[GNUnet-SVN] [taler-merchant-frontend-examples] branch master updated: python tutorial first draft

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The following commit(s) were added to refs/heads/master by this push:
     new 923c7a3  python tutorial first draft
923c7a3 is described below

commit 923c7a3d18753703c175a7b9b143aa775d436576
Author: Marcello Stanisci <address@hidden>
AuthorDate: Wed Feb 22 15:03:47 2017 +0100

    python tutorial first draft
---
 python/doc/Makefile      |  19 ++
 python/doc/fdl-1.3.texi  | 506 +++++++++++++++++++++++++++++++++++++++++++
 python/doc/lgpl.texi     | 549 +++++++++++++++++++++++++++++++++++++++++++++++
 python/doc/tutorial.texi | 441 +++++++++++++++++++++++++++++++++++++
 python/doc/version.texi  |   4 +
 5 files changed, 1519 insertions(+)

diff --git a/python/doc/Makefile b/python/doc/Makefile
new file mode 100644
index 0000000..fc3c7c3
--- /dev/null
+++ b/python/doc/Makefile
@@ -0,0 +1,19 @@
+all: tutorial.pdf tutorial.html
+
+tutorial.pdf: arch.pdf tutorial.texi
+       texi2pdf tutorial.texi
+
+tutorial.html: arch.jpg tutorial.texi
+       texi2html tutorial.texi
+
+arch.pdf:
+       cp ../../common/graphics/arch_nobo.pdf .
+
+arch.jpg:
+       cp ../../common/graphics/arch_nobo.jpg .
+
+clean:
+       rm -f arch.jpg arch.pdf tutorial.html tutorial.pdf
+
+info_TEXINFOS = tutorial.texi
+manual_TEXINFOS = version.texi
diff --git a/python/doc/fdl-1.3.texi b/python/doc/fdl-1.3.texi
new file mode 100644
index 0000000..8805f1a
--- /dev/null
+++ b/python/doc/fdl-1.3.texi
@@ -0,0 +1,506 @@
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diff --git a/python/doc/lgpl.texi b/python/doc/lgpl.texi
new file mode 100644
index 0000000..ab03d6c
--- /dev/null
+++ b/python/doc/lgpl.texi
@@ -0,0 +1,549 @@
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address@hidden line to give the library's name and an idea of what it does.}
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address@hidden smallexample
+
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+
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address@hidden
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+
address@hidden of Ty Coon}, 1 April 1990
+Ty Coon, President of Vice
address@hidden smallexample
+
+That's all there is to it!
diff --git a/python/doc/tutorial.texi b/python/doc/tutorial.texi
new file mode 100644
index 0000000..ccab152
--- /dev/null
+++ b/python/doc/tutorial.texi
@@ -0,0 +1,441 @@
+\input texinfo @c -*-texinfo-*-
address@hidden %**start of header
address@hidden tutorial.info
address@hidden version.texi
address@hidden The GNU Taler tutorial for Web shop developers @value{VERSION}
+
address@hidden Define a new index for options.
address@hidden op
address@hidden Combine everything into one index (arbitrarily chosen to be the
address@hidden concept index).
address@hidden op cp
address@hidden %**end of header
+
address@hidden
+This tutorial is about implementing a merchant frontend to run against a
+GNU Taler merchant backend (version @value{VERSION}, @value{UPDATED}),
+
+Copyright @copyright{} 2016 INRIA
+
address@hidden
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.  A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
address@hidden quotation
address@hidden copying
address@hidden If your tutorial is published on paper by the FSF, it should 
include
address@hidden The standard FSF Front-Cover and Back-Cover Texts, as given in
address@hidden maintain.texi.
address@hidden
address@hidden Titlepage
address@hidden
address@hidden
address@hidden The GNU Taler tutorial for Web shops
address@hidden Version @value{VERSION}
address@hidden @value{UPDATED}
address@hidden Marcello Stanisci (@email{marcello.stanisci@@inria.fr})
address@hidden
address@hidden 0pt plus 1filll
address@hidden
address@hidden titlepage
+
address@hidden
address@hidden
+
address@hidden
address@hidden Top
address@hidden The GNU Taler tutorial for Web shops
address@hidden
address@hidden ifnottex
+
address@hidden
+* Introduction::            Whom this tutorial is addressed to
+* Hello-world::             How to set up a donation page
+* Run                       How to run the code samples
+
+
+Appendices
+
+* GNU-LGPL::                     The GNU Lesser General Public License says 
how you
+                                 can use the code of libtalermerchant.so in 
your own projects.
