View source  
  <?php
namespace Drupal\config_pages\Plugin\Block;
use Drupal\Core\Block\BlockBase;
use Drupal\Core\Block\BlockPluginInterface;
use Drupal\config_pages\Entity\ConfigPages;
use Drupal\config_pages\Entity\ConfigPagesType;
use Drupal\Core\Form\FormStateInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Entity\EntityDisplayRepositoryInterface;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Drupal\Core\Entity\EntityTypeManagerInterface;
class ConfigPagesBlock extends BlockBase implements BlockPluginInterface, ContainerFactoryPluginInterface {
  private $entity_display_repository;
  private $entity_type_manager;
  
  public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityDisplayRepositoryInterface $entity_display_repository, EntityTypeManagerInterface $entity_type_manager) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this
      ->setConfiguration($configuration);
    $this->entity_display_repository = $entity_display_repository;
    $this->entity_type_manager = $entity_type_manager;
  }
  
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($configuration, $plugin_id, $plugin_definition, $container
      ->get('entity_display.repository'), $container
      ->get('entity_type.manager'));
  }
  
  public function getCacheTags() {
    $config = $this
      ->getConfiguration();
    if (!empty($config['config_page_type'])) {
      $config_page = ConfigPages::config($config['config_page_type']);
      return is_object($config_page) ? $config_page
        ->getCacheTags() : [];
    }
    return [];
  }
  
  public function build() {
    $config = $this
      ->getConfiguration();
    if (!empty($config['config_page_type'])) {
      $config_page = ConfigPages::config($config['config_page_type']);
      if (!is_object($config_page)) {
        return [];
      }
      $view_mode = $config['config_page_view_mode'];
      $build = $this->entity_type_manager
        ->getViewBuilder('config_pages')
        ->view($config_page, $view_mode, NULL);
      
      $build['#contextual_links'] = [
        'config_pages_type' => [
          'route_parameters' => [
            'config_pages_type' => $config['config_page_type'],
          ],
        ],
      ];
      return $build;
    }
    return [];
  }
  
  public function defaultConfiguration() {
    $settings = parent::defaultConfiguration();
    
    if (isset($this->pluginDefinition['cache'])) {
      $settings['cache'] = $this->pluginDefinition['cache'];
    }
    return $settings;
  }
  
  public function getMachineNameSuggestion() {
    return 'config_pages';
  }
  
  public function blockForm($form, FormStateInterface $form_state) {
    $form = parent::blockForm($form, $form_state);
    
    $config = $this
      ->getConfiguration();
    $config_pages_types = ConfigPagesType::loadMultiple();
    $options = [];
    foreach ($config_pages_types as $cp_type) {
      $id = $cp_type
        ->id();
      $label = $cp_type
        ->label();
      $options[$id] = $label;
    }
    $form['config_page_type'] = [
      '#type' => 'select',
      '#title' => $this
        ->t('Select ConfigPage type to show'),
      '#options' => $options,
      '#default_value' => isset($config['config_page_type']) ? $config['config_page_type'] : '',
    ];
    $view_modes = $this->entity_display_repository
      ->getViewModes('config_pages');
    $options = [];
    foreach ($view_modes as $id => $view_mode) {
      $options[$id] = $view_mode['label'];
    }
    
    $form['config_page_view_mode'] = [
      '#type' => 'select',
      '#title' => $this
        ->t('Select view mode for ConfigPage to show'),
      '#options' => $options,
      '#default_value' => isset($config['config_page_view_mode']) ? $config['config_page_view_mode'] : '',
    ];
    return $form;
  }
  
  public function blockSubmit($form, FormStateInterface $form_state) {
    $this
      ->setConfigurationValue('config_page_type', $form_state
      ->getValue('config_page_type'));
    $this
      ->setConfigurationValue('config_page_view_mode', $form_state
      ->getValue('config_page_view_mode'));
  }
}