Method clean

/**
 * Clean cache for a group given a mode.
 *
 * group mode    : cleans all cache in the group
 * notgroup mode : cleans all cache not in the group
 *
 * @param   string  $group  The cache data group
 * @param   string  $mode   The mode for cleaning cache [group|notgroup]
 *
 * @return  boolean
 *
 * @since   1.7.0
 */
public function clean($group, $mode = null)
{
    $return = true;
    $folder = $group;
    if (trim($folder) == '') {
        $mode = 'notgroup';
    }
    switch ($mode) {
        case 'notgroup':
            $folders = $this->_folders($this->_root);
            for ($i = 0, $n = \count($folders); $i < $n; $i++) {
                if ($folders[$i] != $folder) {
                    $return |= $this->_deleteFolder($this->_root . '/' . $folders[$i]);
                }
            }
            break;
        case 'group':
        default:
            if (is_dir($this->_root . '/' . $folder)) {
                $return = $this->_deleteFolder($this->_root . '/' . $folder);
            }
            break;
    }
    return (bool) $return;
}