class NodeRevisionRevertTranslationForm

class NodeRevisionRevertTranslationForm extends NodeRevisionRevertForm {
    
    /**
     * The language to be reverted.
     *
     * @var string
     */
    protected $langcode;
    
    /**
     * The language manager.
     *
     * @var \Drupal\Core\Language\LanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * Constructs a new NodeRevisionRevertTranslationForm.
     *
     * @param \Drupal\Core\Entity\EntityStorageInterface $node_storage
     *   The node storage.
     * @param \Drupal\Core\Datetime\DateFormatterInterface $date_formatter
     *   The date formatter service.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     * @param \Drupal\Component\Datetime\TimeInterface $time
     *   The time service.
     */
    public function __construct(EntityStorageInterface $node_storage, DateFormatterInterface $date_formatter, LanguageManagerInterface $language_manager, TimeInterface $time) {
        parent::__construct($node_storage, $date_formatter, $time);
        $this->languageManager = $language_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('entity_type.manager')
            ->getStorage('node'), $container->get('date.formatter'), $container->get('language_manager'), $container->get('datetime.time'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'node_revision_revert_translation_confirm';
    }
    
    /**
     * {@inheritdoc}
     */
    public function getQuestion() {
        return $this->t('Are you sure you want to revert @language translation to the revision from %revision-date?', [
            '@language' => $this->languageManager
                ->getLanguageName($this->langcode),
            '%revision-date' => $this->dateFormatter
                ->format($this->revision
                ->getRevisionCreationTime()),
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDescription() {
        return '';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state, $node_revision = NULL, $langcode = NULL) {
        $this->langcode = $langcode;
        $form = parent::buildForm($form, $form_state, $node_revision);
        // Unless untranslatable fields are configured to affect only the default
        // translation, we need to ask the user whether they should be included in
        // the revert process.
        $default_translation_affected = $this->revision
            ->isDefaultTranslationAffectedOnly();
        $form['revert_untranslated_fields'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Revert content shared among translations'),
            '#default_value' => $default_translation_affected && $this->revision
                ->getTranslation($this->langcode)
                ->isDefaultTranslation(),
            '#access' => !$default_translation_affected,
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function prepareRevertedRevision(NodeInterface $revision, FormStateInterface $form_state) {
        $revert_untranslated_fields = (bool) $form_state->getValue('revert_untranslated_fields');
        $translation = $revision->getTranslation($this->langcode);
        return $this->nodeStorage
            ->createRevision($translation, TRUE, $revert_untranslated_fields);
    }

}