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) {
        
        /** @var \Drupal\Core\Config\Entity\ConfigEntityStorageInterface $storage */
        $storage = $this->entityTypeManager()
            ->getStorage($entity_type_id);
        $ids = $storage->getQuery()
            ->condition('id', $this->getEntityType()
            ->getBundleOf() . '.' . $this->getOriginalId() . '.', 'STARTS_WITH')
            ->execute();
        if ($ids) {
            $storage = $this->entityTypeManager()
                ->getStorage($entity_type_id);
            return $storage->loadMultiple($ids);
        }
        return [];
    }

}