/* $Id$ */

#include "stdafx.h"
#include "openttd.h"
#include "debug.h"
#include "functions.h"
#include "npf.h"
#include "aystar.h"
#include "macros.h"
#include "pathfind.h"
#include "station.h"
#include "tile.h"
#include "depot.h"

static AyStar _npf_aystar;

/* The cost of each trackdir. A diagonal piece is the full NPF_TILE_LENGTH,
 * the shorter piece is sqrt(2)/2*NPF_TILE_LENGTH =~ 0.7071
 */
#define NPF_STRAIGHT_LENGTH (uint)(NPF_TILE_LENGTH * STRAIGHT_TRACK_LENGTH)
static const uint _trackdir_length[TRACKDIR_END] = {
	NPF_TILE_LENGTH, NPF_TILE_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH,
	0, 0,
	NPF_TILE_LENGTH, NPF_TILE_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH
};

/**
 * Calculates the minimum distance traveled to get from t0 to t1 when only
 * using tracks (ie, only making 45 degree turns). Returns the distance in the
 * NPF scale, ie the number of full tiles multiplied by NPF_TILE_LENGTH to
 * prevent rounding.
 */
static uint NPFDistanceTrack(TileIndex t0, TileIndex t1)
{
	const uint dx = abs(TileX(t0) - TileX(t1));
	const uint dy = abs(TileY(t0) - TileY(t1));

	const uint straightTracks = 2 * min(dx, dy); /* The number of straight (not full length) tracks */
	/* OPTIMISATION:
	 * Original: diagTracks = max(dx, dy) - min(dx,dy);
	 * Proof:
	 * (dx+dy) - straightTracks  == (min + max) - straightTracks = min + max - 2 * min = max - min */
	const uint diagTracks = dx + dy - straightTracks; /* The number of diagonal (full tile length) tracks. */

	/* Don't factor out NPF_TILE_LENGTH below, this will round values and lose
	 * precision */
	return diagTracks * NPF_TILE_LENGTH + straightTracks * NPF_TILE_LENGTH * STRAIGHT_TRACK_LENGTH;
}

/**
 * Check if a rail track is the end of the line. Will also consider 1-way signals to be the end of a line.
 * @param tile The tile on which the current track is.
 * @param trackdir The (track)direction in which you want to look.
 * @param enginetype The type of the engine for which we are checking this.
 */
static bool IsEndOfLine(TileIndex tile, Trackdir trackdir, RailType enginetype)
{
	byte exitdir = TrackdirToExitdir(trackdir);
	TileIndex dst_tile;
	uint32 ts;

	/* Can always go into a tunnel */
	if (IsTileType(tile, MP_TUNNELBRIDGE) && (_m[tile].m5 & 0xF0)==0 && (_m[tile].m5 & 3) == exitdir)
		return false;

	/* Cannot go through the back of a depot */
	if (IsTileDepotType(tile, TRANSPORT_RAIL) && (exitdir != GetDepotDirection(tile, TRANSPORT_RAIL)))
		return true;

	/* Calculate next tile */
	dst_tile = tile + TileOffsByDir(exitdir);
	// determine the track status on the next tile.
	ts = GetTileTrackStatus(dst_tile, TRANSPORT_RAIL) & TrackdirReachesTrackdirs(trackdir);

	// when none of the trackdir bits are set, we cant enter the new tile
	if ( (ts & TRACKDIR_BIT_MASK) == 0)
		return true;

	{
		byte dst_type = GetTileRailType(dst_tile, exitdir);
		if (!IsCompatibleRail(enginetype, dst_type))
			return true;
		if (GetTileOwner(tile) != GetTileOwner(dst_tile))
			return true;

		/* Prevent us from entering a depot from behind */
		if (IsTileDepotType(dst_tile, TRANSPORT_RAIL) && (exitdir != ReverseDiagdir(GetDepotDirection(dst_tile, TRANSPORT_RAIL))))
			return true;

		/* Prevent us from falling off a slope into a tunnel exit */
		if (IsTileType(dst_tile, MP_TUNNELBRIDGE) && (_m[dst_tile].m5 & 0xF0)==0 && (DiagDirection)(_m[dst_tile].m5 & 3) == ReverseDiagdir(exitdir))
				return true;

		/* Check for oneway signal against us */
		if (IsTileType(dst_tile, MP_RAILWAY) && GetRailTileType(dst_tile) == RAIL_TYPE_SIGNALS) {
			if (HasSignalOnTrackdir(dst_tile, ReverseTrackdir(FindFirstBit2x64(ts))) && !HasSignalOnTrackdir(dst_tile, FindFirstBit2x64(ts)))
				// if one way signal not pointing towards us, stop going in this direction.
				return true;
		}

		return false;
	}
}

#if 0
static uint NTPHash(uint key1, uint key2)
{
	/* This function uses the old hash, which is fixed on 10 bits (1024 buckets) */
	return PATHFIND_HASH_TILE(key1);
}
#endif

/**
 * Calculates a hash value for use in the NPF.
 * @param key1	The TileIndex of the tile to hash
 * @param key1	The Trackdir of the track on the tile.
 *
 * @todo	Think of a better hash.
 */
static uint NPFHash(uint key1, uint key2)
{
	/* TODO: think of a better hash? */
	uint part1 = TileX(key1) & NPF_HASH_HALFMASK;
	uint part2 = TileY(key1) & NPF_HASH_HALFMASK;

	assert(IsValidTrackdir(key2));
	assert(IsValidTile(key1));
	return ((((part1 << NPF_HASH_HALFBITS) | part2)) + (NPF_HASH_SIZE * key2 / TRACKDIR_END)) % NPF_HASH_SIZE;
}

static int32 NPFCalcZero(AyStar* as, AyStarNode* current, OpenListNode* parent)
{
	return 0;
}

/* Calcs the tile of given station that is closest to a given tile
 * for this we assume the station is a rectangle,
 * as defined by its top tile (st->train_tile) and its width/height (st->trainst_w, st->trainst_h)
 */
static TileIndex CalcClosestStationTile(StationID station, TileIndex tile)
{
	const Station* st = GetStation(station);

	uint minx = TileX(st->train_tile);  // topmost corner of station
	uint miny = TileY(st->train_tile);
	uint maxx = minx + st->trainst_w - 1; // lowermost corner of station
	uint maxy = miny + st->trainst_h - 1;
	uint x;
	uint y;

