..
  This file is part of GNU TALER.
  Copyright (C) 2014-2024 Taler Systems SA

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU Affero General Public License as published by the Free Software
  Foundation; either version 2.1, or (at your option) any later version.

  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>

  @author Florian Dold
  @author Marcello Stanisci
  @author Christian Grothoff


.. target audience: operator

Regional Currency Custom Setup Manual
#####################################

This manual describes how to setup a regional currency manually. If you want a guided setup you can follow the :doc:`automated setup manual<regional-automated-manual>`.

.. contents:: Table of Contents
  :local:

.. include:: ../frags/regional-manual-architecture.rst

Custom Manual Setup
===================

You first need to setup the :ref:`libeufin-bank<libeufin-bank>` and integrate it with a Taler exchange.

If you don't want your regional currency to be backed by a fiat currency, you can stop here.

Enabling Currency Conversion
++++++++++++++++++++++++++++

You need to setup the :ref:`libeufin-nexus<libeufin-nexus>` using a bank account at a bank dealing in fiat currency that
offers an online banking protocol supported by LibEuFin Nexus.

Next, you have to enable conversion and should ensure that at least one TAN
channel for :ref:`multi-factor authentication <libeufin-mfa>` is configured.

The following snippet shows how to enable conversion in ``libeufin-bank`` configuration:

.. code-block:: ini

  [libeufin-bank]
  ALLOW_CONVERSION = YES
  FIAT_CURRENCY = EUR

Make sure to (re)start the libeufin-bank after changing
these configuration options:

.. code-block:: console

  # systemctl restart libeufin-bank


Web-based Configuration
+++++++++++++++++++++++

Now you have to set the conversion rates and the ``admin`` debt limit via the bank's web interface as the ``admin`` user.

.. _regional-conversion-setup:

Configuring the Exchange for Conversion
+++++++++++++++++++++++++++++++++++++++

An exchange that supports currency conversion needs to advertise two bank
accounts, one in the regional currency and a second in the fiat currency. The
conversion logic ensures that wire transfers in either account are
immediately reflected in the other account.

This section explains how to enable currency conversion at the exchange,
which is critical for wallets to know how to wire fiat currency to an
exchange to obtain regional currency.

You will need to use the ``taler-exchange-offline`` tool to inform the
exchange about the **fiat** bank account that can be used for cash in
operations and also specify the URL for currency conversion.  Additionally,
you may also configure restrictions on the bank accounts that may originate
the funds, for example, to prevent international wire transfers that may expose
you to additional compliance risks.

Given the ``$IBAN`` of the fiat currency bank account and ``$NAME`` as
the (URL-encoded) name of the exchange-account owner, the following
``taler-exchange-offline`` invocation can be used to notify wallets about
the possibility of currency conversion (cash in):

.. code-block:: console

  # source config/user.conf
  # sudo -u taler-exchange-offline \
    taler-exchange-offline \
      wire-fee now iban "${CURRENCY}":0 "${CURRENCY}":0 \
      enable-account \
        "${CONVERSION_PAYTO}" \
        conversion-url "${PROTO}://bank.$DOMAIN_NAME/conversion-info/" \
        display-hint 10 "CHF" \
        debit-restriction deny \
        credit-restriction \
          regex \
            'payto://iban/.*/CH.*?receiver-name=.*' \
            'Swiss only' \
            '{"de":"nur Schweiz","fr":"Suisse uniquement"}' \
      upload

Here, the ``$CONVERSION_URL`` must be set to the base URL of the conversion
endpoint of the bank, which should be
``https://bank.$DOMAIN/conversion-info/`` in our setup.

The above commands set up the exchange to perform conversion with a
restriction to only accept credit transfers from Swiss bank accounts.  You may
want to configure such restrictions on the bank accounts that may originate
funds to prevent international wire transfers that may expose you to
additional compliance risks.

You can leave out the "credit-restriction" if you want to allow international
inbound wire transfers.

The "debit-restriction" is largely mandatory as in this setup the
``taler-exchange-transfer`` is only configured to deal with the regional
currency bank.  Crediting fiat bank accounts must thus be done via the
cash-out functionality of the regional currency bank account.

The "display-hint" gives priority (10) for the fiat cash-in account over the
regional currency account in the withdraw dialog of the wallets and labels the
account with "CHF".

.. note::

  The above command adds a **second** bank account to the exchange.
  You (or the guided setup script) should have already enabled the
  regional currency bank account (without any "conversion-url").

.. include:: ../frags/regional-system-on.rst
.. include:: ../frags/deploying-tos.rst


Maintenance
+++++++++++

The ``taler-exchange-offline`` commands given above set fees only for the
current year (``now``). Thus, before January 1st of each year, you must to set
up new fees for the new calendar year.  In a regional currency setup, this
typically requires up to three annual settings:

.. code-block:: console

  # YEAR=2025               # edit if necessary
  # FIAT_CURRENCY=CHF       # edit if necessary
  # REGIO_CURRENCY=NETZBON  # edit if necessary
  # sudo -u taler-exchange-offline \
      taler-exchange-offline \
        wire-fee "$YEAR" \
          iban "${FIAT_CURRENCY}":0 "${FIAT_CURRENCY}":0 \
        wire-fee "$YEAR" \
          x-taler-bank "${REGIO_CURRENCY}":0 "${REGIO_CURRENCY}":0 \
        global-fee $YEAR \
          "${REGIO_CURRENCY}:0" \
          "${REGIO_CURRENCY}:0" \
          "${REGIO_CURRENCY}:0" \
          4w 6y 4 \
        upload

If the fees are not all zero, simply change the respective place to specify
a non-zero fee.

.. note::

  Additionally, the denomination signing keys will only have been
  pre-generated for some time, depending on your ``LOOKAHEAD_SIGN``
  configuration option. Thus, you may need to periodically run
  the "taler-exchange-offline download sign upload" sequence as well!