class ContentEntityNormalizer

class ContentEntityNormalizer extends NormalizerBase {
    use FieldableEntityNormalizerTrait;
    
    /**
     * {@inheritdoc}
     */
    protected $supportedInterfaceOrClass = ContentEntityInterface::class;
    
    /**
     * The hypermedia link manager.
     *
     * @var \Drupal\hal\LinkManager\LinkManagerInterface
     */
    protected $linkManager;
    
    /**
     * The module handler.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * Constructs a ContentEntityNormalizer object.
     *
     * @param \Drupal\hal\LinkManager\LinkManagerInterface $link_manager
     *   The hypermedia link manager.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler.
     * @param \Drupal\Core\Entity\EntityTypeRepositoryInterface $entity_type_repository
     *   The entity type repository.
     * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
     *   The entity field manager.
     */
    public function __construct(LinkManagerInterface $link_manager, EntityTypeManagerInterface $entity_type_manager, ModuleHandlerInterface $module_handler, EntityTypeRepositoryInterface $entity_type_repository, EntityFieldManagerInterface $entity_field_manager) {
        $this->linkManager = $link_manager;
        $this->entityTypeManager = $entity_type_manager;
        $this->moduleHandler = $module_handler;
        $this->entityTypeRepository = $entity_type_repository;
        $this->entityTypeRepository = $entity_type_repository;
        $this->entityFieldManager = $entity_field_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public function normalize($entity, $format = NULL, array $context = []) {
        $context += [
            'account' => NULL,
            'included_fields' => NULL,
        ];
        // Create the array of normalized fields, starting with the URI.
        
        /** @var \Drupal\Core\Entity\ContentEntityInterface $entity */
        $normalized = [
            '_links' => [
                'self' => [
                    'href' => $this->getEntityUri($entity),
                ],
                'type' => [
                    'href' => $this->linkManager
                        ->getTypeUri($entity->getEntityTypeId(), $entity->bundle(), $context),
                ],
            ],
        ];
        $field_items = TypedDataInternalPropertiesHelper::getNonInternalProperties($entity->getTypedData());
        // If the fields to use were specified, only output those field values.
        if (isset($context['included_fields'])) {
            $field_items = array_intersect_key($field_items, array_flip($context['included_fields']));
        }
        foreach ($field_items as $field) {
            // Continue if the current user does not have access to view this field.
            if (!$field->access('view', $context['account'])) {
                continue;
            }
            $normalized_property = $this->serializer
                ->normalize($field, $format, $context);
            $normalized = NestedArray::mergeDeep($normalized, $normalized_property);
        }
        return $normalized;
    }
    
    /**
     * Implements \Symfony\Component\Serializer\Normalizer\DenormalizerInterface::denormalize().
     *
     * @param array $data
     *   Entity data to restore.
     * @param string $class
     *   Unused parameter.
     * @param string $format
     *   Format the given data was extracted from.
     * @param array $context
     *   Options available to the denormalizer. Keys that can be used:
     *   - request_method: if set to "patch" the denormalization will clear out
     *     all default values for entity fields before applying $data to the
     *     entity.
     *
     * @return \Drupal\Core\Entity\EntityInterface
     *   An unserialized entity object containing the data in $data.
     *
     * @throws \Symfony\Component\Serializer\Exception\UnexpectedValueException
     */
    public function denormalize($data, $class, $format = NULL, array $context = []) {
        // Get type, necessary for determining which bundle to create.
        if (!isset($data['_links']['type'])) {
            throw new UnexpectedValueException('The type link relation must be specified.');
        }
        // Create the entity.
        $typed_data_ids = $this->getTypedDataIds($data['_links']['type'], $context);
        $entity_type = $this->getEntityTypeDefinition($typed_data_ids['entity_type']);
        $default_langcode_key = $entity_type->getKey('default_langcode');
        $langcode_key = $entity_type->getKey('langcode');
        $values = [];
        // Figure out the language to use.
        if (isset($data[$default_langcode_key])) {
            // Find the field item for which the default_langcode value is set to 1 and
            // set the langcode the right default language.
            foreach ($data[$default_langcode_key] as $item) {
                if (!empty($item['value']) && isset($item['lang'])) {
                    $values[$langcode_key] = $item['lang'];
                    break;
                }
            }
            // Remove the default langcode so it does not get iterated over below.
            unset($data[$default_langcode_key]);
        }
        if ($entity_type->hasKey('bundle')) {
            $bundle_key = $entity_type->getKey('bundle');
            $values[$bundle_key] = $typed_data_ids['bundle'];
            // Unset the bundle key from data, if it's there.
            unset($data[$bundle_key]);
        }
        $entity = $this->entityTypeManager
            ->getStorage($typed_data_ids['entity_type'])
            ->create($values);
        // Remove links from data array.
        unset($data['_links']);
        // Get embedded resources and remove from data array.
        $embedded = [];
        if (isset($data['_embedded'])) {
            $embedded = $data['_embedded'];
            unset($data['_embedded']);
        }
        // Flatten the embedded values.
        foreach ($embedded as $relation => $field) {
            $field_ids = $this->linkManager
                ->getRelationInternalIds($relation);
            if (!empty($field_ids)) {
                $field_name = $field_ids['field_name'];
                $data[$field_name] = $field;
            }
        }
        $this->denormalizeFieldData($data, $entity, $format, $context);
        // Pass the names of the fields whose values can be merged.
        // @todo https://www.drupal.org/node/2456257 remove this.
        $entity->_restSubmittedFields = array_keys($data);
        return $entity;
    }
    
