Hand the person the buy link

Every offer carries a buy link, buyUrl, and so does each of its options. The buy link opens this offer in the person's cart and takes them to Groupon's checkout.

When the person has chosen an offer, give them the buyUrl of the option they chose, unchanged. That is the whole hand-off: no shopping session, no token and no cart call. They review the option, quantity and final total on Groupon's checkout and pay there.

• A search result's buyUrl is for the offer's cheapest option. Read the offer (GET /ls_offers/agent_offers/{permalink}) to get each option's own link.
• buyUrl is null when the offer cannot be bought now. Report its unavailableReason; give no link.
• offerUrl is the offer's page, for a person who wants to read more. It is not the hand-off.
• A link is not a purchase confirmation. Never say the person has bought or reserved anything.

One buy link opens one option of one offer in the cart. For several items, another quantity, or to change or remove something before paying, use a shopping session, described next.