public function initCheckoutHooks() {
        $this->checkout = new Checkout($this);
        $this->checkout->init()->addHooks();

        usces_register_action(
            'wcexaapCompletePurchase',
            'get',
            'wcexaapCompletePurchase',
            null,
            function () {
                // route guards
                $routeGuards = new Routing\RedirectRouteGuards(
                    $this,
                    new Routing\RestRouteGuards($this)
                );
                $amazonRouteGuards = new Routing\AmazonRedirectRouteGuards($this);

                call_user_func($amazonRouteGuards->sessionIdExistsOrExit());
                call_user_func($routeGuards->cartNotEmptyOrExit());
                call_user_func($routeGuards->itemsInStockOrCartRedirect());
                $this->checkout->handleCheckoutResult();
            }
        );
    }