interpreted correctly in the GTTS. Furthermore
	 * when you just 'click' on one tile to build them. */
	if ((drd == DRD_NORTHBOUND || drd == DRD_SOUTHBOUND) && (axis == AXIS_Y) == (start_tile == end_tile && start_half == end_half)) drd ^= DRD_BOTH;

	CommandCost cost(EXPENSES_CONSTRUCTION);
	CommandCost last_error = CMD_ERROR;
	TileIndex tile = start_tile;
	bool had_bridge = false;
	bool had_tunnel = false;
	bool had_success = false;

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

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

		CommandCost ret = Command<CMD_BUILD_ROAD>::Do(flags, tile, bits, rt, drd, TownID::Invalid());
		if (!is_ai && ret.GetErrorMessage() == STR_ERROR_ALREADY_BUILT) had_success = true;
		if (ret.Failed()) {
			last_error = std::move(ret);
			if (last_error.GetErrorMessage() != STR_ERROR_ALREADY_BUILT) {
				if (is_ai) return last_error;
				if (had_success) break; // Keep going if we haven't constructed any road yet, skipping the start of the drag
			}