class View

class View extends AreaPluginBase {
  
  /**
   * Stores whether the embedded view is actually empty.
   *
   * @var bool
   */
  protected $isEmpty;
  
  /**
   * The view storage.
   *
   * @var \Drupal\Core\Entity\EntityStorageInterface
   */
  protected $viewStorage;
  
  /**
   * Constructs a View 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\Entity\EntityStorageInterface $view_storage
   *   The view storage.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityStorageInterface $view_storage) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->viewStorage = $view_storage;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($configuration, $plugin_id, $plugin_definition, $container->get('entity_type.manager')
      ->getStorage('view'));
  }
  
  /**
   * {@inheritdoc}
   */
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['view_to_insert'] = [
      'default' => '',
    ];
    $options['inherit_arguments'] = [
      'default' => FALSE,
    ];
    return $options;
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
    parent::buildOptionsForm($form, $form_state);
    $view_display = $this->view->storage
      ->id() . ':' . $this->view->current_display;
    $options = [
      '' => $this->t('-Select-'),
    ];
    $options += Views::getViewsAsOptions(FALSE, 'all', $view_display, FALSE, TRUE);
    $form['view_to_insert'] = [
      '#type' => 'select',
      '#title' => $this->t('View to insert'),
      '#default_value' => $this->options['view_to_insert'],
      '#description' => $this->t('The view to insert into this area.'),
      '#options' => $options,
    ];
    $form['inherit_arguments'] = [
      '#type' => 'checkbox',
      '#title' => $this->t('Inherit contextual filters'),
      '#default_value' => $this->options['inherit_arguments'],
      '#description' => $this->t('If checked, this view will receive the same contextual filters as its parent.'),
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function render($empty = FALSE) {
    if (!empty($this->options['view_to_insert'])) {
      [$view_name, $display_id] = explode(':', $this->options['view_to_insert']);
      $view = $this->viewStorage
        ->load($view_name)
        ->getExecutable();
      if (empty($view) || !$view->access($display_id)) {
        return [];
      }
      $view->setDisplay($display_id);
      // Avoid recursion
      $view->parent_views += $this->view->parent_views;
      $view->parent_views[] = "{$view_name}:{$display_id}";
      // Check if the view is part of the parent views of this view
      $search = "{$view_name}:{$display_id}";
      if (in_array($search, $this->view->parent_views)) {
        \Drupal::messenger()->addError($this->t("Recursion detected in view @view display @display.", [
          '@view' => $view_name,
          '@display' => $display_id,
        ]));
      }
      else {
        if (!empty($this->options['inherit_arguments']) && !empty($this->view->args)) {
          $output = $view->preview($display_id, $this->view->args);
        }
        else {
          $output = $view->preview($display_id);
        }
        $this->isEmpty = $view->display_handler
          ->outputIsEmpty();
        return $output;
      }
    }
    return [];
  }
  
  /**
   * {@inheritdoc}
   */
  public function isEmpty() {
    if (isset($this->isEmpty)) {
      return $this->isEmpty;
    }
    else {
      return parent::isEmpty();
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function calculateDependencies() {
    $dependencies = parent::calculateDependencies();
    [$view_id] = explode(':', $this->options['view_to_insert'], 2);
    // Don't call the current view, as it would result into an infinite recursion.
    if ($view_id && $this->view->storage
      ->id() != $view_id) {
      $view = $this->viewStorage
        ->load($view_id);
      $dependencies[$view->getConfigDependencyKey()][] = $view->getConfigDependencyName();
    }
    return $dependencies;
  }

}