Affiliate Help

I need help in connecting my sales with the appropriate affiliate. I do not use the back end of amember for much of anything (mostly because it is very hard to customize). I have a PayPal button that sends my users directly to PayPal while bypassing the amember sales page.

I have a plugin that generates an invoice and sends a unique ID to PayPal, PayPal returns this ID and everything works great...however I need to integrate an affiliate program and need help integrating this into my system. Here's the code that I call when a user clicks a purchase button.

Code:

function createInvoiceAction() {
        $invoice = Am_Di::getInstance()->invoiceRecord;
        $invoice->setUser(Am_Di::getInstance()->userTable->load($this->_getParam('user_id')));
        $product_id = Am_Di::getInstance()->db->selectCell("SELECT product_id FROM am_product WHERE description = ?",$this->_getParam('description'));
        $invoice->add(Am_Di::getInstance()->productTable->load($product_id));
        $invoice->paysys_id = "paypal";
        $invoice->calculate();
        $invoice->insert();
        echo $invoice->public_id;
    }

I'm assuming I need to call something like this:

Code:

$affiliate = Am_Di::getInstance()->affClickRecord;

and then add my invoice and the affiliate to this object but not sure what the commands would be.

Any help would be appreciated.

I received some help back from amember - here's what I have:

Code:

$user = $this->getDi()->userTable->load($this->_getParam('user_id'));
$split_aff_user = explode("-",$this->_getParam('aff_id')); //drop the extra off of the cookie
$affiliate_user = base64_decode($split_aff_user[0]); // decode the affiliate login
$aff_id = Am_Di::getInstance()->db->selectCell("SELECT user_id FROM am_user WHERE login = ?",$affiliate_user);
$user->aff_id = $aff_id;
$user->update();
$coupon = $this->getDi()->couponTable->findFirstByCode('152AB76C');
$coupon->validate($user);
$invoice = Am_Di::getInstance()->invoiceRecord;
$invoice->setUser($user);
$product_id = Am_Di::getInstance()->db->selectCell("SELECT product_id FROM am_product WHERE description = ?",$this->_getParam('description'));
$invoice->add(Am_Di::getInstance()->productTable->load($product_id));
$invoice->paysys_id = "paypal";
$invoice->aff_id = $aff_id;
$invoice->coupon_id = $coupon->coupon_id;
$invoice->calculate();
$invoice->insert();
echo $invoice->public_id;

I'm sure there is a cleaner way of doing this but it works.