#include "vehicle_func.h"

/** Follow a reservation starting from a specific tile to the end. */

static PBSTileInfo FollowReservation(Owner o, RailTypes rts, TileIndex tile, Trackdir trackdir, bool ignore_oneway = false)

{

	/* Do not disallow 90 deg turns as the setting might have changed between reserving and now. */

	CFollowTrackRail ft(o, rts);

	while (ft.Follow(tile, trackdir)) {

		TrackdirBits reserved = (TrackdirBits)(ft.m_new_td_bits & (GetReservedTrackbits(ft.m_new_tile) * 0x101));

		/* No reservation --> path end found */

		if (reserved == TRACKDIR_BIT_NONE) break;

		/* Can't have more than one reserved trackdir */

		Trackdir new_trackdir = FindFirstTrackdir(reserved);

		/* One-way signal against us. The reservation can't be ours as it is not

		 * a safe position from our direction and we can never pass the signal. */

		if (!ignore_oneway && HasOnewaySignalBlockingTrackdir(ft.m_new_tile, new_trackdir)) break;

		tile = ft.m_new_tile;

		trackdir = new_trackdir;

		/* Depot tile? Can't continue. */

		if (IsRailDepotTile(tile)) break;

		/* Non-pbs signal? Reservation can't continue. */

		if (IsTileType(tile, MP_RAILWAY) && HasSignalOnTrackdir(tile, trackdir) && !IsPbsSignal(GetSignalType(tile, TrackdirToTrack(trackdir)))) break;

	}

	return PBSTileInfo(tile, trackdir, false);

}

	PBSTileInfo res = FollowReservation(v->owner, GetRailTypeInfo(v->u.rail.railtype)->compatible_railtypes, tile, trackdir);

	res.okay = IsSafeWaitingPosition(v, res.tile, res.trackdir, true, _settings_game.pf.forbid_90_deg);

	return res;

}

/** Callback for VehicleFromPos to find a train on a specific track. */

static Vehicle *FindTrainOnTrackEnum(Vehicle *v, void *data)

{

	PBSTileInfo info = *(PBSTileInfo *)data;

	if (v->type == VEH_TRAIN && !(v->vehstatus & VS_CRASHED) && HasBit((TrackBits)v->u.rail.track, TrackdirToTrack(info.trackdir))) return v;

	return NULL;

}

/**

 * Find the train which has reserved a specific path.

 *

 * @param tile A tile on the path.

 * @param track A reserved track on the tile.

 * @return The vehicle holding the reservation or NULL if the path is stray.

 */

Vehicle *GetTrainForReservation(TileIndex tile, Track track)

{

	assert(HasReservedTracks(tile, TrackToTrackBits(track)));

	Trackdir  trackdir = TrackToTrackdir(track);

	RailTypes rts = GetRailTypeInfo(GetTileRailType(tile))->compatible_railtypes;

	/* Follow the path from tile to both ends, one of the end tiles should

	 * have a train on it. We need FollowReservation to ignore one-way signals

	 * here, as one of the two search directions will be the "wrong" way. */

	for (int i = 0; i < 2; ++i, trackdir = ReverseTrackdir(trackdir)) {

		PBSTileInfo dest = FollowReservation(GetTileOwner(tile), rts, tile, trackdir, true);

		Vehicle *v = VehicleFromPos(dest.tile, &dest, FindTrainOnTrackEnum);

		if (v != NULL) return v->First();

		/* Special case for stations: check the whole platform for a vehicle. */

		if (IsRailwayStationTile(dest.tile)) {

			TileIndexDiff diff = TileOffsByDiagDir(TrackdirToExitdir(ReverseTrackdir(dest.trackdir)));

			for (TileIndex st_tile = dest.tile + diff; IsCompatibleTrainStationTile(st_tile, dest.tile); st_tile += diff) {

				v = VehicleFromPos(st_tile, &dest, FindTrainOnTrackEnum);

				if (v != NULL) return v->First();

			}

		}

		/* Special case for bridges/tunnels: check the other end as well. */

		if (IsTileType(dest.tile, MP_TUNNELBRIDGE)) {

			v = VehicleFromPos(GetOtherTunnelBridgeEnd(dest.tile), &dest, FindTrainOnTrackEnum);

			if (v != NULL) return v->First();

		}

	return NULL;

Vehicle *GetTrainForReservation(TileIndex tile, Track track);