path: root/texinfo/taler-developer-manual.texi

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@settitle Taler Developer Manual
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@direntry
* MENU ENTRY: (taler-developer-manual.info). DESCRIPTION
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@definfoenclose strong,`,'
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@c %**end of header

@copying
@quotation
GNU Taler 0.9.0, Jun 20, 2022

GNU Taler team

Copyright @copyright{} 2014-2022 Taler Systems SA (GPLv3+ or GFDL 1.3+)
@end quotation

@end copying

@titlepage
@title Taler Developer Manual
@insertcopying
@end titlepage
@contents

@c %** start of user preamble

@c %** end of user preamble

@ifnottex
@node Top
@top Taler Developer Manual
@insertcopying
@end ifnottex

@c %**start of body
@anchor{taler-developer-manual doc}@anchor{0}
@c This file is part of GNU TALER.
@c 
@c Copyright (C) 2014-2021 Taler Systems SA
@c 
@c TALER is free software; you can redistribute it and/or modify it under the
@c terms of the GNU Affero General Public License as published by the Free Software
@c Foundation; either version 2.1, or (at your option) any later version.
@c 
@c TALER is distributed in the hope that it will be useful, but WITHOUT ANY
@c WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
@c A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
@c 
@c You should have received a copy of the GNU Affero General Public License along with
@c TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
@c 
@c @author Christian Grothoff

@menu
* GNU Taler Release Checklist:: 
* GNU Taler Demo Upgrade Checklist:: 
* Fundamentals:: 
* Debian and Ubuntu Repositories:: 
* Language-Specific Guidelines:: 
* Taler Deployment on gv.taler.net: Taler Deployment on gv taler net. 
* Demo Upgrade Procedure:: 
* Environments and Builders on taler.net: Environments and Builders on taler net. 
* Releases:: 
* Continuous integration:: 
* Internationalization:: 
* Android Apps:: 
* Code Coverage:: 
* Coding Conventions:: 
* Testing library:: 
* User-Facing Terminology:: 
* Developer Glossary:: 
* Developer Tools:: 
* Index:: 

@end menu

@node GNU Taler Release Checklist,GNU Taler Demo Upgrade Checklist,Top,Top
@anchor{checklist-release doc}@anchor{1}@anchor{checklist-release developer-s-manual}@anchor{2}@anchor{checklist-release gnu-taler-release-checklist}@anchor{3}
@chapter GNU Taler Release Checklist


Release checklists for GNU Taler:

Wallet:


@itemize -

@item 
[ ] build wallet

@item 
[ ] verify wallet works against 'test.taler.net'

@item 
[ ] tag repo.

@item 
[ ] upgrade 'demo.taler.net' to 'test.taler.net'

@item 
[ ] upload new wallet release to app store

@item 
[ ] Update bug tracker (mark release, resolved -> closed)

@item 
[ ] Send announcement to @email{taler@@gnu.org}

@item 
[ ] Send announcement to @email{info-gnu@@gnu.org} (major releases only)

@item 
[ ] Send announcement to @email{coordinator@@translationproject.org}
@end itemize

For exchange:


@itemize -

@item 
[ ] check no compiler warnings at "-Wall"

@item 
[ ] ensure Coverity static analysis passes

@item 
[ ] make check.

@item 
[ ] upgrade 'demo.taler.net' to 'test.taler.net'

@item 
[ ] make dist, make check on result of 'make dist'.

@item 
[ ] Change version number in configure.ac.

@item 
[ ] make dist for release.

@item 
[ ] tag repo.

@item 
[ ] Upload triplet to ftp-upload.gnu.org/incoming/ftp or /incoming/alpha

@item 
[ ] Update bug tracker (mark release, resolved -> closed)

@item 
[ ] Send announcement to @email{taler@@gnu.org}

@item 
[ ] Send announcement to @email{info-gnu@@gnu.org} (major releases only)

@item 
[ ] Send announcement to @email{coordinator@@translationproject.org}
@end itemize

For merchant (C backend):


@itemize -

@item 
[ ] check no compiler warnings at "-Wall"

@item 
[ ] ensure Coverity static analysis passes

@item 
[ ] make check.

@item 
[ ] upgrade 'demo.taler.net' to 'test.taler.net'

@item 
[ ] make dist, make check on result of 'make dist'.

@item 
[ ] Change version number in configure.ac.

@item 
[ ] make dist for release.

@item 
[ ] tag repo.

@item 
[ ] Upload triplet to ftp-upload.gnu.org/incoming/ftp or /incoming/alpha

@item 
[ ] Update bug tracker (mark release, resolved -> closed)

@item 
[ ] Send announcement to @email{taler@@gnu.org}

@item 
[ ] Send announcement to @email{info-gnu@@gnu.org} (major releases only)

@item 
[ ] Send announcement to @email{coordinator@@translationproject.org}
@end itemize

For bank:


@itemize -

@item 
TBD
@end itemize

For Python merchant frontend:


@itemize -

@item 
TBD
@end itemize

For PHP merchant frontend:


@itemize -

@item 
TBD
@end itemize

For auditor:


@itemize -

@item 
TBD
@end itemize

For libebics:


@itemize -

@item 
TBD
@end itemize

@node GNU Taler Demo Upgrade Checklist,Fundamentals,GNU Taler Release Checklist,Top
@anchor{checklist-demo-upgrade doc}@anchor{4}@anchor{checklist-demo-upgrade gnu-taler-demo-upgrade-checklist}@anchor{5}
@chapter GNU Taler Demo Upgrade Checklist


Post-upgrade checks:


@itemize -

@item 
 Run @code{taler-deployment-arm -I} to verify that all services are running.

@item 
 Run the headless wallet to check that services are actually working:

@example
$ taler-wallet-cli integrationtest \
    -e https://exchange.demo.taler.net/ \
    -m https://backend.demo.taler.net/ \
    -b https://bank.demo.taler.net \
    -w "KUDOS:10" \
    -s "KUDOS:5"
@end example
@end itemize

Basics:


@itemize -

@item 
 Visit @indicateurl{https://demo.taler.net/} to see if the landing page is displayed correctly

@item 
 Visit the wallet installation page, install the wallet, and see if the presence
indicator is updated correctly.

@item 
 Visit @indicateurl{https://bank.demo.taler.net/}, register a new user and withdraw coins into the
browser wallet.
@end itemize

Blog demo:


@itemize -

@item 
 Visit @indicateurl{https://shop.demo.taler.net/} and purchase an article.

@item 
 Verify that the balance in the wallet was updated correctly.

@item 
 Go back to @indicateurl{https://shop.demo.taler.net/} and click on the same article
link.  Verify that the article is shown and @strong{no} repeated payment is
requested.

@item 
 Open the fulfillment page from the previous step in an anonymous browsing session
(without the wallet installed) and verify that it requests a payment again.

@item 
 Delete cookies on @indicateurl{https://shop.demo.taler.net/} and click on the same article again.
Verify that the wallet detects that the article has already purchased and successfully
redirects to the article without spending more money.
@end itemize

Donation demo:


@itemize -

@item 
 Make a donation on @indicateurl{https://donations.demo.taler.net}

@item 
 Make another donation with the same parameters and verify
that the payment is requested again, instead of showing the previous
fulfillment page.
@end itemize

Survey/Tipping:


@itemize -

@item 
 Visit @indicateurl{https://survey.demo.taler.net/} and receive a tip.

@item 
 Verify that the survey stats page (@indicateurl{https://survey.demo.taler.net/survey-stats}) is working,
and that the survey reserve has sufficient funds.
@end itemize

@cartouche
@quotation Note 
This manual contains information for developers working on GNU Taler
and related components.  It is not intended for a general audience.
@end quotation
@end cartouche

@node Fundamentals,Debian and Ubuntu Repositories,GNU Taler Demo Upgrade Checklist,Top
@anchor{taler-developer-manual fundamentals}@anchor{6}
@chapter Fundamentals


@menu
* Bug Tracking:: 
* Code Repositories:: 
* Committing code:: 
* Observing changes:: 
* Communication:: 
* What to put in bootstrap:: 

@end menu

@node Bug Tracking,Code Repositories,,Fundamentals
@anchor{taler-developer-manual bug-tracking}@anchor{7}
@section Bug Tracking


Bug tracking is done with Mantis (@indicateurl{https://www.mantisbt.org/}).  The bug tracker
is available at @indicateurl{https://bugs.taler.net}. A registration on the Web site is
needed in order to use the bug tracker, only read access is granted without a
login.

@node Code Repositories,Committing code,Bug Tracking,Fundamentals
@anchor{taler-developer-manual code-repositories}@anchor{8}
@section Code Repositories


Taler code is versioned with Git. For those users without write access, all the
codebases are found at the following URL:

@example
git://git.taler.net/<repository>
@end example

A complete list of all the existing repositories is currently found at
@indicateurl{https://git.taler.net/}.

@node Committing code,Observing changes,Code Repositories,Fundamentals
@anchor{taler-developer-manual committing-code}@anchor{9}
@section Committing code


Before you can obtain Git write access, you must sign the copyright
agreement. As we collaborate closely with GNUnet, we use their
copyright agreement -- with the understanding that your contributions
to GNU Taler are included in the assignment.  You can find the
agreement on the GNUnet site@footnote{https://gnunet.org/en/copyright.html}.
Please sign and mail it to Christian Grothoff as he currently collects
all the documents for GNUnet e.V.

To obtain Git access, you need to send us your SSH public key. Most core
team members have administrative Git access, so simply contact whoever
is your primary point of contact so far. You can
find instructions on how to generate an SSH key
in the Git book@footnote{https://git-scm.com/book/en/v2/Git-on-the-Server-Generating-Your-SSH-Public-Key}.
If you have been granted write access, you first of all must change the URL of
the respective repository to:

@example
ssh://git@@git.taler.net/<repository>
@end example

For an existing checkout, this can be done by editing the @code{.git/config} file.

The server is configured to reject all commits that have not been signed with
GnuPG. If you do not yet have a GnuPG key, you must create one, as explained
in the GNU Privacy Handbook@footnote{https://www.gnupg.org/gph/en/manual/c14.html}.
You do not need to share the respective public key with us to make commits.
However, we recommend that you upload it to key servers, put it on your
business card and personally meet with other GNU hackers to have it signed
such that others can verify your commits later.

