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/* $Id$ */

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/** @file tunnel_map.cpp */

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#include "stdafx.h"

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#include "openttd.h"

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#include "tile.h"

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#include "tunnel_map.h"

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/**

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 * Gets the other end of the tunnel. Where a vehicle would reappear when it

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 * enters at the given tile.

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 * @param tile the tile to search from.

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 * @return the tile of the other end of the tunnel.

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 */

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TileIndex GetOtherTunnelEnd(TileIndex tile)

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{

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	DiagDirection dir = GetTunnelDirection(tile);

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	TileIndexDiff delta = TileOffsByDiagDir(dir);

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	uint z = GetTileZ(tile);

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	dir = ReverseDiagDir(dir);

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	do {

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		tile += delta;

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	} while (

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		!IsTunnelTile(tile) ||

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		GetTunnelDirection(tile) != dir ||

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		GetTileZ(tile) != z

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	);

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	return tile;

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}

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/**

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 * Is there a tunnel in the way in the given direction?

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 * @param tile the tile to search from.

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 * @param z    the 'z' to search on.

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 * @param dir  the direction to start searching to.

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 * @return true if and only if there is a tunnel.

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 */

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static bool IsTunnelInWayDir(TileIndex tile, uint z, DiagDirection dir)

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{

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	TileIndexDiff delta = TileOffsByDiagDir(dir);

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	uint height;

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	do {

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		tile -= delta;

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		height = GetTileZ(tile);

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	} while (z < height);

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	return

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		z == height &&

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		IsTunnelTile(tile) &&

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		GetTunnelDirection(tile) == dir;

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}

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/**

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 * Is there a tunnel in the way in any direction?

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 * @param tile the tile to search from.

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 * @param z the 'z' to search on.

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 * @return true if and only if there is a tunnel.

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 */

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bool IsTunnelInWay(TileIndex tile, uint z)

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{

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	return

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		IsTunnelInWayDir(tile, z, DIAGDIR_NE) ||

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		IsTunnelInWayDir(tile, z, DIAGDIR_SE) ||

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		IsTunnelInWayDir(tile, z, DIAGDIR_SW) ||

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		IsTunnelInWayDir(tile, z, DIAGDIR_NW);

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}