protected function parseVisibility( $visibility )
	{
		if ( is_null( $visibility ) )
			return null;

		switch ( $visibility )
		{
			case FilesystemContract::VISIBILITY_PUBLIC:
				return AdapterInterface::VISIBILITY_PUBLIC;
			case FilesystemContract::VISIBILITY_PRIVATE:
				return AdapterInterface::VISIBILITY_PRIVATE;
		}

		throw new InvalidArgumentException( 'Unknown visibility: ' . $visibility );
	}