From b93fee2f06120c9caed21fd648ea5bcbc922bb42 Mon Sep 17 00:00:00 2001
From: Oliver Gugger <gugger@gmail.com>
Date: Mon, 6 May 2024 11:11:36 +0200
Subject: [PATCH] rpcserver+config_builder: add AuxDataParser

---
 config_builder.go |  4 +++
 rpcserver.go      | 67 +++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/config_builder.go b/config_builder.go
index a726c63b1..b675cacaa 100644
--- a/config_builder.go
+++ b/config_builder.go
@@ -178,6 +178,10 @@ type AuxComponents struct {
 	// TrafficShaper is an optional traffic shaper that can be used to
 	// control the outgoing channel of a payment.
 	TrafficShaper fn.Option[routing.TlvTrafficShaper]
+
+	// AuxDataParser is an optional data parser that can be used to parse
+	// auxiliary data for certain custom channel types.
+	AuxDataParser fn.Option[AuxDataParser]
 }
 
 // DefaultWalletImpl is the default implementation of our normal, btcwallet
diff --git a/rpcserver.go b/rpcserver.go
index 4c5d0189b..2c3d481a2 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -46,6 +46,7 @@ import (
 	"github.com/lightningnetwork/lnd/contractcourt"
 	"github.com/lightningnetwork/lnd/discovery"
 	"github.com/lightningnetwork/lnd/feature"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/funding"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
@@ -82,6 +83,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/proto"
 	"gopkg.in/macaroon-bakery.v2/bakery"
 )
 
@@ -567,6 +569,17 @@ func MainRPCServerPermissions() map[string][]bakery.Op {
 	}
 }
 
+// AuxDataParser is an interface that is used to parse auxiliary custom data
+// within RPC messages. This is used to transform binary blobs to human-readable
+// JSON representations.
+type AuxDataParser interface {
+	// InlineParseCustomData replaces any custom data binary blob in the
+	// given RPC message with its corresponding JSON formatted data. This
+	// transforms the binary (likely TLV encoded) data to a human-readable
+	// JSON representation (still as byte slice).
+	InlineParseCustomData(msg proto.Message) error
+}
+
 // rpcServer is a gRPC, RPC front end to the lnd daemon.
 // TODO(roasbeef): pagination support for the list-style calls
 type rpcServer struct {
@@ -3478,6 +3491,7 @@ func (r *rpcServer) ChannelBalance(ctx context.Context,
 		unsettledRemoteBalance   lnwire.MilliSatoshi
 		pendingOpenLocalBalance  lnwire.MilliSatoshi
 		pendingOpenRemoteBalance lnwire.MilliSatoshi
+		customDataBuf            bytes.Buffer
 	)
 
 	openChannels, err := r.server.chanStateDB.FetchAllOpenChannels()
@@ -3485,6 +3499,12 @@ func (r *rpcServer) ChannelBalance(ctx context.Context,
 		return nil, err
 	}
 
+	// Encode the number of open channels to the custom data buffer.
+	err = wire.WriteVarInt(&customDataBuf, 0, uint64(len(openChannels)))
+	if err != nil {
+		return nil, err
+	}
+
 	for _, channel := range openChannels {
 		c := channel.LocalCommitment
 		localBalance += c.LocalBalance
@@ -3498,6 +3518,13 @@ func (r *rpcServer) ChannelBalance(ctx context.Context,
 				unsettledRemoteBalance += htlc.Amt
 			}
 		}
+
+		// Encode the custom data for this open channel.
+		openChanData := channel.LocalCommitment.CustomBlob.UnwrapOr(nil)
+		err = wire.WriteVarBytes(&customDataBuf, 0, openChanData)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	pendingChannels, err := r.server.chanStateDB.FetchPendingChannels()
@@ -3505,10 +3532,23 @@ func (r *rpcServer) ChannelBalance(ctx context.Context,
 		return nil, err
 	}
 
+	// Encode the number of pending channels to the custom data buffer.
+	err = wire.WriteVarInt(&customDataBuf, 0, uint64(len(pendingChannels)))
+	if err != nil {
+		return nil, err
+	}
+
 	for _, channel := range pendingChannels {
 		c := channel.LocalCommitment
 		pendingOpenLocalBalance += c.LocalBalance
 		pendingOpenRemoteBalance += c.RemoteBalance
+
+		// Encode the custom data for this pending channel.
+		openChanData := channel.LocalCommitment.CustomBlob.UnwrapOr(nil)
+		err = wire.WriteVarBytes(&customDataBuf, 0, openChanData)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	rpcsLog.Debugf("[channelbalance] local_balance=%v remote_balance=%v "+
@@ -3518,7 +3558,7 @@ func (r *rpcServer) ChannelBalance(ctx context.Context,
 		unsettledRemoteBalance, pendingOpenLocalBalance,
 		pendingOpenRemoteBalance)
 
-	return &lnrpc.ChannelBalanceResponse{
+	resp := &lnrpc.ChannelBalanceResponse{
 		LocalBalance: &lnrpc.Amount{
 			Sat:  uint64(localBalance.ToSatoshis()),
 			Msat: uint64(localBalance),
@@ -3543,11 +3583,24 @@ func (r *rpcServer) ChannelBalance(ctx context.Context,
 			Sat:  uint64(pendingOpenRemoteBalance.ToSatoshis()),
 			Msat: uint64(pendingOpenRemoteBalance),
 		},
+		CustomChannelData: customDataBuf.Bytes(),
 
 		// Deprecated fields.
 		Balance:            int64(localBalance.ToSatoshis()),
 		PendingOpenBalance: int64(pendingOpenLocalBalance.ToSatoshis()),
-	}, nil
+	}
+
+	err = fn.MapOptionZ(
+		r.server.implCfg.AuxDataParser,
+		func(parser AuxDataParser) error {
+			return parser.InlineParseCustomData(resp)
+		},
+	)
+	if err != nil {
+		return nil, fmt.Errorf("error parsing custom data: %w", err)
+	}
+
+	return resp, nil
 }
 
 type (
@@ -4303,6 +4356,16 @@ func (r *rpcServer) ListChannels(ctx context.Context,
 		resp.Channels = append(resp.Channels, channel)
 	}
 
+	err = fn.MapOptionZ(
+		r.server.implCfg.AuxDataParser,
+		func(parser AuxDataParser) error {
+			return parser.InlineParseCustomData(resp)
+		},
+	)
+	if err != nil {
+		return nil, fmt.Errorf("error parsing custom data: %w", err)
+	}
+
 	return resp, nil
 }