[GNUnet-SVN] [taler-merchant-frontend-examples] branch master updated: finishing explanation of X-Taler-Contract-Query

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marcello pushed a commit to branch master
in repository merchant-frontend-examples.

The following commit(s) were added to refs/heads/master by this push:
     new 47b1bda  finishing explanation of X-Taler-Contract-Query
47b1bda is described below

commit 47b1bdaefb0e3e5dc1e5b3a3f7f813f86f02167b
Author: Marcello Stanisci <address@hidden>
AuthorDate: Tue Mar 28 21:21:06 2017 +0200

    finishing explanation of X-Taler-Contract-Query
---
 php/doc/tutorial.texi    |  6 ++++--
 python/doc/tutorial.texi | 10 ++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/php/doc/tutorial.texi b/php/doc/tutorial.texi
index fa2eeff..8e83e61 100644
--- a/php/doc/tutorial.texi
+++ b/php/doc/tutorial.texi
@@ -254,8 +254,8 @@ browser.
 
 @section A helper function to generate the order
 
-We make distinction between *three* different stages of the
-document that describes the purchase being served.
+We make distinction between @emph{three} different stages of what it
+informally called "contract".
 
 In a very first stage, we call it the @emph{order}: that occurs when
 the frontend generates the first JSON that misses some information
@@ -373,6 +373,8 @@ the wallet will pick those coins it spent on that 
fulfillment
 page and resend them (therefore @emph{replaying} the payment).
 In other words, new coins are used only on unknown fulfillment
 pages.
+This header is supposed to be removed in future versions of the
+wallet though, as it only works with the value @code{"fulfillment_url"}.
 @item X-Taler-Offer-Url
 @cindex X-Taler-Offer-Url
 In case that the wallet does not know about this payment already,
diff --git a/python/doc/tutorial.texi b/python/doc/tutorial.texi
index 4f6ba42..2fbeb5e 100644
--- a/python/doc/tutorial.texi
+++ b/python/doc/tutorial.texi
@@ -366,6 +366,16 @@ def fulfillment():
 @end smallexample
 @c FIXME: check with Florian: isn't 'x-taler-contract-query' dead by now?
 
+The @code{X-Taler-Contract-Query} header is crucial for implementing replayable
+payments.  In fact, upon receiving such a header, the wallet will look in its
+internal database if a payment to the current fulfillment URL has already been
+sent.  If that's the case, then the coins from that previous payment will be
+sent to the @emph{pay_url}.
+That is exactly what happens when the user visits some bookmarked fulfillment
+page in order to see again what they already paid for.
+That header is scheduled to be removed in future versions of the wallet,
+as it only works with the value @code{"fulfillment_url"}.
+
 @section Receiving payments via Taler
 
 The final next step for the frontend is to receive the payment from the

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