From ff0339a186debc95e53bd78ba343fa027fed95cf Mon Sep 17 00:00:00 2001
From: Valentine Wallace <vwallace@protonmail.com>
Date: Tue, 22 Jan 2019 18:28:35 -0800
Subject: [PATCH] rpcserver: implement SubscribeChannels RPC call.

---
 rpcserver.go | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

diff --git a/rpcserver.go b/rpcserver.go
index 933be798..b4326ca6 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -30,6 +30,7 @@ import (
 	"github.com/lightningnetwork/lnd/autopilot"
 	"github.com/lightningnetwork/lnd/build"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/channelnotifier"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/invoices"
@@ -245,6 +246,10 @@ var (
 			Entity: "offchain",
 			Action: "read",
 		}},
+		"/lnrpc.Lightning/SubscribeChannelEvents": {{
+			Entity: "offchain",
+			Action: "read",
+		}},
 		"/lnrpc.Lightning/ClosedChannels": {{
 			Entity: "offchain",
 			Action: "read",
@@ -2474,6 +2479,84 @@ func createRPCClosedChannel(
 	}
 }
 
+// SubscribeChannelEvents returns a uni-directional stream (server -> client)
+// for notifying the client of newly active, inactive or closed channels.
+func (r *rpcServer) SubscribeChannelEvents(req *lnrpc.ChannelEventSubscription,
+	updateStream lnrpc.Lightning_SubscribeChannelEventsServer) error {
+
+	channelEventSub, err := r.server.channelNotifier.SubscribeChannelEvents()
+	if err != nil {
+		return err
+	}
+
+	// Ensure that the resources for the client is cleaned up once either
+	// the server, or client exits.
+	defer channelEventSub.Cancel()
+
+	graph := r.server.chanDB.ChannelGraph()
+
+	for {
+		select {
+		// A new update has been sent by the channel router, we'll
+		// marshal it into the form expected by the gRPC client, then
+		// send it off to the client(s).
+		case e := <-channelEventSub.Updates():
+			var update *lnrpc.ChannelEventUpdate
+			switch event := e.(type) {
+			case channelnotifier.OpenChannelEvent:
+				channel := createRPCOpenChannel(r, graph,
+					event.Channel, true)
+				update = &lnrpc.ChannelEventUpdate{
+					Type: lnrpc.ChannelEventUpdate_OPEN_CHANNEL,
+					Channel: &lnrpc.ChannelEventUpdate_OpenChannel{
+						OpenChannel: channel,
+					},
+				}
+			case channelnotifier.ClosedChannelEvent:
+				closedChannel := createRPCClosedChannel(event.CloseSummary)
+				update = &lnrpc.ChannelEventUpdate{
+					Type: lnrpc.ChannelEventUpdate_CLOSED_CHANNEL,
+					Channel: &lnrpc.ChannelEventUpdate_ClosedChannel{
+						ClosedChannel: closedChannel,
+					},
+				}
+			case channelnotifier.ActiveChannelEvent:
+				update = &lnrpc.ChannelEventUpdate{
+					Type: lnrpc.ChannelEventUpdate_ACTIVE_CHANNEL,
+					Channel: &lnrpc.ChannelEventUpdate_ActiveChannel{
+						ActiveChannel: &lnrpc.ChannelPoint{
+							FundingTxid: &lnrpc.ChannelPoint_FundingTxidBytes{
+								FundingTxidBytes: event.ChannelPoint.Hash[:],
+							},
+							OutputIndex: event.ChannelPoint.Index,
+						},
+					},
+				}
+			case channelnotifier.InactiveChannelEvent:
+				update = &lnrpc.ChannelEventUpdate{
+					Type: lnrpc.ChannelEventUpdate_INACTIVE_CHANNEL,
+					Channel: &lnrpc.ChannelEventUpdate_InactiveChannel{
+						InactiveChannel: &lnrpc.ChannelPoint{
+							FundingTxid: &lnrpc.ChannelPoint_FundingTxidBytes{
+								FundingTxidBytes: event.ChannelPoint.Hash[:],
+							},
+							OutputIndex: event.ChannelPoint.Index,
+						},
+					},
+				}
+			default:
+				return fmt.Errorf("unexpected channel event update: %v", event)
+			}
+
+			if err := updateStream.Send(update); err != nil {
+				return err
+			}
+		case <-r.quit:
+			return nil
+		}
+	}
+}
+
 // savePayment saves a successfully completed payment to the database for
 // historical record keeping.
 func (r *rpcServer) savePayment(route *routing.Route,