public function encode($url)
{
list($url, ) = explode('.', $url, 2);
$url = strtolower($url);
$url = str_replace(array_keys(self::$urlMap), array_values(self::$urlMap), $url);
$url = preg_replace('#[^-a-z0-9.]#', '-', $url);
$url = preg_replace('#[-]{2,}#', '-', $url);
return trim($url, '-') . '.htm';
}