/* $Id$ */

/*
 * 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 roadstop_base.h Base class for roadstops. */

#ifndef ROADSTOP_BASE_H
#define ROADSTOP_BASE_H

#include "station_type.h"
#include "core/pool_type.hpp"
#include "core/bitmath_func.hpp"

typedef Pool<RoadStop, RoadStopID, 32, 64000> RoadStopPool;
extern RoadStopPool _roadstop_pool;

/** A Stop for a Road Vehicle */
struct RoadStop : RoadStopPool::PoolItem<&_roadstop_pool> {
	enum RoadStopStatusFlags {
		RSSFB_BAY0_FREE  = 0, ///< Non-zero when bay 0 is free
		RSSFB_BAY1_FREE  = 1, ///< Non-zero when bay 1 is free
		RSSFB_BAY_COUNT  = 2, ///< Max. number of bays
		RSSFB_ENTRY_BUSY = 7, ///< Non-zero when roadstop entry is busy
	};

	static const uint LIMIT           = 16;  ///< The maximum amount of roadstops that are allowed at a single station

	TileIndex        xy;                    ///< Position on the map
	byte             status;                ///< Current status of the Stop, @see RoadStopSatusFlag. Access using *Bay and *Busy functions.
	struct RoadStop  *next;                 ///< Next stop of the given type at this station

	/** Initializes a RoadStop */
	FORCEINLINE RoadStop(TileIndex tile = INVALID_TILE) :
		xy(tile),
		status((1 << RSSFB_BAY_COUNT) - 1)
	{ }

	~RoadStop();

	/**
	 * Checks whether there is a free bay in this road stop
	 * @return is at least one bay free?
	 */
	FORCEINLINE bool HasFreeBay() const
	{
		return GB(this->status, 0, RSSFB_BAY_COUNT) != 0;
	}

	/**
	 * Checks whether the given bay is free in this road stop
	 * @param nr bay to check
	 * @return is given bay free?
	 */
	FORCEINLINE bool IsFreeBay(uint nr) const
	{
		assert(nr < RSSFB_BAY_COUNT);
		return HasBit(this->status, nr);
	}

	/**
	 * Checks whether the entrance of the road stop is occupied by a vehicle
	 * @return is entrance busy?
	 */
	FORCEINLINE bool IsEntranceBusy() const
	{
		return HasBit(this->status, RSSFB_ENTRY_BUSY);
	}

	/**
	 * Makes an entrance occupied or free
	 * @param busy if true, marks busy; free otherwise
	 */
	FORCEINLINE void SetEntranceBusy(bool busy)
	{
		SB(this->status, RSSFB_ENTRY_BUSY, 1, busy);
	}

	void Leave(RoadVehicle *rv);
	bool Enter(RoadVehicle *rv);

	RoadStop *GetNextRoadStop(const struct RoadVehicle *v) const;

	static RoadStop *GetByTile(TileIndex tile, RoadStopType type);

private:
	/**
	 * Allocates a bay
	 * @return the allocated bay number
	 * @pre this->HasFreeBay()
	 */
	FORCEINLINE uint AllocateBay()
	{
		assert(this->HasFreeBay());

		/* Find the first free bay. If the bit is set, the bay is free. */
		uint bay_nr = 0;
		while (!HasBit(this->status, bay_nr)) bay_nr++;

		ClrBit(this->status, bay_nr);
		return bay_nr;
	}

	/**
	 * Allocates a bay in a drive-through road stop
	 * @param nr the number of the bay to allocate
	 */
	FORCEINLINE void AllocateDriveThroughBay(uint nr)
	{
		assert(nr < RSSFB_BAY_COUNT);
		ClrBit(this->status, nr);
	}

	/**
	 * Frees the given bay
	 * @param nr the number of the bay to free
	 */
	FORCEINLINE void FreeBay(uint nr)
	{
		assert(nr < RSSFB_BAY_COUNT);
		SetBit(this->status, nr);
	}
};

#define FOR_ALL_ROADSTOPS_FROM(var, start) FOR_ALL_ITEMS_FROM(RoadStop, roadstop_index, var, start)
#define FOR_ALL_ROADSTOPS(var) FOR_ALL_ROADSTOPS_FROM(var, 0)

#endif /* ROADSTOP_BASE_H */