public function getPayURedirectUrl()
    {
        $mode = parent::$apiContext->get('mode');
        $reference = $this->return->payUReference;

        if (!$mode || !$reference)
            return null;

        $url = sprintf(self::REDIRECT_URL, $mode === 'sandbox' ? 'staging' : 'secure', $reference);

        return $url;
    }