ImportOneCPackage::onBeforeBasketModify

protected function onBeforeBasketModify(ExchangeEntityOrderImport $orderImport, $items)
    {
        $basketItems = array();

        /** @var Order $order */
        $order = $orderImport->getEntity();
        if(empty($order))
            throw new ArgumentNullException('Order');

        $basket = $order->getBasket();

        foreach($items as $item)
        {
            switch($item->getOwnerTypeId())
            {
                case static::getParentEntityTypeId():
                    $params = $item->getFieldValues();
                    $basketItems = $params['ITEMS'];
                    break;
            }
        }

        $basketItemsIndex = $orderImport->calculateDeltaQuantity($basket, $basketItems);

        $result = $orderImport->synchronizeQuantityBasketItems($basketItemsIndex);

        return $result;
    }