    /**
     * Constructs the entity URI.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity.
     * @param array $context
     *   Normalization/serialization context.
     *
     * @return string
     *   The entity URI.
     */
    protected function getEntityUri(EntityInterface $entity, array $context = []) {
        // Some entity types don't provide a canonical link template.
        if ($entity->isNew()) {
            return '';
        }
        $route_name = 'rest.entity.' . $entity->getEntityTypeId() . '.GET';
        if ($entity->hasLinkTemplate('canonical')) {
            $url = $entity->toUrl('canonical');
        }
        elseif (\Drupal::service('router.route_provider')->getRoutesByNames([
            $route_name,
        ])) {
            $url = Url::fromRoute('rest.entity.' . $entity->getEntityTypeId() . '.GET', [
                $entity->getEntityTypeId() => $entity->id(),
            ]);
        }
        else {
            return '';
        }
        $url->setAbsolute(TRUE);
        if (!$url->isExternal()) {
            $url->setRouteParameter('_format', 'hal_json');
        }
        $generated_url = $url->toString(TRUE);
        $this->addCacheableDependency($context, $generated_url);
        return $generated_url->getGeneratedUrl();
    }
    
    /**
     * Gets the typed data IDs for a type URI.
     *
     * @param array $types
     *   The type array(s) (value of the 'type' attribute of the incoming data).
     * @param array $context
     *   Context from the normalizer/serializer operation.
     *
     * @return array
     *   The typed data IDs.
     */
    protected function getTypedDataIds($types, $context = []) {
        // The 'type' can potentially contain an array of type objects. By default,
        // Drupal only uses a single type in serializing, but allows for multiple
        // types when deserializing.
        if (isset($types['href'])) {
            $types = [
                $types,
            ];
        }
        if (empty($types)) {
            throw new UnexpectedValueException('No entity type(s) specified');
        }
        foreach ($types as $type) {
            if (!isset($type['href'])) {
                throw new UnexpectedValueException('Type must contain an \'href\' attribute.');
            }
            $type_uri = $type['href'];
            // Check whether the URI corresponds to a known type on this site. Break
            // once one does.
            if ($typed_data_ids = $this->linkManager
                ->getTypeInternalIds($type['href'], $context)) {
                break;
            }
        }
        // If none of the URIs correspond to an entity type on this site, no entity
        // can be created. Throw an exception.
        if (empty($typed_data_ids)) {
            throw new UnexpectedValueException(sprintf('Type %s does not correspond to an entity on this site.', $type_uri));
        }
        return $typed_data_ids;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasCacheableSupportsMethod() : bool {
        return TRUE;
    }

}