class ResourceObjectNormalizer

class ResourceObjectNormalizer extends NormalizerBase {
    
    /**
     * {@inheritdoc}
     */
    protected $supportedInterfaceOrClass = ResourceObject::class;
    
    /**
     * The entity normalization cacher.
     *
     * @var \Drupal\jsonapi\EventSubscriber\ResourceObjectNormalizationCacher
     */
    protected $cacher;
    
    /**
     * Constructs a ResourceObjectNormalizer object.
     *
     * @param \Drupal\jsonapi\EventSubscriber\ResourceObjectNormalizationCacher $cacher
     *   The entity normalization cacher.
     */
    public function __construct(ResourceObjectNormalizationCacher $cacher) {
        $this->cacher = $cacher;
    }
    
    /**
     * {@inheritdoc}
     */
    public function supportsDenormalization($data, $type, $format = NULL) {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function normalize($object, $format = NULL, array $context = []) {
        assert($object instanceof ResourceObject);
        // If the fields to use were specified, only output those field values.
        $context['resource_object'] = $object;
        $resource_type = $object->getResourceType();
        $resource_type_name = $resource_type->getTypeName();
        $fields = $object->getFields();
        // Get the bundle ID of the requested resource. This is used to determine if
        // this is a bundle level resource or an entity level resource.
        if (!empty($context['sparse_fieldset'][$resource_type_name])) {
            $field_names = $context['sparse_fieldset'][$resource_type_name];
        }
        else {
            $field_names = array_keys($fields);
        }
        $normalization_parts = $this->getNormalization($field_names, $object, $format, $context);
        // Keep only the requested fields (the cached normalization gradually grows
        // to the complete set of fields).
        $fields = $normalization_parts[ResourceObjectNormalizationCacher::RESOURCE_CACHE_SUBSET_FIELDS];
        $field_normalizations = array_intersect_key($fields, array_flip($field_names));
        $relationship_field_names = array_keys($resource_type->getRelatableResourceTypes());
        $attributes = array_diff_key($field_normalizations, array_flip($relationship_field_names));
        $relationships = array_intersect_key($field_normalizations, array_flip($relationship_field_names));
        $entity_normalization = array_filter($normalization_parts[ResourceObjectNormalizationCacher::RESOURCE_CACHE_SUBSET_BASE] + [
            'attributes' => CacheableNormalization::aggregate($attributes)->omitIfEmpty(),
            'relationships' => CacheableNormalization::aggregate($relationships)->omitIfEmpty(),
        ]);
        return CacheableNormalization::aggregate($entity_normalization)->withCacheableDependency($object);
    }
    
    /**
     * Normalizes an entity using the given fieldset.
     *
     * @param string[] $field_names
     *   The field names to normalize (the sparse fieldset, if any).
     * @param \Drupal\jsonapi\JsonApiResource\ResourceObject $object
     *   The resource object to partially normalize.
     * @param string $format
     *   The format in which the normalization will be encoded.
     * @param array $context
     *   Context options for the normalizer.
     *
     * @return array
     *   An array with two key-value pairs:
     *   - 'base': array, the base normalization of the entity, that does not
     *             depend on which sparse fieldset was requested.
     *   - 'fields': CacheableNormalization for all requested fields.
     *
     * @see ::normalize()
     */
    protected function getNormalization(array $field_names, ResourceObject $object, $format = NULL, array $context = []) {
        $cached_normalization_parts = $this->cacher
            ->get($object);
        $normalizer_values = $cached_normalization_parts !== FALSE ? $cached_normalization_parts : static::buildEmptyNormalization($object);
        $fields =& $normalizer_values[ResourceObjectNormalizationCacher::RESOURCE_CACHE_SUBSET_FIELDS];
        $non_cached_fields = array_diff_key($object->getFields(), $fields);
        $non_cached_requested_fields = array_intersect_key($non_cached_fields, array_flip($field_names));
        foreach ($non_cached_requested_fields as $field_name => $field) {
            $fields[$field_name] = $this->serializeField($field, $context, $format);
        }
        // Add links if missing.
        $base =& $normalizer_values[ResourceObjectNormalizationCacher::RESOURCE_CACHE_SUBSET_BASE];
        $base['links'] = $base['links'] ?? $this->serializer
            ->normalize($object->getLinks(), $format, $context)
            ->omitIfEmpty();
        if (!empty($non_cached_requested_fields)) {
            $this->cacher
                ->saveOnTerminate($object, $normalizer_values);
        }
        return $normalizer_values;
    }
    
    /**
     * Builds the empty normalization structure for cache misses.
     *
     * @param \Drupal\jsonapi\JsonApiResource\ResourceObject $object
     *   The resource object being normalized.
     *
     * @return array
     *   The normalization structure as defined in ::getNormalization().
     *
     * @see ::getNormalization()
     */
    protected static function buildEmptyNormalization(ResourceObject $object) {
        return [
            ResourceObjectNormalizationCacher::RESOURCE_CACHE_SUBSET_BASE => [
                'type' => CacheableNormalization::permanent($object->getResourceType()
                    ->getTypeName()),
                'id' => CacheableNormalization::permanent($object->getId()),
            ],
            ResourceObjectNormalizationCacher::RESOURCE_CACHE_SUBSET_FIELDS => [],
        ];
    }
    
    /**
     * Serializes a given field.
     *
     * @param mixed $field
     *   The field to serialize.
     * @param array $context
     *   The normalization context.
     * @param string $format
     *   The serialization format.
     *
     * @return \Drupal\jsonapi\Normalizer\Value\CacheableNormalization
     *   The normalized value.
     */
    protected function serializeField($field, array $context, $format) {
        // Only content entities contain FieldItemListInterface fields. Since config
        // entities do not have "real" fields and therefore do not have field access
        // restrictions.
        if ($field instanceof FieldItemListInterface) {
            $field_access_result = $field->access('view', $context['account'], TRUE);
            if (!$field_access_result->isAllowed()) {
                return new CacheableOmission(CacheableMetadata::createFromObject($field_access_result));
            }
            if ($field instanceof EntityReferenceFieldItemListInterface) {
                // Build the relationship object based on the entity reference and
                // normalize that object instead.
                assert(!empty($context['resource_object']) && $context['resource_object'] instanceof ResourceObject);
                $resource_object = $context['resource_object'];
                $relationship = Relationship::createFromEntityReferenceField($resource_object, $field);
                $normalized_field = $this->serializer
                    ->normalize($relationship, $format, $context);
            }
            else {
                $normalized_field = $this->serializer
                    ->normalize($field, $format, $context);
            }
            assert($normalized_field instanceof CacheableNormalization);
            return $normalized_field->withCacheableDependency(CacheableMetadata::createFromObject($field_access_result));
        }
        else {
            // @todo Replace this workaround after https://www.drupal.org/node/3043245
            //   or remove the need for this in https://www.drupal.org/node/2942975.
            //   See \Drupal\layout_builder\Normalizer\LayoutEntityDisplayNormalizer.
            if (is_a($context['resource_object']->getResourceType()
                ->getDeserializationTargetClass(), 'Drupal\\layout_builder\\Entity\\LayoutBuilderEntityViewDisplay', TRUE) && $context['resource_object']->getField('third_party_settings') === $field) {
                unset($field['layout_builder']['sections']);
            }
            // Config "fields" in this case are arrays or primitives and do not need
            // to be normalized.
            return CacheableNormalization::permanent($field);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasCacheableSupportsMethod() : bool {
        return TRUE;
    }

}