trait EntityCreationTrait in JSON:API Resources 8

trait EntityCreationTrait {
  use ResourceObjectToEntityMapperAwareTrait;
  use EntityValidationTrait;

  /**
   * Process the resource request.
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The request.
   * @param \Drupal\jsonapi\JsonApiResource\JsonApiDocumentTopLevel $request_document
   *   The deserialized request document.
   *
   * @return \Drupal\jsonapi\ResourceResponse
   *   The response.
   *
   * @throws \Symfony\Component\HttpKernel\Exception\ConflictHttpException
   *   Thrown when the entity to be created already exists.
   * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
   *   Thrown if the storage handler couldn't be loaded.
   * @throws \Drupal\Core\Entity\EntityStorageException
   *   Thrown if the entity could not be saved.
   */
  protected function processEntityCreation(Request $request, JsonApiDocumentTopLevel $request_document) {
    $data = $request_document
      ->getData();
    if ($data
      ->getCardinality() !== 1) {
      throw new UnprocessableEntityHttpException("The request document's primary data must not be an array.");
    }
    $entity = $this->resourceObjectToEntityMapper
      ->createEntityFromResourceObject($data
      ->getIterator()
      ->current());

    // Allow the class using this trait to modfiy the created entity before it
    // is saved.
    $this
      ->modifyCreatedEntity($entity, $request);
    static::validate($entity);

    // Return a 409 Conflict response in accordance with the JSON:API spec. See
    // http://jsonapi.org/format/#crud-creating-responses-409.
    try {

      // @todo: remove the assignment of the entity type manager to a variable when an "Aware" interface is added.

      /** @var \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager */

      /** @var \Drupal\Core\Entity\EntityStorageInterface $entity_storage */
      $entity_type_manager = $this->entityTypeManager;
      $entity_storage = $entity_type_manager
        ->getStorage($entity
        ->getEntityTypeId());
    } catch (PluginNotFoundException $e) {
      assert(FALSE, "It is impossible to encounter this exception. An entity can't be created if its entity type ID does not exist.");
    }
    if (!empty($entity_storage
      ->loadByProperties([
      'uuid' => $entity
        ->uuid(),
    ]))) {
      throw new ConflictHttpException('Conflict: Entity already exists.');
    }
    $entity
      ->save();
    $data = $this
      ->createIndividualDataFromEntity($entity);
    $resource_object = $data
      ->getIterator()
      ->current();
    assert($resource_object instanceof ResourceObject);
    $response = $this
      ->createJsonapiResponse($data, $request, 201);

    // According to JSON:API specification, when a new entity was created
    // we should send "Location" header to the frontend.
    if ($resource_object
      ->getResourceType()
      ->isLocatable()) {
      $url = $resource_object
        ->toUrl()
        ->setAbsolute()
        ->toString(TRUE);
      $response->headers
        ->set('Location', $url
        ->getGeneratedUrl());
      if ($response instanceof CacheableResponseInterface) {
        $response
          ->addCacheableDependency($url);
      }
    }
    return $response;
  }

  /**
   * Modifies the created entity before it is saved.
   *
   * This method can be overridden so that custom JSON:API resources can modify
   * the created entity before it is saved.
   *
   * Classes overriding this method have access to the same arguments as a
   * JSON:API resource's process() method by calling
   * $request->arguments->get($arg_name).
   *
   * @param \Drupal\Core\Entity\EntityInterface $created_entity
   *   The created entity.
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The request object.
   */
  protected function modifyCreatedEntity(EntityInterface $created_entity, Request $request) {

    // no-op.
  }

}