Separate receiver and sender logic in steps

CHANGELOG.md

@@ -1,33 +1,47 @@
+## [0.13.0-dev.2]
+
+### Fixed
+
+- Fix `assumeInteractiveReceiver` return type
+
+### Refactor
+
+- Separate receiver and sender logic in example app.
+
 ## [0.13.0]
 
 ### Features & Modules
+
 #### Send module
-- #####  V1
-    - `RequestBuilder` exposes `fromPsbtAndUri`, `buildWithAdditionalFee`, `buildRecommended`, `buildNonIncentivizing`, `alwaysDisableOutputSubstitution`.
-    - `RequestContext` exposes `extractContextV1` & `extractContextV2`.
-    - `ContextV1` exposes `processResponse`.
-- ##### V2 
-    - `ContextV2` exposes `processResponse`.
+
+- ##### V1
+  - `RequestBuilder` exposes `fromPsbtAndUri`, `buildWithAdditionalFee`, `buildRecommended`, `buildNonIncentivizing`, `alwaysDisableOutputSubstitution`.
+  - `RequestContext` exposes `extractContextV1` & `extractContextV2`.
+  - `ContextV1` exposes `processResponse`.
+- ##### V2
+  - `ContextV2` exposes `processResponse`.
+
 #### Receive module
-- #####  V1
-    - `UncheckedProposal` exposes `fromRequest`, `extractTxToScheduleBroadcast`, `checkBroadcastSuitability`, `buildNonIncentivizing`, 
-        `assumeInteractiveReceiver` &`alwaysDisableOutputSubstitution`.
-    - `MaybeInputsOwned` exposes `checkInputsNotOwned`.    
-    - `MaybeMixedInputScripts` exposes `checkNoMixedInputScripts`.    
-    - `MaybeInputsSeen` exposes `checkNoInputsSeenBefore`.   
-    - `OutputsUnknown` exposes `identifyReceiverOutputs`.   
-    - `ProvisionalProposal` exposes `substituteOutputAddress`, `contributeNonWitnessInput`, `contributeWitnessInput`, `tryPreservingPrivacy` & 
-        `finalizeProposal`.
-    - `PayjoinProposal` exposes `isOutputSubstitutionDisabled`, `ownedVouts`, `psbt` & `utxosToBeLocked`.   
-- ##### V2 
-    - `Enroller` exposes `fromDirectoryConfig`, `processResponse` & `extractRequest`.
-    - `Enrolled` exposes `extractRequest`, `processResponse` & `fallbackTarget`.
-    - `UncheckedProposal` exposes  `extractTxToScheduleBroadcast`, `checkBroadcastSuitability` & `assumeInteractiveReceiver`.
-    - `MaybeInputsOwned` exposes `checkInputsNotOwned`.    
-    - `MaybeMixedInputScripts` exposes `checkNoMixedInputScripts`.    
-    - `MaybeInputsSeen` exposes `checkNoInputsSeenBefore`.   
-    - `OutputsUnknown` exposes `identifyReceiverOutputs`.   
-    - `ProvisionalProposal` exposes `substituteOutputAddress`, `contributeNonWitnessInput`, `contributeWitnessInput`, `tryPreservingPrivacy` & 
-        `finalizeProposal`.
-    - `PayjoinProposal` exposes `deserializeRes`, `extractV1Req`, `extractV2Request`, `isOutputSubstitutionDisabled`, `ownedVouts`, `psbt` &
-        `utxosToBeLocked`.     
+
+- ##### V1
+  - `UncheckedProposal` exposes `fromRequest`, `extractTxToScheduleBroadcast`, `checkBroadcastSuitability`, `buildNonIncentivizing`,
+    `assumeInteractiveReceiver` &`alwaysDisableOutputSubstitution`.
+  - `MaybeInputsOwned` exposes `checkInputsNotOwned`.
+  - `MaybeMixedInputScripts` exposes `checkNoMixedInputScripts`.
+  - `MaybeInputsSeen` exposes `checkNoInputsSeenBefore`.
+  - `OutputsUnknown` exposes `identifyReceiverOutputs`.
+  - `ProvisionalProposal` exposes `substituteOutputAddress`, `contributeNonWitnessInput`, `contributeWitnessInput`, `tryPreservingPrivacy` &
+    `finalizeProposal`.
+  - `PayjoinProposal` exposes `isOutputSubstitutionDisabled`, `ownedVouts`, `psbt` & `utxosToBeLocked`.
+- ##### V2
+  - `Enroller` exposes `fromDirectoryConfig`, `processResponse` & `extractRequest`.
+  - `Enrolled` exposes `extractRequest`, `processResponse` & `fallbackTarget`.
+  - `UncheckedProposal` exposes `extractTxToScheduleBroadcast`, `checkBroadcastSuitability` & `assumeInteractiveReceiver`.
+  - `MaybeInputsOwned` exposes `checkInputsNotOwned`.
+  - `MaybeMixedInputScripts` exposes `checkNoMixedInputScripts`.
+  - `MaybeInputsSeen` exposes `checkNoInputsSeenBefore`.
+  - `OutputsUnknown` exposes `identifyReceiverOutputs`.
+  - `ProvisionalProposal` exposes `substituteOutputAddress`, `contributeNonWitnessInput`, `contributeWitnessInput`, `tryPreservingPrivacy` &
+    `finalizeProposal`.
+  - `PayjoinProposal` exposes `deserializeRes`, `extractV1Req`, `extractV2Request`, `isOutputSubstitutionDisabled`, `ownedVouts`, `psbt` &
+    `utxosToBeLocked`.

