/*

 * This file is part of OpenTTD.

 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.

 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.

 */

/** @file npf.cpp Implementation of the NPF pathfinder. */

#include "../../stdafx.h"

#include "../../network/network.h"

#include "../../viewport_func.h"

#include "../../ship.h"

#include "../../roadstop_base.h"

#include "../../vehicle_func.h"

#include "../pathfinder_func.h"

#include "../pathfinder_type.h"

#include "../follow_track.hpp"

#include "aystar.h"

#include "../../safeguards.h"

static const uint NPF_HASH_BITS = 12; ///< The size of the hash used in pathfinding. Just changing this value should be sufficient to change the hash size. Should be an even value.

/* Do no change below values */

static const uint NPF_HASH_SIZE = 1 << NPF_HASH_BITS;

static const uint NPF_HASH_HALFBITS = NPF_HASH_BITS / 2;

static const uint NPF_HASH_HALFMASK = (1 << NPF_HASH_HALFBITS) - 1;

/** Meant to be stored in AyStar.targetdata */

struct NPFFindStationOrTileData {

	TileIndex dest_coords;    ///< An indication of where the station is, for heuristic purposes, or the target tile

	StationID station_index;  ///< station index we're heading for, or INVALID_STATION when we're heading for a tile

	bool reserve_path;        ///< Indicates whether the found path should be reserved

	StationType station_type; ///< The type of station we're heading for

	bool not_articulated;     ///< The (road) vehicle is not articulated

	const Vehicle *v;         ///< The vehicle we are pathfinding for

};

/** Indices into AyStar.userdata[] */

struct AyStarUserData {

	Owner owner;

	TransportType type;

	RailTypes railtypes;

	RoadTypes roadtypes;

	uint subtype;

};

/** Indices into AyStarNode.userdata[] */

enum AyStarNodeUserDataType {

	NPF_TRACKDIR_CHOICE = 0, ///< The trackdir chosen to get here

	NPF_NODE_FLAGS,

};

/** Flags for AyStarNode.userdata[NPF_NODE_FLAGS]. Use NPFSetFlag() and NPFGetFlag() to use them. */

enum NPFNodeFlag {

	NPF_FLAG_SEEN_SIGNAL,       ///< Used to mark that a signal was seen on the way, for rail only

	NPF_FLAG_2ND_SIGNAL,        ///< Used to mark that two signals were seen, rail only

	NPF_FLAG_3RD_SIGNAL,        ///< Used to mark that three signals were seen, rail only

	NPF_FLAG_REVERSE,           ///< Used to mark that this node was reached from the second start node, if applicable

	NPF_FLAG_LAST_SIGNAL_RED,   ///< Used to mark that the last signal on this path was red

	NPF_FLAG_LAST_SIGNAL_BLOCK, ///< Used to mark that the last signal on this path was a block signal

	NPF_FLAG_IGNORE_START_TILE, ///< Used to mark that the start tile is invalid, and searching should start from the second tile on

	NPF_FLAG_TARGET_RESERVED,   ///< Used to mark that the possible reservation target is already reserved

	NPF_FLAG_IGNORE_RESERVED,   ///< Used to mark that reserved tiles should be considered impassable

};

/** Meant to be stored in AyStar.userpath */

struct NPFFoundTargetData {

	uint best_bird_dist;    ///< The best heuristic found. Is 0 if the target was found

	uint best_path_dist;    ///< The shortest path. Is UINT_MAX if no path is found

	Trackdir best_trackdir; ///< The trackdir that leads to the shortest path/closest birds dist

	AyStarNode node;        ///< The node within the target the search led us to

	bool res_okay;          ///< True if a path reservation could be made

};

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

};

/**

 * Returns the current value of the given flag on the given AyStarNode.

 */

static inline bool NPFGetFlag(const AyStarNode *node, NPFNodeFlag flag)

{

	return HasBit(node->user_data[NPF_NODE_FLAGS], flag);

}

/**

 * Sets the given flag on the given AyStarNode to the given value.

 */

static inline void NPFSetFlag(AyStarNode *node, NPFNodeFlag flag, bool value)

{

	SB(node->user_data[NPF_NODE_FLAGS], flag, 1, value);

}

bool CheckIgnoreFirstTile(const PathNode *node)

{

	return (node->parent == nullptr && HasBit(node->node.user_data[NPF_NODE_FLAGS], NPF_FLAG_IGNORE_START_TILE));

}

/**

 * Calculates the minimum distance travelled 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 = Delta(TileX(t0), TileX(t1));

	const uint dy = Delta(TileY(t0), TileY(t1));

	/* 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;

}

/**

 * Calculates a hash value for use in the NPF.

