swapserverrpc: add MuSig2SignSweep function

Author: bhandras

server_mock_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/lightninglabs/lndclient"
+	"github.com/lightninglabs/loop/loopdb"
 	"github.com/lightninglabs/loop/test"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -253,3 +254,9 @@ func (s *serverMock) ReportRoutingResult(_ context.Context, _ lntypes.Hash,
 
 	return nil
 }
+
+func (s *serverMock) MuSig2SignSweep(_ context.Context, _ loopdb.ProtocolVersion,
+	_ lntypes.Hash, _ [32]byte, _ []byte, _ []byte) ([]byte, []byte, error) {
+
+	return nil, nil, nil
+}

swap_server_client.go

@@ -121,6 +121,13 @@ type swapServerClient interface {
 		swapHash lntypes.Hash, paymentAddr [32]byte,
 		plugin RoutingPluginType, success bool, attempts int32,
 		totalTime int64) error
+
+	// MuSig2SignSweep calls the server to cooperatively sign the MuSig2
+	// htlc spend. Returns the server's nonce and partial signature.
+	MuSig2SignSweep(ctx context.Context,
+		protocolVersion loopdb.ProtocolVersion, swapHash lntypes.Hash,
+		paymentAddr [32]byte, nonce []byte, sigHash []byte) (
+		[]byte, []byte, error)
 }
 
 type grpcSwapServerClient struct {
@@ -720,6 +727,32 @@ func (s *grpcSwapServerClient) ReportRoutingResult(ctx context.Context,
 	return err
 }
 
+// MuSig2SignSweep calls the server to cooperatively sign the MuSig2 htlc
+// spend. Returns the server's nonce and partial signature.
+func (s *grpcSwapServerClient) MuSig2SignSweep(ctx context.Context,
+	protocolVersion loopdb.ProtocolVersion, swapHash lntypes.Hash,
+	paymentAddr [32]byte, nonce []byte, sigHash []byte) (
+	[]byte, []byte, error) {
+
+	req := &looprpc.MuSig2SignSweepReq{
+		ProtocolVersion: looprpc.ProtocolVersion(protocolVersion),
+		SwapHash:        swapHash[:],
+		PaymentAddress:  paymentAddr[:],
+		Nonce:           nonce,
+		SigHash:         sigHash,
+	}
+
+	rpcCtx, rpcCancel := context.WithTimeout(ctx, globalCallTimeout)
+	defer rpcCancel()
+
+	res, err := s.server.MuSig2SignSweep(rpcCtx, req)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return res.Nonce, res.PartialSignature, nil
+}
+
 func rpcRouteCancel(details *outCancelDetails) (
 	*looprpc.CancelLoopOutSwapRequest_RouteCancel, error) {