tapchannel: use UpdateTxWitness to insert preimage

Author: Roasbeef

tapchannel/aux_sweeper.go

@@ -1964,7 +1964,7 @@ func newBlobWithWitnessInfo(i input.Input) lfn.Result[blobWithWitnessInfo] {
 	// from the inner struct, so we can update the witness stack.
 	var (
 		preimageInfo lfn.Option[preimageDesc]
-		secondLevel  = true
+		secondLevel  bool
 	)
 	switch i.WitnessType() {
 
@@ -2038,8 +2038,8 @@ func prepVpkts(bRes lfn.Result[blobWithWitnessInfo],
 	if err != nil {
 		return nil, err
 	}
-	var res cmsg.ContractResolution
 
+	var res cmsg.ContractResolution
 	err = res.Decode(bytes.NewReader(b.resolutionBlob))
 	if err != nil {
 		return nil, err
@@ -2051,22 +2051,19 @@ func prepVpkts(bRes lfn.Result[blobWithWitnessInfo],
 	pkts := res.Vpkts1()
 	if secondLevel {
 		pkts = res.Vpkts2()
+		tapSigDesc = res.SigDescs()
 	}
 
 	b.preimageInfo.WhenSome(func(p preimageDesc) {
-		vIns := fn.FlatMap(
-			pkts,
-			func(vPkt *tappsbt.VPacket) []*tappsbt.VInput {
-				return vPkt.Inputs
-			},
-		)
+		for _, pkt := range pkts {
+			newAsset := pkt.Outputs[0].Asset
 
-		for _, vIn := range vIns {
-			prevWitness := vIn.Asset().PrevWitnesses[0].TxWitness
-			vIn.Asset().PrevWitnesses[0].TxWitness = slices.Insert(
+			prevWitness := newAsset.PrevWitnesses[0].TxWitness
+			prevWitness = slices.Insert(
 				prevWitness, p.witnessIndex,
 				p.preimage[:],
 			)
+			newAsset.UpdateTxWitness(0, prevWitness)
 		}
 	})
 
@@ -2138,7 +2135,7 @@ func extractInputVPackets(inputs []input.Input) lfn.Result[sweepVpkts] {
 			return lfn.Err[sweepVpkts](err)
 		}
 
-		vPkts2 = append(vPkts1, *vpkt)
+		vPkts2 = append(vPkts2, *vpkt)
 	}
 
 	return lfn.Ok(sweepVpkts{

tapchannelmsg/records.go

@@ -2201,6 +2201,11 @@ func (c *ContractResolution) Decode(r io.Reader) error {
 	return nil
 }
 
+// SigDescs returns the list of tapscriptSigDescs.
+func (c *ContractResolution) SigDescs() lfn.Option[TapscriptSigDesc] {
+	return c.secondLevelSigDescs.ValOpt()
+}
+
 // Vpkts1 returns the set of first level Vpkts.
 func (c *ContractResolution) Vpkts1() []*tappsbt.VPacket {
 	return c.firstLevelSweepVpkts.Val.Pkts