/**
* Resolves an alias into a Version.
*
* @param string $alias
*
* @param Collection $collection
* @return VersionInterface|null
*/
protected function doResolve($alias, Collection $collection)
{
if (!$collection instanceof Sortable) {
return null;
}
$result = null;
switch (strtolower($alias)) {
case self::LAST:
case self::LATEST:
$result = $collection->last();
break;
case self::FIRST:
case self::EARLIEST:
$result = $collection->first();
break;
default:
}
return $result;
}
