/**
 * Determine if a player could possibly build a ship lock that would cover this tile.
 *
 * @param bridge_ramp The tile to possibly outrule a bridge position
 * @param bridge_dir The bridge direction
 * @return true if a player could possibly build a ship lock on this tile.
 * @see GrowTownWithBridge
 */
static bool IsPossibleLockLocationOnTownBridgeTile(const TileIndex bridge_tile, const DiagDirection bridge_dir)
{
	const DiagDirection dir_side = ChangeDiagDir(bridge_dir, DIAGDIRDIFF_90LEFT);
	const TileIndexDiff delta_side = TileOffsByDiagDir(dir_side);

	if (IsValidTile(bridge_tile) && IsPossibleLockLocationOnDiagDir(bridge_tile, bridge_dir, true) && IsWaterTile(bridge_tile) ||
			IsValidTile(bridge_tile + delta_side) && IsPossibleLockLocationOnDiagDir(bridge_tile + delta_side, dir_side, true) && IsWaterTile(bridge_tile + delta_side) ||
			IsValidTile(bridge_tile - delta_side) && IsPossibleLockLocationOnDiagDir(bridge_tile - delta_side, ReverseDiagDir(dir_side), true) && IsWaterTile(bridge_tile - delta_side)) {
		return true;
	}

	return false;
}

/**
 * Grows the town with a bridge.
 *  At first we check if a bridge is reasonable.
 *  If so we check if we are able to build it.
 *
 * @param t The current town
 * @param tile The current tile
 * @param bridge_dir The valid direction in which to grow a bridge
 * @return true if a bridge has been build else false
 */
static bool GrowTownWithBridge(const Town *t, const TileIndex tile, const DiagDirection bridge_dir)
{
	assert(bridge_dir < DIAGDIR_END);

	const Slope slope = GetTileSlope(tile);

	/* Make sure the direction is compatible with the slope.
	 * Well we check if the slope has an up bit set in the
	 * reverse direction. */
	if (slope != SLOPE_FLAT && slope & InclinedSlope(bridge_dir)) return false;

	/* Assure that the bridge is connectable to the start side */
	if (!(GetTownRoadBits(TileAddByDiagDir(tile, ReverseDiagDir(bridge_dir))) & DiagDirToRoadBits(bridge_dir))) return false;

	/* We are in the right direction */
	uint8 bridge_length = 0;      // This value stores the length of the possible bridge
	TileIndex bridge_tile = tile; // Used to store the other waterside

	const int delta = TileOffsByDiagDir(bridge_dir);
//	const int delta_side = TileOffsByDiagDir(ChangeDiagDir(bridge_dir, DIAGDIRDIFF_90LEFT));

	if (slope == SLOPE_FLAT) {
		/* Bridges starting on flat tiles are only allowed when crossing rivers. */
		do {
			if (bridge_length++ >= 4) {
				/* Allow to cross rivers, not big lakes. */
				return false;
			}
			bridge_tile += delta;
			if (IsPossibleLockLocationOnTownBridgeTile(bridge_tile, bridge_dir)) return false;
//			if (IsValidTile(bridge_tile) && IsPossibleLockLocationOnDiagDir(bridge_tile, bridge_dir, true) && IsWaterTile(bridge_tile) ||
//					IsValidTile(bridge_tile + delta_side) && IsPossibleLockLocationOnDiagDir(bridge_tile + delta_side, ChangeDiagDir(bridge_dir, DIAGDIRDIFF_90LEFT), true) && IsWaterTile(bridge_tile + delta_side) ||
//					IsValidTile(bridge_tile - delta_side) && IsPossibleLockLocationOnDiagDir(bridge_tile - delta_side, ChangeDiagDir(bridge_dir, DIAGDIRDIFF_90RIGHT), true) && IsWaterTile(bridge_tile - delta_side)) {
//				return false;
//			}
		} while (IsValidTile(bridge_tile) && IsWaterTile(bridge_tile) && !IsSea(bridge_tile));
	} else {
		do {
			if (bridge_length++ >= 11) {
				/* Max 11 tile long bridges */
				return false;
			}
			bridge_tile += delta;
			if (IsPossibleLockLocationOnTownBridgeTile(bridge_tile, bridge_dir)) return false;
//			if (IsValidTile(bridge_tile) && IsPossibleLockLocationOnDiagDir(bridge_tile, bridge_dir, true) && IsWaterTile(bridge_tile) ||
//					IsValidTile(bridge_tile + delta_side) && IsPossibleLockLocationOnDiagDir(bridge_tile + delta_side, ChangeDiagDir(bridge_dir, DIAGDIRDIFF_90LEFT), true) && IsWaterTile(bridge_tile + delta_side) ||
//					IsValidTile(bridge_tile - delta_side) && IsPossibleLockLocationOnDiagDir(bridge_tile - delta_side, ChangeDiagDir(bridge_dir, DIAGDIRDIFF_90RIGHT), true) && IsWaterTile(bridge_tile - delta_side)) {
//				return false;
//			}
		} while (IsValidTile(bridge_tile) && IsWaterTile(bridge_tile));
	}

	/* no water tiles in between? */
	if (bridge_length == 1) return false;

	for (uint8 times = 0; times <= 22; times++) {
		byte bridge_type = RandomRange(MAX_BRIDGES - 1);

		/* Can we actually build the bridge? */
		if (DoCommand(tile, bridge_tile, bridge_type | ROADTYPES_ROAD << 8 | TRANSPORT_ROAD << 15, CommandFlagsToDCFlags(GetCommandFlags(CMD_BUILD_BRIDGE)), CMD_BUILD_BRIDGE).Succeeded()) {
			DoCommand(tile, bridge_tile, bridge_type | ROADTYPES_ROAD << 8 | TRANSPORT_ROAD << 15, DC_EXEC | CommandFlagsToDCFlags(GetCommandFlags(CMD_BUILD_BRIDGE)), CMD_BUILD_BRIDGE);
			_grow_town_result = GROWTH_SUCCEED;
			return true;
		}
	}
	/* Quit if it selecting an appropriate bridge type fails a large number of times. */
	return false;
}