[taler-docs] branch master updated: review payment states

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The following commit(s) were added to refs/heads/master by this push:
     new b617c64  review payment states
b617c64 is described below

commit b617c6452ec92c06533e98a26b09c23165fbbf44
Author: Christian Grothoff <christian@grothoff.org>
AuthorDate: Sat Apr 8 22:13:55 2023 +0200

    review payment states
---
 Makefile                                           |   4 +-
 .../037-wallet-transactions-lifecycle.rst          | 137 +++++++++++++--------
 transaction-payment-states.dot                     |  44 +++++++
 3 files changed, 131 insertions(+), 54 deletions(-)

diff --git a/Makefile b/Makefile
index e60c2dd..b3e04e2 100644
--- a/Makefile
+++ b/Makefile
@@ -57,6 +57,8 @@ transaction-common-states.png: transaction-common-states.dot
        dot -Tpng transaction-common-states.dot > transaction-common-states.png
 transaction-withdrawal-states.png: transaction-withdrawal-states.dot
        dot -Tpng transaction-withdrawal-states.dot > 
transaction-withdrawal-states.png
+transaction-payment-states.png: transaction-payment-states.dot
+       dot -Tpng transaction-payment-states.dot > 
transaction-payment-states.png
 coin.png: coin.dot
        dot -Tpng coin.dot > coin.png
 deposit.png: deposit.dot
@@ -64,7 +66,7 @@ deposit.png: deposit.dot
 reserve.png: reserve.dot
        dot -Tpng reserve.dot > reserve.png
 
-diagrams: arch-api.png coin.png deposit.png reserve.png 
transaction-common-states.png transaction-withdrawal-states.png
+diagrams: arch-api.png coin.png deposit.png reserve.png 
transaction-common-states.png transaction-withdrawal-states.png 
transaction-payment-states.png
 
 
 # The html-linked builder does not support caching, so we
diff --git a/design-documents/037-wallet-transactions-lifecycle.rst 
b/design-documents/037-wallet-transactions-lifecycle.rst
index e2a0482..366079a 100644
--- a/design-documents/037-wallet-transactions-lifecycle.rst
+++ b/design-documents/037-wallet-transactions-lifecycle.rst
@@ -286,87 +286,120 @@ shown in the above diagram to keep it on point.
 Transaction Type: Payment to Merchant
 -------------------------------------
 
-XXX: Also consider re-selection when the wallet accidentally double-spends 
coins
-or the selected coins have expired.  Do we ask the user in this case?
+* ``pending(claim-proposal)``
 
-CG: I think no. We correct our balance (after all, we got a proof of
-double-spending) and try other coins. If we do not have enough money left, we
-abort and simply inform the user that their balance was insufficient to make
-the payment after all (very sorry...).
+  Initial state. Download (claim) the proposal from the merchant.  Can fail if
+  the proposal was already claimed by someone else.  If repurchase detection
+  tells us that we already paid for this product, we go immediately to
+  ``delete`` state for this transaction, but with a side-effect of
+  transitioning the UI into a ``pending(repurchase-session-reset)`` on a
+  *different* transaction (which before was in ``done``).
 
-Note that the case of selected coins having expired shouldn't really happen,
-as the wallet should have noticed that when is started up, tried to refresh,
-and if that already failed should have update the balance with a transaction
-history entry saying something like "coins expired, offline too long" or
-something like that.
+  * ``[error: already claimed] => deleted``  -- the proposal was
+    already claimed by someone else; we go directly into the ``deleted``
+    state and only show a transient warning.
+  * ``[error: invalid proposal] => deleted`` -- the merchant provided a
+    proposal that is invalid (e.g. malformed contract
+    terms or bad signature); we go directly into the ``deleted`` state
+    and only show a transient warning.
 
-(??) If transaction can be aborted while in-progress then it should return
-instructedAmount, effectiveAmount and the affectedAmount (partially effective 
amount)
-
-* ``initial(download-proposal)``
-
-  Initial state. Download (claim) the proposal from the merchant.
-
-  XXX: Also consider repurchase detection here?
-
-  CG: Well, we could mention that this is a possible transition from
-  ``pending(download-proposal)`` to ``deleted`` with a side-effect
-  of transitioning the UI into a ``pending(repurchase-session-reset)``
-  on a different transaction (which before was in ``done``).
-
-  (??) should not reset another transaction?
 
