From a15eec55d3136b4f737c68ac41e3042624b8e25f Mon Sep 17 00:00:00 2001
From: Florian Dold <florian@dold.me>
Date: Fri, 15 Sep 2023 16:45:12 +0200
Subject: wallet-core: correctly consider deposit fee in p2p coin selection

---
 .../taler-wallet-core/src/util/coinSelection.ts    | 24 +++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

(limited to 'packages/taler-wallet-core/src/util/coinSelection.ts')

diff --git a/packages/taler-wallet-core/src/util/coinSelection.ts b/packages/taler-wallet-core/src/util/coinSelection.ts
index 0b1be881f..8c90f26f1 100644
--- a/packages/taler-wallet-core/src/util/coinSelection.ts
+++ b/packages/taler-wallet-core/src/util/coinSelection.ts
@@ -419,8 +419,10 @@ interface SelResult {
   };
 }
 
-export function testing_selectGreedy(...args: Parameters<typeof selectGreedy>): ReturnType<typeof selectGreedy>{
-  return selectGreedy(...args)
+export function testing_selectGreedy(
+  ...args: Parameters<typeof selectGreedy>
+): ReturnType<typeof selectGreedy> {
+  return selectGreedy(...args);
 }
 function selectGreedy(
   req: SelectPayCoinRequestNg,
@@ -900,9 +902,12 @@ interface PeerCoinSelectionTally {
 /**
  * exporting for testing
  */
-export function testing_greedySelectPeer(...args: Parameters<typeof greedySelectPeer>): ReturnType<typeof greedySelectPeer> {
-  return greedySelectPeer(...args)
+export function testing_greedySelectPeer(
+  ...args: Parameters<typeof greedySelectPeer>
+): ReturnType<typeof greedySelectPeer> {
+  return greedySelectPeer(...args);
 }
+
 function greedySelectPeer(
   candidates: AvailableDenom[],
   instructedAmount: AmountLike,
@@ -921,11 +926,16 @@ function greedySelectPeer(
         instructedAmount,
         tally.amountAcc,
       ).amount;
-      const coinContrib = Amounts.sub(denom.value, denom.feeDeposit).amount
+      // Maximum amount the coin could effectively contribute.
+      const maxCoinContrib = Amounts.sub(denom.value, denom.feeDeposit).amount;
+
+      const coinSpend = Amounts.min(
+        Amounts.add(amountPayRemaining, denom.feeDeposit).amount,
+        maxCoinContrib,
+      );
 
-      const coinSpend = Amounts.min(amountPayRemaining, coinContrib)
-      
       tally.amountAcc = Amounts.add(tally.amountAcc, coinSpend).amount;
+      tally.amountAcc = Amounts.sub(tally.amountAcc, denom.feeDeposit).amount;
 
       tally.depositFeesAcc = Amounts.add(
         tally.depositFeesAcc,
-- 
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