To sign all commits, you should run

@example
$ git config --global commit.gpgsign true
@end example

You can also sign individual commits only by adding the @code{-S} option to the
@code{git commit} command. If you accidentally already made commits but forgot
to sign them, you can retroactively add signatures using:

@example
$ git rebase -S
@end example

Whether you commit to a personal branch (recommended: @code{dev/$USER/...}),
a feature branch or to @code{master} should
depend on your level of comfort and the nature of the change.  As a general
rule, the code in @code{master} must always build and tests should always pass, at
least on your own system. However, we all make mistakes and you should expect
to receive friendly reminders if your change did not live up to this simple
standard.  We plan to move to a system where the CI guarantees this invariant
in the future.

In order to keep a linear and clean commits history, we advise to avoid
merge commits and instead always rebase your changes before pushing to
the @code{master} branch.  If you commit and later find out that new commits were
pushed, the following command will pull the new commits and rebase yours
on top of them.

@example
# -S instructs Git to (re)sign your commits
$ git pull --rebase -S
@end example

@node Observing changes,Communication,Committing code,Fundamentals
@anchor{taler-developer-manual observing-changes}@anchor{a}
@section Observing changes


Every commit to the @code{master} branch of any of our public repositories
(and almost all are public) is automatically sent to the
@email{gnunet-svn@@gnu.org} mailinglist.  That list is for Git commits only,
and must not be used for discussions. It also carries commits from
our main dependencies, namely GNUnet and GNU libmicrohttpd.  While
it can be high volume, the lists is a good way to follow overall
development.

@node Communication,What to put in bootstrap,Observing changes,Fundamentals
@anchor{taler-developer-manual communication}@anchor{b}
@section Communication


We use the #taler channel on the Freenode IRC network and the @email{taler@@gnu.org}
public mailinglist for discussions.  Not all developers are active on IRC, but
all developers should probably subscribe to the low-volume Taler mailinglist.
There are separate low-volume mailinglists for gnunet-developers (@@gnu.org)
and for libmicrohttpd (@@gnu.org).

@node What to put in bootstrap,,Communication,Fundamentals
@anchor{taler-developer-manual what-to-put-in-bootstrap}@anchor{c}
@section What to put in bootstrap


Each repository has a @code{bootstrap} script, which contains commands for the
developer to run after a repository checkout (i.e., after @code{git clone} or
@code{git pull}).
Typically, this updates and initializes submodules, prepares the tool chain,
and runs @code{autoreconf}.
The last step generates the @code{configure} script, whether for immediate use or
for inclusion in the distribution tarball.

One common submodule is @code{contrib/gana}, which pulls from the
GNUnet GANA repository@footnote{https://git.gnunet.org/gana.git/}.
For example, in the
Taler exchange repository@footnote{https://git.taler.net/exchange.git},
the bootstrap script eventually runs the @code{git submodule update} command
early on, and later runs script @code{./contrib/gana.sh}, which in turn
runs script @code{./contrib/gana-update.sh}, which performs various tasks,
such as generating the file @code{src/include/taler_signatures.h}.

Thus, to update that file, you need to:


@itemize -

@item 
(in GANA repo) Find a suitable (unused) name and number for the Signature
Purposes database.

@item 
Add it to GANA, in @code{gnunet-signatures/registry.rec}.
(You can check for uniqueness with the @code{recfix} utility.)

@item 
Commit the change, and push it to the GANA Git repo.

@item 
(in Taler Repo) Change directory to @code{contrib/gana} and run
command @code{git pull} there.

@item 
Bootstrap, configure, do @code{make install}, @code{make check}, etc.
(Basically, make sure the change does not break anything.)

@item 
Commit the submodule change, and push it to the Taler exchange Git repo.
@end itemize

A similiar procedure is required for other databases in GANA.
See file @code{README} in the various directories for specific instructions.

@node Debian and Ubuntu Repositories,Language-Specific Guidelines,Fundamentals,Top
@anchor{taler-developer-manual debian-and-ubuntu-repositories}@anchor{d}
@chapter Debian and Ubuntu Repositories


We package our software for Debian and Ubuntu.

@menu
* Nightly Repositories:: 

@end menu

@node Nightly Repositories,,,Debian and Ubuntu Repositories
@anchor{taler-developer-manual nightly-repositories}@anchor{e}
@section Nightly Repositories


To try the latest, unstable and untested versions of packages,
you can add the nightly package sources.

@example
# For Ubuntu (focal-fossa)
$ echo "deb https://deb.taler.net/apt-nightly focal-taler-nightly main" > /etc/apt/sources.list.d/taler.list

# For Debian (bullseye)
$ echo "deb https://deb.taler.net/apt-nightly bullseye-taler-nightly main" > /etc/apt/sources.list.d/taler.list

# Both: Install signing key for nightly packages
$ wget -O - https://taler.net/taler-systems-nightly.gpg.key | apt-key add -
@end example

@node Language-Specific Guidelines,Taler Deployment on gv taler net,Debian and Ubuntu Repositories,Top
@anchor{taler-developer-manual language-specific-guidelines}@anchor{f}
@chapter Language-Specific Guidelines



@itemize *

@item 
Python Guidelines
@end itemize

@node Taler Deployment on gv taler net,Demo Upgrade Procedure,Language-Specific Guidelines,Top
@anchor{taler-developer-manual taler-deployment-on-gv-taler-net}@anchor{10}
@chapter Taler Deployment on gv.taler.net


This section describes the GNU Taler deployment on @code{gv.taler.net}.
@code{gv} is our server at BFH. It hosts the Git repositories, Web sites,
CI and other services.  Developers can receive an SSH account and
e-mail alias for the system.  As with Git, ask your primary team
contact for shell access if you think you need it.

Our old server, @code{tripwire}, is currently offline and will likely
go back online to host @code{production} systems for operating real
Taler payments at BFH in the future.

@menu
* DNS:: 
* User Acccounts:: 

@end menu

@node DNS,User Acccounts,,Taler Deployment on gv taler net
@anchor{taler-developer-manual dns}@anchor{11}
@section DNS


DNS records for taler.net are controlled by the GNU Taler
maintainers, specifically Christian and Florian. If you
need a sub-domain to be added, please contact one of them.

@node User Acccounts,,DNS,Taler Deployment on gv taler net
@anchor{taler-developer-manual user-acccounts}@anchor{12}
@section User Acccounts


On @code{gv.taler.net}, there are four system users that are set up to
serve Taler on the Internet:


@itemize -

@item 
@code{taler-test}: serves @code{*.test.taler.net} and gets automatically
built by Buildbot.

@item 
@code{taler-internal}: serves @code{*.int.taler.net}, and does @emph{NOT} get
automatically built.
@end itemize

The following two users are @emph{never} automatically built, and they both
serve @code{*.demo.taler.net}. At any given time, only one is active and
serves the HTTP requests from the outside; the other one can so be
compiled without any downtime. If the compilation succeeds, the inactive
user can be switched to become active (see next section), and vice versa.


@itemize -

@item 
@code{demo-blue}

@item 
@code{demo-green}
@end itemize

@node Demo Upgrade Procedure,Environments and Builders on taler net,Taler Deployment on gv taler net,Top
@anchor{taler-developer-manual demo-upgrade-procedure}@anchor{13}
@chapter Demo Upgrade Procedure


Upgrading the @code{demo} environment should be done with care, and ideally be
coordinated on the mailing list before.  It is our goal for @code{demo} to always
run a "working version" that is compatible with various published wallets.

Before deploying on @code{demo}, the same version of all components @strong{must}
be deployed @emph{and} tested on @code{int}.

Please use the @ref{4,,demo upgrade checklist} to make
sure everything is working.

@menu
* Tagging components:: 
* Environment Layout:: 
* Using envcfg.py: Using envcfg py. 
* Bootstrapping an Environment:: 
* Upgrading an Existing Environment:: 
* Switching Demo Colors:: 

@end menu

@node Tagging components,Environment Layout,,Demo Upgrade Procedure
@anchor{taler-developer-manual tagging-components}@anchor{14}
@section Tagging components


All Taler components must be tagged with git before they are deployed on the
@code{demo} environment, using a tag of the following form:

@example
demo-YYYY-MM-DD-SS
YYYY = year
MM = month
DD = day
SS = serial
@end example

@node Environment Layout,Using envcfg py,Tagging components,Demo Upgrade Procedure
@anchor{taler-developer-manual environment-layout}@anchor{15}
@section Environment Layout


Environments have the following layout:

@example
$HOME/
  deployment (deployment.git checkout)
  envcfg.py  (configuration of the Taler environment)
  activate   (bash file, sourced to set environment variables)
  logs/      (log files)
  local/     (locally installed software)
  sources/   (sources repos of locally build components)
  sockets/   (unix domain sockets of running components)
  taler-data (on-disk state, public and private keys)
  .config/taler.conf (main Taler configuration file)
@end example

On @code{demo-blue} and @code{demo-green}, @code{taler-data} is a symlink pointing to @code{$HOME/demo/shared-data}
instead of a directory.

@node Using envcfg py,Bootstrapping an Environment,Environment Layout,Demo Upgrade Procedure
@anchor{taler-developer-manual using-envcfg-py}@anchor{16}
@section Using envcfg.py


The @code{$HOME/envcfg.py} file contains (1) the name of the environment and (2) the version
of all components we build (in the form of a git rev).

The @code{envcfg.py} for demo looks like this:

@example
env = "demo"
tag = "demo-2019-10-05-01:
tag_gnunet = tag
tag_libmicrohttpd = tag
tag_exchange = tag
tag_merchant = tag
tag_bank = tag
tag_twister = tag
tag_landing = tag
tag_donations = tag
tag_blog = tag
tag_survey = tag
tag_backoffice = tag
tag_sync = tag
@end example

Currently only the variables @code{env} and @code{tag_$@{component@}} are used.

When deploying to @code{demo}, the @code{envcfg.py} should be committed to @code{deployment.git/envcfg/envcfg-demo-YYYY-MM-DD-SS.py}.

