From bcff03949b40d0d37069bdb7af941061e367a093 Mon Sep 17 00:00:00 2001
From: Florian Dold <florian@dold.me>
Date: Mon, 19 Jun 2023 12:02:43 +0200
Subject: wallet-core: implement coin selection repair for p2p payments

---
 .../src/operations/pay-peer-push-debit.ts          | 104 ++++++++++++++++++++-
 1 file changed, 99 insertions(+), 5 deletions(-)

(limited to 'packages/taler-wallet-core/src/operations/pay-peer-push-debit.ts')

diff --git a/packages/taler-wallet-core/src/operations/pay-peer-push-debit.ts b/packages/taler-wallet-core/src/operations/pay-peer-push-debit.ts
index 2835a1f64..33d317c6f 100644
--- a/packages/taler-wallet-core/src/operations/pay-peer-push-debit.ts
+++ b/packages/taler-wallet-core/src/operations/pay-peer-push-debit.ts
@@ -28,6 +28,7 @@ import {
   TalerError,
   TalerErrorCode,
   TalerPreciseTimestamp,
+  TalerProtocolViolationError,
   TalerUriAction,
   TransactionAction,
   TransactionMajorState,
@@ -47,8 +48,13 @@ import {
   getTotalPeerPaymentCost,
   codecForExchangePurseStatus,
   queryCoinInfosForSelection,
+  PeerCoinRepair,
 } from "./pay-peer-common.js";
-import { readSuccessResponseJsonOrThrow } from "@gnu-taler/taler-util/http";
+import {
+  HttpResponse,
+  readSuccessResponseJsonOrThrow,
+  readTalerErrorResponse,
+} from "@gnu-taler/taler-util/http";
 import {
   PeerPushPaymentInitiationRecord,
   PeerPushPaymentInitiationStatus,
@@ -97,6 +103,73 @@ export async function checkPeerPushDebit(
   };
 }
 
+async function handlePurseCreationConflict(
+  ws: InternalWalletState,
+  peerPushInitiation: PeerPushPaymentInitiationRecord,
+  resp: HttpResponse,
+): Promise<OperationAttemptResult> {
+  const pursePub = peerPushInitiation.pursePub;
+  const errResp = await readTalerErrorResponse(resp);
+  if (errResp.code !== TalerErrorCode.EXCHANGE_GENERIC_INSUFFICIENT_FUNDS) {
+    await failPeerPushDebitTransaction(ws, pursePub);
+    return OperationAttemptResult.finishedEmpty();
+  }
+
+  // FIXME: Properly parse!
+  const brokenCoinPub = (errResp as any).coin_pub;
+  logger.trace(`excluded broken coin pub=${brokenCoinPub}`);
+
+  if (!brokenCoinPub) {
+    // FIXME: Details!
+    throw new TalerProtocolViolationError();
+  }
+
+  const instructedAmount = Amounts.parseOrThrow(peerPushInitiation.amount);
+
+  const repair: PeerCoinRepair = {
+    coinPubs: peerPushInitiation.coinSel.coinPubs,
+    contribs: peerPushInitiation.coinSel.contributions.map((x) =>
+      Amounts.parseOrThrow(x),
+    ),
+    exchangeBaseUrl: peerPushInitiation.exchangeBaseUrl,
+  };
+
+  const coinSelRes = await selectPeerCoins(ws, { instructedAmount, repair });
+
+  if (coinSelRes.type == "failure") {
+    // FIXME: Details!
+    throw Error(
+      "insufficient balance to re-select coins to repair double spending",
+    );
+  }
+
+  await ws.db
+    .mktx((x) => [x.peerPushPaymentInitiations])
+    .runReadWrite(async (tx) => {
+      const myPpi = await tx.peerPushPaymentInitiations.get(
+        peerPushInitiation.pursePub,
+      );
+      if (!myPpi) {
+        return;
+      }
+      switch (myPpi.status) {
+        case PeerPushPaymentInitiationStatus.PendingCreatePurse:
+        case PeerPushPaymentInitiationStatus.SuspendedCreatePurse: {
+          const sel = coinSelRes.result;
+          myPpi.coinSel =  {
+            coinPubs: sel.coins.map((x) => x.coinPub),
+            contributions: sel.coins.map((x) => x.contribution),
+          }
+          break;
+        }
+        default:
+          return;
+      }
+      await tx.peerPushPaymentInitiations.put(myPpi);
+    });
+  return OperationAttemptResult.finishedEmpty();
+}
+
 async function processPeerPushDebitCreateReserve(
   ws: InternalWalletState,
   peerPushInitiation: PeerPushPaymentInitiationRecord,
@@ -175,6 +248,27 @@ async function processPeerPushDebitCreateReserve(
 
   logger.info(`resp: ${j2s(resp)}`);
 
+  switch (httpResp.status) {
+    case HttpStatusCode.Ok:
+      break;
+    case HttpStatusCode.Forbidden: {
+      // FIXME: Store this error!
+      await failPeerPushDebitTransaction(ws, pursePub);
+      return OperationAttemptResult.finishedEmpty();
+    }
+    case HttpStatusCode.Conflict: {
+      // Handle double-spending
+      return handlePurseCreationConflict(ws, peerPushInitiation, resp);
+    }
+    default: {
+      const errResp = await readTalerErrorResponse(resp);
+      return {
+        type: OperationAttemptResultType.Error,
+        errorDetail: errResp,
+      };
+    }
+  }
+
   if (httpResp.status !== HttpStatusCode.Ok) {
     // FIXME: do proper error reporting
     throw Error("got error response from exchange");
@@ -710,17 +804,17 @@ export async function failPeerPushDebitTransaction(
       switch (pushDebitRec.status) {
         case PeerPushPaymentInitiationStatus.AbortingRefresh:
         case PeerPushPaymentInitiationStatus.SuspendedAbortingRefresh:
-          // FIXME: We also need to abort the refresh group!
-          newStatus = PeerPushPaymentInitiationStatus.Aborted;
+          // FIXME: What to do about the refresh group?
+          newStatus = PeerPushPaymentInitiationStatus.Failed;
           break;
         case PeerPushPaymentInitiationStatus.AbortingDeletePurse:
         case PeerPushPaymentInitiationStatus.SuspendedAbortingDeletePurse:
-          newStatus = PeerPushPaymentInitiationStatus.Aborted;
-          break;
         case PeerPushPaymentInitiationStatus.PendingReady:
         case PeerPushPaymentInitiationStatus.SuspendedReady:
         case PeerPushPaymentInitiationStatus.SuspendedCreatePurse:
         case PeerPushPaymentInitiationStatus.PendingCreatePurse:
+          newStatus = PeerPushPaymentInitiationStatus.Failed;
+          break;
         case PeerPushPaymentInitiationStatus.Done:
         case PeerPushPaymentInitiationStatus.Aborted:
         case PeerPushPaymentInitiationStatus.Failed:
-- 
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