example/integration_test/bitcoin_core_full_cycle_test.dart

@@ -5,6 +5,7 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:integration_test/integration_test.dart';
 import 'package:payjoin_flutter/common.dart' as common;
+import 'package:payjoin_flutter/send.dart';
 import 'package:payjoin_flutter/uri.dart' as pay_join_uri;
 import 'package:payjoin_flutter_example/btc_client.dart';
 import 'package:payjoin_flutter_example/payjoin_library.dart';
@@ -35,11 +36,15 @@ void main() {
       final amount = await uri.amount();
       final senderPsbt =
           (await sender.walletCreateFundedPsbt(amount, address, 2000))["psbt"];
+      final requestContext = await (await RequestBuilder.fromPsbtAndUri(
+              psbtBase64: senderPsbt, uri: uri))
+          .buildRecommended(minFeeRate: 0);
+      final (_, ctx) = await requestContext.extractContextV1();
       debugPrint(
         "\nOriginal sender psbt: $senderPsbt",
       );
-      final (provisionalProposal, ctx) =
-          await payJoinLib.handlePjRequest(senderPsbt, pjUri, (e) async {
+      final provisionalProposal =
+          await payJoinLib.handlePjRequest(senderPsbt, (e) async {
         final script = ScriptBuf(bytes: e);
         final address = await (await Address.fromScript(
                 script: script, network: Network.regtest))

example/lib/bdk_client.dart

@@ -82,8 +82,6 @@ class BdkClient {
 
   Future<int> getBalance() async {
     final balance = await wallet.getBalance();
-    final res = "Total Balance: ${balance.total.toString()}";
-    debugPrint(res);
     return balance.total;
   }
 

example/lib/main.dart

@@ -4,6 +4,7 @@ import 'package:bdk_flutter/bdk_flutter.dart';
 import 'package:flutter/material.dart';
 import 'package:google_fonts/google_fonts.dart';
 import 'package:payjoin_flutter/common.dart' as common;
+import 'package:payjoin_flutter/send.dart';
 import 'package:payjoin_flutter/uri.dart' as pay_join_uri;
 import 'package:payjoin_flutter_example/bdk_client.dart';
 import 'package:payjoin_flutter_example/payjoin_library.dart';
@@ -50,7 +51,9 @@ class _PayJoinState extends State<PayJoin> {
   String displayText = "";
   String pjUri = "";
   late PartiallySignedTransaction senderPsbt;
-  late PartiallySignedTransaction processedAndFinalizedPsbt;
+  late String receiverPsbtBase64;
+  late ContextV1 contextV1;
+
   @override
   void initState() {
     sender.restoreWallet();
@@ -112,6 +115,8 @@ class _PayJoinState extends State<PayJoin> {
                   setState(() {
                     displayText = "sync complete";
                   });
+                  debugPrint(
+                      "receiver balance: ${(await receiver.getBalance()).toString()}");
                   debugPrint(
                       "sender balance: ${(await sender.getBalance()).toString()}");
                 },
@@ -140,37 +145,50 @@ class _PayJoinState extends State<PayJoin> {
                       fontWeight: FontWeight.w800),
                 )),
             TextButton(
-                onPressed: () async {
-                  final balance = await sender.getBalance();
-                  debugPrint("Sender Balance: ${balance.toString()}");
-                  final uri = await pay_join_uri.Uri.fromString(pjUri);
-                  final address = await uri.address();
-                  int amount =
-                      (((await uri.amount()) ?? 0) * 100000000).toInt();
-                  final psbt = (await sender.createPsbt(address, amount, 2000));
-                  debugPrint(
-                    "\nOriginal sender psbt: ${await psbt.serialize()}",
-                  );
-                  setState(() {
-                    senderPsbt = psbt;
-                  });
-                },
-                child: Text(
-                  "Create Sender psbt using receiver pjUri",
-                  style: GoogleFonts.manrope(
-                      color: Colors.black,
-                      fontSize: 14,
-                      fontWeight: FontWeight.w800),
-                )),
+              onPressed: () async {
+                final balance = await sender.getBalance();
+                debugPrint("Sender Balance: ${balance.toString()}");
+                final uri = await pay_join_uri.Uri.fromString(pjUri);
+                final address = await uri.address();
+                int amount = (((await uri.amount()) ?? 0) * 100000000).toInt();
+                final psbt = (await sender.createPsbt(address, amount, 2000));
+                debugPrint(
+                  "\nOriginal sender psbt: ${await psbt.serialize()}",
+                );
+
+                final requestContext =
+                    (await (await RequestBuilder.fromPsbtAndUri(
+                            psbtBase64: await psbt.serialize(), uri: uri))
+                        .buildRecommended(minFeeRate: 0));
+                // In a real scenario, the sender would send the request to
+                //  the payjoin endpoint of the receiver, here we just keep
+                //  the context for the last step.
+                final (_, ctx) = await requestContext.extractContextV1();
+
+                setState(() {
+                  senderPsbt = psbt;
+                  contextV1 = ctx;
+                });
+              },
+              child: Text(
+                "Create Sender request psbt using receiver pjUri",
+                style: GoogleFonts.manrope(
+                    color: Colors.black,
+                    fontSize: 14,
+                    fontWeight: FontWeight.w800),
+              ),
+            ),
             TextButton(
                 onPressed: () async {
-                  final (provisionalProposal, contextV1) = await payJoinLibrary
-                      .handlePjRequest(await senderPsbt.serialize(), pjUri,
-                          (e) async {
-                    final script = ScriptBuf(bytes: e);
+                  final provisionalProposal =
+                      await payJoinLibrary.handlePjRequest(
+                    await senderPsbt.serialize(),
+                    (e) async {
+                      final script = ScriptBuf(bytes: e);
 
