-document new 409 case

1 files changed, 6 insertions, 2 deletions

diff --git a/core/api-merchant.rst b/core/api-merchant.rst
index d8611c2f..cadc1aa6 100644
--- a/core/api-merchant.rst
+++ b/core/api-merchant.rst
@@ -245,18 +245,22 @@ Making the payment
     The merchant backend could not find the order or the instance and thus cannot process the payment.
   :http:statuscode:`406 Not acceptable`:
     The payment is insufficient (sum is below the required total amount).
+    TODO: Should probably change to a different status code in the future as 406 is technically wrong.
   :http:statuscode:`408 Request timeout`:
     The backend took too long to process the request. Likely the merchant's connection
     to the exchange timed out. Try again.
   :http:statuscode:`409 Conflict`:
-    The exchange rejected the payment because a coin was already spent.
-    The response will include the ``coin_pub`` for which the payment failed,
+    The exchange rejected the payment because a coin was already spent, or
+    the merchant rejected the payment because the order was already fully paid
+    (and then return signatures with refunds). If a coin was already spent,
+    the response will include the ``coin_pub`` for which the payment failed,
     in addition to the response from the exchange to the ``/deposit`` request.
   :http:statuscode:`410 Gone`:
     The offer has expired and is no longer available.
   :http:statuscode:`412 Precondition failed`:
     The given exchange is not acceptable for this merchant, as it is not in the
     list of accepted exchanges and not audited by an approved auditor.
+    TODO: Status code may be changed to 409 in the future as 412 is technically wrong.
   :http:statuscode:`502 Bad gateway`:
     The merchant's interaction with the exchange failed in some way.
     The client might want to try again later.