class Node

class Node extends ArgumentDefaultPluginBase implements CacheableDependencyInterface {
    
    /**
     * The route match.
     *
     * @var \Drupal\Core\Routing\RouteMatchInterface
     */
    protected $routeMatch;
    
    /**
     * Constructs a new Node instance.
     *
     * @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\Routing\RouteMatchInterface $route_match
     *   The route match.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, RouteMatchInterface $route_match) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->routeMatch = $route_match;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('current_route_match'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getArgument() {
        // Get the node object from current route.
        $node = $this->routeMatch
            ->getParameter('node') ?? $this->routeMatch
            ->getParameter('node_preview');
        if ($node instanceof NodeInterface) {
            return $node->id();
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheMaxAge() {
        return Cache::PERMANENT;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheContexts() {
        return [
            'url',
        ];
    }

}