	// we are going the aim for the x coordinate of the closest corner
	// but if we are between those coordinates, we will aim for our own x coordinate
	x = clamp(TileX(tile), minx, maxx);

	// same for y coordinate, see above comment
	y = clamp(TileY(tile), miny, maxy);

	// return the tile of our target coordinates
	return TileXY(x, y);
}

/* On PBS pathfinding runs, this is called before pathfinding ends (BeforeExit aystar callback), and will
 * reserve the appropriate tracks, if needed. */
static void NPFReservePBSPath(AyStar *as)
{
	NPFFoundTargetData* ftd = (NPFFoundTargetData*)as->user_path;
	bool eol_end = false;

	if (ftd->best_trackdir == 0xFF)
		return;

	if (!NPFGetFlag(&ftd->node, NPF_FLAG_PBS_EXIT) && IsEndOfLine(ftd->node.tile, ftd->node.direction, as->user_data[NPF_RAILTYPE]) && !NPFGetFlag(&ftd->node, NPF_FLAG_SEEN_SIGNAL)) {
		/* The path ends in an end of line, we'll need to reserve a path.
		 * We treat and end of line as a red exit signal */
		eol_end = true;
		NPFSetFlag(&ftd->node, NPF_FLAG_PBS_EXIT, true);
		if (!NPFGetFlag(&ftd->node, NPF_FLAG_PBS_TARGET_SEEN))
			NPFSetFlag(&ftd->node, NPF_FLAG_PBS_RED, true);
	}

	if (!NPFGetFlag(&ftd->node, NPF_FLAG_PBS_CHOICE)) {
		/* there have been no choices to make on our path, we dont care if our end signal is red */
		NPFSetFlag(&ftd->node, NPF_FLAG_PBS_RED, false);
	}

	if (NPFGetFlag(&ftd->node, NPF_FLAG_PBS_EXIT) && // we passed an exit signal
		 !NPFGetFlag(&ftd->node, NPF_FLAG_PBS_BLOCKED) && // we didnt encounter reserver tracks
		 ((as->user_data[NPF_PBS_MODE] != PBS_MODE_GREEN) || (!NPFGetFlag(&ftd->node, NPF_FLAG_PBS_RED))) ) { // our mode permits having a red exit signal, or the signal is green
		PathNode parent;
		PathNode *curr;
		PathNode *prev;
		TileIndex start = INVALID_TILE;
		byte trackdir = 0;

		parent.node = ftd->node;
		parent.parent = &ftd->path;
		curr = &parent;
		prev = NULL;

		do {
			if (!NPFGetFlag(&curr->node, NPF_FLAG_PBS_EXIT) || eol_end) {
				/* check for already reserved track on this path, if they clash with what we
				   currently trying to reserve, we have a self-crossing path :-( */
				if ((PBSTileUnavail(curr->node.tile) & (1 << curr->node.direction))
				&& !(PBSTileReserved(curr->node.tile) & (1 << (curr->node.direction & 7)))
				&& (start != INVALID_TILE)) {
					/* It's actually quite bad if this happens, it means the pathfinder
					 * found a path that is intersecting with itself, which is a very bad
					 * thing in a pbs block. Also there is not much we can do about it at
					 * this point....
					 * BUT, you have to have a pretty fucked up junction layout for this to happen,
					 * so we'll just stop this train, the user will eventually notice, so he can fix it.
					 */
					PBSClearPath(start, trackdir, curr->node.tile, curr->node.direction);
					NPFSetFlag(&ftd->node, NPF_FLAG_PBS_BLOCKED, true);
					DEBUG(pbs, 1) ("PBS: Self-crossing path!!!");
					return;
				};

				PBSReserveTrack(curr->node.tile, TrackdirToTrack(curr->node.direction) );

				/* we want to reserve the last tile (with the signal) on the path too
				   also remember this tile, cause its the end of the path (where we exit the block) */
				if (start == INVALID_TILE) {
					if (prev != NULL) {
						PBSReserveTrack(prev->node.tile, TrackdirToTrack(prev->node.direction) );
						start = prev->node.tile;
						trackdir = ReverseTrackdir(prev->node.direction);
					} else {
						start = curr->node.tile;
						trackdir = curr->node.direction;
					}
				}
			}

			prev = curr;
			curr = curr->parent;
		} while (curr != NULL);
		// we remember the tile/track where this path leaves the pbs junction
		ftd->node.tile = start;
		ftd->node.direction = trackdir;
	}
}


/* Calcs the heuristic to the target station or tile. For train stations, it
 * takes into account the direction of approach.
 */
static int32 NPFCalcStationOrTileHeuristic(AyStar* as, AyStarNode* current, OpenListNode* parent)
{
	NPFFindStationOrTileData* fstd = (NPFFindStationOrTileData*)as->user_target;
	NPFFoundTargetData* ftd = (NPFFoundTargetData*)as->user_path;
	TileIndex from = current->tile;
	TileIndex to = fstd->dest_coords;
	uint dist;

	// for train-stations, we are going to aim for the closest station tile
	if ((as->user_data[NPF_TYPE] == TRANSPORT_RAIL) && (fstd->station_index != -1))
		to = CalcClosestStationTile(fstd->station_index, from);

	if (as->user_data[NPF_TYPE] == TRANSPORT_ROAD)
		/* Since roads only have diagonal pieces, we use manhattan distance here */
		dist = DistanceManhattan(from, to) * NPF_TILE_LENGTH;
	else
		/* Ships and trains can also go diagonal, so the minimum distance is shorter */
		dist = NPFDistanceTrack(from, to);

	DEBUG(npf, 4)("Calculating H for: (%d, %d). Result: %d", TileX(current->tile), TileY(current->tile), dist);