@node Bootstrapping an Environment,Upgrading an Existing Environment,Using envcfg py,Demo Upgrade Procedure
@anchor{taler-developer-manual bootstrapping-an-environment}@anchor{17}
@section Bootstrapping an Environment


@example
$ git clone https://git.taler.net/deployment.git ~/deployment
$ cp ~/deployment/envcfg/$ENVCFGFILE ~/envcfg.py
$ ./deployment/bin/taler-deployment bootstrap
$ source ~/activate
$ taler-deployment build
$ taler-deployment-prepare
$ taler-deployment-start
$ taler-deployment-arm -I # check everything works
# The following command sets up the 'blog' and 'donations' instances.
$ taler-config-instances
@end example

@node Upgrading an Existing Environment,Switching Demo Colors,Bootstrapping an Environment,Demo Upgrade Procedure
@anchor{taler-developer-manual upgrading-an-existing-environment}@anchor{18}
@section Upgrading an Existing Environment


@example
$ rm -rf ~/sources ~/local
$ git -C ~/deployment pull
$ cp ~/deployment/envcfg/$ENVCFGFILE ~/envcfg.py
$ taler-deployment bootstrap
$ taler-deployment build
$ taler-deployment-prepare
$ taler-deployment-restart
$ taler-deployment-arm -I # check everything works
@end example

@node Switching Demo Colors,,Upgrading an Existing Environment,Demo Upgrade Procedure
@anchor{taler-developer-manual switching-demo-colors}@anchor{19}
@section Switching Demo Colors


As the @code{demo} user, to switch to color @code{$@{COLOR@}},
run the following script from @code{deployment/bin}:

@example
$ taler-deployment switch-demo
@end example

@node Environments and Builders on taler net,Releases,Demo Upgrade Procedure,Top
@anchor{taler-developer-manual environments-and-builders-on-taler-net}@anchor{1a}
@chapter Environments and Builders on taler.net


@menu
* Buildbot implementation:: 
* Documentation Builder:: 
* Website Builder:: 
* Code coverage:: 
* Service Checker:: 
* Tipping reserve top-up:: 
* Producing auditor reports:: 
* Database schema versioning:: 

@end menu

@node Buildbot implementation,Documentation Builder,,Environments and Builders on taler net
@anchor{taler-developer-manual buildbot-implementation}@anchor{1b}
@section Buildbot implementation


GNU Taler uses a buildbot implementation (front end at @indicateurl{https://buildbot.taler.net}) to manage continuous integration.  Buildbot documentation is at @indicateurl{https://docs.buildbot.net/}.

Here are some highlights:


@itemize -

@item 
The WORKER is the config that that lives on a shell account on a localhost (taler.net), where this host has buildbot-worker installed.  The WORKER executes the commands that perform all end-functions of buildbot.

@item 
The WORKER running buildbot-worker receives these commands by authenticating and communicating with the buildbot server using parameters that were specified when the worker was created in that shell account with the @code{buildbot-worker} command.

@item 
The buildbot server's master.cfg file contains FACTORY declarations which specify the commands that the WORKER will run on localhost.

@item 
The FACTORY is tied to the WORKER in master.cfg by a BUILDER.

@item 
The master.cfg also allows for SCHEDULER that defines how and when the BUILDER is executed.

@item 
Our master.cfg file is checked into git, and then periodically updated on a particular account on taler.net (ask Christian for access if needed).  Do not edit this file directly/locally on taler.net, but check changes into Git.
@end itemize

Best Practices:


@itemize -

@item 
When creating a new WORKER in the @code{master.cfg} file, leave a comment specifying the server and user account that this WORKER is called from.  (At this time, taler.net is the only server used by this implementation, but it's still good practice.)

@item 
Create a worker from a shell account with this command: @code{buildbot-worker create-worker <workername> localhost <username> <password>}
@end itemize

Then make sure there is a WORKER defined in master.cfg like: @code{worker.Worker("<username>", "<password>")}

@node Documentation Builder,Website Builder,Buildbot implementation,Environments and Builders on taler net
@anchor{taler-developer-manual documentation-builder}@anchor{1c}
@section Documentation Builder


All the Taler documentation is built by the user @code{docbuilder} that
runs a Buildbot worker.  The following commands set the @code{docbuilder} up,
starting with an empty home directory.

@example
# Log-in as the 'docbuilder' user.

$ cd $HOME
$ git clone git://git.taler.net/deployment
$ ./deployment/bootstrap-docbuilder

# If the previous step worked, the setup is
# complete and the Buildbot worker can be started.

$ buildbot-worker start worker/
@end example

@node Website Builder,Code coverage,Documentation Builder,Environments and Builders on taler net
@anchor{taler-developer-manual website-builder}@anchor{1d}
@section Website Builder


Taler Websites, @code{www.taler.net} and @code{stage.taler.net}, are built by the
user @code{taler-websites} by the means of a Buildbot worker.  The following
commands set the @code{taler-websites} up, starting with an empty home directory.

@example
# Log-in as the 'taler-websites' user.

$ cd $HOME
$ git clone git://git.taler.net/deployment
$ ./deployment/bootstrap-sitesbuilder

# If the previous step worked, the setup is
# complete and the Buildbot worker can be started.

$ buildbot-worker start worker/
@end example

@node Code coverage,Service Checker,Website Builder,Environments and Builders on taler net
@anchor{taler-developer-manual code-coverage}@anchor{1e}
@section Code coverage


Code coverage tests are run by the @code{lcovworker} user, and are also driven
by Buildbot.

@example
# Log-in as the 'lcovworker' user.

$ cd $HOME
$ git clone git://git.taler.net/deployment
$ ./deployment/bootstrap-taler lcov

# If the previous step worked, the setup is
# complete and the Buildbot worker can be started.

$ buildbot-worker start worker/
@end example

The results are then published at @code{https://lcov.taler.net/}.

@node Service Checker,Tipping reserve top-up,Code coverage,Environments and Builders on taler net
@anchor{taler-developer-manual service-checker}@anchor{1f}
@section Service Checker


The user @code{demo-checker} runs periodic checks to see if all the
@code{*.demo.taler.net} services are up and running.  It is driven by
Buildbot, and can be bootstrapped as follows.

@example
# Log-in as the 'demo-checker' user

$ cd $HOME
$ git clone git://git.taler.net/deployment
$ ./deployment/bootstrap-demochecker

# If the previous step worked, the setup is
# complete and the Buildbot worker can be started.

$ buildbot-worker start worker/
@end example

@node Tipping reserve top-up,Producing auditor reports,Service Checker,Environments and Builders on taler net
@anchor{taler-developer-manual tipping-reserve-top-up}@anchor{20}
@section Tipping reserve top-up


Both 'test' and 'demo' setups get their tip reserve topped up
by a Buildbot worker.  The following steps get the reserve topper
prepared.

@example
# Log-in as <env>-topper, with <env> being either 'test' or 'demo'

$ git clone git://git.taler.net/deployment
$ ./deployment/prepare-reservetopper <env>

# If the previous steps worked, then it should suffice to start
# the worker, with:

$ buildbot-worker start worker/
@end example

@node Producing auditor reports,Database schema versioning,Tipping reserve top-up,Environments and Builders on taler net
@anchor{taler-developer-manual producing-auditor-reports}@anchor{21}
@section Producing auditor reports


Both 'test' and 'demo' setups get their auditor reports compiled
by a Buildbot worker.  The following steps get the reports compiler
prepared.

@example
# Log-in as <env>-auditor, with <env> being either 'test' or 'demo'

$ git clone git://git.taler.net/deployment
$ ./deployment/prepare-auditorreporter <env>

# If the previous steps worked, then it should suffice to start
# the worker, with:

$ buildbot-worker start worker/
@end example

@node Database schema versioning,,Producing auditor reports,Environments and Builders on taler net
@anchor{taler-developer-manual database-schema-versioning}@anchor{22}
@section Database schema versioning


The PostgreSQL databases of the exchange and the auditor are versioned.
See the 0000.sql file in the respective directory for documentation.

Every set of changes to the database schema must be stored in a new
versioned SQL script. The scripts must have contiguous numbers. After
any release (or version being deployed to a production or staging
environment), existing scripts MUST be immutable.

Developers and operators MUST NOT make changes to database schema
outside of this versioning.

@node Releases,Continuous integration,Environments and Builders on taler net,Top
@anchor{taler-developer-manual releases}@anchor{23}
@chapter Releases


@menu
* Release Process and Checklists:: 
* Tagging:: 
* Database for tests:: 
* Exchange@comma{} merchant: Exchange merchant. 
* Wallet WebExtension:: 
* Upload to GNU mirrors:: 
* Creating Debian packages:: 

@end menu

@node Release Process and Checklists,Tagging,,Releases
@anchor{taler-developer-manual release-process-and-checklists}@anchor{24}
@section Release Process and Checklists


Please use the @ref{1,,release checklist}

This document describes the process for releasing a new version of the
various Taler components to the official GNU mirrors.

The following components are published on the GNU mirrors


@itemize -

@item 
taler-exchange (exchange.git)

@item 
taler-merchant (merchant.git)

@item 
talerdonations (donations.git)

@item 
talerblog (blog.git)

@item 
taler-bank (bank.git)

@item 
taler-wallet-webex (wallet-webex.git)
@end itemize

@node Tagging,Database for tests,Release Process and Checklists,Releases
@anchor{taler-developer-manual tagging}@anchor{25}
@section Tagging


Tag releases with an @strong{annotated} commit, like

@example
$ git tag -a v0.1.0 -m "Official release v0.1.0"
$ git push origin v0.1.0
@end example

@node Database for tests,Exchange merchant,Tagging,Releases
@anchor{taler-developer-manual database-for-tests}@anchor{26}
@section Database for tests


For tests in the exchange and merchant to run, make sure that a database
@emph{talercheck} is accessible by @emph{$USER}. Otherwise tests involving the
database logic are skipped.

@cartouche
@quotation Note 
The Taler merchant backend stores private keys and other sensitive
business and customer data in the database.  The backend operator
SHOULD ensure that backup operations are encrypted and secured from
unauthorized access.
@end quotation
@end cartouche

@node Exchange merchant,Wallet WebExtension,Database for tests,Releases
@anchor{taler-developer-manual exchange-merchant}@anchor{27}
@section Exchange, merchant


Set the version in @code{configure.ac}. The commit being tagged should be
the change of the version.

Tag the current GANA version that works with the exchange and merchant and
checkout that tag of gana.git (instead of master). Otherwise, if there are
incompatible changes in GANA (like removed symbols), old builds could break.

Update the Texinfo documentation using the files from docs.git:

@example
# Get the latest documentation repository
$ cd $GIT/docs
$ git pull
$ make texinfo
# The *.texi files are now in _build/texinfo
#
# This checks out the prebuilt branch in the prebuilt directory
$ git worktree add prebuilt prebuilt
$ cd prebuilt
# Copy the pre-built documentation into the prebuilt directory
$ cp -r ../_build/texinfo .
# Push and commit to branch
$ git commit -a -S -m "updating texinfo"
$ git status
# Verify that all files that should be tracked are tracked,
# new files will have to be added to the Makefile.am in
# exchange.git as well!
$ git push
# Remember $REVISION of commit
#
# Go to exchange
$ cd $GIT/exchange/doc/prebuilt
# Update submodule to point to latest commit
$ git checkout $REVISION
@end example

Finally, the Automake @code{Makefile.am} files may have to be adjusted to
include new @code{*.texi} files or images.

