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();
    }

}