	/* for pbs runs, we ignore tiles inside the pbs block for the tracking
	   of the 'closest' tile */
	if ((as->user_data[NPF_PBS_MODE] != PBS_MODE_NONE)
	&&  (!NPFGetFlag(current , NPF_FLAG_SEEN_SIGNAL))
	&&  (!IsEndOfLine(current->tile, current->direction, as->user_data[NPF_RAILTYPE])))
		return dist;

	if ((dist < ftd->best_bird_dist) ||
		/* for pbs runs, prefer tiles that pass a green exit signal to the pbs blocks */
		((as->user_data[NPF_PBS_MODE] != PBS_MODE_NONE) && !NPFGetFlag(current, NPF_FLAG_PBS_RED) && NPFGetFlag(&ftd->node, NPF_FLAG_PBS_RED))
) {
		ftd->best_bird_dist = dist;
		ftd->best_trackdir = current->user_data[NPF_TRACKDIR_CHOICE];
		ftd->path = parent->path;
		ftd->node = *current;
	}
	return dist;
}

/* Fills AyStarNode.user_data[NPF_TRACKDIRCHOICE] with the chosen direction to
 * get here, either getting it from the current choice or from the parent's
 * choice */
static void NPFFillTrackdirChoice(AyStarNode* current, OpenListNode* parent)
{
	if (parent->path.parent == NULL) {
		Trackdir trackdir = (Trackdir)current->direction;
		/* This is a first order decision, so we'd better save the
		 * direction we chose */
		current->user_data[NPF_TRACKDIR_CHOICE] = trackdir;
		DEBUG(npf, 6)("Saving trackdir: %#x", trackdir);
	} else {
		/* We've already made the decision, so just save our parent's
		 * decision */
		current->user_data[NPF_TRACKDIR_CHOICE] = parent->path.node.user_data[NPF_TRACKDIR_CHOICE];
	}

}

/* Will return the cost of the tunnel. If it is an entry, it will return the
 * cost of that tile. If the tile is an exit, it will return the tunnel length
 * including the exit tile. Requires that this is a Tunnel tile */
static uint NPFTunnelCost(AyStarNode* current)
{
	DiagDirection exitdir = TrackdirToExitdir((Trackdir)current->direction);
	TileIndex tile = current->tile;
	if ( (DiagDirection)(_m[tile].m5 & 3) == ReverseDiagdir(exitdir)) {
		/* We just popped out if this tunnel, since were
		 * facing the tunnel exit */
		FindLengthOfTunnelResult flotr;
		flotr = FindLengthOfTunnel(tile, ReverseDiagdir(exitdir));
		return flotr.length * NPF_TILE_LENGTH;
		//TODO: Penalty for tunnels?
	} else {
		/* We are entering the tunnel, the enter tile is just a
		 * straight track */
		return NPF_TILE_LENGTH;
	}
}

static uint NPFSlopeCost(AyStarNode* current)
{
	TileIndex next = current->tile + TileOffsByDir(TrackdirToExitdir(current->direction));
	int x,y;
	int8 z1,z2;

	x = TileX(current->tile) * TILE_SIZE;
	y = TileY(current->tile) * TILE_SIZE;
	/* get the height of the center of the current tile */
	z1 = GetSlopeZ(x+TILE_HEIGHT, y+TILE_HEIGHT);

	x = TileX(next) * TILE_SIZE;
	y = TileY(next) * TILE_SIZE;
	/* get the height of the center of the next tile */
	z2 = GetSlopeZ(x+TILE_HEIGHT, y+TILE_HEIGHT);

	if ((z2 - z1) > 1) {
		/* Slope up */
		return _patches.npf_rail_slope_penalty;
	}
	return 0;
	/* Should we give a bonus for slope down? Probably not, we
	 * could just substract that bonus from the penalty, because
	 * there is only one level of steepness... */
}

/* Mark tiles by mowing the grass when npf debug level >= 1 */
static void NPFMarkTile(TileIndex tile)
{
#ifdef NO_DEBUG_MESSAGES
	return;
#else
	if (_debug_npf_level >= 1)
		switch(GetTileType(tile)) {
			case MP_RAILWAY:
				/* DEBUG: mark visited tiles by mowing the grass under them
				 * ;-) */
				if (!IsTileDepotType(tile, TRANSPORT_RAIL)) {
					_m[tile].m2 &= ~15; /* Clear bits 0-3 */
					MarkTileDirtyByTile(tile);
				}
				break;
			case MP_STREET:
				if (!IsTileDepotType(tile, TRANSPORT_ROAD)) {
					_m[tile].m4 &= ~0x70; /* Clear bits 4-6 */
					MarkTileDirtyByTile(tile);
				}
				break;
			default:
				break;
		}
#endif
}

static int32 NPFWaterPathCost(AyStar* as, AyStarNode* current, OpenListNode* parent)
{
	//TileIndex tile = current->tile;
	int32 cost = 0;
	Trackdir trackdir = (Trackdir)current->direction;

	cost = _trackdir_length[trackdir]; /* Should be different for diagonal tracks */

	if (IsBuoyTile(current->tile) && IsDiagonalTrackdir(trackdir))
		cost += _patches.npf_buoy_penalty; /* A small penalty for going over buoys */

	if (current->direction != NextTrackdir((Trackdir)parent->path.node.direction))
		cost += _patches.npf_water_curve_penalty;

	/* TODO More penalties? */

	return cost;
}

/* Determine the cost of this node, for road tracks */
static int32 NPFRoadPathCost(AyStar* as, AyStarNode* current, OpenListNode* parent)
{
	TileIndex tile = current->tile;
	int32 cost = 0;

	/* Determine base length */
	switch (GetTileType(tile)) {
		case MP_TUNNELBRIDGE:
			if ((_m[tile].m5 & 0xF0)==0) {
				cost = NPFTunnelCost(current);
				break;
			}
			/* Fall through if above if is false, it is a bridge
			 * then. We treat that as ordinary road */
		case MP_STREET:
			cost = NPF_TILE_LENGTH;
			/* Increase the cost for level crossings */
			if ((_m[tile].m5 & 0xF0) == 0x10)
				cost += _patches.npf_crossing_penalty;
			break;
		default:
			break;
	}

	/* Determine extra costs */

	/* Check for slope */
	cost += NPFSlopeCost(current);

	/* Check for turns. Road vehicles only really drive diagonal, turns are
	 * represented by non-diagonal tracks */
	if (!IsDiagonalTrackdir(current->direction))
		cost += _patches.npf_road_curve_penalty;

