class FieldStorageDefinitionListener

class FieldStorageDefinitionListener implements FieldStorageDefinitionListenerInterface {

  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;

  /**
   * The event dispatcher.
   *
   * @var \Symfony\Contracts\EventDispatcher\EventDispatcherInterface
   */
  protected $eventDispatcher;

  /**
   * The entity definition manager.
   *
   * @var \Drupal\Core\Entity\EntityLastInstalledSchemaRepositoryInterface
   */
  protected $entityLastInstalledSchemaRepository;

  /**
   * The entity field manager.
   *
   * @var \Drupal\Core\Entity\EntityFieldManagerInterface
   */
  protected $entityFieldManager;

  /**
   * The deleted fields repository.
   *
   * @var \Drupal\Core\Field\DeletedFieldsRepositoryInterface
   */
  protected $deletedFieldsRepository;

  /**
   * Constructs a new FieldStorageDefinitionListener.
   *
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   * @param \Symfony\Contracts\EventDispatcher\EventDispatcherInterface $event_dispatcher
   *   The event dispatcher.
   * @param \Drupal\Core\Entity\EntityLastInstalledSchemaRepositoryInterface $entity_last_installed_schema_repository
   *   The entity last installed schema repository.
   * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
   *   The entity field manager.
   * @param \Drupal\Core\Field\DeletedFieldsRepositoryInterface $deleted_fields_repository
   *   The deleted fields repository.
   */
  public function __construct(EntityTypeManagerInterface $entity_type_manager, EventDispatcherInterface $event_dispatcher, EntityLastInstalledSchemaRepositoryInterface $entity_last_installed_schema_repository, EntityFieldManagerInterface $entity_field_manager, DeletedFieldsRepositoryInterface $deleted_fields_repository) {
    $this->entityTypeManager = $entity_type_manager;
    $this->eventDispatcher = $event_dispatcher;
    $this->entityLastInstalledSchemaRepository = $entity_last_installed_schema_repository;
    $this->entityFieldManager = $entity_field_manager;
    $this->deletedFieldsRepository = $deleted_fields_repository;
  }

  /**
   * {@inheritdoc}
   */
  public function onFieldStorageDefinitionCreate(FieldStorageDefinitionInterface $storage_definition) {
    $entity_type_id = $storage_definition
      ->getTargetEntityTypeId();

    // @todo Forward this to all interested handlers, not only storage, once
    //   iterating handlers is possible: https://www.drupal.org/node/2332857.
    $storage = $this->entityTypeManager
      ->getStorage($entity_type_id);
    if ($storage instanceof FieldStorageDefinitionListenerInterface) {
      $storage
        ->onFieldStorageDefinitionCreate($storage_definition);
    }
    $this->entityLastInstalledSchemaRepository
      ->setLastInstalledFieldStorageDefinition($storage_definition);
    $this->eventDispatcher
      ->dispatch(new FieldStorageDefinitionEvent($storage_definition), FieldStorageDefinitionEvents::CREATE);
    $this->entityFieldManager
      ->clearCachedFieldDefinitions();
  }

  /**
   * {@inheritdoc}
   */
  public function onFieldStorageDefinitionUpdate(FieldStorageDefinitionInterface $storage_definition, FieldStorageDefinitionInterface $original) {
    $entity_type_id = $storage_definition
      ->getTargetEntityTypeId();

    // @todo Forward this to all interested handlers, not only storage, once
    //   iterating handlers is possible: https://www.drupal.org/node/2332857.
    $storage = $this->entityTypeManager
      ->getStorage($entity_type_id);
    if ($storage instanceof FieldStorageDefinitionListenerInterface) {
      $storage
        ->onFieldStorageDefinitionUpdate($storage_definition, $original);
    }
    $this->entityLastInstalledSchemaRepository
      ->setLastInstalledFieldStorageDefinition($storage_definition);
    $this->eventDispatcher
      ->dispatch(new FieldStorageDefinitionEvent($storage_definition, $original), FieldStorageDefinitionEvents::UPDATE);
    $this->entityFieldManager
      ->clearCachedFieldDefinitions();
  }

  /**
   * {@inheritdoc}
   */
  public function onFieldStorageDefinitionDelete(FieldStorageDefinitionInterface $storage_definition) {
    $entity_type_id = $storage_definition
      ->getTargetEntityTypeId();

    // @todo Forward this to all interested handlers, not only storage, once
    //   iterating handlers is possible: https://www.drupal.org/node/2332857.
    $storage = $this->entityTypeManager
      ->getStorage($entity_type_id);

    // Keep the field definition in the deleted fields repository so we can use
    // it later during field_purge_batch(), but only if the field has data.
    if ($storage_definition instanceof BaseFieldDefinition && $storage instanceof FieldableEntityStorageInterface && $storage
      ->countFieldData($storage_definition, TRUE)) {
      $deleted_storage_definition = clone $storage_definition;
      $deleted_storage_definition
        ->setDeleted(TRUE);
      $this->deletedFieldsRepository
        ->addFieldDefinition($deleted_storage_definition);
      $this->deletedFieldsRepository
        ->addFieldStorageDefinition($deleted_storage_definition);
    }
    if ($storage instanceof FieldStorageDefinitionListenerInterface) {
      $storage
        ->onFieldStorageDefinitionDelete($storage_definition);
    }
    $this->entityLastInstalledSchemaRepository
      ->deleteLastInstalledFieldStorageDefinition($storage_definition);
    $this->eventDispatcher
      ->dispatch(new FieldStorageDefinitionEvent($storage_definition), FieldStorageDefinitionEvents::DELETE);
    $this->entityFieldManager
      ->clearCachedFieldDefinitions();
  }

}