interface EntityStorageInterface

interface EntityStorageInterface {
    
    /**
     * Load the most recent version of an entity's field data.
     */
    const FIELD_LOAD_CURRENT = 'FIELD_LOAD_CURRENT';
    
    /**
     * Load the version of an entity's field data specified in the entity.
     */
    const FIELD_LOAD_REVISION = 'FIELD_LOAD_REVISION';
    
    /**
     * Resets the internal entity cache.
     *
     * @param $ids
     *   (optional) If specified, the cache is reset for the entities with the
     *   given ids only.
     */
    public function resetCache(?array $ids = NULL);
    
    /**
     * Loads one or more entities.
     *
     * @param $ids
     *   An array of entity IDs, or NULL to load all entities.
     *
     * @return \Drupal\Core\Entity\EntityInterface[]
     *   An array of entity objects indexed by their IDs. Returns an empty array
     *   if no matching entities are found.
     */
    public function loadMultiple(?array $ids = NULL);
    
    /**
     * Loads one entity.
     *
     * @param mixed $id
     *   The ID of the entity to load.
     *
     * @return \Drupal\Core\Entity\EntityInterface|null
     *   An entity object. NULL if no matching entity is found.
     */
    public function load($id);
    
    /**
     * Loads an unchanged entity from the database.
     *
     * @param mixed $id
     *   The ID of the entity to load.
     *
     * @return \Drupal\Core\Entity\EntityInterface|null
     *   The unchanged entity, or NULL if the entity cannot be loaded.
     *
     * @todo Remove this method once we have a reliable way to retrieve the
     *   unchanged entity from the entity object.
     */
    public function loadUnchanged($id);
    
    /**
     * Load entities by their property values without any access checks.
     *
     * @param array $values
     *   An associative array where the keys are the property names and the
     *   values are the values those properties must have. If a property takes
     *   multiple values, passing an array of values will produce an IN condition.
     *
     * @return \Drupal\Core\Entity\EntityInterface[]
     *   An array of entity objects indexed by their ids.
     */
    public function loadByProperties(array $values = []);
    
    /**
     * Constructs a new entity object, without permanently saving it.
     *
     * @param array $values
     *   (optional) An array of values to set, keyed by property name. If the
     *   entity type has bundles, the bundle key has to be specified.
     *
     * @return \Drupal\Core\Entity\EntityInterface
     *   A new entity object.
     */
    public function create(array $values = []);
    
    /**
     * Deletes permanently saved entities.
     *
     * @param array $entities
     *   An array of entity objects to delete.
     *
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   In case of failures, an exception is thrown.
     */
    public function delete(array $entities);
    
    /**
     * Saves the entity permanently.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity to save.
     *
     * @return int|null
     *   SAVED_NEW or SAVED_UPDATED is returned depending on the operation
     *   performed.
     *
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   In case of failures, an exception is thrown.
     */
    public function save(EntityInterface $entity);
    
    /**
     * Restores a previously saved entity.
     *
     * Note that the entity is assumed to be in a valid state for the storage, so
     * the restore process does not invoke any hooks, nor does it perform any pre
     * or post-save operations.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity to restore.
     *
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   In case of failures, an exception is thrown.
     *
     * @internal
     *   This method should never be used to perform a regular entity save. Its
     *   only use-case is to assist updating entity types when there are complex
     *   schema changes, for example, to make them revisionable. Note that
     *   overriding this method to fix data prior to restoring is a likely sign
     *   that the current data is corrupt.
     */
    public function restore(EntityInterface $entity);
    
    /**
     * Determines if the storage contains any data.
     *
     * @return bool
     *   TRUE if the storage contains data, FALSE if not.
     */
    public function hasData();
    
    /**
     * Gets an entity query instance.
     *
     * @param string $conjunction
     *   (optional) The logical operator for the query, either:
     *   - AND: all of the conditions on the query need to match.
     *   - OR: at least one of the conditions on the query need to match.
     *
     * @return \Drupal\Core\Entity\Query\QueryInterface
     *   The query instance.
     *
     * @see \Drupal\Core\Entity\EntityStorageBase::getQueryServiceName()
     */
    public function getQuery($conjunction = 'AND');
    
    /**
     * Gets an aggregated query instance.
     *
     * @param string $conjunction
     *   (optional) The logical operator for the query, either:
     *   - AND: all of the conditions on the query need to match.
     *   - OR: at least one of the conditions on the query need to match.
     *
     * @return \Drupal\Core\Entity\Query\QueryAggregateInterface
     *   The aggregated query object that can query the given entity type.
     *
     * @see \Drupal\Core\Entity\EntityStorageBase::getQueryServiceName()
     */
    public function getAggregateQuery($conjunction = 'AND');
    
    /**
     * Gets the entity type ID.
     *
     * @return string
     *   The entity type ID.
     */
    public function getEntityTypeId();
    
    /**
     * Gets the entity type definition.
     *
     * @return \Drupal\Core\Entity\EntityTypeInterface
     *   Entity type definition.
     */
    public function getEntityType();
    
    /**
     * Retrieves the class name used to create the entity.
     *
     * @param string|null $bundle
     *   (optional) A specific entity type bundle identifier. Can be omitted in
     *   the case of entity types without bundles, like User.
     *
     * @return string
     *   The entity class name.
     */
    public function getEntityClass(?string $bundle = NULL) : string;

}