public function describeRate($maxRequests, $timeWindow)
    {
        if ($maxRequests && $timeWindow) {
            list($value, $unit) = $this->splitTimeWindow($timeWindow);
            switch ($unit) {
                case 60:
                    $duration = Unit::format($value, 'duration/minute', 'long');
                    break;
                case 3600:
                    $duration = Unit::format($value, 'duration/hour', 'long');
                    break;
                case 86400:
                    $duration = Unit::format($value, 'duration/day', 'long');
                    break;
                case 604800:
                    $duration = Unit::format($value, 'duration/week', 'long');
                    break;
                default:
                    $duration = Unit::format($timeWindow, 'duration/second', 'long');
                    break;
            }
            $result = t2('%1$d request every %2$s', '%1$d requests every %2$s', $maxRequests, $duration);
        } else {
            $result = '';
        }

        return $result;
    }