class RelationshipNormalizer

class RelationshipNormalizer extends NormalizerBase {
    use SchematicNormalizerTrait;
    
    /**
     * Constructor.
     *
     * @param \Drupal\jsonapi\ResourceType\ResourceTypeRepositoryInterface $resourceTypeRepository
     *   Resource type repository.
     */
    public function __construct(ResourceTypeRepositoryInterface $resourceTypeRepository) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function doNormalize($object, $format = NULL, array $context = []) : array|string|int|float|bool|\ArrayObject|null {
        assert($object instanceof Relationship);
        return CacheableNormalization::aggregate([
            'data' => $this->serializer
                ->normalize($object->getData(), $format, $context),
            'links' => $this->serializer
                ->normalize($object->getLinks(), $format, $context)
                ->omitIfEmpty(),
            'meta' => CacheableNormalization::permanent($object->getMeta())
                ->omitIfEmpty(),
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getNormalizationSchema(mixed $object, array $context = []) : array {
        assert($object instanceof Relationship);
        $schema = [
            'allOf' => [
                [
                    '$ref' => JsonApiSpec::SUPPORTED_SPECIFICATION_JSON_SCHEMA . '#/definitions/relationship',
                ],
            ],
        ];
        $field_definition = $object->getContext()
            ->getField($object->getFieldName())?->getFieldDefinition();
        $item_class = $field_definition?->getItemDefinition()->getClass();
        assert($item_class, sprintf('The context ResourceObject for Relationship being normalized is missing field %s.', $object->getFieldName()));
        if (!$item_class || !is_subclass_of($item_class, EntityReferenceItemInterface::class)) {
            return $schema;
        }
        $targets = $item_class::getReferenceableBundles($field_definition);
        $target_types = array_reduce(array_keys($targets), function (array $carry, string $entity_type_id) use ($targets) {
            foreach ($targets[$entity_type_id] as $bundle) {
                // Even if a resource is internal, it can be referenced.
                if (!($resource = $this->resourceTypeRepository
                    ->get($entity_type_id, $bundle)) || in_array($resource->getTypeName(), $carry)) {
                    continue;
                }
                $carry[] = $resource->getTypeName();
            }
            return $carry;
        }, []);
        if ($target_types) {
            $schema['properties']['type'] = [
                'oneOf' => array_map(fn(string $resource_type_name) => [
                    'const' => $resource_type_name,
                ], $target_types),
            ];
        }
        return $schema;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getSupportedTypes(?string $format) : array {
        return [
            Relationship::class => TRUE,
        ];
    }

}