For bootstrap, you will need to install
GNU Recutils@footnote{https://www.gnu.org/software/recutils/}.

For the exchange test cases to pass, @code{make install} must be run first.
Without it, test cases will fail because plugins can't be located.

@example
$ ./bootstrap
$ ./configure # add required options for your system
$ make dist
$ tar -xf taler-$COMPONENT-$VERSION.tar.gz
$ cd taler-$COMPONENT-$VERSION
$ make install check
@end example

@node Wallet WebExtension,Upload to GNU mirrors,Exchange merchant,Releases
@anchor{taler-developer-manual wallet-webextension}@anchor{28}
@section Wallet WebExtension


The version of the wallet is in @emph{manifest.json}. The @code{version_name}
should be adjusted, and @emph{version} should be increased independently on
every upload to the WebStore.

@example
$ ./configure
$ make dist
@end example

@node Upload to GNU mirrors,Creating Debian packages,Wallet WebExtension,Releases
@anchor{taler-developer-manual upload-to-gnu-mirrors}@anchor{29}
@section Upload to GNU mirrors


See @indicateurl{https://www.gnu.org/prep/maintain/maintain.html#Automated-FTP-Uploads}

Directive file:

@example
version: 1.2
directory: taler
filename: taler-exchange-0.1.0.tar.gz
@end example

Upload the files in @strong{binary mode} to the ftp servers.

@node Creating Debian packages,,Upload to GNU mirrors,Releases
@anchor{taler-developer-manual creating-debian-packages}@anchor{2a}
@section Creating Debian packages


Our general setup is based on
@indicateurl{https://wiki.debian.org/DebianRepository/SetupWithReprepro}

First, update at least the version of the Debian package in
debian/changelog, and then run:

@example
$ dpkg-buildpackage -rfakeroot -b -uc -us
@end example

in the respective source directory (GNUnet, exchange, merchant) to create the
@code{.deb} files. Note that they will be created in the parent directory.  This
can be done on gv.taler.net, or on another (secure) machine.

On @code{gv}, we use the @code{aptbuilder} user to manage the reprepro repository.

Next, the @code{*.deb} files should be copied to gv.taler.net, say to
@code{/home/aptbuilder/incoming}.  Then, run

@example
# cd /home/aptbuilder/apt
# reprepro includedeb bullseye ~/incoming/*.deb
@end example

to import all Debian files from @code{~/incoming/} into the @code{bullseye}
distribution.  If Debian packages were build against other distributions,
reprepro may need to be first configured for those and the import command
updated accordingly.

Finally, make sure to clean up @code{~/incoming/} (by deleting the
now imported @code{*.deb} files).

@node Continuous integration,Internationalization,Releases,Top
@anchor{taler-developer-manual continuous-integration}@anchor{2b}
@chapter Continuous integration


CI is done with Buildbot (@indicateurl{https://buildbot.net/}), and builds are
triggered by the means of Git hooks. The results are published at
@indicateurl{https://buildbot.taler.net/} .

In order to avoid downtimes, CI uses a "blue/green" deployment
technique. In detail, there are two users building code on the system,
the "green" and the "blue" user; and at any given time, one is running
Taler services and the other one is either building the code or waiting
for that.

There is also the possibility to trigger builds manually, but this is
only reserved to "admin" users.

@node Internationalization,Android Apps,Continuous integration,Top
@anchor{taler-developer-manual internationalization}@anchor{2c}
@chapter Internationalization


Internationalization (a.k.a "Translation") is handled with Weblate (@indicateurl{https://weblate.org}) via our instance at @indicateurl{https://weblate.taler.net/} .

At this time, this system is still very new for Taler.net and this documentation may be incorrect and is certainly incomplete.

@menu
* Who can Register:: 
* About Privilege Levels:: 
* Upgrading Privileges:: 
* How to Create a Project:: 
* How to Create a Component:: 
* How to Create a Translation:: 
* Translation Standards and Practices:: 
* GPG Signing of Translations:: 

@end menu

@node Who can Register,About Privilege Levels,,Internationalization
@anchor{taler-developer-manual who-can-register}@anchor{2d}
@section Who can Register


At this time, anyone can register an account at @indicateurl{https://weblate.taler.net/} to create translations.  Registered users default to the @strong{Users} and @strong{Viewers} privilege level.

@node About Privilege Levels,Upgrading Privileges,Who can Register,Internationalization
@anchor{taler-developer-manual about-privilege-levels}@anchor{2e}
@section About Privilege Levels


This is the breakdown of privilege levels in Weblate:


@itemize *

@item 
@strong{Users}/@strong{Viewers} = Can log in, view Translations  (@emph{applies to new users})

@item 
@strong{Reviewers} = Can contribute Translations to existing @emph{Components}

@item 
@strong{Managers} = Can create new @emph{Components} of existing @emph{Projects}

@item 
@strong{Superusers} = Can create new @emph{Projects}
@end itemize

@node Upgrading Privileges,How to Create a Project,About Privilege Levels,Internationalization
@anchor{taler-developer-manual upgrading-privileges}@anchor{2f}
@section Upgrading Privileges


To upgrade from @strong{Users}/@strong{Viewers}, a superuser must manually augment your privileges.  At this time, superusers are Christian, Florian, and Buck.

@node How to Create a Project,How to Create a Component,Upgrading Privileges,Internationalization
@anchor{taler-developer-manual how-to-create-a-project}@anchor{30}
@section How to Create a Project


The @emph{GNU Taler} project is probably the correct project for most Components and Translations falling under this guide.  Please contact a superuser if you need another Project created.

@node How to Create a Component,How to Create a Translation,How to Create a Project,Internationalization
@anchor{taler-developer-manual how-to-create-a-component}@anchor{31}
@section How to Create a Component


Reference: @indicateurl{https://docs.weblate.org/en/weblate-4.0.3/admin/projects.html#component-configuration}

In Weblate, a @emph{Component} is a subset of a @emph{Project} and each Component contains N translations.  A Component is generally associated with a Git repo.

To create a Component, log into @indicateurl{https://weblate.taler.net/} with your @emph{Manager} or higher credentials and choose @strong{+ Add} from the upper-right corner.

What follows is a sort of Wizard.  You can find detailed docs at @indicateurl{https://docs.weblate.org/}.  Here are some important notes about connecting your Component to the Taler Git repository:

Under @emph{https://weblate.taler.net/create/component/vcs/}:


@itemize *

@item 
@strong{Source code repository} - Generally @code{git+ssh://git@@git.taler.net/<reponame>`}.  Check with @code{git remote -v}.

@item 
@strong{Repository branch} - Choose the correct branch to draw from and commit to.

@item 
@strong{Repository push URL} - This is generally @code{git+ssh://git@@git.taler.net/<reponame>`}  Check with @code{git remote -v}.

@item 
@strong{Repository browser} - This is the www URL of the Git repo's file browser.  Example @code{https://git.taler.net/<repositoryname>.git/tree/@{@{filename@}@}?h=@{@{branch@}@}#n@{@{line@}@}} where @code{<repositoryname>} gets replaced but @code{@{@{filename@}@}} and other items in braces are actual variables in the string.

@item 
@strong{Merge style} - @emph{Rebase}, in line with GNU Taler development procedures

@item 
@strong{Translation license} - @emph{GNU Affero General Public License v3.0 or Later}

@item 
@strong{Adding new translation} - Decide how to handle adding new translations
@end itemize

@node How to Create a Translation,Translation Standards and Practices,How to Create a Component,Internationalization
@anchor{taler-developer-manual how-to-create-a-translation}@anchor{32}
@section How to Create a Translation


1 - Log into @indicateurl{https://weblate.taler.net}

2 - Navigate to @emph{Projects} > @emph{Browse all projects}

3 - Choose the @emph{Project} you wish to contribute to.

4 - Choose the @emph{Component} you wish to contribute to.

5 - Find the language you want to translate into.  Click "Translate" on that line.

6 - Find a phrase and translate it.

You may also wish to refer to @indicateurl{https://docs.weblate.org/} .

@node Translation Standards and Practices,GPG Signing of Translations,How to Create a Translation,Internationalization
@anchor{taler-developer-manual translation-standards-and-practices}@anchor{33}
@section Translation Standards and Practices


By default, our Weblate instance is set to accept translations in English, French, German, Italian, Russian, Spanish, and Portuguese.  If you want to contribute a translation in a different language, navigate to the @emph{Component} you want to translate for, and click "Start new translation" to begin.  If you require a privilege upgrade, please contact a superuser with your request.

When asked, set the license to GPLv3 or later.

Set commit/push to manual only.

@node GPG Signing of Translations,,Translation Standards and Practices,Internationalization
@anchor{taler-developer-manual gpg-signing-of-translations}@anchor{34}
@section GPG Signing of Translations


weblate.taler.net signs GPG commits with the GPG key CD33CE35801462FA5EB0B695F2664BF474BFE502, and the corresponding public key can be found at @indicateurl{https://weblate.taler.net/keys/}.

This means that contributions made through weblate will not be signed with the individual contributor's key when they are checked into the Git repository, but with the weblate key.

@node Android Apps,Code Coverage,Internationalization,Top
@anchor{taler-developer-manual android-apps}@anchor{35}
@chapter Android Apps


@menu
* Android App Nightly Builds:: 
* Building apps from source:: 
* Update translations:: 
* Release process:: 

@end menu

@node Android App Nightly Builds,Building apps from source,,Android Apps
@anchor{taler-developer-manual android-app-nightly-builds}@anchor{36}
@section Android App Nightly Builds


There are currently three Android apps in
the official Git repository@footnote{https://git.taler.net/taler-android.git}:


@itemize *

@item 
Wallet
[CI@footnote{https://git.taler.net/taler-android.git/tree/wallet/.gitlab-ci.yml}]

@item 
Merchant PoS Terminal
[CI@footnote{https://git.taler.net/taler-android.git/tree/merchant-terminal/.gitlab-ci.yml}]

@item 
Cashier
[CI@footnote{https://git.taler.net/taler-android.git/tree/cashier/.gitlab-ci.yml}]
@end itemize

Their git repositories are mirrored at Gitlab@footnote{https://gitlab.com/gnu-taler/taler-android}
to utilize their CI
and F-Droid@footnote{https://f-droid.org}'s Gitlab integration
to publish automatic nightly builds@footnote{https://f-droid.org/docs/Publishing_Nightly_Builds/}
for each change on the @code{master} branch.

