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/* $Id$ */

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#ifndef  FOLLOW_TRACK_HPP

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#define  FOLLOW_TRACK_HPP

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#include "yapf.hpp"

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/** Track follower helper template class (can serve pathfinders and vehicle

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    controllers). See 6 different typedefs below for 3 different transport

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    types w/ of w/o 90-deg turns allowed */

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template <TransportType Ttr_type_, bool T90deg_turns_allowed_ = true>

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struct CFollowTrackT : public FollowTrack_t

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{

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	CPerformanceTimer* m_pPerf;

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	FORCEINLINE CFollowTrackT(const Vehicle* v = NULL, CPerformanceTimer* pPerf = NULL)

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	{

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		Init(v, pPerf);

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	}

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	FORCEINLINE void Init(const Vehicle* v, CPerformanceTimer* pPerf)

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	{

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		assert(!IsRailTT() || (v != NULL && v->type == VEH_Train));

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		m_veh = v;

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		m_pPerf = pPerf;

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		// don't worry, all is inlined so compiler should remove unnecessary initializations

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		m_new_tile = INVALID_TILE;

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		m_new_td_bits = TRACKDIR_BIT_NONE;

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		m_exitdir = INVALID_DIAGDIR;

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		m_tiles_skipped = 0;

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	}

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	FORCEINLINE static TransportType TT() {return Ttr_type_;}

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	FORCEINLINE static bool IsWaterTT() {return TT() == TRANSPORT_WATER;}

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	FORCEINLINE static bool IsRailTT() {return TT() == TRANSPORT_RAIL;}

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	FORCEINLINE static bool IsRoadTT() {return TT() == TRANSPORT_ROAD;}

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	FORCEINLINE static bool Allow90degTurns() {return T90deg_turns_allowed_;}

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	/** main follower routine. Fills all members and return true on success.

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	    Otherwise returns false if track can't be followed. */

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	FORCEINLINE bool Follow(TileIndex old_tile, Trackdir old_td)

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	{

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		m_old_tile = old_tile;

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		m_old_td = old_td;

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		assert((GetTileTrackStatus(m_old_tile, TT()) & TrackdirToTrackdirBits(m_old_td)) != 0);

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		m_exitdir = TrackdirToExitdir(m_old_td);

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		if (EnteredRailDepot()) return true;

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		if (!CanExitOldTile()) return false;

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		FollowTileExit();

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		if (!QueryNewTileTrackStatus()) return false;

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		if (!CanEnterNewTile()) return false;

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		m_new_td_bits &= DiagdirReachesTrackdirs(m_exitdir);

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		if (!Allow90degTurns())

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			m_new_td_bits &= (TrackdirBits)~(int)TrackdirCrossesTrackdirs(m_old_td);

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		return (m_new_td_bits != TRACKDIR_BIT_NONE);

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	}

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protected:

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	/** Follow the m_exitdir from m_old_tile and fill m_new_tile and m_tiles_skipped */

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	FORCEINLINE void FollowTileExit()

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	{

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		// extra handling for tunnels in our direction

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		if (IsTunnelTile(m_old_tile)) {

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			DiagDirection tunnel_enterdir = GetTunnelDirection(m_old_tile);

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			if (tunnel_enterdir == m_exitdir) {

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				// we are entering the tunnel

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				FindLengthOfTunnelResult flotr = FindLengthOfTunnel(m_old_tile, m_exitdir);

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				m_new_tile = flotr.tile;

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				m_is_tunnel = true;

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				m_tiles_skipped = flotr.length - 1;

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				return;

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			}

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			assert(ReverseDiagDir(tunnel_enterdir) == m_exitdir);

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		}

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		TileIndexDiff diff = TileOffsByDir(m_exitdir);

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		m_new_tile = TILE_ADD(m_old_tile, diff);

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		// special handling for stations

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		if (IsRailTT() && IsRailwayStationTile(m_new_tile)) {

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			m_is_station = true;

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		} else if (IsRoadTT() && IsRoadStopTile(m_new_tile)) {

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			m_is_station = true;

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		} else {

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			m_is_station = false;

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		}

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	}

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	/** stores track status (available trackdirs) for the new tile into m_new_td_bits */

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	FORCEINLINE bool QueryNewTileTrackStatus()

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	{

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		CPerfStart perf(*m_pPerf);

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		if (IsRailTT() && GetTileType(m_new_tile) == MP_RAILWAY && IsPlainRailTile(m_new_tile)) {

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			m_new_td_bits = (TrackdirBits)(GetTrackBits(m_new_tile) * 0x101);

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		} else {

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			uint32 ts = GetTileTrackStatus(m_new_tile, TT());

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			m_new_td_bits = (TrackdirBits)(ts & TRACKDIR_BIT_MASK);

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		}

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		return (m_new_td_bits != TRACKDIR_BIT_NONE);

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	}

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	/** return true if we can leave m_old_tile in m_exitdir */