+* GNU-FDL::                      The GNU Free Documentation License says how 
you
+                                 can copy and share the documentation of GNU 
Taler.
+
+Indices
+
+* Concept Index::               Index of concepts and programs.
address@hidden menu
+
+
address@hidden Introduction
address@hidden Introduction
+
address@hidden About GNU Taler
+
+GNU Taler is an open protocol for an electronic payment system with a
+free software reference implementation.  GNU Taler offers secure, fast
+and easy payment processing using well understood cryptographic
+techniques.  GNU Taler allows customers to remain anonymous, while
+ensuring that merchants can be held accountable by governments.
+Hence, GNU Taler is compatible with anti-money-laundering (AML) and
+know-your-customer (KYC) regulation, as well as data protection
+regulation (such as GDPR).
+
+
address@hidden About this tutorial
+
+This tutorial is for Web developers and addresses how to integrate GNU
+Taler with Web shops. It describes how to create a Web shop that
+processes payments with the help of a GNU Taler merchant
address@hidden  In the second chapter, you will learn how to trigger
+the payment process from the Web site, how to communicate with the
+backend, how to generate a contract and process the payment.
+
address@hidden examples
address@hidden git
+You can download all of the code examples given in this tutorial from
address@hidden://git.taler.net/merchant-frontend-examples.git/tree/python/example/}.
+
address@hidden Add section giving an overview of what we will do in the 
tutorial!
+
+
address@hidden Architecture overview
+
+The Taler software stack for a merchant consists of the following
+main components:
+
address@hidden
address@hidden frontend
address@hidden A frontend which interacts with the customer's browser. The
+  frontend enables the customer to build a shopping cart and place
+  an order.  Upon payment, it triggers the respective business logic
+  to satisfy the order.  This component is not included with Taler,
+  but rather assumed to exist at the merchant. This tutorial
+  describes how to develop a Taler frontend.
address@hidden backend
address@hidden A Taler-specific payment backend which makes it easy for the
+  frontend to process financial transactions with Taler.  For this
+  tutorial, you will use a public backend, but for a production
+  deployment a merchant-specific backend will need to be setup
+  by a system administrator.
address@hidden itemize
+
+The following image illustrates the various interactions of these
+key components:
+
address@hidden, 3in, 4in}
+
+
+Basically, the backend provides the cryptographic protocol support,
+stores Taler-specific financial information and communicates
+with the GNU Taler exchange over the Internet.  The frontend accesses
+the backend via a RESTful API.  As a result, the frontend never has to
+directly communicate with the exchange, and also does not deal with
+sensitive data.  In particular, the merchant's signing keys and bank
+account information are encapsulated within the Taler backend.
+
address@hidden Hello-world
address@hidden Setting up a simple donation page
+
+This section describes how to setup a simple shop, which exposes a
+button to get donations via Taler. The expected behaviour is that once
+the ``donate'' button is clicked, the customer will receive a Taler
+proposal offering him the opportunity to make a fixed donation,
+for example to donate 1.0 KUDOS to the charity operating the shop.
+
+All the code samples shown below in the tutorial can be found at
address@hidden://git.taler.net/merchant-frontend-examples.git/tree/python/example/}.
+Each sample is part of a 100% functional frontend that the reader
+can run and modify to suit their needs.
+The language is Python, and the Web is served by Flask.
+
address@hidden NOTE: include explaining wallet installation to Web developer 
here!
+
+A error message will be prompted to the user if no Taler wallet is
+installed in the browser.
+
address@hidden Specifying the backend
+
address@hidden backend
address@hidden configuration
address@hidden currency
+For many critical operations, the frontend needs to communicate
+with a Taler backend.  Assuming that you do not yet have a backend
+configured, you can use the public backend provided by the Taler
+project for testing.  This public backend has been set-up at
address@hidden://backend.test.taler.net/} specifically for testing
+frontends.  It uses the currency ``PUDOS'' and all payments will
+go into the ``Tutorial'' account at the Taler ``bank'' running at
address@hidden://bank.test.taler.net/public-accounts}.
+
+In our example, backend and currency are specified by setting two
+global variables, as shown below.
+
address@hidden
+..
+CURRENCY = "PUDOS"
+BACKEND_URL = "http://backend.test.taler.net/";
+..
address@hidden smallexample
+
+
address@hidden Talking to the backend
+
address@hidden backend
+The frontend only needs to issue HTTP POST requests to the backend;
+this is easily made by the `requests` library.  See below.
