private function formatSize($bytes)
    {
        $units = ['B', 'KB', 'MB', 'GB', 'TB'];

        $bytes = max($bytes, 0);
        $pow = $bytes ? floor(log($bytes, 1024)) : 0;
        $pow = min($pow, count($units) - 1);

        $bytes /= pow(1024, $pow);

        return number_format($bytes, 2).' '.$units[$pow];
    }