multi: add p2tr keyspend wallet support

input/size.go

@@ -77,6 +77,18 @@ const (
 	//      - pkscript (p2sh): 23 bytes
 	P2SHOutputSize = 8 + 1 + P2SHSize
 
+	// P2TRSize 34 bytes
+	//	- OP_0: 1 byte
+	//	- OP_DATA: 1 byte (x-only public key length)
+	//	- x-only public key length: 32 bytes
+	P2TRSize = 34
+
+	// P2TROutputSize 43 bytes
+	//      - value: 8 bytes
+	//      - var_int: 1 byte (pkscript_length)
+	//      - pkscript (p2tr): 34 bytes
+	P2TROutputSize = 8 + 1 + P2TRSize
+
 	// P2PKHScriptSigSize 108 bytes
 	//      - OP_DATA: 1 byte (signature length)
 	//      - signature
@@ -519,6 +531,19 @@ const (
 	//      - witness_script_length: 1 byte
 	//      - witness_script (anchor_script)
 	AnchorWitnessSize = 1 + 1 + 73 + 1 + AnchorScriptSize
+
+	// TaprootKeyPathWitnessSize 66 bytes
+	//	- NumberOfWitnessElements: 1 byte
+	//	- sigLength: 1 byte
+	//	- sig: 64 bytes
+	TaprootKeyPathWitnessSize = 1 + 1 + 64
+
+	// TaprootKeyPathCustomSighashWitnessSize 67 bytes
+	//	- NumberOfWitnessElements: 1 byte
+	//	- sigLength: 1 byte
+	//	- sig: 64 bytes
+	//      - sighashFlag: 1 byte
+	TaprootKeyPathCustomSighashWitnessSize = TaprootKeyPathWitnessSize + 1
 )
 
 // EstimateCommitTxWeight estimate commitment transaction weight depending on
@@ -639,6 +664,15 @@ func (twe *TxWeightEstimator) AddP2WSHOutput() *TxWeightEstimator {
 	return twe
 }
 
+// AddP2TROutput updates the weight estimate to account for an additional native
+// SegWit v1 P2TR output.
+func (twe *TxWeightEstimator) AddP2TROutput() *TxWeightEstimator {
+	twe.outputSize += P2TROutputSize
+	twe.outputCount++
+
+	return twe
+}
+
 // AddP2SHOutput updates the weight estimate to account for an additional P2SH
 // output.
 func (twe *TxWeightEstimator) AddP2SHOutput() *TxWeightEstimator {

input/witnessgen.go

@@ -175,6 +175,11 @@ const (
 	// and CLTV locktime as part of the script enforced lease commitment
 	// type.
 	LeaseHtlcAcceptedSuccessSecondLevel StandardWitnessType = 20
+
+	// TaprootPubKeySpend is a witness type that allows us to spend a
+	// regular p2tr output that's sent to an output which is under complete
+	// control of the backing wallet.
+	TaprootPubKeySpend StandardWitnessType = 21
 )
 
 // String returns a human readable version of the target WitnessType.
@@ -245,6 +250,9 @@ func (wt StandardWitnessType) String() string {
 	case LeaseHtlcAcceptedSuccessSecondLevel:
 		return "LeaseHtlcAcceptedSuccessSecondLevel"
 
+	case TaprootPubKeySpend:
+		return "TaprootPubKeySpend"
+
 	default:
 		return fmt.Sprintf("Unknown WitnessType: %v", uint32(wt))
 	}
@@ -388,6 +396,8 @@ func (wt StandardWitnessType) WitnessGenerator(signer Signer,
 
 		case WitnessKeyHash:
 			fallthrough
+		case TaprootPubKeySpend:
+			fallthrough
 		case NestedWitnessKeyHash:
 			return signer.ComputeInputScript(tx, desc)
 
@@ -494,6 +504,9 @@ func (wt StandardWitnessType) SizeUpperBound() (int, bool, error) {
 	// The revocation output of a second level output of an HTLC.
 	case HtlcSecondLevelRevoke:
 		return ToLocalPenaltyWitnessSize, false, nil
+
+	case TaprootPubKeySpend:
+		return TaprootKeyPathCustomSighashWitnessSize, false, nil
 	}
 
 	return 0, false, fmt.Errorf("unexpected witness type: %v", wt)