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(ConfigFactoryInterface $configFactory, TransliterationInterface $transliteration, 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, NULL) . '[' . preg_quote($replacement, NULL) . ']*/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);
    }

}