class MessageAction

class MessageAction extends ConfigurableActionBase implements ContainerFactoryPluginInterface {
  
  /**
   * The token service.
   *
   * @var \Drupal\Core\Utility\Token
   */
  protected $token;
  
  /**
   * The renderer.
   *
   * @var \Drupal\Core\Render\RendererInterface
   */
  protected $renderer;
  
  /**
   * The messenger.
   *
   * @var \Drupal\Core\Messenger\MessengerInterface
   */
  protected $messenger;
  
  /**
   * Constructs a MessageAction object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin ID for the plugin instance.
   * @param mixed $plugin_definition
   *   The plugin implementation definition.
   * @param \Drupal\Core\Utility\Token $token
   *   The token service.
   * @param \Drupal\Core\Render\RendererInterface $renderer
   *   The renderer.
   * @param \Drupal\Core\Messenger\MessengerInterface $messenger
   *   The messenger.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, Token $token, RendererInterface $renderer, MessengerInterface $messenger) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->token = $token;
    $this->renderer = $renderer;
    $this->messenger = $messenger;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($configuration, $plugin_id, $plugin_definition, $container->get('token'), $container->get('renderer'), $container->get('messenger'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function execute($entity = NULL) {
    if (empty($this->configuration['node'])) {
      $this->configuration['node'] = $entity;
    }
    $message = $this->token
      ->replace($this->configuration['message'], $this->configuration);
    $build = [
      '#markup' => $message,
    ];
    // @todo Fix in https://www.drupal.org/node/2577827
    $this->messenger
      ->addStatus($this->renderer
      ->renderInIsolation($build));
  }
  
  /**
   * {@inheritdoc}
   */
  public function defaultConfiguration() {
    return [
      'message' => '',
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
    $form['message'] = [
      '#type' => 'textarea',
      '#title' => $this->t('Message'),
      '#default_value' => $this->configuration['message'],
      '#required' => TRUE,
      '#rows' => '8',
      '#description' => $this->t('The message to be displayed to the current user. You may include placeholders like [node:title], [user:account-name], [user:display-name] and [comment:body] to represent data that will be different each time message is sent. Not all placeholders will be available in all contexts.'),
    ];
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
    $this->configuration['message'] = $form_state->getValue('message');
    unset($this->configuration['node']);
  }
  
  /**
   * {@inheritdoc}
   */
  public function access($object, ?AccountInterface $account = NULL, $return_as_object = FALSE) {
    $result = AccessResult::allowed();
    return $return_as_object ? $result : $result->isAllowed();
  }

}