	NPFMarkTile(tile);
	DEBUG(npf, 4)("Calculating G for: (%d, %d). Result: %d", TileX(current->tile), TileY(current->tile), cost);
	return cost;
}


/* Determine the cost of this node, for railway tracks */
static int32 NPFRailPathCost(AyStar* as, AyStarNode* current, OpenListNode* parent)
{
	TileIndex tile = current->tile;
	Trackdir trackdir = (Trackdir)current->direction;
	int32 cost = 0;
	/* HACK: We create a OpenListNode manualy, so we can call EndNodeCheck */
	OpenListNode new_node;

	/* Determine base length */
	switch (GetTileType(tile)) {
		case MP_TUNNELBRIDGE:
			if ((_m[tile].m5 & 0xF0)==0) {
				cost = NPFTunnelCost(current);
				break;
			}
			/* Fall through if above if is false, it is a bridge
			 * then. We treat that as ordinary rail */
		case MP_RAILWAY:
			cost = _trackdir_length[trackdir]; /* Should be different for diagonal tracks */
			break;
		case MP_STREET: /* Railway crossing */
			cost = NPF_TILE_LENGTH;
			break;
		case MP_STATION:
			/* We give a station tile a penalty. Logically we would only
					* want to give station tiles that are not our destination
					* this penalty. This would discourage trains to drive through
					* busy stations. But, we can just give any station tile a
					* penalty, because every possible route will get this penalty
					* exactly once, on its end tile (if it's a station) and it
			* will therefore not make a difference. */
			cost = NPF_TILE_LENGTH + _patches.npf_rail_station_penalty;
			break;
		default:
			break;
	}

	/* Determine extra costs */

	/* Check for reserved tracks (PBS) */
	if ((as->user_data[NPF_PBS_MODE] != PBS_MODE_NONE) && !(NPFGetFlag(current, NPF_FLAG_PBS_EXIT)) && !(NPFGetFlag(current, NPF_FLAG_PBS_BLOCKED)) && (PBSTileUnavail(tile) & (1<<trackdir))) {
		NPFSetFlag(current, NPF_FLAG_PBS_BLOCKED, true);
	};

	/* Check for signals */
	if (IsTileType(tile, MP_RAILWAY) && HasSignalOnTrackdir(tile, trackdir)) {
		/* Ordinary track with signals */
		if (GetSignalState(tile, trackdir) == SIGNAL_STATE_RED) {
			/* Signal facing us is red */
			if (!NPFGetFlag(current, NPF_FLAG_SEEN_SIGNAL)) {
				/* Penalize the first signal we
				 * encounter, if it is red */

				/* Is this a presignal exit or combo? */
				SignalType sigtype = GetSignalType(tile, TrackdirToTrack(trackdir));
				if (sigtype == SIGTYPE_EXIT || sigtype == SIGTYPE_COMBO)
					/* Penalise exit and combo signals differently (heavier) */
					cost += _patches.npf_rail_firstred_exit_penalty;
				else
					cost += _patches.npf_rail_firstred_penalty;

				/* for pbs runs, store the fact that the exit signal to the pbs block was red */
				if (!(NPFGetFlag(current, NPF_FLAG_PBS_EXIT)) && !(NPFGetFlag(current, NPF_FLAG_PBS_RED)) && NPFGetFlag(current, NPF_FLAG_PBS_CHOICE))
					NPFSetFlag(current, NPF_FLAG_PBS_RED, true);
			}
			/* Record the state of this signal */
			NPFSetFlag(current, NPF_FLAG_LAST_SIGNAL_RED, true);
		} else {
			/* Record the state of this signal */
			NPFSetFlag(current, NPF_FLAG_LAST_SIGNAL_RED, false);
		}

		if (!NPFGetFlag(current, NPF_FLAG_SEEN_SIGNAL) && NPFGetFlag(current, NPF_FLAG_PBS_BLOCKED)) {
			/* penalise a path through the pbs block if it crosses reserved tracks */
			cost += 1000;
		}
		if ((PBSIsPbsSignal(tile, trackdir)) && !NPFGetFlag(current, NPF_FLAG_SEEN_SIGNAL)) {
			/* we've encountered an exit signal to the pbs block */
			NPFSetFlag(current, NPF_FLAG_PBS_EXIT, true);
		}
		NPFSetFlag(current, NPF_FLAG_SEEN_SIGNAL, true);
	}

	/* Penalise the tile if it is a target tile and the last signal was
	 * red */
	/* HACK: We create a new_node here so we can call EndNodeCheck. Ugly as hell
	 * of course... */
	new_node.path.node = *current;
	if (as->EndNodeCheck(as, &new_node) == AYSTAR_FOUND_END_NODE && NPFGetFlag(current, NPF_FLAG_LAST_SIGNAL_RED))
		cost += _patches.npf_rail_lastred_penalty;

	/* Check for slope */
	cost += NPFSlopeCost(current);

	/* Check for turns */
	if (current->direction != NextTrackdir((Trackdir)parent->path.node.direction))
		cost += _patches.npf_rail_curve_penalty;
	//TODO, with realistic acceleration, also the amount of straight track between
	//      curves should be taken into account, as this affects the speed limit.


	/* Check for depots */
	if (IsTileDepotType(tile, TRANSPORT_RAIL)) {
		/* Penalise any depot tile that is not the last tile in the path. This
		 * _should_ penalise every occurence of reversing in a depot (and only
		 * that) */
		if (as->EndNodeCheck(as, &new_node) != AYSTAR_FOUND_END_NODE)
			cost += _patches.npf_rail_depot_reverse_penalty;

		/* Do we treat this depot as a pbs signal? */
		if (!NPFGetFlag(current, NPF_FLAG_SEEN_SIGNAL)) {
			if (NPFGetFlag(current, NPF_FLAG_PBS_BLOCKED)) {
				cost += 1000;
			}
			if (PBSIsPbsSegment(tile, ReverseTrackdir(trackdir))) {
				NPFSetFlag(current, NPF_FLAG_PBS_EXIT, true);
				NPFSetFlag(current, NPF_FLAG_SEEN_SIGNAL, true);
			}
		}
		NPFSetFlag(current, NPF_FLAG_LAST_SIGNAL_RED, false);
	}

