class ConfigEvents

final class ConfigEvents {
    
    /**
     * Name of the event fired when saving a configuration object.
     *
     * This event allows modules to perform an action whenever a configuration
     * object is saved. The event listener method receives a
     * \Drupal\Core\Config\ConfigCrudEvent instance.
     *
     * See hook_update_N() documentation for safe configuration API usage and
     * restrictions as this event will be fired when configuration is saved by
     * hook_update_N().
     *
     * @Event
     *
     * @see \Drupal\Core\Config\ConfigCrudEvent
     * @see \Drupal\Core\Config\Config::save()
     * @see \Drupal\Core\Config\ConfigFactory::onConfigSave()
     * @see hook_update_N()
     *
     * @var string
     */
    const SAVE = 'config.save';
    
    /**
     * Name of the event fired when deleting a configuration object.
     *
     * This event allows modules to perform an action whenever a configuration
     * object is deleted. The event listener method receives a
     * \Drupal\Core\Config\ConfigCrudEvent instance.
     *
     * See hook_update_N() documentation for safe configuration API usage and
     * restrictions as this event will be fired when configuration is deleted by
     * hook_update_N().
     *
     * @Event
     *
     * @see \Drupal\Core\Config\ConfigCrudEvent
     * @see \Drupal\Core\Config\Config::delete()
     * @see \Drupal\Core\Config\ConfigFactory::onConfigDelete()
     * @see hook_update_N()
     *
     * @var string
     */
    const DELETE = 'config.delete';
    
    /**
     * Name of the event fired when renaming a configuration object.
     *
     * This event allows modules to perform an action whenever a configuration
     * object's name is changed. The event listener method receives a
     * \Drupal\Core\Config\ConfigRenameEvent instance.
     *
     * See hook_update_N() documentation for safe configuration API usage and
     * restrictions as this event will be fired when configuration is renamed by
     * hook_update_N().
     *
     * @Event
     *
     * @see \Drupal\Core\Config\ConfigRenameEvent
     * @see \Drupal\Core\Config\ConfigFactoryInterface::rename()
     * @see hook_update_N()
     *
     * @var string
     */
    const RENAME = 'config.rename';
    
    /**
     * Name of the event fired when validating imported configuration.
     *
     * This event allows modules to perform additional validation operations when
     * configuration is being imported. The event listener method receives a
     * \Drupal\Core\Config\ConfigImporterEvent instance.
     *
     * @Event
     *
     * @see \Drupal\Core\Config\ConfigImporterEvent
     * @see \Drupal\Core\Config\ConfigImporter::validate().
     * @see \Drupal\Core\EventSubscriber\ConfigImportSubscriber::onConfigImporterValidate().
     *
     * @var string
     */
    const IMPORT_VALIDATE = 'config.importer.validate';
    
    /**
     * Name of the event fired when importing configuration to target storage.
     *
     * This event allows modules to perform additional actions when configuration
     * is imported. The event listener method receives a
     * \Drupal\Core\Config\ConfigImporterEvent instance.
     *
     * @Event
     *
     * @see \Drupal\Core\Config\ConfigImporterEvent
     * @see \Drupal\Core\Config\ConfigImporter::import().
     * @see \Drupal\Core\EventSubscriber\ConfigSnapshotSubscriber::onConfigImporterImport().
     *
     * @var string
     */
    const IMPORT = 'config.importer.import';
    
    /**
     * Name of event fired when missing content dependencies are detected.
     *
     * Events subscribers are fired as part of the configuration import batch.
     * Each subscribe should call
     * \Drupal\Core\Config\MissingContentEvent::resolveMissingContent() when they
     * address a missing dependency. To address large amounts of dependencies
     * subscribers can call
     * \Drupal\Core\Config\MissingContentEvent::stopPropagation() which will stop
     * calling other events and guarantee that the configuration import batch will
     * fire the event again to continue processing missing content dependencies.
     *
     * @see \Drupal\Core\Config\ConfigImporter::processMissingContent()
     * @see \Drupal\Core\Config\Importer\MissingContentEvent
     */
    const IMPORT_MISSING_CONTENT = 'config.importer.missing_content';
    
    /**
     * Name of the event fired just before importing configuration.
     *
     * This event allows subscribers to modify the configuration which is about to
     * be imported. The event listener method receives a
     * \Drupal\Core\Config\StorageTransformEvent instance. This event contains a
     * config storage which subscribers can interact with and which will finally
     * be used to import the configuration from.
     * Together with \Drupal\Core\Config\ConfigEvents::STORAGE_TRANSFORM_EXPORT
     * subscribers can alter the active configuration in a config sync workflow
     * instead of just overriding at runtime via the config-override system.
     * This allows a complete customization of the workflow including additional
     * modules and editable configuration in different environments.
     *
     * @code
     *   $storage = $event->getStorage();
     * @endcode
     *
     * This event is also fired when just viewing the difference of configuration
     * to be imported independently of whether the import takes place or not.
     * Use the \Drupal\Core\Config\ConfigEvents::IMPORT event to subscribe to the
     * import having taken place.
     *
     * @Event
     *
     * @see \Drupal\Core\Config\StorageTransformEvent
     * @see \Drupal\Core\Config\ConfigEvents::STORAGE_TRANSFORM_EXPORT
     * @see \Drupal\Core\Config\ImportStorageTransformer::transform
     *
     * @var string
     */
    const STORAGE_TRANSFORM_IMPORT = 'config.transform.import';
    
    /**
     * Name of the event fired when the export storage is used.
     *
     * This event allows subscribers to modify the configuration which is about to
     * be exported. The event listener method receives a
     * \Drupal\Core\Config\StorageTransformEvent instance. This event contains a
     * config storage which subscribers can interact with and which will finally
     * be used to export the configuration from.
     *
     * @code
     *   $storage = $event->getStorage();
     * @endcode
     *
     * Typically subscribers will want to perform the reverse operation on the
     * storage than for \Drupal\Core\Config\ConfigEvents::STORAGE_TRANSFORM_IMPORT
     * to make sure successive exports and imports yield no difference.
     *
     * @Event
     *
     * @see \Drupal\Core\Config\StorageTransformEvent
     * @see \Drupal\Core\Config\ConfigEvents::STORAGE_TRANSFORM_IMPORT
     * @see \Drupal\Core\Config\ExportStorageManager::getStorage
     *
     * @var string
     */
    const STORAGE_TRANSFORM_EXPORT = 'config.transform.export';

}