class Importer

final class Importer implements LoggerAwareInterface {
    use LoggerAwareTrait;
    
    /**
     * The dependencies of the currently importing entity, if any.
     *
     * The keys are the UUIDs of the dependencies, and the values are arrays with
     * two members: the entity type ID of the dependency, and the UUID to load.
     *
     * @var array<string, string[]>|null
     */
    private ?array $dependencies = NULL;
    public function __construct(EntityTypeManagerInterface $entityTypeManager, AdminAccountSwitcher $accountSwitcher, FileSystemInterface $fileSystem, LanguageManagerInterface $languageManager, EntityRepositoryInterface $entityRepository) {
    }
    
    /**
     * Imports content entities from disk.
     *
     * @param \Drupal\Core\DefaultContent\Finder $content
     *   The content finder, which has information on the entities to create
     *   in the necessary dependency order.
     * @param \Drupal\Core\DefaultContent\Existing $existing
     *   (optional) What to do if one of the entities being imported already
     *   exists, by UUID:
     *   - \Drupal\Core\DefaultContent\Existing::Error: Throw an exception.
     *   - \Drupal\Core\DefaultContent\Existing::Skip: Leave the existing entity
     *     as-is.
     *
     * @throws \Drupal\Core\DefaultContent\ImportException
     *   - If any of the entities being imported are not content entities.
     *   - If any of the entities being imported already exists, by UUID, and
     *     $existing is \Drupal\Core\DefaultContent\Existing::Error.
     */
    public function importContent(Finder $content, Existing $existing = Existing::Error) : void {
        if (count($content->data) === 0) {
            return;
        }
        $account = $this->accountSwitcher
            ->switchToAdministrator();
        try {
            
            /** @var array{_meta: array<mixed>} $decoded */
            foreach ($content->data as $decoded) {
                [
                    'uuid' => $uuid,
                    'entity_type' => $entity_type_id,
                    'path' => $path,
                ] = $decoded['_meta'];
                assert(is_string($uuid));
                assert(is_string($entity_type_id));
                assert(is_string($path));
                $entity_type = $this->entityTypeManager
                    ->getDefinition($entity_type_id);
                
                /** @var \Drupal\Core\Entity\EntityTypeInterface $entity_type */
                if (!$entity_type->entityClassImplements(ContentEntityInterface::class)) {
                    throw new ImportException("Content entity {$uuid} is a '{$entity_type_id}', which is not a content entity type.");
                }
                $entity = $this->entityRepository
                    ->loadEntityByUuid($entity_type_id, $uuid);
                if ($entity) {
                    if ($existing === Existing::Skip) {
                        continue;
                    }
                    else {
                        throw new ImportException("{$entity_type_id} {$uuid} already exists.");
                    }
                }
                $entity = $this->toEntity($decoded)
                    ->enforceIsNew();
                // Ensure that the entity is not owned by the anonymous user.
                if ($entity instanceof EntityOwnerInterface && empty($entity->getOwnerId())) {
                    $entity->setOwnerId($account->id());
                }
                // If a file exists in the same folder, copy it to the designated
                // target URI.
                if ($entity instanceof FileInterface) {
                    $this->copyFileAssociatedWithEntity(dirname($path), $entity);
                }
                $violations = $entity->validate();
                if (count($violations) > 0) {
                    throw new InvalidEntityException($violations, $path);
                }
                $entity->save();
            }
        } finally {
            $this->accountSwitcher
                ->switchBack();
        }
    }
    
    /**
     * Copies a file from default content directory to the site's file system.
     *
     * @param string $path
     *   The path to the file to copy.
     * @param \Drupal\file\FileInterface $entity
     *   The file entity.
     */
    private function copyFileAssociatedWithEntity(string $path, FileInterface &$entity) : void {
        $destination = $entity->getFileUri();
        assert(is_string($destination));
        // If the source file doesn't exist, there's nothing we can do.
        $source = $path . '/' . basename($destination);
        if (!file_exists($source)) {
            $this->logger?->warning("File entity %name was imported, but the associated file (@path) was not found.", [
                '%name' => $entity->label(),
                '@path' => $source,
            ]);
            return;
        }
        $copy_file = TRUE;
        if (file_exists($destination)) {
            $source_hash = hash_file('sha256', $source);
            assert(is_string($source_hash));
            $destination_hash = hash_file('sha256', $destination);
            assert(is_string($destination_hash));
            if (hash_equals($source_hash, $destination_hash) && $this->entityTypeManager
                ->getStorage('file')
                ->loadByProperties([
                'uri' => $destination,
            ]) === []) {
                // If the file hashes match and the file is not already a managed file
                // then do not copy a new version to the file system. This prevents
                // re-installs during development from creating unnecessary duplicates.
                $copy_file = FALSE;
            }
        }
        $target_directory = dirname($destination);
        $this->fileSystem
            ->prepareDirectory($target_directory, FileSystemInterface::CREATE_DIRECTORY);
        if ($copy_file) {
            $uri = $this->fileSystem
                ->copy($source, $destination);
            $entity->setFileUri($uri);
        }
    }
    
