feat: save LDK static channel backups to disk

lnclient/ldk/ldk.go

@@ -19,6 +19,7 @@ import (
 	// "github.com/getAlby/hub/ldk_node"
 
 	"encoding/hex"
+	"encoding/json"
 
 	decodepay "github.com/nbd-wtf/ln-decodepay"
 	"github.com/sirupsen/logrus"
@@ -1302,7 +1303,7 @@ func (ls *LDKService) handleLdkEvent(event *ldk_node.Event) {
 			},
 		})
 
-		ls.publishChannelsBackupEvent()
+		ls.backupChannels()
 
 		if eventType.CounterpartyNodeId == nil {
 			logger.Logger.WithField("event", eventType).Error("channel ready event has no counterparty node ID")
@@ -1406,7 +1407,7 @@ func (ls *LDKService) handleLdkEvent(event *ldk_node.Event) {
 	}
 }
 
-func (ls *LDKService) publishChannelsBackupEvent() {
+func (ls *LDKService) backupChannels() {
 	ldkChannels := ls.node.ListChannels()
 	channels := make([]events.ChannelBackupInfo, 0, len(ldkChannels))
 	for _, ldkChannel := range ldkChannels {
@@ -1427,6 +1428,28 @@ func (ls *LDKService) publishChannelsBackupEvent() {
 		})
 	}
 
+	func() {
+		backupDirectory := filepath.Join(ls.workdir, "static_channel_backups")
+		err := os.MkdirAll(backupDirectory, os.ModePerm)
+		if err != nil {
+			logger.Logger.WithError(err).Error("Failed to make static channel backup directory")
+			return
+		}
+
+		backupFilePath := filepath.Join(backupDirectory, time.Now().Format(time.RFC3339)+".json")
+		channelsBytes, err := json.Marshal(channels)
+		if err != nil {
+			logger.Logger.WithError(err).Error("Failed to serialize static channel backup to json")
+			return
+		}
+		err = os.WriteFile(backupFilePath, channelsBytes, 0644)
+		if err != nil {
+			logger.Logger.WithError(err).Error("Failed to write static channel backup to disk")
+			return
+		}
+		logger.Logger.WithField("backupPath", backupFilePath).Debug("Saved static channel backup to disk")
+	}()
+
 	ls.eventPublisher.Publish(&events.Event{
 		Event: "nwc_backup_channels",
 		Properties: &events.ChannelBackupEvent{