All three apps publish their builds to the same F-Droid nightly repository
(which is stored as a git repository):
@indicateurl{https://gitlab.com/gnu-taler/fdroid-repo-nightly}

You can download the APK files directly from that repository
or add it to the F-Droid app for automatic updates
by clicking the following link (on the phone that has F-Droid installed).

@quotation

GNU Taler Nightly F-Droid Repository@footnote{fdroidrepos://gnu-taler.gitlab.io/fdroid-repo-nightly/fdroid/repo?fingerprint=55F8A24F97FAB7B0960016AF393B7E57E7A0B13C2D2D36BAC50E1205923A7843}
@end quotation

@cartouche
@quotation Note 
Nightly apps can be installed alongside official releases
and thus are meant @strong{only for testing purposes}.
Use at your own risk!
@end quotation
@end cartouche

@node Building apps from source,Update translations,Android App Nightly Builds,Android Apps
@anchor{taler-developer-manual build-apps-from-source}@anchor{37}@anchor{taler-developer-manual building-apps-from-source}@anchor{38}
@section Building apps from source


Note that this guide is different from other guides for building Android apps,
because it does not require you to run non-free software.
It uses the Merchant PoS Terminal as an example, but works as well for the other apps
if you replace @code{merchant-terminal} with @code{wallet} or @code{cashier}.

First, ensure that you have the required dependencies installed:


@itemize *

@item 
Java Development Kit 8 or higher (default-jdk-headless)

@item 
git

@item 
unzip
@end itemize

Then you can get the app's source code using git:

@example
# Start by cloning the Android git repository
$ git clone https://git.taler.net/taler-android.git

# Change into the directory of the cloned repository
$ cd taler-android

# Find out which Android SDK version you will need
$ grep -i compileSdkVersion merchant-terminal/build.gradle
@end example

The last command will return something like @code{compileSdkVersion 29}.
So visit the Android Rebuilds@footnote{http://android-rebuilds.beuc.net/} project
and look for that version of the Android SDK there.
If the SDK version is not yet available as a free rebuild,
you can try to lower the @code{compileSdkVersion} in the app's @code{merchant-terminal/build.gradle} file.
Note that this might break things
or require you to also lower other versions such as @code{targetSdkVersion}.

In our example, the version is @code{29} which is available,
so download the "SDK Platform" package of "Android 10.0.0 (API 29)"
and unpack it:

@example
# Change into the directory that contains your downloaded SDK
$ cd $HOME

# Unpack/extract the Android SDK
$ unzip android-sdk_eng.10.0.0_r14_linux-x86.zip

# Tell the build system where to find the SDK
$ export ANDROID_SDK_ROOT="$HOME/android-sdk_eng.10.0.0_r14_linux-x86"

# Change into the directory of the cloned repository
$ cd taler-android

# Build the merchant-terminal app
$ ./gradlew :merchant-terminal:assembleRelease
@end example

If you get an error message complaining about build-tools

@quotation


@table @asis

@item > Failed to install the following Android SDK packages as some licences have not been accepted.

build-tools;29.0.3 Android SDK Build-Tools 29.0.3
@end table
@end quotation

you can try changing the @code{buildToolsVersion} in the app's @code{merchant-terminal/build.gradle} file
to the latest "Android SDK build tools" version supported by the Android Rebuilds project.

After the build finished successfully,
you will find your APK in @code{merchant-terminal/build/outputs/apk/release/}.

@node Update translations,Release process,Building apps from source,Android Apps
@anchor{taler-developer-manual update-translations}@anchor{39}
@section Update translations


Translations are managed with Taler's weblate instance:
@indicateurl{https://weblate.taler.net/projects/gnu-taler/}

To update translations, enter the taler-android git repository
and ensure that the weblate remote exists:

@example
$ git config -l | grep weblate
@end example

If it does not yet exist (empty output), you can add it like this:

@example
$ git remote add weblate https://weblate.taler.net/git/gnu-taler/wallet-android/
@end example

Then you can merge in translations commit from the weblate remote:

@example
# ensure you have latest version
$ git fetch weblate

# merge in translation commits
$ git merge weblate/master
@end example

Afterwards, build the entire project from source and test the UI
to ensure that no erroneous translations (missing placeholders) are breaking things.

@node Release process,,Update translations,Android Apps
@anchor{taler-developer-manual release-process}@anchor{3a}
@section Release process


After extensive testing, the code making up a new release should get a signed git tag.
The current tag format is:


@itemize *

@item 
cashier-$VERSION

@item 
pos-$VERSION

@item 
wallet-$VERSION (where $VERSION has a v prefix)
@end itemize

@example
$ git tag -s $APP-$VERSION
@end example

@menu
* F-Droid:: 
* Google Play:: 

@end menu

@node F-Droid,Google Play,,Release process
@anchor{taler-developer-manual id1}@anchor{3b}
@subsection F-Droid


Nightly builds get published automatically (see above) after pushing code to the official repo.
Actual releases get picked up by F-Droid's official repository via git tags.
So ensure that all releases get tagged properly.

Some information for F-Droid official repository debugging:


@itemize *

@item 
Wallet: [metadata@footnote{https://gitlab.com/fdroid/fdroiddata/-/blob/master/metadata/net.taler.wallet.fdroid.yml}] [build log@footnote{https://f-droid.org/wiki/page/net.taler.wallet.fdroid/lastbuild}]

@item 
Cashier: [metadata@footnote{https://gitlab.com/fdroid/fdroiddata/-/blob/master/metadata/net.taler.cashier.yml}] [build log@footnote{https://f-droid.org/wiki/page/net.taler.cashier/lastbuild}]

@item 
PoS: [metadata@footnote{https://gitlab.com/fdroid/fdroiddata/-/blob/master/metadata/net.taler.merchantpos.yml}] [build log@footnote{https://f-droid.org/wiki/page/net.taler.merchantpos/lastbuild}]
@end itemize

@node Google Play,,F-Droid,Release process
@anchor{taler-developer-manual google-play}@anchor{3c}
@subsection Google Play


Google Play uploads are managed via Fastlane@footnote{https://docs.fastlane.tools/getting-started/android/setup/}.
Before proceeding, ensure that this is properly set up
and that you have access to the Google Play API.

To release an app, enter into its respective folder and run fastlane:

@example
$ bundle exec fastlane
@end example

Then select the deploy option.
Note this requires access to the Google Play upload signing key
set via the various environment variables in $app/fastlane/Fastfile.

All uploads are going to the beta track by default.
These can be promoted to production later or immediately after upload if you feel daring.

@node Code Coverage,Coding Conventions,Android Apps,Top
@anchor{taler-developer-manual id2}@anchor{3d}@anchor{taler-developer-manual id3}@anchor{3e}
@chapter Code Coverage


Code coverage is done with the Gcov / Lcov
(@indicateurl{http://ltp.sourceforge.net/coverage/lcov.php}) combo, and it is run
nightly (once a day) by a Buildbot worker. The coverage results are
then published at @indicateurl{https://lcov.taler.net/} .

@node Coding Conventions,Testing library,Code Coverage,Top
@anchor{taler-developer-manual coding-conventions}@anchor{3f}
@chapter Coding Conventions


GNU Taler is developed primarily in C, Kotlin, Python and TypeScript.

@menu
* Components written in C:: 
* Shell Scripts:: 
* Kotlin:: 
* Python:: 

@end menu

@node Components written in C,Shell Scripts,,Coding Conventions
@anchor{taler-developer-manual components-written-in-c}@anchor{40}
@section Components written in C


These are the general coding style rules for Taler.


@itemize *

@item 
Baseline rules are to follow GNU guidelines, modified or extended
by the GNUnet style: @indicateurl{https://docs.gnunet.org/handbook/gnunet.html#Coding-style}
@end itemize

@menu
* Naming conventions:: 

@end menu

@node Naming conventions,,,Components written in C
@anchor{taler-developer-manual naming-conventions}@anchor{41}
@subsection Naming conventions



@itemize *

@item 
include files (very similar to GNUnet):


@itemize *

@item 
if installed, must start with "@code{taler_}" (exception: platform.h),
and MUST live in src/include/

@item 
if NOT installed, must NOT start with "@code{taler_}" and
MUST NOT live in src/include/ and
SHOULD NOT be included from outside of their own directory

@item 
end in "_lib" for "simple" libraries

@item 
end in "_plugin" for plugins

@item 
end in "_service" for libraries accessing a service, i.e. the exchange
@end itemize

@item 
binaries:


@itemize *

@item 
taler-exchange-xxx: exchange programs

@item 
taler-merchant-xxx: merchant programs (demos)

@item 
taler-wallet-xxx: wallet programs

@item 
plugins should be libtaler_plugin_xxx_yyy.so: plugin yyy for API xxx

@item 
libtalerxxx: library for API xxx
@end itemize

@item 
logging


@itemize *

@item 
tools use their full name in GNUNET_log_setup
(i.e. 'taler-exchange-offline') and log using plain 'GNUNET_log'.

@item 
pure libraries (without associated service) use 'GNUNET_log_from'
with the component set to their library name (without lib or '.so'),
which should also be their directory name (i.e. 'util')

@item 
plugin libraries (without associated service) use 'GNUNET_log_from'
with the component set to their type and plugin name (without lib or '.so'),
which should also be their directory name (i.e. 'exchangedb-postgres')

@item 
libraries with associated service) use 'GNUNET_log_from'
with the name of the service,  which should also be their
directory name (i.e. 'exchange')

@item 
for tools with @code{-l LOGFILE}, its absence means write logs to stderr
@end itemize

@item 
configuration


@itemize *

@item 
same rules as for GNUnet
@end itemize

@item 
exported symbols


@itemize *

@item 
must start with TALER_[SUBSYSTEMNAME]_ where SUBSYSTEMNAME
MUST match the subdirectory of src/ in which the symbol is defined

@item 
from libtalerutil start just with @code{TALER_}, without subsystemname

@item 
if scope is ONE binary and symbols are not in a shared library,
use binary-specific prefix (such as TMH = taler-exchange-httpd) for
globals, possibly followed by the subsystem (TMH_DB_xxx).
@end itemize

@item 
structs:


@itemize *

@item 
structs that are 'packed' and do not contain pointers and are
thus suitable for hashing or similar operations are distinguished
by adding a "P" at the end of the name. (NEW)  Note that this
convention does not hold for the GNUnet-structs (yet).

