Re: [Taler] replay and merchant backend/frontend protocol

[Florian Dold]

On second thought, it might be cleaner to have the extra information
that is only needed by the merchant frontent in the wrapper around the
contract (e.g. as a "frontend_data" field).  This extra field then
shouldn't ever be sent to the customer.

Implementation-wise it's almost the same though, the info is just
outside the contract and not inside.

- Florian

On 01/25/2016 11:15 PM, Florian Dold wrote:
> Hi!
> 
> if my understanding is correct, there is currently a deficit in the
> backend/frontend protocol.
> 
> The information we get from /backend/pay is not sufficient to restore
> the client's session state, since the response is empty on success.
> 
> For example in the donation shop demo, the missing information would be
> the payment amount and the payment receiver ("taler", "tor", "gnunet").
> 
> Of course there are other possibilities to get this information, but for
> our case it seems very convenient to just have the whole contract as a
> response to /backend/pay in the frontend.
> 
> For both our demos, the information that the frontend needs from the
> backend can be assembled from the contract (and if not, there should be
> an "extra" field in the contract for the merchant to store
> machine-readable, small pieces of information).
> 
> Now you could argue that always returning the full contract on
> /backend/pay is overhead, but consider that we're talking about loopback
> here in practice, and that it would make the implementation quite easy.
> 
> Thoughts?
> 
> Christian or Marcello:  Any volunteers to implement this in the backend,
> while I hack on the wallet and the shop frontend?
> 
> - Florian
>