 * @param key1 The TileIndex of the tile to hash

 * @param key2 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((Trackdir)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;

}

/* Calculates 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;

	AyStarUserData *user = (AyStarUserData *)as->user_data;

	/* aim for the closest station tile */

	if (fstd->station_index != INVALID_STATION) {

		to = CalcClosestStationTile(fstd->station_index, from, fstd->station_type);

	}

	if (user->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);

	if (dist < ftd->best_bird_dist) {

		ftd->best_bird_dist = dist;

		ftd->best_trackdir = (Trackdir)current->user_data[NPF_TRACKDIR_CHOICE];

	}

	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 == nullptr) {

		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: 0x%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(current->direction);

	TileIndex tile = current->tile;

	if (GetTunnelBridgeDirection(tile) == ReverseDiagDir(exitdir)) {

		/* We just popped out if this tunnel, since were

		 * facing the tunnel exit */

		return NPF_TILE_LENGTH * (GetTunnelBridgeLength(current->tile, GetOtherTunnelEnd(current->tile)) + 1);

		/* @todo: Penalty for tunnels? */

	} else {

		/* We are entering the tunnel, the enter tile is just a

		 * straight track */

		return NPF_TILE_LENGTH;

	}

}

static inline uint NPFBridgeCost(AyStarNode *current)

{

	return NPF_TILE_LENGTH * GetTunnelBridgeLength(current->tile, GetOtherBridgeEnd(current->tile));

}

static uint NPFSlopeCost(AyStarNode *current)

{

	TileIndex next = current->tile + TileOffsByDiagDir(TrackdirToExitdir(current->direction));

	/* Get center of tiles */

	int x1 = TileX(current->tile) * TILE_SIZE + TILE_SIZE / 2;

	int y1 = TileY(current->tile) * TILE_SIZE + TILE_SIZE / 2;

	int x2 = TileX(next) * TILE_SIZE + TILE_SIZE / 2;

	int y2 = TileY(next) * TILE_SIZE + TILE_SIZE / 2;

	int dx4 = (x2 - x1) / 4;

	int dy4 = (y2 - y1) / 4;

	/* Get the height on both sides of the tile edge.

	 * Avoid testing the height on the tile-center. This will fail for halftile-foundations.

	 */

	int z1 = GetSlopePixelZ(x1 + dx4, y1 + dy4);

	int z2 = GetSlopePixelZ(x2 - dx4, y2 - dy4);

	if (z2 - z1 > 1) {

		/* Slope up */

		return _settings_game.pf.npf.npf_rail_slope_penalty;

	}

	return 0;

	/* Should we give a bonus for slope down? Probably not, we

	 * could just subtract that bonus from the penalty, because

	 * there is only one level of steepness... */

}

static uint NPFReservedTrackCost(AyStarNode *current)

{

	TileIndex tile = current->tile;

	TrackBits track = TrackToTrackBits(TrackdirToTrack(current->direction));

	TrackBits res = GetReservedTrackbits(tile);

	if (NPFGetFlag(current, NPF_FLAG_3RD_SIGNAL) || NPFGetFlag(current, NPF_FLAG_LAST_SIGNAL_BLOCK) || ((res & track) == TRACK_BIT_NONE && !TracksOverlap(res | track))) return 0;

	if (IsTileType(tile, MP_TUNNELBRIDGE)) {

		DiagDirection exitdir = TrackdirToExitdir(current->direction);

		if (GetTunnelBridgeDirection(tile) == ReverseDiagDir(exitdir)) {

			return  _settings_game.pf.npf.npf_rail_pbs_cross_penalty * (GetTunnelBridgeLength(tile, GetOtherTunnelBridgeEnd(tile)) + 1);

		}

	}

	return  _settings_game.pf.npf.npf_rail_pbs_cross_penalty;

}

/**

 * Mark tiles by mowing the grass when npf debug level >= 1.

 * Will not work for multiplayer games, since it can (will) cause desyncs.

 */

static void NPFMarkTile(TileIndex tile)

{

	if (_debug_npf_level < 1 || _networking) return;

	switch (GetTileType(tile)) {

		case MP_RAILWAY:

			/* DEBUG: mark visited tiles by mowing the grass under them ;-) */

			if (!IsRailDepot(tile)) {

				SetRailGroundType(tile, RAIL_GROUND_BARREN);

				MarkTileDirtyByTile(tile);

			}

			break;

		case MP_ROAD:

			if (!IsRoadDepot(tile)) {

				SetRoadside(tile, ROADSIDE_BARREN);

				MarkTileDirtyByTile(tile);

			}

			break;

		default:

			break;

	}

}

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

{

	uint *count = (uint *)data;

	/* Ignore other vehicles (aircraft) and ships inside depot. */

	if (v->type == VEH_SHIP && (v->vehstatus & VS_HIDDEN) == 0) (*count)++;

	return nullptr;

}