class Actions

class Actions extends Container {

  /**
   * {@inheritdoc}
   */
  public function getInfo() {
    $class = static::class;
    return [
      '#process' => [
        // @todo Move this to #pre_render.
        [
          $class,
          'preRenderActionsDropbutton',
        ],
        [
          $class,
          'processActions',
        ],
        [
          $class,
          'processContainer',
        ],
      ],
      '#weight' => 100,
      '#theme_wrappers' => [
        'container',
      ],
    ];
  }

  /**
   * Processes a form actions container element.
   *
   * @param array $element
   *   An associative array containing the properties and children of the
   *   form actions container.
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   *   The current state of the form.
   * @param array $complete_form
   *   The complete form structure.
   *
   * @return array
   *   The processed element.
   */
  public static function processActions(&$element, FormStateInterface $form_state, &$complete_form) {
    $element['#attributes']['class'][] = 'form-actions';
    return $element;
  }

  /**
   * #pre_render callback for #type 'actions'.
   *
   * This callback iterates over all child elements of the #type 'actions'
   * container to look for elements with a #dropbutton property, so as to group
   * those elements into dropbuttons. As such, it works similar to #group, but is
   * specialized for dropbuttons.
   *
   * The value of #dropbutton denotes the dropbutton to group the child element
   * into. For example, two different values of 'foo' and 'bar' on child elements
   * would generate two separate dropbuttons, which each contain the corresponding
   * buttons.
   *
   * @param array $element
   *   The #type 'actions' element to process.
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   *   The current state of the form.
   * @param array $complete_form
   *   The complete form structure.
   *
   * @return array
   *   The processed #type 'actions' element, including individual buttons grouped
   *   into new #type 'dropbutton' elements.
   */
  public static function preRenderActionsDropbutton(&$element, FormStateInterface $form_state, &$complete_form) {
    $dropbuttons = [];
    foreach (Element::children($element, TRUE) as $key) {
      if (isset($element[$key]['#dropbutton'])) {
        $dropbutton = $element[$key]['#dropbutton'];

        // If there is no dropbutton for this button group yet, create one.
        if (!isset($dropbuttons[$dropbutton])) {
          $dropbuttons[$dropbutton] = [
            '#type' => 'dropbutton',
          ];
        }

        // Add this button to the corresponding dropbutton.
        // @todo Change #type 'dropbutton' to be based on item-list.html.twig
        //   instead of links.html.twig to avoid this preemptive rendering.
        $button = \Drupal::service('renderer')
          ->renderInIsolation($element[$key]);
        $dropbuttons[$dropbutton]['#links'][$key] = [
          'title' => $button,
        ];

        // Merge metadata like drupalSettings.
        BubbleableMetadata::createFromRenderArray($dropbuttons[$dropbutton])
          ->merge(BubbleableMetadata::createFromRenderArray($element[$key]))
          ->applyTo($dropbuttons[$dropbutton]);
      }
    }

    // @todo For now, all dropbuttons appear first. Consider to invent a more
    //   fancy sorting/injection algorithm here.
    return $dropbuttons + $element;
  }

}