@item 
structs that are used with a purpose for signatures, additionally
get an "S" at the end of the name.
@end itemize

@item 
private (library-internal) symbols (including structs and macros)


@itemize *

@item 
must not start with @code{TALER_} or any other prefix
@end itemize

@item 
testcases


@itemize *

@item 
must be called "test_module-under-test_case-description.c"
@end itemize

@item 
performance tests


@itemize *

@item 
must be called "perf_module-under-test_case-description.c"
@end itemize
@end itemize

@node Shell Scripts,Kotlin,Components written in C,Coding Conventions
@anchor{taler-developer-manual shell-scripts}@anchor{42}
@section Shell Scripts


Shell scripts should be avoided if at all possible.  The only permissible uses of shell scripts
in GNU Taler are:


@itemize *

@item 
Trivial invocation of other commands.

@item 
Scripts for compatibility (e.g. @code{./configure}) that must run on
as many systems as possible.
@end itemize

When shell scripts are used, they @code{MUST} begin with the following @code{set} command:

@example
# Make the shell fail on undefined variables and
# commands with non-zero exit status.
$ set -eu
@end example

@node Kotlin,Python,Shell Scripts,Coding Conventions
@anchor{taler-developer-manual kotlin}@anchor{43}
@section Kotlin


We so far have no specific guidelines, please follow best practices
for the language.

@node Python,,Kotlin,Coding Conventions
@anchor{taler-developer-manual python}@anchor{44}
@section Python


@menu
* Supported Python Versions:: 
* Style:: 
* Python for Scripting:: 

@end menu

@node Supported Python Versions,Style,,Python
@anchor{taler-developer-manual supported-python-versions}@anchor{45}
@subsection Supported Python Versions


Python code should be written and build against version 3.7 of Python.

@node Style,Python for Scripting,Supported Python Versions,Python
@anchor{taler-developer-manual style}@anchor{46}
@subsection Style


We use yapf@footnote{https://github.com/google/yapf} to reformat the
code to conform to our style instructions.
A reusable yapf style file can be found in @code{build-common},
which is intended to be used as a git submodule.

@node Python for Scripting,,Style,Python
@anchor{taler-developer-manual python-for-scripting}@anchor{47}
@subsection Python for Scripting


When using Python for writing small utilities, the following libraries
are useful:


@itemize *

@item 
@code{click} for argument parsing (should be preferred over argparse)

@item 
@code{pathlib} for path manipulation (part of the standard library)

@item 
@code{subprocess} for "shelling out" to other programs.  Prefer @code{subprocess.run}
over the older APIs.
@end itemize

@node Testing library,User-Facing Terminology,Coding Conventions,Top
@anchor{taler-developer-manual testing-library}@anchor{48}
@chapter Testing library


This chapter is a VERY ABSTRACT description of how testing is
implemented in Taler, and in NO WAY wants to substitute the reading of
the actual source code by the user.

In Taler, a test case is an array of @code{struct TALER_TESTING_Command},
informally referred to as @code{CMD}, that is iteratively executed by the
testing interpreter. This latter is transparently initiated by the
testing library.

However, the developer does not have to defined CMDs manually, but
rather call the proper constructor provided by the library. For example,
if a CMD is supposed to test feature @code{x}, then the library would
provide the @code{TALER_TESTING_cmd_x ()} constructor for it. Obviously,
each constructor has its own particular arguments that make sense to
test @code{x}, and all constructor are thoroughly commented within the
source code.

Internally, each CMD has two methods: @code{run ()} and @code{cleanup ()}. The
former contains the main logic to test feature @code{x}, whereas the latter
cleans the memory up after execution.

In a test life, each CMD needs some internal state, made by values it
keeps in memory. Often, the test has to @emph{share} those values with other
CMDs: for example, CMD1 may create some key material and CMD2 needs this
key material to encrypt data.

The offering of internal values from CMD1 to CMD2 is made by @emph{traits}. A
trait is a @code{struct TALER_TESTING_Trait}, and each CMD contains an array
of traits, that it offers via the public trait interface to other
commands. The definition and filling of such array happens transparently
to the test developer.

For example, the following example shows how CMD2 takes an amount object
offered by CMD1 via the trait interface.

Note: the main interpreter and the most part of CMDs and traits are
hosted inside the exchange codebase, but nothing prevents the developer
from implementing new CMDs and traits within other codebases.

@example
/* Without loss of generality, let's consider the
 * following logic to exist inside the run() method of CMD1 */
...

struct TALER_Amount *a;
/**
 * the second argument (0) points to the first amount object offered,
 * in case multiple are available.
 */
if (GNUNET_OK != TALER_TESTING_get_trait_amount_obj (cmd2, 0, &a))
  return GNUNET_SYSERR;
...

use(a); /* 'a' points straight into the internal state of CMD2 */
@end example

In the Taler realm, there is also the possibility to alter the behaviour
of supposedly well-behaved components. This is needed when, for example,
we want the exchange to return some corrupted signature in order to
check if the merchant backend detects it.

This alteration is accomplished by another service called @emph{twister}. The
twister acts as a proxy between service A and B, and can be programmed
to tamper with the data exchanged by A and B.

Please refer to the Twister codebase (under the @code{test} directory) in
order to see how to configure it.

@node User-Facing Terminology,Developer Glossary,Testing library,Top
@anchor{taler-developer-manual user-facing-terminology}@anchor{49}
@chapter User-Facing Terminology


This section contains terminology that should be used and that should not be
used in the user interface and help materials.

@menu
* Terms to Avoid:: 
* Terms to Use:: 

@end menu

@node Terms to Avoid,Terms to Use,,User-Facing Terminology
@anchor{taler-developer-manual terms-to-avoid}@anchor{4a}
@section Terms to Avoid



@table @asis

@item Refreshing

Refreshing is the internal technical terminology for the protocol to
give change for partially spent coins

@strong{Use instead}: "Obtaining change"

@item Coin

Coins are an internal construct, the user should never be aware that their balance
is represented by coins if different denominations.

@strong{Use instead}: "(Digital) Cash" or "(Wallet) Balance"

@item Consumer

Has bad connotation of consumption.

@strong{Use instead}: Customer or user.

@item Proposal

The term used to describe the process of the merchant facilitating the download
of the signed contract terms for an order.

@strong{Avoid}.  Generally events that relate to proposal downloads
should not be shown to normal users, only developers.  Instead, use
"communication with mechant failed" if a proposed order can't be downloaded.

@item Anonymous E-Cash

Should be generally avoided, since Taler is only anonymous for
the customer. Also some people are scared of anonymity (which as
a term is also way too absolute, as anonymity is hardly ever perfect).

@strong{Use instead}:  "Privacy-preserving", "Privacy-friendly"

@item Payment Replay

The process of proving to the merchant that the customer is entitled
to view a digital product again, as they already paid for it.

@strong{Use instead}:  In the event history, "re-activated digital content purchase"
could be used. (FIXME: this is still not nice.)

@item Session ID

See Payment Replay.

@item Order

Too ambiguous in the wallet.

@strong{Use instead}: Purchase

@item Fulfillment URL

URL that the serves the digital content that the user purchased
with their payment.  Can also be something like a donation receipt.
@end table

@node Terms to Use,,Terms to Avoid,User-Facing Terminology
@anchor{taler-developer-manual terms-to-use}@anchor{4b}
@section Terms to Use



@table @asis

@item Auditor

Regulatory entity that certifies exchanges and oversees their operation.

@item Exchange Operator

The entity/service that gives out digital cash in exchange for some
other means of payment.

In some contexts, using "Issuer" could also be appropriate.
When showing a balance breakdown,
we can say "100 Eur (issued by exchange.euro.taler.net)".
Sometimes we may also use the more generic term "Payment Service Provider"
when the concept of an "Exchange" is still unclear to the reader.

@item Refund

A refund is given by a merchant to the customer (rather the customer's wallet)
and "undoes" a previous payment operation.

@item Payment

The act of sending digital cash to a merchant to pay for an order.

@item Purchase

Used to refer to the "result" of a payment, as in "view purchase".
Use sparsingly, as the word doesn't fit for all payments, such as donations.

@item Contract Terms

Partially machine-readable representation of the merchant's obligation after the
customer makes a payment.

@item Merchant

Party that receives a payment.

@item Wallet

Also "Taler Wallet".  Software component that manages the user's digital cash
and payments.
@end table

@node Developer Glossary,Developer Tools,User-Facing Terminology,Top
@anchor{taler-developer-manual developer-glossary}@anchor{4c}
@chapter Developer Glossary


This glossary is meant for developers.  It contains some terms that we usually do not
use when talking to end users or even system administrators.


@table @asis
@anchor{taler-developer-manual term-absolute-time}@anchor{4d}
@geindex absolute time

@item absolute time

method of keeping time in @ref{4e,,GNUnet} where the time is represented
as the number of microseconds since 1.1.1970 (UNIX epoch).  Called
absolute time in contrast to @ref{4f,,relative time}.
@anchor{taler-developer-manual term-aggregate}@anchor{50}
@geindex aggregate

@item aggregate

the @ref{51,,exchange} combines multiple payments received by the
same @ref{52,,merchant} into one larger @ref{53,,wire transfer} to
the respective merchant's @ref{54,,bank} account
@anchor{taler-developer-manual term-auditor}@anchor{55}
@geindex auditor

@item auditor

trusted third party that verifies that the @ref{51,,exchange} is operating correctly
@anchor{taler-developer-manual term-bank}@anchor{54}
@geindex bank

@item bank

traditional financial service provider who offers wire @ref{56,,transfers} between accounts
@anchor{taler-developer-manual term-buyer}@anchor{57}
@geindex buyer

@item buyer

individual in control of a Taler @ref{58,,wallet}, usually using it to
@ref{59,,spend} the @ref{5a,,coins} on @ref{5b,,contracts} (see also @ref{5c,,customer}).
@anchor{taler-developer-manual term-close}@anchor{5d}
@geindex close

@item close@anchor{taler-developer-manual term-closes}@anchor{5e}
@geindex closes

@itemx closes@anchor{taler-developer-manual term-closed}@anchor{5f}
@geindex closed

@itemx closed@anchor{taler-developer-manual term-closing}@anchor{60}
@geindex closing

@itemx closing

operation an @ref{51,,exchange} performs on a @ref{61,,reserve} that has not been
@ref{62,,drained} by @ref{63,,withdraw} operations. When closing a reserve, the
exchange wires the remaining funds back to the customer, minus a @ref{64,,fee}
for closing
@anchor{taler-developer-manual term-coin}@anchor{65}
@geindex coin