	/* Check for occupied track */
	//TODO

	NPFMarkTile(tile);
	DEBUG(npf, 4)("Calculating G for: (%d, %d). Result: %d", TileX(current->tile), TileY(current->tile), cost);
	return cost;
}

/* Will find any depot */
static int32 NPFFindDepot(AyStar* as, OpenListNode *current)
{
	TileIndex tile = current->path.node.tile;

	/* It's not worth caching the result with NPF_FLAG_IS_TARGET here as below,
	 * since checking the cache not that much faster than the actual check */
	if (IsTileDepotType(tile, as->user_data[NPF_TYPE]))
		return AYSTAR_FOUND_END_NODE;
	else
		return AYSTAR_DONE;
}

/* Will find a station identified using the NPFFindStationOrTileData */
static int32 NPFFindStationOrTile(AyStar* as, OpenListNode *current)
{
	NPFFindStationOrTileData* fstd = (NPFFindStationOrTileData*)as->user_target;
	AyStarNode *node = &current->path.node;
	TileIndex tile = node->tile;

	if (tile == 0x4611c) {
		tile++;
		tile--;
	}

	/* If GetNeighbours said we could get here, we assume the station type
	 * is correct */
	if (
		(fstd->station_index == -1 && tile == fstd->dest_coords) || /* We've found the tile, or */
		(IsTileType(tile, MP_STATION) && _m[tile].m2 == fstd->station_index) || /* the station */
		(NPFGetFlag(node, NPF_FLAG_PBS_TARGET_SEEN)) /* or, we've passed it already (for pbs) */
	) {
		NPFSetFlag(&current->path.node, NPF_FLAG_PBS_TARGET_SEEN, true);
		/* for pbs runs, only accept we've found the target if we've also found a way out of the block */
		if ((as->user_data[NPF_PBS_MODE] != PBS_MODE_NONE) && !NPFGetFlag(node, NPF_FLAG_SEEN_SIGNAL) && !IsEndOfLine(node->tile, node->direction, as->user_data[NPF_RAILTYPE]))
			return AYSTAR_DONE;
		return AYSTAR_FOUND_END_NODE;
	} else {
		return AYSTAR_DONE;
	}
}

/* To be called when current contains the (shortest route to) the target node.
 * Will fill the contents of the NPFFoundTargetData using
 * AyStarNode[NPF_TRACKDIR_CHOICE].
 */
static void NPFSaveTargetData(AyStar* as, OpenListNode* current)
{
	NPFFoundTargetData* ftd = (NPFFoundTargetData*)as->user_path;
	ftd->best_trackdir = (Trackdir)current->path.node.user_data[NPF_TRACKDIR_CHOICE];
	ftd->best_path_dist = current->g;
	ftd->best_bird_dist = 0;
	ftd->node = current->path.node;
	ftd->path = current->path;
}

/**
 * Finds out if a given player's vehicles are allowed to enter a given tile.
 * @param owner    The owner of the vehicle.
 * @param tile     The tile that is about to be entered.
 * @param enterdir The direction from which the vehicle wants to enter the tile.
 * @return         true if the vehicle can enter the tile.
 * @todo           This function should be used in other places than just NPF,
 *                 maybe moved to another file too.
 */
static bool VehicleMayEnterTile(Owner owner, TileIndex tile, DiagDirection enterdir)
{
	if (
		IsTileType(tile, MP_RAILWAY) /* Rail tile (also rail depot) */
		|| IsTrainStationTile(tile) /* Rail station tile */
		|| IsTileDepotType(tile, TRANSPORT_ROAD) /* Road depot tile */
		|| IsRoadStationTile(tile) /* Road station tile */
		|| IsTileDepotType(tile, TRANSPORT_WATER) /* Water depot tile */
		)
		return IsTileOwner(tile, owner); /* You need to own these tiles entirely to use them */

	switch (GetTileType(tile)) {
		case MP_STREET:
			/* rail-road crossing : are we looking at the railway part? */
			if (IsLevelCrossing(tile) && GetCrossingTransportType(tile, TrackdirToTrack(DiagdirToDiagTrackdir(enterdir))) == TRANSPORT_RAIL)
				return IsTileOwner(tile, owner); /* Railway needs owner check, while the street is public */
			break;
		case MP_TUNNELBRIDGE:
#if 0
/* OPTIMISATION: If we are on the middle of a bridge, we will not do the cpu
 * intensive owner check, instead we will just assume that if the vehicle
 * managed to get on the bridge, it is probably allowed to :-)
 */
			if ((_m[tile].m5 & 0xC6) == 0xC0 && (unsigned)(_m[tile].m5 & 0x1) == (enterdir & 0x1)) {
				/* on the middle part of a railway bridge: find bridge ending */
				while (IsTileType(tile, MP_TUNNELBRIDGE) && !((_m[tile].m5 & 0xC6) == 0x80)) {
					tile += TileOffsByDir(_m[tile].m5 & 0x1);
				}
			}
			/* if we were on a railway middle part, we are now at a railway bridge ending */
#endif
			if (
				(_m[tile].m5 & 0xFC) == 0 /* railway tunnel */
				|| (_m[tile].m5 & 0xC6) == 0x80 /* railway bridge ending */
				|| ((_m[tile].m5 & 0xF8) == 0xE0 && ((unsigned)_m[tile].m5 & 0x1) != (enterdir & 0x1)) /* railway under bridge */
				)
				return IsTileOwner(tile, owner);
			break;
		default:
			break;
	}

	return true; /* no need to check */
}

/* Will just follow the results of GetTileTrackStatus concerning where we can
 * go and where not. Uses AyStar.user_data[NPF_TYPE] as the transport type and
 * an argument to GetTileTrackStatus. Will skip tunnels, meaning that the
 * entry and exit are neighbours. Will fill
 * AyStarNode.user_data[NPF_TRACKDIR_CHOICE] with an appropriate value, and
 * copy AyStarNode.user_data[NPF_NODE_FLAGS] from the parent */
static void NPFFollowTrack(AyStar* aystar, OpenListNode* current)
{
	Trackdir src_trackdir = (Trackdir)current->path.node.direction;
	TileIndex src_tile = current->path.node.tile;
	DiagDirection src_exitdir = TrackdirToExitdir(src_trackdir);
	FindLengthOfTunnelResult flotr;
	TileIndex dst_tile;
	int i;
	TrackdirBits trackdirbits, ts;
	TransportType type = aystar->user_data[NPF_TYPE];
	/* Initialize to 0, so we can jump out (return) somewhere an have no neighbours */
	aystar->num_neighbours = 0;
	DEBUG(npf, 4)("Expanding: (%d, %d, %d) [%d]", TileX(src_tile), TileY(src_tile), src_trackdir, src_tile);

	aystar->EndNodeCheck(aystar, current);

