class AssetDumper

class AssetDumper implements AssetDumperInterface {
    
    /**
     * The file system service.
     *
     * @var \Drupal\Core\File\FileSystemInterface
     */
    protected $fileSystem;
    
    /**
     * AssetDumper constructor.
     *
     * @param \Drupal\Core\File\FileSystemInterface $file_system
     *   The file handler.
     */
    public function __construct(FileSystemInterface $file_system) {
        $this->fileSystem = $file_system;
    }
    
    /**
     * {@inheritdoc}
     *
     * The file name for the CSS or JS cache file is generated from the hash of
     * the aggregated contents of the files in $data. This forces proxies and
     * browsers to download new CSS when the CSS changes.
     */
    public function dump($data, $file_extension) {
        // Prefix filename to prevent blocking by firewalls which reject files
        // starting with "ad*".
        $filename = $file_extension . '_' . Crypt::hashBase64($data) . '.' . $file_extension;
        // Create the css/ or js/ path within the files folder.
        $path = 'public://' . $file_extension;
        $uri = $path . '/' . $filename;
        // Create the CSS or JS file.
        $this->fileSystem
            ->prepareDirectory($path, FileSystemInterface::CREATE_DIRECTORY);
        try {
            if (!file_exists($uri) && !$this->fileSystem
                ->saveData($data, $uri, FileSystemInterface::EXISTS_REPLACE)) {
                return FALSE;
            }
        } catch (FileException $e) {
            return FALSE;
        }
        // If CSS/JS gzip compression is enabled and the zlib extension is available
        // then create a gzipped version of this file. This file is served
        // conditionally to browsers that accept gzip using .htaccess rules.
        // It's possible that the rewrite rules in .htaccess aren't working on this
        // server, but there's no harm (other than the time spent generating the
        // file) in generating the file anyway. Sites on servers where rewrite rules
        // aren't working can set css.gzip to FALSE in order to skip
        // generating a file that won't be used.
        if (extension_loaded('zlib') && \Drupal::config('system.performance')->get($file_extension . '.gzip')) {
            try {
                if (!file_exists($uri . '.gz') && !$this->fileSystem
                    ->saveData(gzencode($data, 9, FORCE_GZIP), $uri . '.gz', FileSystemInterface::EXISTS_REPLACE)) {
                    return FALSE;
                }
            } catch (FileException $e) {
                return FALSE;
            }
        }
        return $uri;
    }

}