protected function setFirstAndLastClick(Pap_Common_Transaction $transaction, Pap_Tracking_Common_VisitorAffiliateCollection $collection) {
        if ($collection->getSize() == 0) {
            throw new Gpf_Exception('VisitorAffiliates for this visitor are empty');
        }
        
        $firstVisitorAffiliate = $collection->get(0);
        $transaction->setFirstClickTime($firstVisitorAffiliate->getDateVisit());
        $transaction->setFirstClickReferer($firstVisitorAffiliate->getReferrerUrl());
        $transaction->setFirstClickIp($firstVisitorAffiliate->getIp());
        $transaction->setFirstClickData1($firstVisitorAffiliate->getData1());
        $transaction->setFirstClickData2($firstVisitorAffiliate->getData2());

        $lastVisitorAffiliate = $collection->get($collection->getSize()-1);
        $transaction->setLastClickTime($lastVisitorAffiliate->getDateVisit());
        $transaction->setLastClickReferer($lastVisitorAffiliate->getReferrerUrl());
        $transaction->setLastClickIp($lastVisitorAffiliate->getIp());
        $transaction->setLastClickData1($lastVisitorAffiliate->getData1());
        $transaction->setLastClickData2($lastVisitorAffiliate->getData2());
    }