input: add CommitmentToRemoteConfirmed witness type

input/witnessgen.go

@@ -48,8 +48,9 @@ type StandardWitnessType uint16
 var _ WitnessType = (StandardWitnessType)(0)
 
 const (
-	// CommitmentTimeLock is a witness that allows us to spend the output of
-	// a commitment transaction after a relative lock-time lockout.
+	// CommitmentTimeLock is a witness that allows us to spend our output
+	// on our local commitment transaction after a relative lock-time
+	// lockout.
 	CommitmentTimeLock StandardWitnessType = 0
 
 	// CommitmentNoDelay is a witness that allows us to spend a settled
@@ -119,6 +120,11 @@ const (
 	// type, but it omits the tweak that randomizes the key we need to
 	// spend with a channel peer supplied set of randomness.
 	CommitSpendNoDelayTweakless StandardWitnessType = 12
+
+	// CommitmentToRemoteConfirmed is a witness that allows us to spend our
+	// output on the counterparty's commitment transaction after a
+	// confirmation.
+	CommitmentToRemoteConfirmed StandardWitnessType = 13
 )
 
 // String returns a human readable version of the target WitnessType.
@@ -129,6 +135,9 @@ func (wt StandardWitnessType) String() string {
 	case CommitmentTimeLock:
 		return "CommitmentTimeLock"
 
+	case CommitmentToRemoteConfirmed:
+		return "CommitmentToRemoteConfirmed"
+
 	case CommitmentNoDelay:
 		return "CommitmentNoDelay"
 
@@ -197,6 +206,18 @@ func (wt StandardWitnessType) WitnessGenerator(signer Signer,
 				Witness: witness,
 			}, nil
 
+		case CommitmentToRemoteConfirmed:
+			witness, err := CommitSpendToRemoteConfirmed(
+				signer, desc, tx,
+			)
+			if err != nil {
+				return nil, err
+			}
+
+			return &Script{
+				Witness: witness,
+			}, nil
+
 		case CommitmentNoDelay:
 			witness, err := CommitSpendNoDelay(signer, desc, tx, false)
 			if err != nil {
@@ -323,6 +344,10 @@ func (wt StandardWitnessType) SizeUpperBound() (int, bool, error) {
 	case CommitmentTimeLock:
 		return ToLocalTimeoutWitnessSize, false, nil
 
+	// 1 CSV time locked output to us on remote commitment.
+	case CommitmentToRemoteConfirmed:
+		return ToRemoteConfirmedWitnessSize, false, nil
+
 	// Outgoing second layer HTLC's that have confirmed within the
 	// chain, and the output they produced is now mature enough to
 	// sweep.