@item coin@anchor{taler-developer-manual term-coins}@anchor{5a}
@geindex coins

@itemx coins

coins are individual token representing a certain amount of value, also known as the @ref{66,,denomination} of the coin
@anchor{taler-developer-manual term-commitment}@anchor{67}
@geindex commitment

@item commitment@anchor{taler-developer-manual term-refresh-commitment}@anchor{68}
@geindex refresh commitment

@itemx refresh commitment

data that the wallet commits to during the @ref{69,,melt} stage of the
@ref{6a,,refresh} protocol where it
has to prove to the @ref{51,,exchange} that it is deriving the @ref{6b,,fresh}
coins as specified by the Taler protocol.  The commitment is verified
probabilistically (see: @ref{6c,,kappa}) during the @ref{6d,,reveal} stage.
@anchor{taler-developer-manual term-contract}@anchor{6e}
@geindex contract

@item contract@anchor{taler-developer-manual term-contracts}@anchor{5b}
@geindex contracts

@itemx contracts

formal agreement between @ref{52,,merchant} and @ref{5c,,customer} specifying the
@ref{6f,,contract terms} and signed by the merchant and the @ref{5a,,coins} of the
customer
@anchor{taler-developer-manual term-contract-terms}@anchor{6f}
@geindex contract terms

@item contract terms

the individual clauses specifying what the buyer is purchasing from the
@ref{52,,merchant}
@anchor{taler-developer-manual term-customer}@anchor{5c}
@geindex customer

@item customer

individual that directs the buyer (perhaps the same individual) to make a purchase
@anchor{taler-developer-manual term-denomination}@anchor{66}
@geindex denomination

@item denomination

unit of currency, specifies both the currency and the face value of a @ref{65,,coin},
as well as associated fees and validity periods
@anchor{taler-developer-manual term-denomination-key}@anchor{70}
@geindex denomination key

@item denomination key

(RSA) key used by the exchange to certify that a given @ref{65,,coin} is valid and of a
particular @ref{66,,denomination}
@anchor{taler-developer-manual term-deposit}@anchor{71}
@geindex deposit

@item deposit@anchor{taler-developer-manual term-deposits}@anchor{72}
@geindex deposits

@itemx deposits@anchor{taler-developer-manual term-depositing}@anchor{73}
@geindex depositing

@itemx depositing

operation by which a merchant passes coins to an exchange, expecting the
exchange to credit his bank account in the future using an
@ref{50,,aggregate} @ref{53,,wire transfer}
@anchor{taler-developer-manual term-dirty}@anchor{74}
@geindex dirty

@item dirty@anchor{taler-developer-manual term-dirty-coin}@anchor{75}
@geindex dirty coin

@itemx dirty coin

a coin is dirty if its public key may be known to an entity other than
the customer, thereby creating the danger of some entity being able to
link multiple transactions of coin's owner if the coin is not refreshed
@anchor{taler-developer-manual term-drain}@anchor{76}
@geindex drain

@item drain@anchor{taler-developer-manual term-drained}@anchor{62}
@geindex drained

@itemx drained

a @ref{61,,reserve} is being drained when a @ref{58,,wallet} is using the
reserve's private key to @ref{63,,withdraw} coins from it. This reduces
the balance of the reserve. Once the balance reaches zero, we say that
the reserve has been (fully) drained.  Reserves that are not drained
(which is the normal process) are @ref{5f,,closed} by the exchange.
@anchor{taler-developer-manual term-exchange}@anchor{51}
@geindex exchange

@item exchange

Taler's payment service operator.  Issues electronic coins during
withdrawal and redeems them when they are deposited by merchants
@anchor{taler-developer-manual term-expired}@anchor{77}
@geindex expired

@item expired@anchor{taler-developer-manual term-expiration}@anchor{78}
@geindex expiration

@itemx expiration

Various operations come with time limits. In particular, denomination keys
come with strict time limits for the various operations involving the
coin issued under the denomination. The most important limit is the
deposit expiration, which specifies until when wallets are allowed to
use the coin in deposit or refreshing operations. There is also a "legal"
expiration, which specifies how long the exchange keeps records beyond the
deposit expiration time.  This latter expiration matters for legal disputes
in courts and also creates an upper limit for refreshing operations on
special zombie coin
@anchor{taler-developer-manual term-fakebank}@anchor{79}
@geindex fakebank

@item fakebank

implementation of the @ref{54,,bank} API in memory to be used only for test
cases.
@anchor{taler-developer-manual term-fee}@anchor{64}
@geindex fee

@item fee

an @ref{51,,exchange} charges various fees for its service. The different
fees are specified in the protocol. There are fees per coin for
@ref{7a,,withdrawing}, @ref{73,,depositing}, @ref{7b,,melting}, and
@ref{7c,,refunding}.  Furthermore, there are fees per wire transfer
for @ref{60,,closing} a @ref{61,,reserve}: and for
@ref{50,,aggregate} @ref{7d,,wire transfers} to the @ref{52,,merchant}.
@anchor{taler-developer-manual term-fresh}@anchor{6b}
@geindex fresh

@item fresh@anchor{taler-developer-manual term-fresh-coin}@anchor{7e}
@geindex fresh coin

@itemx fresh coin

a coin is fresh if its public key is only known to the customer
@anchor{taler-developer-manual term-GNUnet}@anchor{4e}
@geindex GNUnet

@item GNUnet

Codebase of various libraries for a better Internet, some of which
GNU Taler depends upon.
@anchor{taler-developer-manual term-json}@anchor{7f}
@geindex json

@item json@anchor{taler-developer-manual term-JSON}@anchor{80}
@geindex JSON

@itemx JSON@anchor{taler-developer-manual term-JavaScript-Object-Notation}@anchor{81}
@geindex JavaScript Object Notation

@itemx JavaScript Object Notation

serialization format derived from the JavaScript language which is
commonly used in the Taler protocol as the payload of HTTP requests
and responses.
@anchor{taler-developer-manual term-kappa}@anchor{6c}
@geindex kappa

@item kappa

security parameter used in the @ref{6a,,refresh} protocol. Defined to be 3.
The probability of successfully evading the income transparency with the
refresh protocol is 1:kappa.
@anchor{taler-developer-manual term-LibEuFin}@anchor{82}
@geindex LibEuFin

@item LibEuFin

FIXME: explain
@anchor{taler-developer-manual term-link}@anchor{83}
@geindex link

@item link@anchor{taler-developer-manual term-linking}@anchor{84}
@geindex linking

@itemx linking

specific step in the @ref{6a,,refresh} protocol that an exchange must offer
to prevent abuse of the @ref{6a,,refresh} mechanism.  The link step is
not needed in normal operation, it just must be offered.
@anchor{taler-developer-manual term-master-key}@anchor{85}
@geindex master key

@item master key

offline key used by the exchange to certify denomination keys and
message signing keys
@anchor{taler-developer-manual term-melt}@anchor{69}
@geindex melt

@item melt@anchor{taler-developer-manual term-melted}@anchor{86}
@geindex melted

@itemx melted@anchor{taler-developer-manual term-melting}@anchor{7b}
@geindex melting

@itemx melting

step of the @ref{6a,,refresh} protocol where a @ref{75,,dirty coin}
is invalidated to be reborn @ref{6b,,fresh} in a subsequent
@ref{6d,,reveal} step.
@anchor{taler-developer-manual term-merchant}@anchor{52}
@geindex merchant

@item merchant

party receiving payments (usually in return for goods or services)
@anchor{taler-developer-manual term-message-signing-key}@anchor{87}
@geindex message signing key

@item message signing key

key used by the exchange to sign online messages, other than coins
@anchor{taler-developer-manual term-order}@anchor{88}
@geindex order

@item order

FIXME: to be written!
@anchor{taler-developer-manual term-owner}@anchor{89}
@geindex owner

@item owner

a coin is owned by the entity that knows the private key of the coin
@anchor{taler-developer-manual term-planchet}@anchor{8a}
@geindex planchet

@item planchet

precursor data for a @ref{65,,coin}. A planchet includes the coin's internal
secrets (coin private key, blinding factor), but lacks the RSA signature
of the @ref{51,,exchange}.  When @ref{7a,,withdrawing}, a @ref{58,,wallet}
creates and persists a planchet before asking the exchange to sign it to
get the coin.
@anchor{taler-developer-manual term-privacy-policy}@anchor{8b}
@geindex privacy policy

@item privacy policy

Statement of an operator how they will protect the privacy of users.
@anchor{taler-developer-manual term-proof}@anchor{8c}
@geindex proof

@item proof

Message that cryptographically demonstrates that a particular claim is correct.
@anchor{taler-developer-manual term-proposal}@anchor{8d}
@geindex proposal

@item proposal

a list of @ref{6f,,contract terms} that has been completed and signed by the
merchant backend.
@anchor{taler-developer-manual term-purchase}@anchor{8e}
@geindex purchase

@item purchase

Refers to the overall process of negotiating a @ref{6e,,contract} and then
making a payment with @ref{5a,,coins} to a @ref{52,,merchant}.
@anchor{taler-developer-manual term-recoup}@anchor{8f}
@geindex recoup

@item recoup

Operation by which an exchange returns the value of coins affected
by a @ref{90,,revocation} to their @ref{89,,owner}, either by allowing the owner to
withdraw new coins or wiring funds back to the bank account of the @ref{89,,owner}.
@anchor{taler-developer-manual term-refresh}@anchor{6a}
@geindex refresh

@item refresh@anchor{taler-developer-manual term-refreshing}@anchor{91}
@geindex refreshing

@itemx refreshing

operation by which a @ref{75,,dirty coin} is converted into one or more
@ref{6b,,fresh} coins.  Involves @ref{7b,,melting} the @ref{75,,dirty coin} and
then @ref{92,,revealing} so-called @ref{93,,transfer keys}.
@anchor{taler-developer-manual term-refund}@anchor{94}
@geindex refund

@item refund@anchor{taler-developer-manual term-refunding}@anchor{7c}
@geindex refunding

@itemx refunding

operation by which a merchant steps back from the right to funds that he
obtained from a @ref{71,,deposit} operation, giving the right to the funds back
to the customer
@anchor{taler-developer-manual term-refund-transaction-id}@anchor{95}
@geindex refund transaction id

@item refund transaction id

unique number by which a merchant identifies a @ref{94,,refund}. Needed
as refunds can be partial and thus there could be multiple refunds for
the same @ref{8e,,purchase}.
@anchor{taler-developer-manual term-relative-time}@anchor{4f}
@geindex relative time

@item relative time

method of keeping time in @ref{4e,,GNUnet} where the time is represented
as a relative number of microseconds.  Thus, a relative time specifies
an offset or a duration, but not a date.  Called relative time in
contrast to @ref{4d,,absolute time}.
@anchor{taler-developer-manual term-reserve}@anchor{61}
@geindex reserve

@item reserve

accounting mechanism used by the exchange to track customer funds
from incoming @ref{7d,,wire transfers}.  A reserve is created whenever
a customer wires money to the exchange using a well-formed public key
in the subject.  The exchange then allows the customer's @ref{58,,wallet}
to @ref{63,,withdraw} up to the amount received in @ref{6b,,fresh}
@ref{5a,,coins} from the reserve, thereby draining the reserve. If a
reserve is not drained, the exchange eventually @ref{5e,,closes} it.