	/* Find dest tile */
	if (IsTileType(src_tile, MP_TUNNELBRIDGE) && (_m[src_tile].m5 & 0xF0)==0 && (DiagDirection)(_m[src_tile].m5 & 3) == src_exitdir) {
		/* This is a tunnel. We know this tunnel is our type,
		 * otherwise we wouldn't have got here. It is also facing us,
		 * so we should skip it's body */
		flotr = FindLengthOfTunnel(src_tile, src_exitdir);
		dst_tile = flotr.tile;
	} else {
		if (type != TRANSPORT_WATER && (IsRoadStationTile(src_tile) || IsTileDepotType(src_tile, type))){
			/* This is a road station or a train or road depot. We can enter and exit
			 * those from one side only. Trackdirs don't support that (yet), so we'll
			 * do this here. */

			DiagDirection exitdir;
			/* Find out the exit direction first */
			if (IsRoadStationTile(src_tile))
				exitdir = GetRoadStationDir(src_tile);
			else /* Train or road depot. Direction is stored the same for both, in map5 */
				exitdir = GetDepotDirection(src_tile, type);

			/* Let's see if were headed the right way into the depot, and reverse
			 * otherwise (only for trains, since only with trains you can
			 * (sometimes) reach tiles after reversing that you couldn't reach
			 * without reversing. */
			if (src_trackdir == DiagdirToDiagTrackdir(ReverseDiagdir(exitdir)) && type == TRANSPORT_RAIL)
				/* We are headed inwards. We can only reverse here, so we'll not
				 * consider this direction, but jump ahead to the reverse direction.
				 * It would be nicer to return one neighbour here (the reverse
				 * trackdir of the one we are considering now) and then considering
				 * that one to return the tracks outside of the depot. But, because
				 * the code layout is cleaner this way, we will just pretend we are
				 * reversed already */
				src_trackdir = ReverseTrackdir(src_trackdir);
		}
		/* This a normal tile, a bridge, a tunnel exit, etc. */
		dst_tile = AddTileIndexDiffCWrap(src_tile, TileIndexDiffCByDir(TrackdirToExitdir(src_trackdir)));
		if (dst_tile == INVALID_TILE) {
			/* We reached the border of the map */
			/* TODO Nicer control flow for this */
			return;
		}
	}

	/* I can't enter a tunnel entry/exit tile from a tile above the tunnel. Note
	 * that I can enter the tunnel from a tile below the tunnel entrance. This
	 * solves the problem of vehicles wanting to drive off a tunnel entrance */
	if (IsTileType(dst_tile, MP_TUNNELBRIDGE) && (_m[dst_tile].m5 & 0xF0) == 0 && GetTileZ(dst_tile) < GetTileZ(src_tile))
		return;

	/* check correct rail type (mono, maglev, etc) */
	if (type == TRANSPORT_RAIL) {
		RailType dst_type = GetTileRailType(dst_tile, src_trackdir);
		if (!IsCompatibleRail(aystar->user_data[NPF_RAILTYPE], dst_type))
			return;
	}

	/* Check the owner of the tile */
	if (!VehicleMayEnterTile(aystar->user_data[NPF_OWNER], dst_tile, TrackdirToExitdir(src_trackdir))) {
		return;
	}

	/* Determine available tracks */
	if (type != TRANSPORT_WATER && (IsRoadStationTile(dst_tile) || IsTileDepotType(dst_tile, type))){
		/* Road stations and road and train depots return 0 on GTTS, so we have to do this by hand... */
		DiagDirection exitdir;
		if (IsRoadStationTile(dst_tile))
			exitdir = GetRoadStationDir(dst_tile);
		else /* Road or train depot */
			exitdir = GetDepotDirection(dst_tile, type);
		/* Find the trackdirs that are available for a depot or station with this
		 * orientation. They are only "inwards", since we are reaching this tile
		 * from some other tile. This prevents vehicles driving into depots from
		 * the back */
		ts = TrackdirToTrackdirBits(DiagdirToDiagTrackdir(ReverseDiagdir(exitdir)));
	} else {
		ts = GetTileTrackStatus(dst_tile, type);
	}
	trackdirbits = ts & TRACKDIR_BIT_MASK; /* Filter out signal status and the unused bits */

	DEBUG(npf, 4)("Next node: (%d, %d) [%d], possible trackdirs: %#x", TileX(dst_tile), TileY(dst_tile), dst_tile, trackdirbits);
	/* Select only trackdirs we can reach from our current trackdir */
	trackdirbits &= TrackdirReachesTrackdirs(src_trackdir);
	if (_patches.forbid_90_deg && (type == TRANSPORT_RAIL || type == TRANSPORT_WATER)) /* Filter out trackdirs that would make 90 deg turns for trains */

	trackdirbits &= ~TrackdirCrossesTrackdirs(src_trackdir);

	if (KillFirstBit2x64(trackdirbits) != 0)
		NPFSetFlag(&current->path.node, NPF_FLAG_PBS_CHOICE, true);

	/* When looking for 'any' route, ie when already inside a pbs block, discard all tracks that would cross
	   other reserved tracks, so we *always* will find a valid route if there is one */
	if (!(NPFGetFlag(&current->path.node, NPF_FLAG_PBS_EXIT)) && (aystar->user_data[NPF_PBS_MODE] == PBS_MODE_ANY))
		trackdirbits &= ~PBSTileUnavail(dst_tile);