 * ``pending(proposed)``
 
   Let the user accept (or refuse) the payment.
 
   * ``[action:pay-accept] => pending(submit-payment)``
-  * ``[action:abort] => deleted`` -- user explicitly decides not
-    to proceed
-  * ``[action:expired] => deleted`` -- when the offer expires
-    before the user decides to make the payment! (We can keep
-    pending contracts even in a 'pending transaction' list to
-    allow the user to choose to not proceed, but then this
-    transition would clean up that list).
+  * ``[action:pay-refuse] => ``aborting(unclaim)`` -- The user explicitly
+    decided not to proceed (at least not with this wallet).
+  * ``[expired] => deleted`` -- The offer has expired before the user made any
+    decision. (We can keep pending contracts even in a 'pending transaction'
+    list to allow the user to choose to not proceed, but then this transition
+    would clean up that list). Note that we should use this transition at
+    least a few seconds before the offer *actually* expires to avoid
+    encountering an expiration during ``pending(submit-payment)`` in most
+    real-world scenarios. Basically, we should prevent last-second payments to
+    be event attempted client-side.
+
+* ``aborting(unclaim)``
+
+  Tells the merchant that some *other* wallet is now again free to claim this
+  offer.
 
 * ``pending(submit-payment)``
 
-Submit coin by coin (or in bulk groups) until payment is complete.
-
-  * ``[action:abort] => aborting(refund)``
-  * ``[processed-success(auto-refund-enabled)] => pending(refundable)``
-  * ``[processed-success(auto-refund-disabled)] => done``
-  * ``[processed-error(expired)] => aborting(refresh)`` XXX: If the order is 
expired but the payment
-    succeeded partially before, do we still try an abort-refund? CG: YES, but 
of course
-    we probably should use the ``expired`` transition above a few seconds 
before the
-    offer *actually* expires to avoid this problem in 99.9% of real-world 
scenarios
-    ("prevent last-second payments client-side")
+  Submit coin-by-coin (or in bulk groups) until payment is complete.
+
+  * ``[action:abort] => aborting(refund)`` -- The user explicitly decided to
+    abort the process while the payment was happening.  Note that if the
+    payment was already completed (and hence the merchant refuses any
+    refunds), it is theoretically possible that pressing the abort button will
+    nevertheless end up in a ``pending(refundable)`` state (and subsequently
+    a ``done`` state) instead!
+  * ``[success] => pending(refundable)`` -- Upon receiving confirmation from
+    the merchant that the purchase was completed.
+  * ``[error(insufficient balance)] => aborting(refresh)`` This transition
+    happens if we detect double-spending and our balance is not sufficient
+    after the double-spending. It is also conceivable (but should be rare)
+    that this transition happens because the offer expired.
 
 * ``pending(refundable)``
 
-The payment succeed but if auto-refund-check is active it will be checking for 
refunds
+  The payment succeed. We remain in this tate as long as an auto-refund-check
+  is active.  If auto refunds are not enabled, we immediately continue to
+  ``done``.
 
-  * ``[auto-refund-timeout] => done``
+  * ``[timeout] => done`` -- This happens when the auto refund set by the 
contract expired.
+  * ``[action:abort] => done`` -- The user may explicitly request to abort the 
auto-refund processing (for example to enable subsequent deletion before the 
auto-refund delay expires).
 
 * ``aborting(refund)``
 
-  * ``[processed-success] => aborted(refunded)``
-  * ``[processed-failure] => aborting(refresh)``
+  The wallet should interact with the merchant to confirm that a refund
+  was approved.
 
-* ``aborting(refresh)``
+  * ``[success] => aborted(refunded)``
+  * ``[failure] => aborting(refresh)``
 
-* ``failed(invalid-proposal)``
+* ``aborting(refresh)``
 
-  The merchant provided a proposal that is invalid (e.g. malformed contract 
terms or bad signature).
+  The wallet should interact with the exchange to obtain fresh coins for
+  the refunded balance.
 
