Function CmdBuildSingleRail

src/rail_cmd.cpp:423–603

* Build a single piece of rail * @param flags operation to perform * @param tile tile to build on * @param railtype railtype of being built piece (normal, mono, maglev) * @param track track-orientation * @param auto_remove_signals false = error on signal in the way, true = auto remove signals when in the way * @return the cost of this operation or an error */

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

	if (!ValParamRailType(railtype) || !ValParamTrackOrientation(track)) return CMD_ERROR;

	Slope tileh = GetTileSlope(tile);
	TrackBits trackbit = TrackToTrackBits(track);

	switch (GetTileType(tile)) {
		case MP_RAILWAY: {
			CommandCost ret = CheckTileOwnership(tile);
			if (ret.Failed()) return ret;

			if (!IsPlainRail(tile)) return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile); // just get appropriate error message

			if (!IsCompatibleRail(GetRailType(tile), railtype)) return CommandCost(STR_ERROR_IMPOSSIBLE_TRACK_COMBINATION);

			ret = CheckTrackCombination(tile, trackbit);
			if (ret.Succeeded()) ret = EnsureNoTrainOnTrack(tile, track);
			if (ret.Failed()) return ret;

			ret = CheckRailSlope(tileh, trackbit, GetTrackBits(tile), tile);
			if (ret.Failed()) return ret;
			cost.AddCost(ret.GetCost());

			if (HasSignals(tile) && TracksOverlap(GetTrackBits(tile) | TrackToTrackBits(track))) {
				/* If adding the new track causes any overlap, all signals must be removed first */
				if (!auto_remove_signals) return CommandCost(STR_ERROR_MUST_REMOVE_SIGNALS_FIRST);

				for (Track track_it = TRACK_BEGIN; track_it < TRACK_END; track_it++) {
					if (HasTrack(tile, track_it) && HasSignalOnTrack(tile, track_it)) {
						CommandCost ret_remove_signals = Command<CMD_REMOVE_SINGLE_SIGNAL>::Do(flags, tile, track_it);
						if (ret_remove_signals.Failed()) return ret_remove_signals;
						cost.AddCost(ret_remove_signals.GetCost());
					}
				}
			}

			/* If the rail types don't match, try to convert only if engines of
			 * the new rail type are not powered on the present rail type and engines of
			 * the present rail type are powered on the new rail type. */
			if (GetRailType(tile) != railtype && !HasPowerOnRail(railtype, GetRailType(tile))) {
				if (HasPowerOnRail(GetRailType(tile), railtype)) {
					ret = Command<CMD_CONVERT_RAIL>::Do(flags, tile, tile, railtype, false);
					if (ret.Failed()) return ret;
					cost.AddCost(ret.GetCost());
				} else {
					return CMD_ERROR;
				}
			}

			if (flags.Test(DoCommandFlag::Execute)) {
				SetRailGroundType(tile, RailGroundType::Barren);
				TrackBits bits = GetTrackBits(tile);
				SetTrackBits(tile, bits | trackbit);
				/* Subtract old infrastructure count. */
				uint pieces = CountBits(bits);