	DEBUG(npf,6)("After filtering: (%d, %d), possible trackdirs: %#x", TileX(dst_tile), TileY(dst_tile), trackdirbits);

	i = 0;
	/* Enumerate possible track */
	while (trackdirbits != 0) {
		Trackdir dst_trackdir;
		dst_trackdir =  FindFirstBit2x64(trackdirbits);
		trackdirbits = KillFirstBit2x64(trackdirbits);
		DEBUG(npf, 5)("Expanded into trackdir: %d, remaining trackdirs: %#x", dst_trackdir, trackdirbits);

		/* Check for oneway signal against us */
		if (IsTileType(dst_tile, MP_RAILWAY) && GetRailTileType(dst_tile) == RAIL_TYPE_SIGNALS) {
			if (HasSignalOnTrackdir(dst_tile, ReverseTrackdir(dst_trackdir)) && !HasSignalOnTrackdir(dst_tile, dst_trackdir))
				// if one way signal not pointing towards us, stop going in this direction.
				break;
		}
		{
			/* We've found ourselves a neighbour :-) */
			AyStarNode* neighbour = &aystar->neighbours[i];
			neighbour->tile = dst_tile;
			neighbour->direction = dst_trackdir;
			/* Save user data */
			neighbour->user_data[NPF_NODE_FLAGS] = current->path.node.user_data[NPF_NODE_FLAGS];
			NPFFillTrackdirChoice(neighbour, current);
		}
		i++;
	}
	aystar->num_neighbours = i;
}

/*
 * Plan a route to the specified target (which is checked by target_proc),
 * from start1 and if not NULL, from start2 as well. The type of transport we
 * are checking is in type. reverse_penalty is applied to all routes that
 * originate from the second start node.
 * When we are looking for one specific target (optionally multiple tiles), we
 * should use a good heuristic to perform aystar search. When we search for
 * multiple targets that are spread around, we should perform a breadth first
 * search by specifiying CalcZero as our heuristic.
 */
static NPFFoundTargetData NPFRouteInternal(AyStarNode* start1, AyStarNode* start2, NPFFindStationOrTileData* target, AyStar_EndNodeCheck target_proc, AyStar_CalculateH heuristic_proc, TransportType type, Owner owner, RailType railtype, uint reverse_penalty, byte pbs_mode)
{
	int r;
	NPFFoundTargetData result;

	/* Initialize procs */
	_npf_aystar.CalculateH = heuristic_proc;
	_npf_aystar.EndNodeCheck = target_proc;
	_npf_aystar.FoundEndNode = NPFSaveTargetData;
	_npf_aystar.GetNeighbours = NPFFollowTrack;
	if (type == TRANSPORT_RAIL)
		_npf_aystar.CalculateG = NPFRailPathCost;
	else if (type == TRANSPORT_ROAD)
		_npf_aystar.CalculateG = NPFRoadPathCost;
	else if (type == TRANSPORT_WATER)
		_npf_aystar.CalculateG = NPFWaterPathCost;
	else
		assert(0);

	if (pbs_mode != PBS_MODE_NONE)
		_npf_aystar.BeforeExit = NPFReservePBSPath;
	else
		_npf_aystar.BeforeExit = NULL;

	/* Initialize Start Node(s) */
	start1->user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
	start1->user_data[NPF_NODE_FLAGS] = 0;
	_npf_aystar.addstart(&_npf_aystar, start1, 0);
	if (start2) {
		start2->user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
		start2->user_data[NPF_NODE_FLAGS] = 0;
		NPFSetFlag(start2, NPF_FLAG_REVERSE, true);
		_npf_aystar.addstart(&_npf_aystar, start2, reverse_penalty);
	}

	/* Initialize result */
	result.best_bird_dist = (uint)-1;
	result.best_path_dist = (uint)-1;
	result.best_trackdir = INVALID_TRACKDIR;
	_npf_aystar.user_path = &result;

	/* Initialize target */
	_npf_aystar.user_target = target;

	/* Initialize user_data */
	_npf_aystar.user_data[NPF_TYPE] = type;
	_npf_aystar.user_data[NPF_OWNER] = owner;
	_npf_aystar.user_data[NPF_RAILTYPE] = railtype;
	_npf_aystar.user_data[NPF_PBS_MODE] = pbs_mode;

	/* GO! */
	r = AyStarMain_Main(&_npf_aystar);
	assert(r != AYSTAR_STILL_BUSY);

	if (result.best_bird_dist != 0) {
		if (target) {
			DEBUG(misc, 1) ("NPF: Could not find route to 0x%x from 0x%x.", target->dest_coords, start1->tile);
		} else {
			/* Assumption: target == NULL, so we are looking for a depot */
			DEBUG(misc, 1) ("NPF: Could not find route to a depot from 0x%x.", start1->tile);
		}

	}
	return result;
}

NPFFoundTargetData NPFRouteToStationOrTileTwoWay(TileIndex tile1, Trackdir trackdir1, TileIndex tile2, Trackdir trackdir2, NPFFindStationOrTileData* target, TransportType type, Owner owner, RailType railtype, byte pbs_mode)
{
	AyStarNode start1;
	AyStarNode start2;

	start1.tile = tile1;
	start2.tile = tile2;
	/* We set this in case the target is also the start tile, we will just
	 * return a not found then */
	start1.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
	start1.direction = trackdir1;
	start2.direction = trackdir2;
	start2.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;

	return NPFRouteInternal(&start1, (IsValidTile(tile2) ? &start2 : NULL), target, NPFFindStationOrTile, NPFCalcStationOrTileHeuristic, type, owner, railtype, 0, pbs_mode);
}

NPFFoundTargetData NPFRouteToStationOrTile(TileIndex tile, Trackdir trackdir, NPFFindStationOrTileData* target, TransportType type, Owner owner, RailType railtype, byte pbs_mode)
{
	return NPFRouteToStationOrTileTwoWay(tile, trackdir, INVALID_TILE, 0, target, type, owner, railtype, pbs_mode);
}

NPFFoundTargetData NPFRouteToDepotBreadthFirstTwoWay(TileIndex tile1, Trackdir trackdir1, TileIndex tile2, Trackdir trackdir2, TransportType type, Owner owner, RailType railtype, uint reverse_penalty)
{
	AyStarNode start1;
	AyStarNode start2;

	start1.tile = tile1;
	start2.tile = tile2;
	/* We set this in case the target is also the start tile, we will just
	 * return a not found then */
	start1.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
	start1.direction = trackdir1;
	start2.direction = trackdir2;
	start2.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;

