class FileUpload

class FileUpload {
    use EntityValidationTrait;
    
    /**
     * The current user making the request.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * The field manager.
     *
     * @var \Drupal\Core\Entity\EntityFieldManagerInterface
     */
    protected $fieldManager;
    
    /**
     * The file uploader.
     *
     * @var \Drupal\jsonapi\Controller\TemporaryJsonapiFileFieldUploader
     */
    protected $fileUploader;
    
    /**
     * An HTTP kernel for making subrequests.
     *
     * @var \Symfony\Component\HttpKernel\HttpKernelInterface
     */
    protected $httpKernel;
    
    /**
     * Creates a new FileUpload instance.
     *
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     * @param \Drupal\Core\Entity\EntityFieldManagerInterface $field_manager
     *   The entity field manager.
     * @param \Drupal\jsonapi\Controller\TemporaryJsonapiFileFieldUploader $file_uploader
     *   The file uploader.
     * @param \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel
     *   An HTTP kernel for making subrequests.
     */
    public function __construct(AccountInterface $current_user, EntityFieldManagerInterface $field_manager, TemporaryJsonapiFileFieldUploader $file_uploader, HttpKernelInterface $http_kernel) {
        $this->currentUser = $current_user;
        $this->fieldManager = $field_manager;
        $this->fileUploader = $file_uploader;
        $this->httpKernel = $http_kernel;
    }
    
    /**
     * Handles JSON:API file upload requests.
     *
     * @param \Symfony\Component\HttpFoundation\Request $request
     *   The HTTP request object.
     * @param \Drupal\jsonapi\ResourceType\ResourceType $resource_type
     *   The JSON:API resource type for the current request.
     * @param string $file_field_name
     *   The file field for which the file is to be uploaded.
     * @param \Drupal\Core\Entity\FieldableEntityInterface $entity
     *   The entity for which the file is to be uploaded.
     *
     * @return \Drupal\jsonapi\ResourceResponse
     *   The response object.
     *
     * @throws \Symfony\Component\HttpKernel\Exception\UnprocessableEntityHttpException
     *   Thrown when there are validation errors.
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   Thrown if the upload's target resource could not be saved.
     * @throws \Exception
     *   Thrown if an exception occurs during a subrequest to fetch the newly
     *   created file entity.
     */
    public function handleFileUploadForExistingResource(Request $request, ResourceType $resource_type, $file_field_name, FieldableEntityInterface $entity) {
        $file_field_name = $resource_type->getInternalName($file_field_name);
        $field_definition = $this->validateAndLoadFieldDefinition($resource_type->getEntityTypeId(), $resource_type->getBundle(), $file_field_name);
        static::ensureFileUploadAccess($this->currentUser, $field_definition, $entity);
        $filename = $this->fileUploader
            ->validateAndParseContentDispositionHeader($request);
        $file = $this->fileUploader
            ->handleFileUploadForField($field_definition, $filename, $this->currentUser);
        if ($file instanceof EntityConstraintViolationListInterface) {
            $violations = $file;
            $message = "Unprocessable Entity: file validation failed.\n";
            $message .= implode("\n", array_map(function (ConstraintViolationInterface $violation) {
                return PlainTextOutput::renderFromHtml($violation->getMessage());
            }, (array) $violations->getIterator()));
            throw new UnprocessableEntityHttpException($message);
        }
        if ($resource_type->getFieldByInternalName($file_field_name)
            ->hasOne()) {
            $entity->{$file_field_name} = $file;
        }
        else {
            $entity->get($file_field_name)
                ->appendItem($file);
        }
        static::validate($entity, [
            $file_field_name,
        ]);
        $entity->save();
        $route_parameters = [
            'entity' => $entity->uuid(),
        ];
        $route_name = sprintf('jsonapi.%s.%s.related', $resource_type->getTypeName(), $resource_type->getPublicName($file_field_name));
        $related_url = Url::fromRoute($route_name, $route_parameters)->toString(TRUE);
        $request = Request::create($related_url->getGeneratedUrl(), 'GET', [], $request->cookies
            ->all(), [], $request->server
            ->all());
        return $this->httpKernel
            ->handle($request, HttpKernelInterface::SUB_REQUEST);
    }
    
