class FileEventSubscriber

class FileEventSubscriber implements EventSubscriberInterface {
  
  /**
   * Constructs a new file event listener.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $configFactory
   *   The config factory.
   * @param \Drupal\Component\Transliteration\TransliterationInterface $transliteration
   *   The transliteration service.
   * @param \Drupal\Core\Language\LanguageManagerInterface $languageManager
   *   The language manager.
   */
  public function __construct(protected ConfigFactoryInterface $configFactory, protected TransliterationInterface $transliteration, protected LanguageManagerInterface $languageManager) {
  }
  
  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() : array {
    return [
      FileUploadSanitizeNameEvent::class => 'sanitizeFilename',
    ];
  }
  
  /**
   * Sanitizes the filename of a file being uploaded.
   *
   * @param \Drupal\Core\File\Event\FileUploadSanitizeNameEvent $event
   *   File upload sanitize name event.
   *
   * @see file_form_system_file_system_settings_alter()
   */
  public function sanitizeFilename(FileUploadSanitizeNameEvent $event) {
    $fileSettings = $this->configFactory
      ->get('file.settings');
    $transliterate = $fileSettings->get('filename_sanitization.transliterate');
    $filename = $event->getFilename();
    $extension = pathinfo($filename, PATHINFO_EXTENSION);
    if ($extension !== '') {
      $extension = '.' . $extension;
      $filename = pathinfo($filename, PATHINFO_FILENAME);
    }
    // Sanitize the filename according to configuration.
    $alphanumeric = $fileSettings->get('filename_sanitization.replace_non_alphanumeric');
    $replacement = $fileSettings->get('filename_sanitization.replacement_character');
    if ($transliterate) {
      $transliterated_filename = $this->transliteration
        ->transliterate($filename, $this->languageManager
        ->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)
        ->getId(), $replacement);
      if (mb_strlen($transliterated_filename) > 0) {
        $filename = $transliterated_filename;
      }
      else {
        // If transliteration has resulted in a zero length string enable the
        // 'replace_non_alphanumeric' option and ignore the result of
        // transliteration.
        $alphanumeric = TRUE;
      }
    }
    if ($fileSettings->get('filename_sanitization.replace_whitespace')) {
      $filename = preg_replace('/\\s/u', $replacement, trim($filename));
    }
    // Only honor replace_non_alphanumeric if transliterate is enabled.
    if ($transliterate && $alphanumeric) {
      $filename = preg_replace('/[^0-9A-Za-z_.-]/u', $replacement, $filename);
    }
    if ($fileSettings->get('filename_sanitization.deduplicate_separators')) {
      $filename = preg_replace('/(_)_+|(\\.)\\.+|(-)-+/u', $replacement, $filename);
      // Replace multiple separators with single one.
      $filename = preg_replace('/(_|\\.|\\-)[(_|\\.|\\-)]+/u', $replacement, $filename);
      $filename = preg_replace('/' . preg_quote($replacement) . '[' . preg_quote($replacement) . ']*/u', $replacement, $filename);
      // Remove replacement character from the end of the filename.
      $filename = rtrim($filename, $replacement);
      // If there is an extension remove dots from the end of the filename to
      // prevent duplicate dots.
      if (!empty($extension)) {
        $filename = rtrim($filename, '.');
      }
    }
    if ($fileSettings->get('filename_sanitization.lowercase')) {
      // Force lowercase to prevent issues on case-insensitive file systems.
      $filename = mb_strtolower($filename);
    }
    $event->setFilename($filename . $extension);
  }

}