class ConfigImporterBatch

class ConfigImporterBatch {
    
    /**
     * Processes the config import batch and persists the importer.
     *
     * @param \Drupal\Core\Config\ConfigImporter $config_importer
     *   The batch config importer object to persist.
     * @param string $sync_step
     *   The synchronization step to do.
     * @param array $context
     *   The batch context.
     */
    public static function process(ConfigImporter $config_importer, $sync_step, &$context) {
        if (!isset($context['sandbox']['config_importer'])) {
            $context['sandbox']['config_importer'] = $config_importer;
        }
        $config_importer = $context['sandbox']['config_importer'];
        $config_importer->doSyncStep($sync_step, $context);
        if ($errors = $config_importer->getErrors()) {
            if (!isset($context['results']['errors'])) {
                $context['results']['errors'] = [];
            }
            $context['results']['errors'] = array_merge($errors, $context['results']['errors']);
        }
    }
    
    /**
     * Finish batch.
     *
     * This function is a static function to avoid serializing the ConfigSync
     * object unnecessarily.
     *
     * @param bool $success
     *   Indicate that the batch API tasks were all completed successfully.
     * @param array $results
     *   An array of all the results that were updated in update_do_one().
     * @param array $operations
     *   A list of the operations that had not been completed by the batch API.
     */
    public static function finish($success, $results, $operations) {
        $messenger = \Drupal::messenger();
        if ($success) {
            if (!empty($results['errors'])) {
                $logger = \Drupal::logger('config_sync');
                foreach ($results['errors'] as $error) {
                    $messenger->addError($error);
                    $logger->error($error);
                }
                $messenger->addWarning(t('The configuration was imported with errors.'));
            }
            elseif (!InstallerKernel::installationAttempted()) {
                // Display a success message when not installing Drupal.
                $messenger->addStatus(t('The configuration was imported successfully.'));
            }
        }
        else {
            // An error occurred.
            // $operations contains the operations that remained unprocessed.
            $error_operation = reset($operations);
            $message = t('An error occurred while processing %error_operation with arguments: @arguments', [
                '%error_operation' => $error_operation[0],
                '@arguments' => print_r($error_operation[1], TRUE),
            ]);
            $messenger->addError($message);
        }
    }

}