class ConfigEntityBundleBase

abstract class ConfigEntityBundleBase extends ConfigEntityBase {
  
  /**
   * Deletes display if a bundle is deleted.
   */
  protected function deleteDisplays() {
    // Remove entity displays of the deleted bundle.
    if ($displays = $this->loadDisplays('entity_view_display')) {
      $storage = $this->entityTypeManager()
        ->getStorage('entity_view_display');
      $storage->delete($displays);
    }
    // Remove entity form displays of the deleted bundle.
    if ($displays = $this->loadDisplays('entity_form_display')) {
      $storage = $this->entityTypeManager()
        ->getStorage('entity_form_display');
      $storage->delete($displays);
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
    parent::postSave($storage, $update);
    $entity_type_manager = $this->entityTypeManager();
    $bundle_of = $this->getEntityType()
      ->getBundleOf();
    if (!$update) {
      \Drupal::service('entity_bundle.listener')->onBundleCreate($this->id(), $bundle_of);
    }
    else {
      // Invalidate the render cache of entities for which this entity
      // is a bundle.
      if ($entity_type_manager->hasHandler($bundle_of, 'view_builder')) {
        $entity_type_manager->getViewBuilder($bundle_of)
          ->resetCache();
      }
      // Entity bundle field definitions may depend on bundle settings.
      \Drupal::service('entity_field.manager')->clearCachedFieldDefinitions();
      $this->entityTypeBundleInfo()
        ->clearCachedBundles();
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public static function postDelete(EntityStorageInterface $storage, array $entities) {
    parent::postDelete($storage, $entities);
    foreach ($entities as $entity) {
      $entity->deleteDisplays();
      \Drupal::service('entity_bundle.listener')->onBundleDelete($entity->id(), $entity->getEntityType()
        ->getBundleOf());
    }
  }
  
  /**
   * Acts on an entity before the presave hook is invoked.
   *
   * Used before the entity is saved and before invoking the presave hook.
   *
   * Ensure that config entities which are bundles of other entities cannot have
   * their ID changed.
   *
   * @param \Drupal\Core\Entity\EntityStorageInterface $storage
   *   The entity storage object.
   *
   * @throws \Drupal\Core\Config\ConfigNameException
   *   Thrown when attempting to rename a bundle entity.
   */
  public function preSave(EntityStorageInterface $storage) {
    parent::preSave($storage);
    // Only handle renames, not creations.
    if (!$this->isNew() && $this->getOriginalId() !== $this->id()) {
      $bundle_type = $this->getEntityType();
      $bundle_of = $bundle_type->getBundleOf();
      if (!empty($bundle_of)) {
        throw new ConfigNameException("The machine name of the '{$bundle_type->getLabel()}' bundle cannot be changed.");
      }
    }
  }
  
  /**
   * Returns view or form displays for this bundle.
   *
   * @param string $entity_type_id
   *   The entity type ID of the display type to load.
   *
   * @return \Drupal\Core\Entity\Display\EntityDisplayInterface[]
   *   A list of matching displays.
   */
  protected function loadDisplays($entity_type_id) {
    $ids = \Drupal::entityQuery($entity_type_id)->condition('id', $this->getEntityType()
      ->getBundleOf() . '.' . $this->getOriginalId() . '.', 'STARTS_WITH')
      ->execute();
    if ($ids) {
      $storage = $this->entityTypeManager()
        ->getStorage($entity_type_id);
      return $storage->loadMultiple($ids);
    }
    return [];
  }

}