+
+
address@hidden
+import flask
+import requests
+from urllib.parse import urljoin
+..
+
+# In this example we use the /proposal API offered by the
+# backend, which is in charge of signing orders.
+r = requests.post(urljoin(BACKEND_URL, 'proposal'), json=dict(order=order))
+
+if r.status_code != 200:
+    logger.error("failed to POST to '%s'", url)
+    return r.text, r.status_code
+
address@hidden smallexample
+
address@hidden Prompting for payment
address@hidden Prompting for payment
+
address@hidden button
+Our goal is to trigger a Taler payment once the customer has clicked
+on a donation button.  We will use a button that issues an HTTP GET
+to the frontend @code{/donate.php} URL.  For this, the HTML would be as
+follows:
+
address@hidden
+// ../example/templates/index.html
address@hidden ../example/templates/index.html
address@hidden smallexample
+
+When the server-side handler for @code{/donate} receives the form submission,
+it will return a HTML page that will take care of:
+
address@hidden
address@hidden showing a error message if no wallet is installed
address@hidden instruct the wallet to download the proposal related to this 
donation
address@hidden itemize
+
+The @code{/donate} endpoint would then look like follows.
+
address@hidden pay handler
address@hidden 402
address@hidden X-Taler-Contract-Url
address@hidden
+@@app.route("/donate")
+def donate():
+   response = flask.Response("No wallet installed!", status=402)
+   response.headers["X-Taler-Contract-Url"] = "/generate-proposal"
+   return response
address@hidden smallexample
+Whenever the wallet detects the 402 status, it reacts by downloading
+the proposal from @code{/generate-proposal}.
+
+If the wallet is not present, the error message will be shown and
+the Taler headers and the 402 status code ought to be ignored by
+the browser.
+
address@hidden A helper function to generate the proposed contract
+The next step is then to generate the proposal whenever the
+wallet tries to GET @code{/generate-proposal}.  In our example,
+this logic is implemented by the function @code{generate_proposal()},
+as shown below.
+
address@hidden contract
address@hidden
+..
+CURRENCY = "PUDOS"
+..
+@@app.route("/generate-proposal")
+def generate_proposal():
+    DONATION = amounts.string_to_amount("0.1:%s" % CURRENCY) 
+    MAX_FEE = amounts.string_to_amount("0.05:%s" % CURRENCY) 
+    order = dict(
+        nonce=flask.request.args.get("nonce"),
+        amount=DONATION,
+        max_fee=MAX_FEE,
+        products=[
+            dict(
+                description="Donation",
+                quantity=1,
+                product_id=0,
+                price=DONATION,
+            ),
+        ],
+        fulfillment_url=make_url("/fulfillment"),
+        merchant=dict(
+            address="nowhere",
+            name="Donation tutorial",
+            jurisdiction="none",
+        ),
+    )
+
+    url = urljoin(BACKEND_URL, "proposal")
+
+    r = requests.post(url, json=dict(order=order))
+    if r.status_code != 200:
+        logger.error("failed to POST to '%s'", url)
+        return r.text, r.status_code
+    proposal_resp = r.json()
+    return flask.jsonify(**proposal_resp)
address@hidden smallexample
+The function @code{amounts.string_to_amount()} is defined by the
+`pytaler` library, and it's used to convert amount given as strings
+(in the form @code{"1.2:EUR"}) to amount as `dict` (in the form
address@hidden@{value:1, fraction:20000000, currency:"EUR"@}}).
address@hidden signature
address@hidden backend
address@hidden proposal
+One important thing that @code{generate_proposal()} needs to do is to
+POST the ``order'' to the backend.  This is needed because the backend
+has to fill some missing fields and sign the whole order; once the backend
+has done that, it returns the completed data and its signature to the
+frontend that can eventually relay it to the wallet.
+
+The @code{make_url} function is used to ``attach'' paths to the shop's
+base URL.  For example, if the shop is run at @code{https://shop.com},
+then @code{make_url("/path")} would result in @code{https://shop.com/path}.
+
+
address@hidden Initiating the payment process
address@hidden Initiating the payment process
+
address@hidden fulfillment URL
+After the wallet has fetched the proposal, the user will be
+given the opportunity to affirm the payment.  Assuming the user
+affirms, the browser will navigate to the ``fulfillment_url'' that
+was specified in the offer.
