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/* $Id$ */

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/** @file ai_tunnel.hpp Everything to query and build tunnels. */

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#ifndef AI_TUNNEL_HPP

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#define AI_TUNNEL_HPP

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#include "ai_object.hpp"

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#include "ai_vehicle.hpp"

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/**

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 * Class that handles all tunnel related functions.

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 */

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class AITunnel : public AIObject {

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public:

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	static const char *GetClassName() { return "AITunnel"; }

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	/**

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	 * All tunnel related errors.

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	 */

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	enum ErrorMessages {

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		/** Base for bridge related errors */

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		ERR_TUNNEL_BASE = AIError::ERR_CAT_TUNNEL << AIError::ERR_CAT_BIT_SIZE,

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		/** Can't build tunnels on water */

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		ERR_TUNNEL_CANNOT_BUILD_ON_WATER,            // [STR_3807_CAN_T_BUILD_ON_WATER]

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		/** The start tile must slope either North, South, West or East */

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		ERR_TUNNEL_START_SITE_UNSUITABLE,            // [STR_500B_SITE_UNSUITABLE_FOR_TUNNEL]

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		/** An other tunnel is in the way */

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		ERR_TUNNEL_ANOTHER_TUNNEL_IN_THE_WAY,        // [STR_5003_ANOTHER_TUNNEL_IN_THE_WAY]

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		/** Unable to excavate land at the end to create the tunnel's exit */

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		ERR_TUNNEL_END_SITE_UNSUITABLE,              // [STR_5005_UNABLE_TO_EXCAVATE_LAND]

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	};

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	/**

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	 * Check whether the tile is an entrance to a tunnel.

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	 * @param tile The tile to check.

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	 * @pre AIMap::IsValidTile(tile).

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	 * @return True if and only if the tile is the beginning or end of a tunnel.

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	 */

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	static bool IsTunnelTile(TileIndex tile);

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	/**

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	 * Get the tile that exits on the other end of a (would be) tunnel starting

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	 *  at tile.

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	 * @param tile The tile that is an entrance to a tunnel or the tile where you may want to build a tunnel.

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	 * @pre AIMap::IsValidTile(tile).

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	 * @return The TileIndex that is the other end of the (would be) tunnel, or

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	 *  INVALID_TILE if no other end was found (can't build tunnel).

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	 */

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	static TileIndex GetOtherTunnelEnd(TileIndex tile);

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	/**

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	 * Builds a tunnel starting at start. The direction of the tunnel depends

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	 *  on the slope of the start tile. Tunnels can be created for either

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	 *  rails or roads; use the appropriate AIVehicle::VehicleType.

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	 * As an extra for road, this functions builds two half-pieces of road on

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	 *  each end of the tunnel, making it easier for you to connect it to your

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	 *  network.

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	 * @param start Where to start the tunnel.

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	 * @param vehicle_type The vehicle-type of tunnel to build.

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	 * @pre AIMap::IsValidTile(start).

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	 * @pre 'vehicle_type' is either AIVehicle::VEHICLE_RAIL or AIVEHICLE::VEHICLE_ROAD.

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	 * @exception AIError::ERR_AREA_NOT_CLEAR

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	 * @exception AITunnel::ERR_TUNNEL_CANNOT_BUILD_ON_WATER

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	 * @exception AITunnel::ERR_TUNNEL_START_SITE_UNSUITABLE

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	 * @exception AITunnel::ERR_TUNNEL_ANOTHER_TUNNEL_IN_THE_WAY

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	 * @exception AITunnel::ERR_TUNNEL_END_SITE_UNSUITABLE

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	 * @return Whether the tunnel has been/can be build or not.

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	 * @note The slope of a tile can be determined by AITile::GetSlope(TileIndex).

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	 * @note No matter if the road pieces were build or not, if building the

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	 *  tunnel succeeded, this function returns true.

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	 */

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	static bool BuildTunnel(AIVehicle::VehicleType vehicle_type, TileIndex start);

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	/**

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	 * Remove the tunnel whose entrance is located at tile.

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	 * @param tile The tile that is an entrance to a tunnel.

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	 * @pre AIMap::IsValidTile(tile) && IsTunnelTile(tile).

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	 * @exception AIError::ERR_OWNED_BY_ANOTHER_COMPANY

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	 * @return Whether the tunnel has been/can be removed or not.

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	 */

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	static bool RemoveTunnel(TileIndex tile);

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};

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#endif /* AI_TUNNEL_HPP */