aMember (site.php): Limit usage of coupon by IP address

site.php

<?php

Am_Di::getInstance()->hook->add(Am_Event::VALIDATE_COUPON, function(Am_Event $e) {
    $batch = $e->getCouponBatch();
    $coupon = $e->getCoupon();

    $used = $e->getDi()->invoiceTable->countBy([
        'coupon_id' => $coupon->pk(),
        'remote_addr' => $_SERVER['REMOTE_ADDR']
    ]);
    if ($used >= $batch->user_use_count) {
        $e->addReturn(___('Coupon usage limit exceeded'));
    }
});