public function buildPackageDownloadUrl($version = 'stable')
{
if ($this->getPackageName() == null) {
throw new Exception('Repository invalid.');
}
$xml = $this->getPackageXml($this->getPackageName(), $version);
if (!$xml) {
throw new Exception('Unable to fetch package xml');
}
$g = $xml->getElementsByTagName('g');
$url = $g->item(0)->nodeValue;
// just use tgz format file.
return $url . '.tgz';
}