[Taler] Pointing taler-exchange to my libeufin nexus / sandbox setup

[Florian Jung]

Hey everyone,

By now, I have setup with libeufin-sandbox and libeufin-nexus. I have an 
ebics connection and have imported the sandboxed bank account to my nexus:

libeufin-cli connections import-bank-account --offered-account-id 
jrluser --nexus-bank-account-id myconn_jrluser myconn

taler and anastasis facades are set up (even though I don't understand 
what the latter is for. Can you explain?)

The nexus has a superuser (god / supersecret) and a normal user (myuser 
/ mypass).


What I now don't understand is how to proceed: How do I setup my 
exchange to use that bank account? In detail, what config options are 
required and how does the payto uri need to look like: Is

[exchange-account-1]
PAYTO_URI = "payto://iban/AB123456" # output of `libeufin cli accounts show`
WIRE_GATEWAY_URL = http://nexus-host:5017/ # same as LIBEUFIN_NEXUS_URL. 
Or do i need trailing paths?

WIRE_GATEWAY_AUTH_METHOD = basic
USERNAME = myuser
PASSWORD = mypass

correct?

Does it only allow to "load" taler wallets by wiring money *into* this 
AB123456 account? Or can we already "pay out" money by wiring money 
*from* this account to an user-specified account (destroying their Talers)?


I guess in the real world, this would be equivalent to the exchange's 
account at a higher-level bank (possibly the central bank), correct?


And how does this account interact with the Taler Cashier app? IIUC, the 
Cashier can transfer money from one taler wallet to another. So do I 
assume correctly that I need to fake a sandbox transaction into the 
AB123456 account, so the exchange believes that the cashier's wallet has 
been loaded with *lots of money*?

Or can I configure the exchange / the libeufin sandbox (which?) such 
that the cashier's account may go into debt?



My goal is to handle the payment of drinks and food at a (hacker) event 
over Taler; there would be a (human-operated) place where you can swap 
money into taler, and then you can pay it.

It would be very handy if that "cashier account" would just go into 
debt, so that in the end, we can check that the amount of physical money 
in the box equals the negative account balance. Can it work that way?


Thank you for all the help so far, and I hope I can contribute back by 
improving the manual a bit more :).


Cheers,

Florian