class ConfigEntityStorage

class ConfigEntityStorage extends EntityStorageBase implements ConfigEntityStorageInterface, ImportableEntityStorageInterface {
  
  /**
   * Length limit of the configuration entity ID.
   *
   * Most file systems limit a file name's length to 255 characters, so
   * ConfigBase::MAX_NAME_LENGTH restricts the full configuration object name
   * to 250 characters (leaving 5 for the file extension). The config prefix
   * is limited by ConfigEntityType::PREFIX_LENGTH to 83 characters, so this
   * leaves 166 remaining characters for the configuration entity ID, with 1
   * additional character needed for the joining dot.
   *
   * @see \Drupal\Core\Config\ConfigBase::MAX_NAME_LENGTH
   * @see \Drupal\Core\Config\Entity\ConfigEntityType::PREFIX_LENGTH
   */
  const MAX_ID_LENGTH = 166;
  
  /**
   * {@inheritdoc}
   */
  protected $uuidKey = 'uuid';
  
  /**
   * The config factory service.
   *
   * @var \Drupal\Core\Config\ConfigFactoryInterface
   */
  protected $configFactory;
  
  /**
   * The config storage service.
   *
   * @var \Drupal\Core\Config\StorageInterface
   */
  protected $configStorage;
  
  /**
   * The language manager.
   *
   * @var \Drupal\Core\Language\LanguageManagerInterface
   */
  protected $languageManager;
  
  /**
   * Determines if the underlying configuration is retrieved override free.
   *
   * @var bool
   */
  protected $overrideFree = FALSE;
  
  /**
   * Constructs a ConfigEntityStorage object.
   *
   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
   *   The entity type definition.
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The config factory service.
   * @param \Drupal\Component\Uuid\UuidInterface $uuid_service
   *   The UUID service.
   * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
   *   The language manager.
   * @param \Drupal\Core\Cache\MemoryCache\MemoryCacheInterface $memory_cache
   *   The memory cache backend.
   */
  public function __construct(EntityTypeInterface $entity_type, ConfigFactoryInterface $config_factory, UuidInterface $uuid_service, LanguageManagerInterface $language_manager, MemoryCacheInterface $memory_cache) {
    parent::__construct($entity_type, $memory_cache);
    $this->configFactory = $config_factory;
    $this->uuidService = $uuid_service;
    $this->languageManager = $language_manager;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
    return new static($entity_type, $container->get('config.factory'), $container->get('uuid'), $container->get('language_manager'), $container->get('entity.memory_cache'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function loadRevision($revision_id) {
    return NULL;
  }
  
  /**
   * {@inheritdoc}
   */
  public function deleteRevision($revision_id) {
    return NULL;
  }
  
  /**
   * Returns the prefix used to create the configuration name.
   *
   * The prefix consists of the config prefix from the entity type plus a dot
   * for separating from the ID.
   *
   * @return string
   *   The full configuration prefix, for example 'views.view.'.
   */
  protected function getPrefix() {
    return $this->entityType
      ->getConfigPrefix() . '.';
  }
  
  /**
   * {@inheritdoc}
   */
  public static function getIDFromConfigName($config_name, $config_prefix) {
    return substr($config_name, strlen($config_prefix . '.'));
  }
  
  /**
   * {@inheritdoc}
   */
  protected function doLoadMultiple(array $ids = NULL) {
    $prefix = $this->getPrefix();
    // Get the names of the configuration entities we are going to load.
    if ($ids === NULL) {
      $names = $this->configFactory
        ->listAll($prefix);
    }
    else {
      $names = [];
      foreach ($ids as $id) {
        // Add the prefix to the ID to serve as the configuration object name.
        $names[] = $prefix . $id;
      }
    }
    // Load all of the configuration entities.
    /** @var \Drupal\Core\Config\Config[] $configs */
    $configs = [];
    $records = [];
    foreach ($this->configFactory
      ->loadMultiple($names) as $config) {
      $id = $config->get($this->idKey);
      $records[$id] = $this->overrideFree ? $config->getOriginal(NULL, FALSE) : $config->get();
      $configs[$id] = $config;
    }
    $entities = $this->mapFromStorageRecords($records);
    // Config entities wrap config objects, and therefore they need to inherit
    // the cacheability metadata of config objects (to ensure e.g. additional
    // cacheability metadata added by config overrides is not lost).
    foreach ($entities as $id => $entity) {
      // But rather than simply inheriting all cacheability metadata of config
      // objects, we need to make sure the self-referring cache tag that is
      // present on Config objects is not added to the Config entity. It must be
      // removed for 3 reasons:
      // 1. When renaming/duplicating a Config entity, the cache tag of the
      //    original config object would remain present, which would be wrong.
      // 2. Some Config entities choose to not use the cache tag that the under-
      //    lying Config object provides by default (For performance and
      //    cacheability reasons it may not make sense to have a unique cache
      //    tag for every Config entity. The DateFormat Config entity specifies
      //    the 'rendered' cache tag for example, because A) date formats are
      //    changed extremely rarely, so invalidating all render cache items is
      //    fine, B) it means fewer cache tags per page.).
      // 3. Fewer cache tags is better for performance.
      $self_referring_cache_tag = [
        'config:' . $configs[$id]->getName(),
      ];
      $config_cacheability = CacheableMetadata::createFromObject($configs[$id]);
      $config_cacheability->setCacheTags(array_diff($config_cacheability->getCacheTags(), $self_referring_cache_tag));
      $entity->addCacheableDependency($config_cacheability);
    }
    return $entities;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function doCreate(array $values) {
    // Set default language to current language if not provided.
    $values += [
      $this->langcodeKey => $this->languageManager
        ->getCurrentLanguage()
        ->getId(),
    ];
    $entity_class = $this->getEntityClass();
    $entity = new $entity_class($values, $this->entityTypeId);
    return $entity;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function doDelete($entities) {
    foreach ($entities as $entity) {
      $this->configFactory
        ->getEditable($this->getPrefix() . $entity->id())
        ->delete();
    }
  }
  