    /**
     * Handles JSON:API file upload requests.
     *
     * @param \Symfony\Component\HttpFoundation\Request $request
     *   The HTTP request object.
     * @param \Drupal\jsonapi\ResourceType\ResourceType $resource_type
     *   The JSON:API resource type for the current request.
     * @param string $file_field_name
     *   The file field for which the file is to be uploaded.
     *
     * @return \Drupal\jsonapi\ResourceResponse
     *   The response object.
     *
     * @throws \Symfony\Component\HttpKernel\Exception\UnprocessableEntityHttpException
     *   Thrown when there are validation errors.
     */
    public function handleFileUploadForNewResource(Request $request, ResourceType $resource_type, $file_field_name) {
        $file_field_name = $resource_type->getInternalName($file_field_name);
        $field_definition = $this->validateAndLoadFieldDefinition($resource_type->getEntityTypeId(), $resource_type->getBundle(), $file_field_name);
        static::ensureFileUploadAccess($this->currentUser, $field_definition);
        $filename = $this->fileUploader
            ->validateAndParseContentDispositionHeader($request);
        $file = $this->fileUploader
            ->handleFileUploadForField($field_definition, $filename, $this->currentUser);
        if ($file instanceof EntityConstraintViolationListInterface) {
            $violations = $file;
            $message = "Unprocessable Entity: file validation failed.\n";
            $message .= implode("\n", array_map(function (ConstraintViolationInterface $violation) {
                return PlainTextOutput::renderFromHtml($violation->getMessage());
            }, iterator_to_array($violations)));
            throw new UnprocessableEntityHttpException($message);
        }
        // @todo Remove line below in favor of commented line in https://www.drupal.org/project/drupal/issues/2878463.
        $self_link = new Link(new CacheableMetadata(), Url::fromRoute('jsonapi.file--file.individual', [
            'entity' => $file->uuid(),
        ]), 'self');
        
        /* $self_link = new Link(new CacheableMetadata(), $this->entity->toUrl('jsonapi'), ['self']); */
        $links = new LinkCollection([
            'self' => $self_link,
        ]);
        $relatable_resource_types = $resource_type->getRelatableResourceTypesByField($resource_type->getPublicName($file_field_name));
        $file_resource_type = reset($relatable_resource_types);
        $resource_object = ResourceObject::createFromEntity($file_resource_type, $file);
        return new ResourceResponse(new JsonApiDocumentTopLevel(new ResourceObjectData([
            $resource_object,
        ], 1), new NullIncludedData(), $links), 201, []);
    }
    
    /**
     * Ensures that the given account is allowed to upload a file.
     *
     * @param \Drupal\Core\Session\AccountInterface $account
     *   The account for which access should be checked.
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The field for which the file is to be uploaded.
     * @param \Drupal\Core\Entity\FieldableEntityInterface|null $entity
     *   The entity, if one exists, for which the file is to be uploaded.
     */
    protected static function ensureFileUploadAccess(AccountInterface $account, FieldDefinitionInterface $field_definition, FieldableEntityInterface $entity = NULL) {
        $access_result = $entity ? TemporaryJsonapiFileFieldUploader::checkFileUploadAccess($account, $field_definition, $entity) : TemporaryJsonapiFileFieldUploader::checkFileUploadAccess($account, $field_definition);
        if (!$access_result->isAllowed()) {
            $reason = 'The current user is not permitted to upload a file for this field.';
            if ($access_result instanceof AccessResultReasonInterface) {
                $reason .= ' ' . $access_result->getReason();
            }
            throw new AccessDeniedHttpException($reason);
        }
    }
    
    /**
     * Validates and loads a field definition instance.
     *
     * @param string $entity_type_id
     *   The entity type ID the field is attached to.
     * @param string $bundle
     *   The bundle the field is attached to.
     * @param string $field_name
     *   The field name.
     *
     * @return \Drupal\Core\Field\FieldDefinitionInterface
     *   The field definition.
     *
     * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
     *   Thrown when the field does not exist.
     * @throws \Symfony\Component\HttpFoundation\File\Exception\AccessDeniedException
     *   Thrown when the target type of the field is not a file, or the current
     *   user does not have 'edit' access for the field.
     */
    protected function validateAndLoadFieldDefinition($entity_type_id, $bundle, $field_name) {
        $field_definitions = $this->fieldManager
            ->getFieldDefinitions($entity_type_id, $bundle);
        if (!isset($field_definitions[$field_name])) {
            throw new NotFoundHttpException(sprintf('Field "%s" does not exist.', $field_name));
        }
        
        /** @var \Drupal\Core\Field\FieldDefinitionInterface $field_definition */
        $field_definition = $field_definitions[$field_name];
        if ($field_definition->getSetting('target_type') !== 'file') {
            throw new AccessDeniedException(sprintf('"%s" is not a file field', $field_name));
        }
        return $field_definition;
    }

}