class FieldItemNormalizer

class FieldItemNormalizer extends NormalizerBase implements DenormalizerInterface {
    use SerializedColumnNormalizerTrait;
    
    /**
     * The interface or class that this Normalizer supports.
     *
     * @var string
     */
    protected $supportedInterfaceOrClass = FieldItemInterface::class;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * FieldItemNormalizer constructor.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager) {
        $this->entityTypeManager = $entity_type_manager;
    }
    
    /**
     * {@inheritdoc}
     *
     * This normalizer leaves JSON:API normalizer land and enters the land of
     * Drupal core's serialization system. That system was never designed with
     * cacheability in mind, and hence bubbles cacheability out of band. This must
     * catch it, and pass it to the value object that JSON:API uses.
     */
    public function normalize($field_item, $format = NULL, array $context = []) {
        assert($field_item instanceof FieldItemInterface);
        
        /** @var \Drupal\Core\TypedData\TypedDataInterface $property */
        $values = [];
        $context[CacheableNormalizerInterface::SERIALIZATION_CONTEXT_CACHEABILITY] = new CacheableMetadata();
        if (!empty($field_item->getProperties(TRUE))) {
            // We normalize each individual value, so each can do their own casting,
            // if needed.
            $field_properties = TypedDataInternalPropertiesHelper::getNonInternalProperties($field_item);
            foreach ($field_properties as $property_name => $property) {
                $values[$property_name] = $this->serializer
                    ->normalize($property, $format, $context);
            }
            // Flatten if there is only a single property to normalize.
            $flatten = count($field_properties) === 1 && $field_item::mainPropertyName() !== NULL;
            $values = static::rasterizeValueRecursive($flatten ? reset($values) : $values);
        }
        else {
            $values = $field_item->getValue();
        }
        $normalization = new CacheableNormalization($context[CacheableNormalizerInterface::SERIALIZATION_CONTEXT_CACHEABILITY], $values);
        unset($context[CacheableNormalizerInterface::SERIALIZATION_CONTEXT_CACHEABILITY]);
        return $normalization;
    }
    
    /**
     * {@inheritdoc}
     */
    public function denormalize($data, $class, $format = NULL, array $context = []) {
        $item_definition = $context['field_definition']->getItemDefinition();
        assert($item_definition instanceof FieldItemDataDefinitionInterface);
        $field_item = $this->getFieldItemInstance($context['resource_type'], $item_definition);
        $this->checkForSerializedStrings($data, $class, $field_item);
        $property_definitions = $item_definition->getPropertyDefinitions();
        $serialized_property_names = $this->getCustomSerializedPropertyNames($field_item);
        $denormalize_property = function ($property_name, $property_value, $property_value_class, $format, $context) use ($serialized_property_names) {
            if ($this->serializer
                ->supportsDenormalization($property_value, $property_value_class, $format, $context)) {
                return $this->serializer
                    ->denormalize($property_value, $property_value_class, $format, $context);
            }
            else {
                if (in_array($property_name, $serialized_property_names, TRUE)) {
                    $property_value = serialize($property_value);
                }
                return $property_value;
            }
        };
        // Because e.g. the 'bundle' entity key field requires field values to not
        // be expanded to an array of all properties, we special-case single-value
        // properties.
        if (!is_array($data)) {
            // The NULL normalization means there is no value, hence we can return
            // early. Note that this is not just an optimization but a necessity for
            // field types without main properties (such as the "map" field type).
            if ($data === NULL) {
                return $data;
            }
            $property_value = $data;
            $property_name = $item_definition->getMainPropertyName();
            $property_value_class = $property_definitions[$property_name]->getClass();
            return $denormalize_property($property_name, $property_value, $property_value_class, $format, $context);
        }
        $data_internal = [];
        if (!empty($property_definitions)) {
            $writable_properties = array_keys(array_filter($property_definitions, function (DataDefinitionInterface $data_definition) : bool {
                return !$data_definition->isReadOnly();
            }));
            $invalid_property_names = [];
            foreach ($data as $property_name => $property_value) {
                if (!isset($property_definitions[$property_name])) {
                    $alt = static::getAlternatives($property_name, $writable_properties);
                    $invalid_property_names[$property_name] = reset($alt);
                }
            }
            if (!empty($invalid_property_names)) {
                $suggestions = array_values(array_filter($invalid_property_names));
                // Only use the "Did you mean"-style error message if there is a
                // suggestion for every invalid property name.
                if (count($suggestions) === count($invalid_property_names)) {
                    $format = count($invalid_property_names) === 1 ? "The property '%s' does not exist on the '%s' field of type '%s'. Did you mean '%s'?" : "The properties '%s' do not exist on the '%s' field of type '%s'. Did you mean '%s'?";
                    throw new UnexpectedValueException(sprintf($format, implode("', '", array_keys($invalid_property_names)), $item_definition->getFieldDefinition()
                        ->getName(), $item_definition->getFieldDefinition()
                        ->getType(), implode("', '", $suggestions)));
                }
                else {
                    $format = count($invalid_property_names) === 1 ? "The property '%s' does not exist on the '%s' field of type '%s'. Writable properties are: '%s'." : "The properties '%s' do not exist on the '%s' field of type '%s'. Writable properties are: '%s'.";
                    throw new UnexpectedValueException(sprintf($format, implode("', '", array_keys($invalid_property_names)), $item_definition->getFieldDefinition()
                        ->getName(), $item_definition->getFieldDefinition()
                        ->getType(), implode("', '", $writable_properties)));
                }
            }
            foreach ($data as $property_name => $property_value) {
                $property_value_class = $property_definitions[$property_name]->getClass();
                $data_internal[$property_name] = $denormalize_property($property_name, $property_value, $property_value_class, $format, $context);
            }
        }
        else {
            $data_internal = $data;
        }
        return $data_internal;
    }
    