+
+The fulfillment page can be called by users that have already paid for
+the item, as well as by users that have not yet paid at all.  The
+fulfillment page must thus use the HTTP session state to detect if the
+payment has been performed already, and if not request payment from
+the wallet.
+
+The fulfillment handler at @code{/fulfillment} will firstly figure out
+if the user has already paid, and if so confirm the donation.
+If the user has not yet paid, it will instead return another ``402 Payment
+Required'' header, requesting the wallet to pay:
+
address@hidden 402 payment required
address@hidden
+@@app.route("/fulfillment")
+def fulfillment():
+    # Ask the state whether the user has paid or not
+    paid = flask.session.get("paid", False)
+    if paid:
+        return "Thank you!"
+    
+    # At this point, the user did not pay yet, so we set some
+    # appropriate HTTP headers that will instruct the wallet to
+    # accomplish the payment
+    response = flask.Response(status=402)
+    response.headers["X-Taler-Contract-Url"] = make_url("/generate-proposal")
+    response.headers["X-Taler-Contract-Query"] = "fulfillment_url"
+    # At this URL the wallet can sand the coins.
+    response.headers["X-Taler-Pay-Url"] = make_url("/pay")
+    # This URL will be visited in case the user has clicked
+    # on someone else's fulfillment URL.  As a result, the
+    # user will be prompted by a new proposal.
+    response.headers["X-Taler-Offer-Url"] = make_url("/donate")
+
+    return response
address@hidden smallexample
+
address@hidden Receiving payments via Taler
+
+The final next step for the frontend is to accept the payment from the
+wallet.  For this, the frontend must implement a payment handler at
+the URI specified in the @code{X-Taler-Pay-Url} header, as explained
+above.
+
+The role of the @code{/pay} handler is to receive the payment
+from the wallet and forward it to the backend.  If the backend
+reports that the payment was successful, the handler needs to update
+the session state with the browser to remember that the user paid.
+
+In our example, that is done by the @code{pay} function; see below.
+
address@hidden
+@@app.route("/pay", methods=["POST"])
+def pay():
+    # Here we get the payment from the wallet.  The
+    # "payment" is a JSON containing coins and proposal
+    # signed by the wallet, plus some other metadata.
+    deposit_permission = flask.request.get_json()
+    if deposit_permission is None:
+        e = flask.jsonify(error="no json in body")
+        return e, 400
+
+    # Forwarding the payment to the backend that will cryptographically
+    # verify it.
+    r = requests.post(urljoin(BACKEND_URL, 'pay'), json=deposit_permission)
+
+    if 200 != r.status_code:
+        return r.text, r.status_code
+    
+    # The payment went through, so we can set the state as "paid".
+    # Note that once this page will return "200 OK", the wallet will
+    # automatically re-visit the fulfillment page (and get the "Thank
+    # you" message now).
+    flask.session["paid"] = True
+
+    return flask.Response(status=200)
address@hidden smallexample
+
address@hidden Run
address@hidden Run
+The file @code{python/example/example.py} contains all the code samples
+seen so far, plus some additional helper function, and it is fully operational.
+It is run as a normal Flask application, by the following commands:
+
address@hidden
+$ cd python/example/
+$ export FLASK_APP=example.py
+$ flask run
address@hidden smallexample
+
+At this point you should have the site running at localhost on port 5000.
+
+Before proceeding with a paying experience, you need to withdraw a few coins
+from our demonstration bank running at @code{https://bank.test.taler.net/}.
+After that, you should be able to point your browser at 
@code{http://localhost:5000/}
+and start making donations!
+
+Please visit @code{https://test.taler.net/} to know how to install the Taler
+wallet.
+
+
address@hidden **********************************************************
address@hidden *******************  Appendices  *************************
address@hidden **********************************************************
+
address@hidden GNU-LGPL
address@hidden GNU-LGPL
address@hidden license
address@hidden LGPL
address@hidden lgpl.texi
+
address@hidden GNU-FDL
address@hidden GNU-FDL
address@hidden license
address@hidden GNU Free Documentation License
address@hidden fdl-1.3.texi
+
address@hidden Concept Index
address@hidden Concept Index
+
address@hidden cp
+
address@hidden
diff --git a/python/doc/version.texi b/python/doc/version.texi
new file mode 100644
index 0000000..530e1dc
--- /dev/null
+++ b/python/doc/version.texi
@@ -0,0 +1,4 @@
address@hidden UPDATED 11 November 2016
address@hidden UPDATED-MONTH November 2016
address@hidden EDITION 0.2.0
address@hidden VERSION 0.2.0

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address@hidden