OrderRequestBuilder

class OrderRequestBuilder {
    private $siteId,$shippingMethodId;
    private $items = array();

    function __construct($orderOrSiteId) {
        if ( $orderOrSiteId instanceof Order ) {
            $this->siteId = $orderOrSiteId->getSite()->getId();
            $this->shippingMethodId =
                $orderOrSiteId->getShippingMethod()->getId();
            foreach ( $orderOrSiteId->getLines() as $line ) {
                $this->items[$line->getSaleableItem()->getId()] =
                    $line->getQuantity();
            }
        } else {
            $this->siteId = $orderOrSiteId;
        }
    }

    function setItem($saleableItemId, $quantity) {
        $this->items[$saleableItemId] = $quantity;
    }

    function setShippingMethod($shippingMethodId) {
        $this->shippingMethodId = $shippingMethodId;
    }

    function buildParams() {
        $items = array();
        foreach ( $this->items as $id => $qty ) {
            $items[] = sprintf('%d:%d', $id, $qty);
        }
        if ( ! $items ) {
            throw new OrderRequestBuilderException('No items');
        }
        if ( ! $this->shippingMethodId ) {
            throw new OrderRequestBuilderException('Shipping method undefined');
        }
        return array(
            'site' => $this->siteId,
            'method' => $this->shippingMethodId,
            'items' => implode(',', $items),
        );
    }

}