Other definition: Funds set aside for future use; either the balance of a customer at the
exchange ready for withdrawal, or the funds kept in the exchange;s bank
account to cover obligations from coins in circulation.
@anchor{taler-developer-manual term-reveal}@anchor{6d}
@geindex reveal

@item reveal@anchor{taler-developer-manual term-revealing}@anchor{92}
@geindex revealing

@itemx revealing

step in the @ref{6a,,refresh} protocol where some of the transfer private
keys are revealed to prove honest behavior on the part of the wallet.
In the reveal step, the exchange returns the signed @ref{6b,,fresh} coins.
@anchor{taler-developer-manual term-revoke}@anchor{96}
@geindex revoke

@item revoke@anchor{taler-developer-manual term-revocation}@anchor{90}
@geindex revocation

@itemx revocation

exceptional operation by which an exchange withdraws a denomination from
circulation, either because the signing key was compromised or because
the exchange is going out of operation; unspent coins of a revoked
denomination are subjected to recoup.
@anchor{taler-developer-manual term-sharing}@anchor{97}
@geindex sharing

@item sharing

users can share ownership of a @ref{65,,coin} by sharing access to the coin&#39;s
private key, thereby allowing all co-owners to spend the coin at any
time.
@anchor{taler-developer-manual term-spend}@anchor{59}
@geindex spend

@item spend@anchor{taler-developer-manual term-spending}@anchor{98}
@geindex spending

@itemx spending

operation by which a customer gives a merchant the right to deposit
coins in return for merchandise
@anchor{taler-developer-manual term-terms}@anchor{99}
@geindex terms

@item terms

the general terms of service of an operator, possibly including
the @ref{8b,,privacy policy}.  Not to be confused with the
@ref{6f,,contract terms} which are about the specific purchase.
@anchor{taler-developer-manual term-transaction}@anchor{9a}
@geindex transaction

@item transaction

method by which ownership is exclusively transferred from one entity
@anchor{taler-developer-manual term-transfer}@anchor{56}
@geindex transfer

@item transfer@anchor{taler-developer-manual term-transfers}@anchor{9b}
@geindex transfers

@itemx transfers@anchor{taler-developer-manual term-wire-transfer}@anchor{53}
@geindex wire transfer

@itemx wire transfer@anchor{taler-developer-manual term-wire-transfers}@anchor{7d}
@geindex wire transfers

@itemx wire transfers

method of sending funds between @ref{54,,bank} accounts
@anchor{taler-developer-manual term-transfer-key}@anchor{9c}
@geindex transfer key

@item transfer key@anchor{taler-developer-manual term-transfer-keys}@anchor{93}
@geindex transfer keys

@itemx transfer keys

special cryptographic key used in the @ref{6a,,refresh} protocol, some of which
are revealed during the @ref{6d,,reveal} step. Note that transfer keys have,
despite the name, no relationship to @ref{7d,,wire transfers}.  They merely
help to transfer the value from a @ref{75,,dirty coin} to a @ref{7e,,fresh coin}
@anchor{taler-developer-manual term-user}@anchor{9d}
@geindex user

@item user

any individual using the Taler payment system
(see @ref{5c,,customer}, @ref{57,,buyer}, @ref{52,,merchant}).
@anchor{taler-developer-manual term-version}@anchor{9e}
@geindex version

@item version

Taler uses various forms of versioning. There is a database
schema version (stored itself in the database, see *-0000.sql) describing
the state of the table structure in the database of an @ref{51,,exchange},
@ref{55,,auditor} or @ref{52,,merchant}. There is a protocol
version (CURRENT:REVISION:AGE, see GNU libtool) which specifies
the network protocol spoken by an @ref{51,,exchange} or @ref{52,,merchant}
including backwards-compatibility. And finally there is the software
release version (MAJOR.MINOR.PATCH, see @indicateurl{https://semver.org/}) of
the respective code base.
@anchor{taler-developer-manual term-wallet}@anchor{58}
@geindex wallet

@item wallet

software running on a customer's computer; withdraws, stores and
spends coins
@anchor{taler-developer-manual term-WebExtension}@anchor{9f}
@geindex WebExtension

@item WebExtension

Cross-browser API used to implement the GNU Taler wallet browser extension.
@anchor{taler-developer-manual term-wire-gateway}@anchor{a0}
@geindex wire gateway

@item wire gateway

FIXME: explain
@anchor{taler-developer-manual term-wire-transfer-identifier}@anchor{a1}
@geindex wire transfer identifier

@item wire transfer identifier@anchor{taler-developer-manual term-wtid}@anchor{a2}
@geindex wtid

@itemx wtid

Subject of a wire transfer from the exchange to a merchant;
set by the aggregator to a random nonce which uniquely
identifies the transfer.
@anchor{taler-developer-manual term-withdraw}@anchor{63}
@geindex withdraw

@item withdraw@anchor{taler-developer-manual term-withdrawing}@anchor{7a}
@geindex withdrawing

@itemx withdrawing@anchor{taler-developer-manual term-withdrawal}@anchor{a3}
@geindex withdrawal

@itemx withdrawal

operation by which a @ref{58,,wallet} can convert funds from a @ref{61,,reserve} to
fresh coins
@anchor{taler-developer-manual term-zombie}@anchor{a4}
@geindex zombie

@item zombie@anchor{taler-developer-manual term-zombie-coin}@anchor{a5}
@geindex zombie coin

@itemx zombie coin

coin where the respective @ref{70,,denomination key} is past its
@ref{71,,deposit} @ref{78,,expiration} time, but which is still (again) valid
for an operation because it was @ref{86,,melted} while it was still
valid, and then later again credited during a @ref{8f,,recoup} process
@end table

@node Developer Tools,Index,Developer Glossary,Top
@anchor{taler-developer-manual developer-tools}@anchor{a6}
@chapter Developer Tools


This section describes various internal programs to make life easier for the
developer.

@menu
* taler-config-generate:: 

@end menu

@node taler-config-generate,,,Developer Tools
@anchor{taler-developer-manual taler-config-generate}@anchor{a7}
@section taler-config-generate


@strong{taler-config-generate} - tool to simplify Taler configuration generation

@strong{taler-config-generate}
[@strong{-C} @emph{CURRENCY} | @strong{--currency=}‌@emph{CURRENCY}]
[@strong{-c} @emph{FILENAME} | @strong{--config=}‌@emph{FILENAME}]
[@strong{-e} | @strong{--exchange}]
[@strong{-f} @emph{AMOUNT} | @emph{--wirefee=}‌@emph{AMOUNT}]
[@strong{-h} | @strong{--help}]
[@strong{-J} @emph{JSON} | @strong{--wire-json-exchange=}‌@emph{JSON}]
[@strong{-j} @emph{JSON} | @strong{--wire-json-merchant=}‌@emph{JSON}]
[@strong{-L} @emph{LOGLEVEL} | @strong{--loglevel=}‌@emph{LOGLEVEL}]
[@strong{-m} | @strong{--merchant}]
[@strong{-t} | @strong{--trusted}]
[@strong{-v} | @strong{--version}]
[@strong{-w} @emph{WIREFORMAT} | @strong{--wire} @emph{WIREFORMAT}]
[@strong{--bank-uri}]
[@strong{--exchange-bank-account}]
[@strong{--merchant-bank-account}]

@strong{taler-config-generate} can be used to generate configuration files
for the Taler exchange or Taler merchants.


@table @asis

@item @strong{-C} @emph{CURRENCY} | @strong{--currency=}‌@emph{CURRENCY}

Which currency should we use in the configuration.

@item @strong{-c} @emph{FILENAME} | @strong{--config=}‌@emph{FILENAME}

Location where to write the generated configuration. Existing file
will be updated, not overwritten.

@item @strong{-e} | @strong{--exchange}

Generate configuration for a Taler exchange.

@item @strong{-f} @emph{AMOUNT} | @emph{-wirefee=}‌@emph{AMOUNT}

Setup wire transfer fees for the next 5 years for the exchange (for
all wire methods).

@item @strong{-h} | @strong{--help}

Shows this man page.

@item @strong{-J} @emph{JSON} | @strong{--wire-json-exchange=}‌@emph{JSON}

Wire configuration to use for the exchange.

@item @strong{-j} @emph{JSON} | @strong{--wire-json-merchant=}‌@emph{JSON}

Wire configuration to use for the merchant.

@item @strong{-L} @emph{LOGLEVEL} | @strong{--loglevel=}‌@emph{LOGLEVEL}

Use LOGLEVEL for logging. Valid values are DEBUG, INFO, WARNING and
ERROR.

@item @strong{-m} | @strong{--merchant}

Generate configuration for a Taler merchant.

@item @strong{-t} | @strong{--trusted}

Setup current exchange as trusted with current merchant. Generally
only useful when configuring for testcases.

@item @strong{-v} | @strong{--version}

Print version information.

@item @strong{-w} @emph{WIREFORMAT} | @strong{--wire} @emph{WIREFORMAT}

Specifies which wire format to use (i.e. “x-talerbank” or “iban”)

@item @strong{--bank-uri}

Alternative to specify wire configuration to use for the exchange and
merchant for the “test” wire method. Only useful if WIREFORMAT was
set to “test”. Specifies the URI of the bank.

@item @strong{--exchange-bank-account}

Alternative to specify wire configuration to use for the exchange for
the “test” wire method. Only useful if WIREFORMAT was set to “test”.
Specifies the bank account number of the exchange.

@item @strong{--merchant-bank-account}

Alternative to specify wire configuration to use for the merchant for
the “test” wire method. Only useful if WIREFORMAT was set to “test”.
Specifies the bank account number of the merchant.
@end table

@node Index,,Developer Tools,Top
@unnumbered Index


@printindex ge


@c %**end of body
@bye