  /**
   * Implements Drupal\Core\Entity\EntityStorageInterface::save().
   *
   * @throws \Drupal\Core\Entity\EntityMalformedException
   *   When attempting to save a configuration entity that has no ID.
   */
  public function save(EntityInterface $entity) {
    // Configuration entity IDs are strings, and '0' is a valid ID.
    $id = $entity->id();
    if ($id === NULL || $id === '') {
      throw new EntityMalformedException('The entity does not have an ID.');
    }
    // Check the configuration entity ID length.
    // @see \Drupal\Core\Config\Entity\ConfigEntityStorage::MAX_ID_LENGTH
    // @todo Consider moving this to a protected method on the parent class, and
    //   abstracting it for all entity types.
    if (strlen($id) > static::MAX_ID_LENGTH) {
      throw new ConfigEntityIdLengthException("Configuration entity ID {$id} exceeds maximum allowed length of " . static::MAX_ID_LENGTH . " characters.");
    }
    return parent::save($entity);
  }
  
  /**
   * {@inheritdoc}
   */
  protected function doSave($id, EntityInterface $entity) {
    $is_new = $entity->isNew();
    $prefix = $this->getPrefix();
    $config_name = $prefix . $entity->id();
    if ($id !== $entity->id()) {
      // Renaming a config object needs to cater for:
      // - Storage needs to access the original object.
      // - The object needs to be renamed/copied in ConfigFactory and reloaded.
      // - All instances of the object need to be renamed.
      $this->configFactory
        ->rename($prefix . $id, $config_name);
    }
    $config = $this->configFactory
      ->getEditable($config_name);
    // Retrieve the desired properties and set them in config.
    $config->setData($this->mapToStorageRecord($entity));
    $config->save($entity->hasTrustedData());
    // Update the entity with the values stored in configuration. It is possible
    // that configuration schema has casted some of the values.
    if (!$entity->hasTrustedData()) {
      $data = $this->mapFromStorageRecords([
        $config->get(),
      ]);
      $updated_entity = current($data);
      foreach (array_keys($config->get()) as $property) {
        $value = $updated_entity->get($property);
        $entity->set($property, $value);
      }
    }
    return $is_new ? SAVED_NEW : SAVED_UPDATED;
  }
  
  /**
   * Maps from an entity object to the storage record.
   *
   * @param \Drupal\Core\Entity\EntityInterface $entity
   *   The entity object.
   *
   * @return array
   *   The record to store.
   */
  protected function mapToStorageRecord(EntityInterface $entity) {
    return $entity->toArray();
  }
  
  /**
   * {@inheritdoc}
   */
  protected function has($id, EntityInterface $entity) {
    $prefix = $this->getPrefix();
    $config = $this->configFactory
      ->get($prefix . $id);
    return !$config->isNew();
  }
  
  /**
   * {@inheritdoc}
   */
  public function hasData() {
    return (bool) $this->configFactory
      ->listAll($this->getPrefix());
  }
  
  /**
   * {@inheritdoc}
   */
  protected function buildCacheId($id) {
    return parent::buildCacheId($id) . ':' . ($this->overrideFree ? '' : implode(':', $this->configFactory
      ->getCacheKeys()));
  }
  
  /**
   * Invokes a hook on behalf of the entity.
   *
   * @param $hook
   *   One of 'presave', 'insert', 'update', 'predelete', or 'delete'.
   * @param $entity
   *   The entity object.
   */
  protected function invokeHook($hook, EntityInterface $entity) {
    // Invoke the hook.
    $this->moduleHandler
      ->invokeAll($this->entityTypeId . '_' . $hook, [
      $entity,
    ]);
    // Invoke the respective entity-level hook.
    $this->moduleHandler
      ->invokeAll('entity_' . $hook, [
      $entity,
      $this->entityTypeId,
    ]);
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getQueryServiceName() {
    return 'entity.query.config';
  }
  
