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Nexus How-To
############
.. contents:: Table of Contents
Nexus is a Web service that provides a JSON abstraction layer to
access bank accounts. It is **not** itself a bank, but a translator
between JSON requests and more structured banking protocols (like
EBICS, for example.), that are offered by actual banks.
This document explains how to setup Nexus to access a bank account
via the EBICS protocol. In order to follow all the steps below, the
reader should already have one EBICS subscriber activated at their bank.
Obtain Nexus
============
Nexus belongs to the LibEuFin project, and can be downloaded via Git:
``$ git clone git://git.taler.net/libeufin``
Note that Kotlin+Gradle should already work on the host system.
Install Nexus
=============
Navigate into the `libeufin` local repository, and from top-level run:
.. code-block:: shell
$ ./gradlew -Pprefix=$PREFIX nexus:installToPrefix
$ ./gradlew -Pprefix=$PREFIX cli:installToPrefix
In case of success, the two following commands should be found:
.. code-block:: shell
$ which libeufin-nexus
$ which libeufin-cli
Connect Nexus with a EBICS account
==================================
Use the following command to *(1) run the nexus service*:
.. code-block:: shell
$ libeufin-nexus
After the startup, Nexus should have created a ``.sqlite3`` file in
its current working directory. Feel free to use the ``--with-db`` option
to change the database name and path. In future releases, the support
for Postgresql will be provided.
At this point a *(2) superuser account needs to be activated
into the system*:
.. code-block:: shell
$ libeufin-nexus superuser foo # Will interactively ask for password
For simplicity, we'll enable the superuser to access the bank account
via the EBICS protocol, but a API to create less privileged users is
as well offered.
Nexus needs now to associate the user to a EBICS subscriber that was
activated on the bank. In the Nexus terminology, this is called *(3)
creating a EBICS connection*.
.. code-block:: shell
libeufin-cli \
connections \
new-ebics-connection \
--connection-name $NEXUS_BANK_CONNECTION_NAME \
--ebics-url $EBICS_BASE_URL \
--host-id $EBICS_HOST_ID \
--partner-id $EBICS_PARTNER_ID \
--ebics-user-id $EBICS_USER_ID \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
$NEXUS_URL
If the step above executed correctly, Nexus created all the cryptographic
material that is needed on the client side; in this EBICS example, it created
the signature and identification keys. It is therefore advisable to *(4) make
a backup copy* of such keys.
.. code-block:: shell
libeufin-cli \
connections \
--connection-name $NEXUS_BANK_CONNECTION_NAME \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
--passphrase $SECRET \
--outputfile $BACKUP_FILE \
$NEXUS_URL
At this point, Nexus must communicate all the details to the bank. Therefore,
it will *(4) synchronize the connection*. In this EBICS example, Nexus will send
the *INI* and *HIA* messages to the bank.
.. code-block:: shell
libeufin-cli \
connections \
sync \
--connection-name $NEXUS_BANK_CONNECTION_NAME \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
$NEXUS_URL
Once the connection is synchronized, Nexus needs to import locally the data
corresponding to the bank accounts offered by the bank connection just made.
The command below *(5) downloads the list of the bank accounts offered by the*
``$NEXUS_BANK_CONNECTION_NAME``.
.. code-block:: shell
libeufin-cli \
connections \
download-bank-accounts \
--connection-name $NEXUS_BANK_CONNECTION_NAME \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
$NEXUS_URL
It is now possible to *(6) list the accounts offered by the connection*.
.. code-block:: shell
libeufin-cli \
connections \
list-offered-bank-accounts \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
$NEXUS_URL
Nexus now needs an explicit *(7) import of the accounts it needs to manage*.
This step is needed to let the user pick a custom name for such accounts.
.. code-block:: shell
libeufin-cli
connections \
import-bank-account \
--connection-name $NEXUS_BANK_CONNECTION_NAME \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
--offered-account-id $ACCOUNT_NATIVE_NAME \
--nexus-bank-account-id $CUSTOM_RENAMING_FOR_ACCOUNT \
$NEXUS_URL
Once a Nexus user imported a bank account (``$CUSTOM_RENAMING_FOR_ACCOUNT``)
under a certain connection (``$NEXUS_BANK_CONNECTION_NAME``), it is possible
to accomplish the usual operations for any bank account: asking for the
list of transactions, and making a payment.
Request history of transactions
===============================
It is first needed to tell Nexus to download the latest news
from the bank, and then ask it again to return the results.
This command asks Nexus to *download the latest bank statements*:
.. code-block:: shell
libeufin-cli \
accounts \
fetch-transactions \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
--account-name $CUSTOM_RENAMING_FOR_ACCOUNT \
$NEXUS_URL
Once Nexus stored all the information in the database, the
client can ask to actually **see** the transactions:
.. code-block:: shell
libeufin-cli
accounts \
transactions \
--nexus-user-id $NEXUS_USER \
--nexus-password $NEXUS_PASSWORD \
--account-name $CUSTOM_RENAMING_FOR_ACCOUNT \
$NEXUS_URL
Make a payment
==============
TBD.
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