-                    return (await receiver.getAddressInfo(script));
-                  });
+                      return (await receiver.getAddressInfo(script));
+                    },
+                  );
                   final unspent = await receiver.listUnspent();
                   // Select receiver payjoin inputs.
                   Map<int, common.OutPoint> candidateInputs = {
@@ -183,7 +201,7 @@ class _PayJoinState extends State<PayJoin> {
                       .tryPreservingPrivacy(candidateInputs: candidateInputs);
                   var selectedUtxo = unspent.firstWhere(
                       (i) =>
-                          i.outpoint.txid.toString() == selectedOutpoint.txid &&
+                          i.outpoint.txid == selectedOutpoint.txid &&
                           i.outpoint.vout == selectedOutpoint.vout,
                       orElse: () => throw Exception('UTXO not found'));
                   var txoToContribute = common.TxOut(
@@ -203,37 +221,39 @@ class _PayJoinState extends State<PayJoin> {
                       address: await newReceiverAddress.address.asString());
                   final payJoinProposal = await provisionalProposal
                       .finalizeProposal(processPsbt: (e) async {
-                    debugPrint("\n Original receiver unsigned psbt: $e");
+                    debugPrint("\n Receiver response unsigned psbt: $e");
                     return await (await receiver.signPsbt(
                             await PartiallySignedTransaction.fromString(e)))
                         .serialize();
                   });
                   final receiverPsbt = await payJoinProposal.psbt();
-                  debugPrint("\n Original receiver psbt: $receiverPsbt");
-                  final receiverProcessedPsbt = await contextV1.processResponse(
-                      response: utf8.encode(receiverPsbt));
-                  final senderProcessedPsbt = (await sender.signPsbt(
-                      await PartiallySignedTransaction.fromString(
-                          receiverProcessedPsbt)));
+                  debugPrint("\n Receiver response psbt: $receiverPsbt");
                   setState(() {
-                    processedAndFinalizedPsbt = senderProcessedPsbt;
+                    receiverPsbtBase64 = receiverPsbt;
                   });
                 },
                 child: Text(
-                  "Process and finalize receiver Pj request",
+                  "Create Receiver response psbt",
                   style: GoogleFonts.manrope(
                       color: Colors.black,
                       fontSize: 14,
                       fontWeight: FontWeight.w800),
                 )),
             TextButton(
                 onPressed: () async {
-                  final res =
-                      await sender.broadcastPsbt(processedAndFinalizedPsbt);
+                  final processedReceiverResponsePsbt =
+                      await contextV1.processResponse(
+                          response: utf8.encode(receiverPsbtBase64));
+                  final finalizedPsbt = (await sender.signPsbt(
+                      await PartiallySignedTransaction.fromString(
+                          processedReceiverResponsePsbt)));
+                  debugPrint(
+                      'Processed and finalized sender psbt: ${await finalizedPsbt.serialize()}');
+                  final res = await sender.broadcastPsbt(finalizedPsbt);
                   debugPrint("Broadcast success: $res");
                 },
                 child: Text(
-                  "Broadcast processed psbt",
+                  "Process response and broadcast final Sender psbt",
                   style: GoogleFonts.manrope(
                       color: Colors.black,
                       fontSize: 14,

example/lib/payjoin_library.dart

@@ -1,9 +1,11 @@
 import 'dart:async';
+import 'dart:convert';
 import 'dart:typed_data';
 
 import 'package:flutter/cupertino.dart';
 import 'package:payjoin_flutter/common.dart' as common;
 import 'package:payjoin_flutter/receive/v1.dart' as v1;
+import 'package:payjoin_flutter/receive/v2.dart';
 import 'package:payjoin_flutter/send.dart' as send;
 import 'package:payjoin_flutter/uri.dart' as pj_uri;
 
