class LocalTasksBlock

class LocalTasksBlock extends BlockBase implements ContainerFactoryPluginInterface {
    
    /**
     * The local task manager.
     *
     * @var \Drupal\Core\Menu\LocalTaskManagerInterface
     */
    protected $localTaskManager;
    
    /**
     * The route match.
     *
     * @var \Drupal\Core\Routing\RouteMatchInterface
     */
    protected $routeMatch;
    
    /**
     * Creates a LocalTasksBlock 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\Menu\LocalTaskManagerInterface $local_task_manager
     *   The local task manager.
     * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
     *   The route match.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, LocalTaskManagerInterface $local_task_manager, RouteMatchInterface $route_match) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->localTaskManager = $local_task_manager;
        $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('plugin.manager.menu.local_task'), $container->get('current_route_match'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultConfiguration() {
        return [
            'label_display' => FALSE,
            'primary' => TRUE,
            'secondary' => TRUE,
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function build() {
        $config = $this->configuration;
        $cacheability = new CacheableMetadata();
        $cacheability->addCacheableDependency($this->localTaskManager);
        // If the current route belongs to an entity, include cache tags of that
        // entity as well.
        $route_parameters = $this->routeMatch
            ->getParameters()
            ->all();
        foreach ($route_parameters as $parameter) {
            if ($parameter instanceof CacheableDependencyInterface) {
                $cacheability->addCacheableDependency($parameter);
            }
        }
        $tabs = [
            '#theme' => 'menu_local_tasks',
        ];
        // Add only selected levels for the printed output.
        if ($config['primary']) {
            $links = $this->localTaskManager
                ->getLocalTasks($this->routeMatch
                ->getRouteName(), 0);
            $cacheability = $cacheability->merge($links['cacheability']);
            // Do not display single tabs.
            $tabs += [
                '#primary' => count(Element::getVisibleChildren($links['tabs'])) > 1 ? $links['tabs'] : [],
            ];
        }
        if ($config['secondary']) {
            $links = $this->localTaskManager
                ->getLocalTasks($this->routeMatch
                ->getRouteName(), 1);
            $cacheability = $cacheability->merge($links['cacheability']);
            // Do not display single tabs.
            $tabs += [
                '#secondary' => count(Element::getVisibleChildren($links['tabs'])) > 1 ? $links['tabs'] : [],
            ];
        }
        $build = [];
        $cacheability->applyTo($build);
        if (empty($tabs['#primary']) && empty($tabs['#secondary'])) {
            return $build;
        }
        return $build + $tabs;
    }
    
    /**
     * {@inheritdoc}
     */
    public function blockForm($form, FormStateInterface $form_state) {
        $config = $this->configuration;
        $defaults = $this->defaultConfiguration();
        $form['levels'] = [
            '#type' => 'details',
            '#title' => $this->t('Shown tabs'),
            '#description' => $this->t('Select tabs being shown in the block'),
            // Open if not set to defaults.
'#open' => $defaults['primary'] !== $config['primary'] || $defaults['secondary'] !== $config['secondary'],
        ];
        $form['levels']['primary'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Show primary tabs'),
            '#default_value' => $config['primary'],
        ];
        $form['levels']['secondary'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Show secondary tabs'),
            '#default_value' => $config['secondary'],
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function blockSubmit($form, FormStateInterface $form_state) {
        $levels = $form_state->getValue('levels');
        $this->configuration['primary'] = $levels['primary'];
        $this->configuration['secondary'] = $levels['secondary'];
    }

}