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	FORCEINLINE bool CanExitOldTile()

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	{

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		// road stop can be left at one direction only

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		if (IsRoadTT() && IsRoadStopTile(m_old_tile)) {

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			DiagDirection exitdir = GetRoadStopDir(m_old_tile);

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			if (exitdir != m_exitdir)

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				return false;

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		}

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		// road depots can be also left in one direction only

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		if (IsRoadTT() && IsTileDepotType(m_old_tile, TT())) {

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			DiagDirection exitdir = GetRoadDepotDirection(m_old_tile);

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			if (exitdir != m_exitdir)

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				return false;

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		}

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		return true;

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	}

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	/** return true if we can enter m_new_tile from m_exitdir */

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	FORCEINLINE bool CanEnterNewTile()

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	{

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		if (IsRoadTT() && IsRoadStopTile(m_new_tile)) {

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			// road stop can be entered from one direction only

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			DiagDirection exitdir = GetRoadStopDir(m_new_tile);

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			if (ReverseDiagDir(exitdir) != m_exitdir)

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				return false;

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		}

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		// road and rail depots can also be entered from one direction only

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		if (IsRoadTT() && IsTileDepotType(m_new_tile, TT())) {

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			DiagDirection exitdir = GetRoadDepotDirection(m_new_tile);

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			if (ReverseDiagDir(exitdir) != m_exitdir)

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				return false;

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		}

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		if (IsRailTT() && IsTileDepotType(m_new_tile, TT())) {

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			DiagDirection exitdir = GetRailDepotDirection(m_new_tile);

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			if (ReverseDiagDir(exitdir) != m_exitdir)

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				return false;

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		}

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		// rail transport is possible only on tiles with the same owner as vehicle

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		if (IsRailTT() && GetTileOwner(m_new_tile) != m_veh->owner) {

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			// different owner

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		}

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		// rail transport is possible only on compatible rail types

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		if (IsRailTT()) {

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			RailType rail_type = GetTileRailType(m_new_tile, DiagdirToDiagTrackdir(m_exitdir));

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			if (((1 << rail_type) & m_veh->u.rail.compatible_railtypes) == 0) {

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				// incompatible rail type

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				return false;

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			}

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		}

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		// tunnel tiles can be entered only from proper direction

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		if (!IsWaterTT() && !m_is_tunnel && IsTunnelTile(m_new_tile)) {

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			DiagDirection tunnel_enterdir = GetTunnelDirection(m_new_tile);

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			if (tunnel_enterdir != m_exitdir)

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				return false;

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		}

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		// special handling for rail stations - get to the end of platform

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		if (IsRailTT() && m_is_station) {

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			// entered railway station

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			// get platform length

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			uint length = GetPlatformLength(m_new_tile, TrackdirToExitdir(m_old_td));

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			// how big step we must do to get to the last platform tile;

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			m_tiles_skipped = length - 1;

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			// move to the platform end

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			TileIndexDiff diff = TileOffsByDir(m_exitdir);

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			diff *= m_tiles_skipped;

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			m_new_tile = TILE_ADD(m_new_tile, diff);

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			return true;

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		}

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		return true;

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	}

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	FORCEINLINE bool EnteredRailDepot()

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	{

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		// rail depots cause reversing

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		if (IsRailTT() && IsTileDepotType(m_old_tile, TT())) {

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			DiagDirection exitdir = GetRailDepotDirection(m_old_tile);

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			if (exitdir != m_exitdir) {

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				// reverse

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				m_new_tile = m_old_tile;

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				m_new_td_bits = TrackdirToTrackdirBits(ReverseTrackdir(m_old_td));

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				m_exitdir = exitdir;

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				m_tiles_skipped = 0;

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				m_is_tunnel = false;

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				return true;

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			}

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		}

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		return false;

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	}

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public:

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	/** Helper for pathfinders - get min/max speed on the m_old_tile/m_old_td */

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	int GetSpeedLimit(int *pmin_speed = NULL)

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	{

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		int min_speed = 0;

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		int max_speed = INT_MAX; // no limit

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		// for now we handle only on-bridge speed limit

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		}

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		// if min speed was requested, return it

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		if (pmin_speed) *pmin_speed = min_speed;

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		return max_speed;

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	}

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};

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typedef CFollowTrackT<TRANSPORT_WATER, true > CFollowTrackWater;

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typedef CFollowTrackT<TRANSPORT_ROAD , true > CFollowTrackRoad;

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typedef CFollowTrackT<TRANSPORT_RAIL , true > CFollowTrackRail;

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typedef CFollowTrackT<TRANSPORT_WATER, false> CFollowTrackWaterNo90;

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typedef CFollowTrackT<TRANSPORT_ROAD , false> CFollowTrackRoadNo90;

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typedef CFollowTrackT<TRANSPORT_RAIL , false> CFollowTrackRailNo90;

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#endif /* FOLLOW_TRACK_HPP */