public function execute()
 {
     $cart = new shopCart();
     $item_id = waRequest::post('id');
     $cart_items_model = new shopCartItemsModel();
     $item = $cart_items_model->getById($item_id);
     $is_html = waRequest::request('html');
     if ($q = waRequest::post('quantity', 0, 'int')) {
         if (!wa()->getSetting('ignore_stock_count')) {
             if ($item['type'] == 'product') {
                 $product_model = new shopProductModel();
                 $p = $product_model->getById($item['product_id']);
                 $sku_model = new shopProductSkusModel();
                 $sku = $sku_model->getById($item['sku_id']);
                 // check quantity
                 if ($sku['count'] !== null && $q > $sku['count']) {
                     $q = $sku['count'];
                     $name = $p['name'] . ($sku['name'] ? ' (' . $sku['name'] . ')' : '');
                     $this->response['error'] = sprintf(_w('Only %d pcs of %s are available, and you already have all of them in your shopping cart.'), $q, $name);
                     $this->response['q'] = $q;
                 }
             }
         }
         $cart->setQuantity($item_id, $q);
         $this->response['item_total'] = $is_html ? shop_currency_html($cart->getItemTotal($item_id), true) : shop_currency($cart->getItemTotal($item_id), true);
     } elseif ($v = waRequest::post('service_variant_id')) {
         $cart->setServiceVariantId($item_id, $v);
         $this->response['item_total'] = $is_html ? shop_currency_html($cart->getItemTotal($item['parent_id']), true) : shop_currency($cart->getItemTotal($item['parent_id']), true);
     }
     $total = $cart->total();
     $discount = $cart->discount();
     $this->response['total'] = $is_html ? shop_currency_html($total, true) : shop_currency($total, true);
     $this->response['discount'] = $is_html ? shop_currency_html($discount, true) : shop_currency($discount, true);
     $this->response['discount_numeric'] = $discount;
     $this->response['count'] = $cart->count();
     if (shopAffiliate::isEnabled()) {
         $add_affiliate_bonus = shopAffiliate::calculateBonus(array('total' => $total, 'discount' => $discount, 'items' => $cart->items(false)));
         $this->response['add_affiliate_bonus'] = sprintf(_w("This order will add +%s points to your affiliate bonus."), round($add_affiliate_bonus, 2));
     }
 }