================================= Merchant Reference Implementation ================================= ----------------------- Architectural Overview ----------------------- The merchant reference implementationis divided into two independent compontents, the `frontend` and the `backend`. The `frontend` is the existing shopping portal of the merchant. The architecture tries to minimize the amount of modifications necessary to the `frontend` as well as the trust that needs to be placed into the `frontend` logic. Taler requires the frontend to facilitate two JSON-based interactions between the wallet and the `backend`, and one of those is trivial. The `backend` is a standalone C application intended to implement all the cryptographic routines required to interact with the Taler wallet and a Taler mint. ------------------------------ The Merchant Backend HTTP API ------------------------------ The following API are made available by the merchant's `backend` to the merchant's `frontend`. .. http:post:: /contract Ask the backend to add some missing (mostly related to cryptography) information to the contract. :reqheader Content-Type: application/json The `proposition` that is to be sent from the frontend is a `contract` object without the fields * `merchant_pub` * `mints` * `H_wire` The `backend` then completes this information based on its configuration. **Success Response** :status 200 OK: The backend has successfully created the contract. :resheader Content-Type: application/json The `frontend` should pass this response verbatim to the wallet. **Failure Responses: Bad contract** :status 400 Bad Request: Request not understood. The JSON was invalid. Possibly due to some error in formatting the JSON by the `frontend`. .. http:post:: /pay Asks the `backend` to execute the transaction with the mint and deposit the coins. :reqheader Content-Type: application/json The `frontend` passes the :ref:`deposit permission ` received from the wallet, by adding the fields `max_fee`, `amount` (see :ref:`contract`) and optionally adding a field named `edate`, indicating a deadline by which he would expect to receive the bank transfer for this deal **Success Response: OK** :status 200 OK: The mint accepted all of the coins. The `frontend` should now fullfill the contract. This response has no meaningful body, the frontend needs to generate the fullfillment page. **Failure Responses: Bad mint** :status 400 Precondition failed: The given mint is not acceptable for this merchant, as it is not in the list of accepted mints and not audited by an approved auditor. **Failure Responses: Mint trouble** The `backend` will return verbatim the error codes received from the mint's :ref:`deposit ` API. If the wallet made a mistake, like by double-spending for example, the `frontend` should pass the reply verbatim to the browser/wallet. This should be the expected case, as the `frontend` cannot really make mistakes; the only reasonable exception is if the `backend` is unavailable, in which case the customer might appreciate some reassurance that the merchant is working on getting his systems back online.