	/* perform a breadth first search. Target is NULL,
	 * since we are just looking for any depot...*/
	return NPFRouteInternal(&start1, (IsValidTile(tile2) ? &start2 : NULL), NULL, NPFFindDepot, NPFCalcZero, type, owner, railtype, reverse_penalty, PBS_MODE_NONE);
}

NPFFoundTargetData NPFRouteToDepotBreadthFirst(TileIndex tile, Trackdir trackdir, TransportType type, Owner owner, RailType railtype)
{
	return NPFRouteToDepotBreadthFirstTwoWay(tile, trackdir, INVALID_TILE, 0, type, owner, railtype, 0);
}

NPFFoundTargetData NPFRouteToDepotTrialError(TileIndex tile, Trackdir trackdir, TransportType type, Owner owner, RailType railtype)
{
	/* Okay, what we're gonna do. First, we look at all depots, calculate
	 * the manhatten distance to get to each depot. We then sort them by
	 * distance. We start by trying to plan a route to the closest, then
	 * the next closest, etc. We stop when the best route we have found so
	 * far, is shorter than the manhattan distance. This will obviously
	 * always find the closest depot. It will probably be most efficient
	 * for ships, since the heuristic will not be to far off then. I hope.
	 */
	Queue depots;
	int r;
	NPFFoundTargetData best_result;
	NPFFoundTargetData result;
	NPFFindStationOrTileData target;
	AyStarNode start;
	Depot* current;
	Depot *depot;

	init_InsSort(&depots);
	/* Okay, let's find all depots that we can use first */
	FOR_ALL_DEPOTS(depot) {
		/* Check if this is really a valid depot, it is of the needed type and
		 * owner */
		if (IsValidDepot(depot) && IsTileDepotType(depot->xy, type) && IsTileOwner(depot->xy, owner))
			/* If so, let's add it to the queue, sorted by distance */
			depots.push(&depots, depot, DistanceManhattan(tile, depot->xy));
	}

	/* Now, let's initialise the aystar */

	/* Initialize procs */
	_npf_aystar.CalculateH = NPFCalcStationOrTileHeuristic;
	_npf_aystar.EndNodeCheck = NPFFindStationOrTile;
	_npf_aystar.FoundEndNode = NPFSaveTargetData;
	_npf_aystar.GetNeighbours = NPFFollowTrack;
	if (type == TRANSPORT_RAIL)
		_npf_aystar.CalculateG = NPFRailPathCost;
	else if (type == TRANSPORT_ROAD)
		_npf_aystar.CalculateG = NPFRoadPathCost;
	else if (type == TRANSPORT_WATER)
		_npf_aystar.CalculateG = NPFWaterPathCost;
	else
		assert(0);

	_npf_aystar.BeforeExit = NULL;

	/* Initialize target */
	target.station_index = -1; /* We will initialize dest_coords inside the loop below */
	_npf_aystar.user_target = &target;

	/* Initialize user_data */
	_npf_aystar.user_data[NPF_TYPE] = type;
	_npf_aystar.user_data[NPF_OWNER] = owner;
	_npf_aystar.user_data[NPF_PBS_MODE] = PBS_MODE_NONE;

	/* Initialize Start Node */
	start.tile = tile;
	start.direction = trackdir; /* We will initialize user_data inside the loop below */

	/* Initialize Result */
	_npf_aystar.user_path = &result;
	best_result.best_path_dist = (uint)-1;
	best_result.best_bird_dist = (uint)-1;

	/* Just iterate the depots in order of increasing distance */
	while ((current = depots.pop(&depots))) {
		/* Check to see if we already have a path shorter than this
		 * depot's manhattan distance. HACK: We call DistanceManhattan
		 * again, we should probably modify the queue to give us that
		 * value... */
		if ( DistanceManhattan(tile, current->xy * NPF_TILE_LENGTH) > best_result.best_path_dist)
			break;

		/* Initialize Start Node */
		/* We set this in case the target is also the start tile, we will just
		 * return a not found then */
		start.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
		start.user_data[NPF_NODE_FLAGS] = 0;
		_npf_aystar.addstart(&_npf_aystar, &start, 0);

		/* Initialize result */
		result.best_bird_dist = (uint)-1;
		result.best_path_dist = (uint)-1;
		result.best_trackdir = INVALID_TRACKDIR;

		/* Initialize target */
		target.dest_coords = current->xy;

		/* GO! */
		r = AyStarMain_Main(&_npf_aystar);
		assert(r != AYSTAR_STILL_BUSY);

		/* This depot is closer */
		if (result.best_path_dist < best_result.best_path_dist)
			best_result = result;
	}
	if (result.best_bird_dist != 0) {
		DEBUG(misc, 1) ("NPF: Could not find route to any depot from 0x%x.", tile);
	}
	return best_result;
}

void InitializeNPF(void)
{
	init_AyStar(&_npf_aystar, NPFHash, NPF_HASH_SIZE);
	_npf_aystar.loops_per_tick = 0;
	_npf_aystar.max_path_cost = 0;
	//_npf_aystar.max_search_nodes = 0;
	/* We will limit the number of nodes for now, until we have a better
	 * solution to really fix performance */
	_npf_aystar.max_search_nodes = _patches.npf_max_search_nodes;
}

void NPFFillWithOrderData(NPFFindStationOrTileData* fstd, Vehicle* v)
{
	/* Ships don't really reach their stations, but the tile in front. So don't
	 * save the station id for ships. For roadvehs we don't store it either,
	 * because multistop depends on vehicles actually reaching the exact
	 * dest_tile, not just any stop of that station.
	 * So only for train orders to stations we fill fstd->station_index, for all
	 * others only dest_coords */
	if ((v->current_order.type) == OT_GOTO_STATION && v->type == VEH_Train) {
		fstd->station_index = v->current_order.station;
		/* Let's take the closest tile of the station as our target for trains */
		fstd->dest_coords = CalcClosestStationTile(v->current_order.station, v->tile);
	} else {
		fstd->dest_coords = v->dest_tile;
		fstd->station_index = -1;
	}
}