From 823f1a1b17212b26c9062d185b8516fe906aeaae Mon Sep 17 00:00:00 2001
From: Florian Dold <florian.dold@gmail.com>
Date: Fri, 3 Jul 2020 00:21:18 +0530
Subject: notes on amount handling

---
 libeufin/iso20022.rst | 77 ++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 73 insertions(+), 4 deletions(-)

(limited to 'libeufin')

diff --git a/libeufin/iso20022.rst b/libeufin/iso20022.rst
index aa6df201..d87098a3 100644
--- a/libeufin/iso20022.rst
+++ b/libeufin/iso20022.rst
@@ -32,15 +32,84 @@ on a customer's bank account.
 We also flatten the hierarchy a bit and only have entries ("money movement in one go")
 and transactions.
 
+Types of amounts in camt messages
+---------------------------------
+
+* Entry amount
+
+ * ISO 20022:  Mandatory, with debit/credit indicator.  Indicates money
+   moving in/out of the account in the account's currency.
+ * LibEuFin: Same.
+
+* Entry transaction amount
+
+ * ISO 20022:  Optional, direction-less.  Amount of money
+   moving between the debtor and creditor bank, may not be
+   in the account's currency (but the "native" currency between
+   the two banks).
+ * LibEuFin: Same.
+
+* Entry instructed amount
+
+ * ISO 20022:  Optional, direction-less.  Amount of money specified in the
+   payment initiation message.  Usually only specified when the amount is in a
+   different currency than the account currency.
+ * LibEuFin: Same.
+
+* Entry counter value amount
+
+  * ISO 20022: Optional, direction-less. Amount in the account's
+    currency before charges.
+  * LibEuFin: Same.
+
+* Entry announced posting amount
+
+  * (not used by LibEuFin)
+
+* EntryDetails amount
+
+  * ISO 20022: Optional, with debit-credit indicator.  Same as "Entry amount"
+    but for EntryDetails (= logical transactions).
+  * LibEuFin:  Always present.  In Swiss camt messages, the element is always
+    present.  In German/Swedish/... camt, we take the "Entry amount" for
+    non-batch entries, whereas in batch entries we use the "EntryDetails
+    transaction amount" with the same debit credit indicator as the whole
+    entry, which by local rules is always in the bank account currency.
+
+* EntryDetails (transaction / instructed / counter value) amount
+
+  * ISO 20022: Optional, direction-less.  Same as "Entry ... amount"
+    but for EntryDetails (= logical transactions).
+  * Same.
+
+* EntryDetails announced posting amount
+
+  * (not used by LibEuFin)
+
+
+LibEuFin schema for account history
+-----------------------------------
+
+FIXME: This is not complete yet.
+
 .. code-block:: typescript
 
-   interface AccountTransactionItem {
-     // LibEuFin-internal identifier for the transaction
-     nexusTransactionId: string;
+   interface NexusTransactionsReponse {
+     entries: NexusAccountEntryItem[];
+   }
 
-     // Link to the entry that contains the transaction
+   interface NexusAccountEntryItem {
      nexusEntryId: string;
 
+     // Serial number that will increase with each update
+     // to the entry.
+     nexusStatusSequenceId: number;
+
+     entry: AccountEntryItem;
+   }
+
+   interface AccountEntryItem {
+
      // At least one of entryId or accountServicerRef
      // must be non-null
      entryId?: string;
-- 
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