src/Composer/Downloader/DownloadManager.php
public function getDownloader($type)
    {
        $type = strtolower($type);
        if (!isset($this->downloaders[$type])) {
            throw new \InvalidArgumentException(sprintf('Unknown downloader type: %s. Available types: %s.', $type, implode(', ', array_keys($this->downloaders))));
        }

        return $this->downloaders[$type];
    }
public function getDownloader($type)
    {
        $type = strtolower($type);
        if (!isset($this->downloaders[$type])) {
            throw new \InvalidArgumentException(sprintf('Unknown downloader type: %s. Available types: %s.', $type, implode(', ', array_keys($this->downloaders))));
        }

        return $this->downloaders[$type];
    }
Returns downloader for a specific installation type.

@param  string                    $type installation type
@throws \InvalidArgumentException if downloader for provided type is not registered
@return DownloaderInterface