 * ``aborted(refunded)``
 
+  The purchase ended with a (partial) refund. The state (and UI) should show
+  the specific provenance of the state, which may include an insufficient
+  balance (due to double-spending being detected during payment), and one or
+  more partial or full refunds.
+
+  * ``[URI:refund] => aborting(refund)`` -- The previous refund was partial,
+    and we have received an additional refund for this transaction.
+  * ``[action:delete] => deleted``
+
+* ``done``
+
+  The purchase is completed.
+
   * ``[action:delete] => deleted``
+  * ``[refund URI trigger] => aborting(refund)`` -- A refund was initiated for 
the purchase.
+  * ``[repurchase] => pending(repurchase-session-reset)`` -- Another offer 
became pending for this product.
+
+* ``pending(repurchase-session-reset)``
+
+  The wallet should reset the associated session for the already purchased 
item.
+
+  * ``[success] => done``
+  * ``[action:abort] => done`` -- User aborted the session reset.
 
 * ``deleted``
 
-  When a payment is deleted, associated refunds are always deleted with it
+  When a payment is deleted, associated refunds are always deleted with it.
 
+.. image:: ../transaction-payment-states.png
+  :width: 800
+
+Purple arrows are used to indicate transitions triggered in special ways 
outside
+of the user interface for this transaction, such as side-effects of repurchase
+detection for another purchase or opening of a refund URI.
 
 
 Transaction Type: Refund
@@ -709,8 +742,6 @@ Alternatives
   not ask again."). Probably at best a post-1.0 feature.
 
 
-
-
 Drawbacks
 =========
 
diff --git a/transaction-payment-states.dot b/transaction-payment-states.dot
new file mode 100644
index 0000000..066fb02
--- /dev/null
+++ b/transaction-payment-states.dot
@@ -0,0 +1,44 @@
+digraph G {
+
+  initial[label="", shape="circle"];
+  pending_dp[label="pending(claim-proposal)"];
+  pending_pr[label="pending(proposed)"];
+  pending_sp[label="pending(submit-payment)"];
+  pending_rf[label="pending(refundable)"];
+  pending_re[label="pending(repurchase-session-reset)"];
+  aborting_unclaim[label="aborting(unclaim)"];
+  aborting_refund[label="aborting(refund)"];
+  aborting_refresh[label="aborting(refresh)"];
+  aborted_refund[label="aborted(refunded)", shape="box"];
+  done[label="done", shape="box"];
+  deleted[label="deleted", shape="box"];
+
+  subgraph {
+    rank = same; pending_dp; pending_pr; pending_sp; pending_rf;
+  }
+
+  initial->pending_dp [color="blue", label="URI trigger"];
+  pending_dp->pending_pr;
+  pending_re->done;
+  pending_dp->deleted [label="repurchase\ndetected"];
+  pending_dp->deleted [color="red", label="already\nclaimed"];
+  pending_dp->deleted [color="red", label="invalid\nproposal"];
+  pending_pr->pending_sp [color="blue", label="action:pay-accept"];
+  pending_pr->aborting_unclaim [color="blue", label="action:pay-refuse"];
+  pending_pr->deleted [label="expired"];
+  pending_sp->pending_rf;
+  pending_sp->aborting_refund [color="blue", label="action:abort"];  
pending_sp->aborting_refund [color="red", label="insufficient balance"];
+  pending_rf->aborting_refund [label="long-poll:refund"];
+  done->aborting_refund [color="purple", xlabel="refund URI trigger"];
+  aborted_refund->aborting_refund [color="purple", label="refund URI trigger"];
+  aborting_refund->aborting_refresh;
+  aborting_refund->aborted_refund [color="red", label="failure"];
+  aborting_refresh->aborted_refund;
+  aborted_refund->deleted [color="blue", label="action:delete"];
+  pending_rf->done [label="timeout"];
+  pending_rf->done [color="blue", label="action:abort"];
+  aborting_unclaim->deleted;
+  done->deleted [color="blue", xlabel="action:delete"];
+  done->pending_re [color="purple", label="repurchase"];
+  pending_re->done [color="blue", label="action:abort"];
+}

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