    /**
     * Converts an array of content entity data to a content entity object.
     *
     * @param array<string, array<mixed>> $data
     *   The entity data.
     *
     * @return \Drupal\Core\Entity\ContentEntityInterface
     *   The unsaved entity.
     *
     * @throws \Drupal\Core\DefaultContent\ImportException
     *   If the `entity_type` or `uuid` meta keys are not set.
     */
    private function toEntity(array $data) : ContentEntityInterface {
        if (empty($data['_meta']['entity_type'])) {
            throw new ImportException('The entity type metadata must be specified.');
        }
        if (empty($data['_meta']['uuid'])) {
            throw new ImportException('The uuid metadata must be specified.');
        }
        $is_root = FALSE;
        // @see ::loadEntityDependency()
        if ($this->dependencies === NULL && !empty($data['_meta']['depends'])) {
            $is_root = TRUE;
            foreach ($data['_meta']['depends'] as $uuid => $entity_type) {
                assert(is_string($uuid));
                assert(is_string($entity_type));
                $this->dependencies[$uuid] = [
                    $entity_type,
                    $uuid,
                ];
            }
        }
        [
            'entity_type' => $entity_type,
        ] = $data['_meta'];
        assert(is_string($entity_type));
        
        /** @var \Drupal\Core\Entity\EntityTypeInterface $entity_type */
        $entity_type = $this->entityTypeManager
            ->getDefinition($entity_type);
        $values = [
            'uuid' => $data['_meta']['uuid'],
        ];
        if (!empty($data['_meta']['bundle'])) {
            $values[$entity_type->getKey('bundle')] = $data['_meta']['bundle'];
        }
        if (!empty($data['_meta']['default_langcode'])) {
            $data = $this->verifyNormalizedLanguage($data);
            $values[$entity_type->getKey('langcode')] = $data['_meta']['default_langcode'];
        }
        
        /** @var \Drupal\Core\Entity\ContentEntityInterface $entity */
        $entity = $this->entityTypeManager
            ->getStorage($entity_type->id())
            ->create($values);
        foreach ($data['default'] as $field_name => $values) {
            $this->setFieldValues($entity, $field_name, $values);
        }
        foreach ($data['translations'] ?? [] as $langcode => $translation_data) {
            if ($this->languageManager
                ->getLanguage($langcode)) {
                $translation = $entity->addTranslation($langcode, $entity->toArray());
                foreach ($translation_data as $field_name => $values) {
                    $this->setFieldValues($translation, $field_name, $values);
                }
            }
        }
        if ($is_root) {
            $this->dependencies = NULL;
        }
        return $entity;
    }
    
    /**
     * Sets field values based on the normalized data.
     *
     * @param \Drupal\Core\Entity\ContentEntityInterface $entity
     *   The content entity.
     * @param string $field_name
     *   The name of the field.
     * @param array $values
     *   The normalized data for the field.
     */
    private function setFieldValues(ContentEntityInterface $entity, string $field_name, array $values) : void {
        foreach ($values as $delta => $item_value) {
            if (!$entity->get($field_name)
                ->get($delta)) {
                $entity->get($field_name)
                    ->appendItem();
            }
            
