class Rss

class Rss extends RssPluginBase {
    // Basic properties that let the row style follow relationships.
    public $base_table = 'node_field_data';
    public $base_field = 'nid';
    // Stores the nodes loaded with preRender.
    public $nodes = [];
    
    /**
     * {@inheritdoc}
     */
    protected $entityTypeId = 'node';
    
    /**
     * The node storage
     *
     * @var \Drupal\node\NodeStorageInterface
     */
    protected $nodeStorage;
    
    /**
     * Constructs the Rss 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\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Entity\EntityDisplayRepositoryInterface $entity_display_repository
     *   The entity display repository.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager, EntityDisplayRepositoryInterface $entity_display_repository = NULL) {
        parent::__construct($configuration, $plugin_id, $plugin_definition, $entity_type_manager, $entity_display_repository);
        $this->nodeStorage = $entity_type_manager->getStorage('node');
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm_summary_options() {
        $options = parent::buildOptionsForm_summary_options();
        $options['title'] = $this->t('Title only');
        $options['default'] = $this->t('Use site default RSS settings');
        return $options;
    }
    public function summaryTitle() {
        $options = $this->buildOptionsForm_summary_options();
        return $options[$this->options['view_mode']];
    }
    public function preRender($values) {
        $nids = [];
        foreach ($values as $row) {
            $nids[] = $row->{$this->field_alias};
        }
        if (!empty($nids)) {
            $this->nodes = $this->nodeStorage
                ->loadMultiple($nids);
        }
    }
    public function render($row) {
        global $base_url;
        $nid = $row->{$this->field_alias};
        if (!is_numeric($nid)) {
            return;
        }
        $display_mode = $this->options['view_mode'];
        if ($display_mode == 'default') {
            $display_mode = \Drupal::config('system.rss')->get('items.view_mode');
        }
        // Load the specified node:
        
        /** @var \Drupal\node\NodeInterface $node */
        $node = $this->nodes[$nid];
        if (empty($node)) {
            return;
        }
        $node->link = $node->toUrl('canonical', [
            'absolute' => TRUE,
        ])
            ->toString();
        $node->rss_namespaces = [];
        $node->rss_elements = [
            [
                'key' => 'pubDate',
                'value' => gmdate('r', $node->getCreatedTime()),
            ],
            [
                'key' => 'dc:creator',
                'value' => $node->getOwner()
                    ->getDisplayName(),
            ],
            [
                'key' => 'guid',
                'value' => $node->id() . ' at ' . $base_url,
                'attributes' => [
                    'isPermaLink' => 'false',
                ],
            ],
        ];
        // The node gets built and modules add to or modify $node->rss_elements
        // and $node->rss_namespaces.
        $build_mode = $display_mode;
        $build = \Drupal::entityTypeManager()->getViewBuilder('node')
            ->view($node, $build_mode);
        unset($build['#theme']);
        if (!empty($node->rss_namespaces)) {
            $this->view->style_plugin->namespaces = array_merge($this->view->style_plugin->namespaces, $node->rss_namespaces);
        }
        elseif (function_exists('rdf_get_namespaces')) {
            // Merge RDF namespaces in the XML namespaces in case they are used
            // further in the RSS content.
            $xml_rdf_namespaces = [];
            foreach (rdf_get_namespaces() as $prefix => $uri) {
                $xml_rdf_namespaces['xmlns:' . $prefix] = $uri;
            }
            $this->view->style_plugin->namespaces += $xml_rdf_namespaces;
        }
        $item = new \stdClass();
        if ($display_mode != 'title') {
            // We render node contents.
            $item->description = $build;
        }
        $item->title = $node->label();
        $item->link = $node->link;
        // Provide a reference so that the render call in
        // template_preprocess_views_view_row_rss() can still access it.
        $item->elements =& $node->rss_elements;
        $item->nid = $node->id();
        $build = [
            '#theme' => $this->themeFunctions(),
            '#view' => $this->view,
            '#options' => $this->options,
            '#row' => $item,
        ];
        return $build;
    }

}