class FeedViewBuilder

class FeedViewBuilder extends EntityViewBuilder {
    
    /**
     * The 'aggregator.settings' config.
     *
     * @var \Drupal\Core\Config\Config
     */
    protected $config;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * Constructs a new FeedViewBuilder.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The entity type definition.
     * @param \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository
     *   The entity repository service.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     * @param \Drupal\Core\Config\Config $config
     *   The 'aggregator.settings' config.
     * @param \Drupal\Core\Theme\Registry $theme_registry
     *   The theme registry.
     * @param \Drupal\Core\Entity\EntityDisplayRepositoryInterface $entity_display_repository
     *   The entity display repository.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(EntityTypeInterface $entity_type, EntityRepositoryInterface $entity_repository, LanguageManagerInterface $language_manager, Config $config, Registry $theme_registry, EntityDisplayRepositoryInterface $entity_display_repository, EntityTypeManagerInterface $entity_type_manager) {
        parent::__construct($entity_type, $entity_repository, $language_manager, $theme_registry, $entity_display_repository);
        $this->config = $config;
        $this->entityTypeManager = $entity_type_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
        return new static($entity_type, $container->get('entity.repository'), $container->get('language_manager'), $container->get('config.factory')
            ->get('aggregator.settings'), $container->get('theme.registry'), $container->get('entity_display.repository'), $container->get('entity_type.manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildComponents(array &$build, array $entities, array $displays, $view_mode) {
        parent::buildComponents($build, $entities, $displays, $view_mode);
        foreach ($entities as $id => $entity) {
            $bundle = $entity->bundle();
            $display = $displays[$bundle];
            if ($display->getComponent('items')) {
                // When in summary view mode, respect the list_max setting.
                $limit = $view_mode == 'summary' ? $this->config
                    ->get('source.list_max') : 20;
                // Retrieve the items attached to this feed.
                $items = $this->entityTypeManager
                    ->getStorage('aggregator_item')
                    ->loadByFeed($entity->id(), $limit);
                $build[$id]['items'] = $this->entityTypeManager
                    ->getViewBuilder('aggregator_item')
                    ->viewMultiple($items, $view_mode, $entity->language()
                    ->getId());
                if ($view_mode == 'full') {
                    // Also add the pager.
                    $build[$id]['pager'] = [
                        '#type' => 'pager',
                    ];
                }
            }
            // By default, the description and image fields are exposed as
            // pseudo-fields rendered in this function. However they can optionally
            // be rendered directly using a field formatter. Skip rendering here if a
            // field formatter type is set.
            $component = $display->getComponent('description');
            if ($component && !isset($component['type'])) {
                $build[$id]['description'] = [
                    '#markup' => $entity->getDescription(),
                    '#allowed_tags' => _aggregator_allowed_tags(),
                    '#prefix' => '<div class="feed-description">',
                    '#suffix' => '</div>',
                ];
            }
            $component = $display->getComponent('image');
            if ($component && !isset($component['type'])) {
                $image_link = [];
                // Render the image as link if it is available.
                $image = $entity->getImage();
                $label = $entity->label();
                $link_href = $entity->getWebsiteUrl();
                if ($image && $label && $link_href) {
                    $link_title = [
                        '#theme' => 'image',
                        '#uri' => $image,
                        '#alt' => $label,
                    ];
                    $image_link = [
                        '#type' => 'link',
                        '#title' => $link_title,
                        '#url' => Url::fromUri($link_href),
                        '#options' => [
                            'attributes' => [
                                'class' => [
                                    'feed-image',
                                ],
                            ],
                        ],
                    ];
                }
                $build[$id]['image'] = $image_link;
            }
            if ($display->getComponent('feed_icon')) {
                $build[$id]['feed_icon'] = [
                    '#theme' => 'feed_icon',
                    '#url' => $entity->getUrl(),
                    '#title' => t('@title feed', [
                        '@title' => $entity->label(),
                    ]),
                ];
            }
            if ($display->getComponent('more_link')) {
                $title_stripped = strip_tags($entity->label());
                $build[$id]['more_link'] = [
                    '#type' => 'link',
                    '#title' => t('More<span class="visually-hidden"> posts about @title</span>', [
                        '@title' => $title_stripped,
                    ]),
                    '#url' => Url::fromRoute('entity.aggregator_feed.canonical', [
                        'aggregator_feed' => $entity->id(),
                    ]),
                    '#options' => [
                        'attributes' => [
                            'title' => $title_stripped,
                        ],
                    ],
                ];
            }
        }
    }

}