public static function getSelection($skuMetaId, array $groupIds) {
        $comboset = API\ComboSet::getComboSetBySkuMetaId($skuMetaId);
        if ($comboset instanceof GenericError) {
            return $comboset;
        }

        $response = [];
        $response['instock'] = true;

        $groupmap = [];
        foreach ($groupIds as $groupId => $itemIds) {
            $combogroup = API\ComboGroup::getComboGroupById($groupId);
            $groupmap[$groupId]['group'] = $combogroup;
            if (empty($combogroup)) {
                $response['instock'] = false;
            } else {
                foreach ($itemIds as $itemId) {
                    $groupitem = API\GroupItem::getGroupItemById($itemId);
                    $groupmap[$groupId]['items'][$itemId] = $groupitem;
                    if (empty($groupitem)) {
                        $response['instock'] = false;
                    }
                }
            }
        }

        $response['groupmap'] = $groupmap;

        return $response;
    }