class ImageStyleFlushForm

class ImageStyleFlushForm extends EntityConfirmFormBase {
  
  /**
   * {@inheritdoc}
   */
  public function getQuestion() {
    return $this->t('Are you sure you want to apply the updated %name image effect to all images?', [
      '%name' => $this->entity
        ->label(),
    ]);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getDescription() {
    return $this->t('This operation does not change the original images but the copies created for this style will be recreated.');
  }
  
  /**
   * {@inheritdoc}
   */
  public function getConfirmText() {
    return $this->t('Flush');
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCancelUrl() {
    return $this->entity
      ->toUrl('collection');
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $this->entity
      ->flush();
    $this->messenger()
      ->addStatus($this->t('The image style %name has been flushed.', [
      '%name' => $this->entity
        ->label(),
    ]));
    $form_state->setRedirectUrl($this->getCancelUrl());
  }

}