@@ -22,39 +24,52 @@ class PayJoinLibrary {
     }
   }
 
-  Future<(v1.ProvisionalProposal, send.ContextV1)> handlePjRequest(
-      String psbtBase64,
-      String uriStr,
-      Future<bool> Function(Uint8List) isOwned) async {
-    final uri = await pj_uri.Uri.fromString(uriStr);
-    final (req, cxt) = await (await (await send.RequestBuilder.fromPsbtAndUri(
-                psbtBase64: psbtBase64, uri: uri))
-            .buildWithAdditionalFee(
-                maxFeeContribution: 10000,
-                minFeeRate: 0,
-                clampFeeContribution: false))
-        .extractContextV1();
+  Future<v1.ProvisionalProposal> handlePjRequest(
+      String psbtBase64, Future<bool> Function(Uint8List) isOwned) async {
+    final body = utf8.encode(psbtBase64);
+
     final headers = common.Headers(map: {
       'content-type': 'text/plain',
-      'content-length': req.body.length.toString(),
+      'content-length': body.length.toString(),
     });
     final unchecked = await v1.UncheckedProposal.fromRequest(
-        body: req.body.toList(),
-        query: (await req.url.query())!,
-        headers: headers);
-    final provisionalProposal = await handleUnckedProposal(unchecked, isOwned);
-    return (provisionalProposal, cxt);
+        body: body.toList(), query: '', headers: headers);
+    final provisionalProposal =
+        await handleUncheckedProposal(unchecked, isOwned);
+    return provisionalProposal;
   }
 
-  Future<v1.ProvisionalProposal> handleUnckedProposal(
+  Future<v1.ProvisionalProposal> handleUncheckedProposal(
       v1.UncheckedProposal uncheckedProposal,
       Future<bool> Function(Uint8List) isOwned) async {
-    // in a payment processor where the sender could go offline, this is where you schedule to broadcast the original_tx
-    var _ = await uncheckedProposal.extractTxToScheduleBroadcast();
-    final inputsOwned = await uncheckedProposal.checkBroadcastSuitability(
-        canBroadcast: (e) async {
-      return true;
-    });
+    // A consumer wallet has some manual interaction to initiate a payjoin, it
+    //  is not a server that can receive a lot of requests without the user
+    //  being aware of it. Therefore we say a consumer wallet app is an
+    //  interactive receiver and an automatic payment processor is
+    //  non-interactive.
+    //
+    //  The way to check a proposal for these cases are different:
+    //   - For an interactive receiver, you can just call
+    //      `assumeInteractiveReceiver` as used here in the example code.
+    //   - For a non-interactive receiver, you would extract the original tx
+    //      with `extractTxToScheduleBroadcast` and check if it can be
+    //      broadcasted in `checkBroadcastSuitability`. This way, if the sender
+    //      doesn't complete the payjoin, you can still broadcast the original
+    //      tx and get your funds. This protects against sender maliciousness of
+    //      probing your utxo set amongst other things.
+
+    final inputsOwned = await uncheckedProposal.assumeInteractiveReceiver();
+    /*
+      // Non-interactive receiver example code:
+      final originalTx = await uncheckedProposal.extractTxToScheduleBroadcast();
+      final inputsOwned = await uncheckedProposal.checkBroadcastSuitability(
+          canBroadcast: (e) async {
+        // Here you would check if the original tx is a valid tx that pays you 
+        //  and that can be broadcasted.
+        return true;
+      });
+    */
+
     // Receive Check 2: receiver can't sign for proposal inputs
     final mixedInputScripts =
         await inputsOwned.checkInputsNotOwned(isOwned: isOwned);

example/pubspec.lock

@@ -37,8 +37,8 @@ packages:
     dependency: "direct main"
     description:
       path: "."
-      ref: "v0.31.2-dev.2"
-      resolved-ref: "18649436038282f379e9a4679656bcd084434ddd"
+      ref: main
+      resolved-ref: "821fe90d20c955e3cdfbfecea3b91fe24885552a"
       url: "https://github.com/LtbLightning/bdk-flutter"
     source: git
     version: "0.31.2-dev.2"