(to squash) sweepbatcher: send sweep fee in conf notification

Author: starius

sweepbatcher/sweep_batch.go

@@ -2165,6 +2165,16 @@ func (b *batch) handleConf(ctx context.Context,
 		return fmt.Errorf("failed to store confirmed state: %w", err)
 	}
 
+	// Calculate the fee portion that each sweep should pay for the batch.
+	// TODO: make sure spendTx matches b.sweeps.
+	var totalSweptAmt btcutil.Amount
+	for _, s := range b.sweeps {
+		totalSweptAmt += s.value
+	}
+	feePortionPaidPerSweep, roundingDifference := getFeePortionForSweep(
+		spendTx, len(b.sweeps), totalSweptAmt,
+	)
+
 	// Send the confirmation to all the notifiers.
 	for _, s := range b.sweeps {
 		// If the sweep's notifier is empty then this means that
@@ -2174,6 +2184,14 @@ func (b *batch) handleConf(ctx context.Context,
 			continue
 		}
 
+		confDetail := &ConfDetail{
+			TxConfirmation: conf,
+			OnChainFeePortion: getFeePortionPaidBySweep(
+				spendTx, feePortionPaidPerSweep,
+				roundingDifference, &s,
+			),
+		}
+
 		// Notify the caller in a goroutine to avoid possible dead-lock.
 		go func(notifier *SpendNotifier) {
 			// Note that we don't unblock on ctx, because it will
@@ -2182,7 +2200,7 @@ func (b *batch) handleConf(ctx context.Context,
 			select {
 			// Try to write the confirmation to the notification
 			// channel.
-			case notifier.ConfChan <- conf:
+			case notifier.ConfChan <- confDetail:
 
 			// If a quit signal was provided by the swap,
 			// continue.

sweepbatcher/sweep_batcher.go

@@ -281,6 +281,8 @@ type addSweepsRequest struct {
 	parentBatch *dbBatch
 }
 
+// SpendDetail is a notification that is send to the user of sweepbatcher when
+// a batch gets the first confirmation.
 type SpendDetail struct {
 	// Tx is the transaction that spent the outpoint.
 	Tx *wire.MsgTx
@@ -292,6 +294,19 @@ type SpendDetail struct {
 	OnChainFeePortion btcutil.Amount
 }
 
+// ConfDetail is a notification that is send to the user of sweepbatcher when
+// a batch is fully confirmed, i.e. gets batchConfHeight confirmations.
+type ConfDetail struct {
+	// TxConfirmation has data about the confirmation of the transaction.
+	*chainntnfs.TxConfirmation
+
+	// OnChainFeePortion is the fee portion that was paid to get this sweep
+	// confirmed on chain. This is the difference between the value of the
+	// outpoint and the value of all sweeps that were included in the batch
+	// divided by the number of sweeps.
+	OnChainFeePortion btcutil.Amount
+}
+
 // SpendNotifier is a notifier that is used to notify the requester of a sweep
 // that the sweep was successful.
 type SpendNotifier struct {
@@ -303,7 +318,7 @@ type SpendNotifier struct {
 
 	// ConfChan is a channel where the confirmation details are received.
 	// This channel is optional.
-	ConfChan chan<- *chainntnfs.TxConfirmation
+	ConfChan chan<- *ConfDetail
 
 	// ConfErrChan is a channel where confirmation errors are received.
 	// This channel is optional.
@@ -1185,6 +1200,7 @@ func (b *Batcher) monitorSpendAndNotify(ctx context.Context, sweep *sweep,
 			case notifier.SpendChan <- spendDetail:
 				err := b.monitorConfAndNotify(
 					ctx, sweep, notifier, spendTx,
+					onChainFeePortion,
 				)
 				if err != nil {
 					b.writeToErrChan(
@@ -1240,7 +1256,8 @@ func (b *Batcher) monitorSpendAndNotify(ctx context.Context, sweep *sweep,
 // is fully confirmed and we just need to deliver the data back to the caller
 // though SpendNotifier.
 func (b *Batcher) monitorConfAndNotify(ctx context.Context, sweep *sweep,
-	notifier *SpendNotifier, spendTx *wire.MsgTx) error {
+	notifier *SpendNotifier, spendTx *wire.MsgTx,
+	onChainFeePortion btcutil.Amount) error {
 
 	// If confirmation notifications were not requested, stop.
 	if notifier.ConfChan == nil && notifier.ConfErrChan == nil {
@@ -1276,8 +1293,13 @@ func (b *Batcher) monitorConfAndNotify(ctx context.Context, sweep *sweep,
 		select {
 		case conf := <-confChan:
 			if notifier.ConfChan != nil {
+				confDetail := &ConfDetail{
+					TxConfirmation:    conf,
+					OnChainFeePortion: onChainFeePortion,
+				}
+
 				select {
-				case notifier.ConfChan <- conf:
+				case notifier.ConfChan <- confDetail:
 				case <-notifier.QuitChan:
 				case <-ctx.Done():
 				}

sweepbatcher/sweep_batcher_test.go

@@ -992,7 +992,7 @@ func testSweepBatcherSimpleLifecycle(t *testing.T, store testStore,
 
 	// Deliver sweep request to batcher.
 	spendChan = make(chan *SpendDetail, 1)
-	confChan := make(chan *chainntnfs.TxConfirmation)
+	confChan := make(chan *ConfDetail)
 	notifier = &SpendNotifier{
 		SpendChan:    spendChan,
 		SpendErrChan: make(chan error, 1),
@@ -1059,6 +1059,7 @@ func testSweepBatcherSimpleLifecycle(t *testing.T, store testStore,
 	conf := <-confChan
 	require.Equal(t, uint32(604), conf.BlockHeight)
 	require.Equal(t, spendingTx.TxHash(), conf.Tx.TxHash())
+	require.Equal(t, btcutil.Amount(fee), conf.OnChainFeePortion)
 
 	// Eventually the batch receives the confirmation notification and
 	// confirms itself.
@@ -1074,7 +1075,7 @@ func testSweepBatcherSimpleLifecycle(t *testing.T, store testStore,
 	// Now emulate adding the sweep again after it was fully confirmed.
 	// This triggers another code path (monitorSpendAndNotify).
 	spendChan = make(chan *SpendDetail, 1)
-	confChan = make(chan *chainntnfs.TxConfirmation)
+	confChan = make(chan *ConfDetail)
 	notifier = &SpendNotifier{
 		SpendChan:    spendChan,
 		SpendErrChan: make(chan error, 1),
@@ -1106,6 +1107,7 @@ func testSweepBatcherSimpleLifecycle(t *testing.T, store testStore,
 	conf = <-confChan
 	require.Equal(t, uint32(604), conf.BlockHeight)
 	require.Equal(t, spendingTx.TxHash(), conf.Tx.TxHash())
+	require.Equal(t, btcutil.Amount(fee), conf.OnChainFeePortion)
 
 	// Now check what happens in case of a spending error.
 	spendErrChan = make(chan error, 1)