            /** @var \Drupal\Core\Field\FieldItemInterface $item */
            $item = $entity->get($field_name)
                ->get($delta);
            // Update the URI based on the target UUID for link fields.
            if (isset($item_value['target_uuid']) && $item instanceof LinkItem) {
                $target_entity = $this->loadEntityDependency($item_value['target_uuid']);
                if ($target_entity) {
                    $item_value['uri'] = 'entity:' . $target_entity->getEntityTypeId() . '/' . $target_entity->id();
                }
                unset($item_value['target_uuid']);
            }
            $serialized_property_names = $this->getCustomSerializedPropertyNames($item);
            foreach ($item_value as $property_name => $value) {
                if (\in_array($property_name, $serialized_property_names)) {
                    if (\is_string($value)) {
                        throw new ImportException("Received string for serialized property {$field_name}.{$delta}.{$property_name}");
                    }
                    $value = serialize($value);
                }
                $property = $item->get($property_name);
                if ($property instanceof EntityReference) {
                    if (is_array($value)) {
                        $value = $this->toEntity($value);
                    }
                    else {
                        $value = $this->loadEntityDependency($value);
                    }
                }
                $property->setValue($value);
            }
        }
    }
    
    /**
     * Gets the names of all properties the plugin treats as serialized data.
     *
     * This allows the field storage definition or entity type to provide a
     * setting for serialized properties. This can be used for fields that
     * handle serialized data themselves and do not rely on the serialized schema
     * flag.
     *
     * @param \Drupal\Core\Field\FieldItemInterface $field_item
     *   The field item.
     *
     * @return string[]
     *   The property names for serialized properties.
     *
     * @see \Drupal\serialization\Normalizer\SerializedColumnNormalizerTrait::getCustomSerializedPropertyNames
     */
    private function getCustomSerializedPropertyNames(FieldItemInterface $field_item) : array {
        if ($field_item instanceof PluginInspectionInterface) {
            $definition = $field_item->getPluginDefinition();
            $serialized_fields = $field_item->getEntity()
                ->getEntityType()
                ->get('serialized_field_property_names');
            $field_name = $field_item->getFieldDefinition()
                ->getName();
            if (is_array($serialized_fields) && isset($serialized_fields[$field_name]) && is_array($serialized_fields[$field_name])) {
                return $serialized_fields[$field_name];
            }
            if (isset($definition['serialized_property_names']) && is_array($definition['serialized_property_names'])) {
                return $definition['serialized_property_names'];
            }
        }
        return [];
    }
    
    /**
     * Loads the entity dependency by its UUID.
     *
     * @param string $target_uuid
     *   The entity UUID.
     *
     * @return \Drupal\Core\Entity\ContentEntityInterface|null
     *   The loaded entity.
     */
    private function loadEntityDependency(string $target_uuid) : ?ContentEntityInterface {
        if ($this->dependencies && array_key_exists($target_uuid, $this->dependencies)) {
            $entity = $this->entityRepository
                ->loadEntityByUuid(...$this->dependencies[$target_uuid]);
            assert($entity instanceof ContentEntityInterface || $entity === NULL);
            return $entity;
        }
        return NULL;
    }
    
    /**
     * Verifies that the site knows the default language of the normalized entity.
     *
     * Will attempt to switch to an alternative translation or just import it
     * with the site default language.
     *
     * @param array $data
     *   The normalized entity data.
     *
     * @return array
     *   The normalized entity data, possibly with altered default language
     *   and translations.
     */
    private function verifyNormalizedLanguage(array $data) : array {
        $default_langcode = $data['_meta']['default_langcode'];
        $default_language = $this->languageManager
            ->getDefaultLanguage();
        // Check the language. If the default language isn't known, import as one
        // of the available translations if one exists with those values. If none
        // exists, create the entity in the default language.
        // During the installer, when installing with an alternative language,
        // `en` is still the default when modules are installed so check the default language
        // instead.
        if (!$this->languageManager
            ->getLanguage($default_langcode) || InstallerKernel::installationAttempted() && $default_language->getId() !== $default_langcode) {
            $use_default = TRUE;
            foreach ($data['translations'] ?? [] as $langcode => $translation_data) {
                if ($this->languageManager
                    ->getLanguage($langcode)) {
                    $data['_meta']['default_langcode'] = $langcode;
                    $data['default'] = \array_merge($data['default'], $translation_data);
                    unset($data['translations'][$langcode]);
                    $use_default = FALSE;
                    break;
                }
            }
            if ($use_default) {
                $data['_meta']['default_langcode'] = $default_language->getId();
            }
        }
        return $data;
    }

}