  /**
   * {@inheritdoc}
   */
  public function importCreate($name, Config $new_config, Config $old_config) {
    $entity = $this->_doCreateFromStorageRecord($new_config->get(), TRUE);
    $entity->save();
    return TRUE;
  }
  
  /**
   * {@inheritdoc}
   */
  public function importUpdate($name, Config $new_config, Config $old_config) {
    $id = static::getIDFromConfigName($name, $this->entityType
      ->getConfigPrefix());
    $entity = $this->load($id);
    if (!$entity) {
      throw new ConfigImporterException("Attempt to update non-existing entity '{$id}'.");
    }
    $entity->setSyncing(TRUE);
    $entity = $this->updateFromStorageRecord($entity, $new_config->get());
    $entity->save();
    return TRUE;
  }
  
  /**
   * {@inheritdoc}
   */
  public function importDelete($name, Config $new_config, Config $old_config) {
    $id = static::getIDFromConfigName($name, $this->entityType
      ->getConfigPrefix());
    $entity = $this->load($id);
    $entity->setSyncing(TRUE);
    $entity->delete();
    return TRUE;
  }
  
  /**
   * {@inheritdoc}
   */
  public function importRename($old_name, Config $new_config, Config $old_config) {
    return $this->importUpdate($old_name, $new_config, $old_config);
  }
  
  /**
   * {@inheritdoc}
   */
  public function createFromStorageRecord(array $values) {
    return $this->_doCreateFromStorageRecord($values);
  }
  
  /**
   * Helps create a configuration entity from storage values.
   *
   * Allows the configuration entity storage to massage storage values before
   * creating an entity.
   *
   * @param array $values
   *   The array of values from the configuration storage.
   * @param bool $is_syncing
   *   Is the configuration entity being created as part of a config sync.
   *
   * @return \Drupal\Core\Config\ConfigEntityInterface
   *   The configuration entity.
   *
   * @see \Drupal\Core\Config\Entity\ConfigEntityStorageInterface::createFromStorageRecord()
   * @see \Drupal\Core\Config\Entity\ImportableEntityStorageInterface::importCreate()
   */
  protected function _doCreateFromStorageRecord(array $values, $is_syncing = FALSE) {
    // Assign a new UUID if there is none yet.
    if ($this->uuidKey && $this->uuidService && !isset($values[$this->uuidKey])) {
      $values[$this->uuidKey] = $this->uuidService
        ->generate();
    }
    $data = $this->mapFromStorageRecords([
      $values,
    ]);
    $entity = current($data);
    $entity->original = clone $entity;
    $entity->setSyncing($is_syncing);
    $entity->enforceIsNew();
    $entity->postCreate($this);
    // Modules might need to add or change the data initially held by the new
    // entity object, for instance to fill-in default values.
    $this->invokeHook('create', $entity);
    return $entity;
  }
  
  /**
   * {@inheritdoc}
   */
  public function updateFromStorageRecord(ConfigEntityInterface $entity, array $values) {
    $entity->original = clone $entity;
    $data = $this->mapFromStorageRecords([
      $values,
    ]);
    $updated_entity = current($data);
    /** @var \Drupal\Core\Config\Entity\ConfigEntityTypeInterface $entity_type */
    $entity_type = $this->getEntityType();
    $id_key = $entity_type->getKey('id');
    $properties = $entity_type->getPropertiesToExport($updated_entity->get($id_key));
    if (empty($properties)) {
      // Fallback to using the provided values. If the properties cannot be
      // determined for the config entity type annotation or configuration
      // schema.
      $properties = array_keys($values);
    }
    foreach ($properties as $property) {
      if ($property === $this->uuidKey) {
        // During an update the UUID field should not be copied. Under regular
        // circumstances the values will be equal. If configuration is written
        // twice during configuration install the updated entity will not have a
        // UUID.
        // @see \Drupal\Core\Config\ConfigInstaller::createConfiguration()
        continue;
      }
      $entity->set($property, $updated_entity->get($property));
    }
    return $entity;
  }
  
  /**
   * {@inheritdoc}
   */
  public function loadOverrideFree($id) {
    $entities = $this->loadMultipleOverrideFree([
      $id,
    ]);
    return $entities[$id] ?? NULL;
  }
  
  /**
   * {@inheritdoc}
   */
  public function loadMultipleOverrideFree(array $ids = NULL) {
    $this->overrideFree = TRUE;
    $entities = $this->loadMultiple($ids);
    $this->overrideFree = FALSE;
    return $entities;
  }

}