[Taler] Taler wallet charge terminal

[Florian Jung]

Hi,

I want to build a wallet recharge terminal, i.e. a machine that eats 
real money banknotes and gives you Taler; for this project, I have a 
couple of questions:

Does previous work on this exist already? I know about the Taler snack 
vending machine, but IIUC, this is the opposite direction (eats taler, 
gives food). How are people charging their wallet in this setup?

What bank- or nonbank/nexus setup would be appropriate for such a 
terminal? Does it make sense to use a libeufin demobank setup where, for 
every real euro fed into the machine, the "central bank" wires a 
currency unit to the exchange's demobank account? Or would it be more 
appropriate to have a "banknote acceptor backend" for the nexus, and 
skip the demobank completely?

I'm gonna run this with a local currency, but am looking forward to 
Taler being offered by a real bank someday; in such a future, I would my 
merchants (all under my control) to support payments both in local 
currency *and* in euro-taler. I've seen that the contracts v1 protocol 
supports "alternative contracts".

Do I correctly assume that this would allow for "pay in euro only" and 
"pay in local currency only", but not (easily) allow the user to freely 
choose the ratio between EUR and LC (i.e. pay 81% by LC but the 
remaining 19% with euro)? (Though I could offer them a lot of such 
alternatives, so they could at least choose in steps of 10cent or something)

Also, what is the current state of NFC support in taler? Can I already 
use NFC for buying and charging my wallet? What specs would a NFC reader 
need to fulfil for that?

Thank you and cheers,

Florian