Function CmdRailTrackHelper

src/rail_cmd.cpp:873–915

* Build or remove a stretch of railroad tracks. * @param flags operation to perform * @param tile start tile of drag * @param end_tile end tile of drag * @param railtype railroad type normal/maglev (0 = normal, 1 = mono, 2 = maglev), only used for building * @param track track-orientation * @param remove remove tracks? * @param auto_remove_signals false = error on signal in the way, true =

 * @return the cost of this operation or an error
 */
static CommandCost CmdRailTrackHelper(DoCommandFlags flags, TileIndex tile, TileIndex end_tile, RailType railtype, Track track, bool remove, bool auto_remove_signals, bool fail_on_obstacle)
{
	CommandCost total_cost(EXPENSES_CONSTRUCTION);

	if ((!remove && !ValParamRailType(railtype)) || !ValParamTrackOrientation(track)) return CMD_ERROR;
	if (end_tile >= Map::Size() || tile >= Map::Size()) return CMD_ERROR;

	Trackdir trackdir = TrackToTrackdir(track);

	CommandCost ret = ValidateAutoDrag(&trackdir, tile, end_tile);
	if (ret.Failed()) return ret;

	bool had_success = false;
	CommandCost last_error = CMD_ERROR;
	for (;;) {
		ret = remove ? Command<CMD_REMOVE_SINGLE_RAIL>::Do(flags, tile, TrackdirToTrack(trackdir)) : Command<CMD_BUILD_SINGLE_RAIL>::Do(flags, tile, railtype, TrackdirToTrack(trackdir), auto_remove_signals);
		if (!remove && !fail_on_obstacle && last_error.GetErrorMessage() == STR_ERROR_ALREADY_BUILT) had_success = true;

		if (ret.Failed()) {
			last_error = std::move(ret);
			if (last_error.GetErrorMessage() != STR_ERROR_ALREADY_BUILT && !remove) {
				if (fail_on_obstacle) return last_error;
				if (had_success) break; // Keep going if we haven't constructed any rail yet, skipping the start of the drag
			}

			/* Ownership errors are more important. */
			if (last_error.GetErrorMessage() == STR_ERROR_OWNED_BY && remove) break;
		} else {
			had_success = true;
			total_cost.AddCost(ret.GetCost());
		}

		if (tile == end_tile) break;

		tile += ToTileIndexDiff(_trackdelta[trackdir]);

		/* toggle railbit for the non-diagonal tracks */
		if (!IsDiagonalTrackdir(trackdir)) ToggleBit(trackdir, 0);
	}

	if (had_success) return total_cost;
	return last_error;
}

/**
 * Build rail on a stretch of track.