    /**
     * Provides alternatives for a given array and key.
     *
     * @param string $search_key
     *   The search key to get alternatives for.
     * @param array $keys
     *   The search space to search for alternatives in.
     *
     * @return string[]
     *   An array of strings with suitable alternatives.
     *
     * @see \Drupal\Component\DependencyInjection\Container::getAlternatives()
     */
    private static function getAlternatives(string $search_key, array $keys) : array {
        // $search_key is user input and could be longer than the 255 string length
        // limit of levenshtein().
        if (strlen($search_key) > 255) {
            return [];
        }
        $alternatives = [];
        foreach ($keys as $key) {
            $lev = levenshtein($search_key, $key);
            if ($lev <= strlen($search_key) / 3 || strpos($key, $search_key) !== FALSE) {
                $alternatives[] = $key;
            }
        }
        return $alternatives;
    }
    
    /**
     * Gets a field item instance for use with SerializedColumnNormalizerTrait.
     *
     * @param \Drupal\jsonapi\ResourceType\ResourceType $resource_type
     *   The JSON:API resource type of the entity being denormalized.
     * @param \Drupal\Core\Field\TypedData\FieldItemDataDefinitionInterface $item_definition
     *   The field item definition of the instance to get.
     *
     * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
     * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
     */
    protected function getFieldItemInstance(ResourceType $resource_type, FieldItemDataDefinitionInterface $item_definition) {
        if ($bundle_key = $this->entityTypeManager
            ->getDefinition($resource_type->getEntityTypeId())
            ->getKey('bundle')) {
            $create_values = [
                $bundle_key => $resource_type->getBundle(),
            ];
        }
        else {
            $create_values = [];
        }
        $entity = $this->entityTypeManager
            ->getStorage($resource_type->getEntityTypeId())
            ->create($create_values);
        $field = $entity->get($item_definition->getFieldDefinition()
            ->getName());
        assert($field instanceof FieldItemListInterface);
        $field_item = $field->appendItem();
        assert($field_item instanceof FieldItemInterface);
        return $field_item;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasCacheableSupportsMethod() : bool {
        return TRUE;
    }

}