multi: consume and log sever state updates

updates.go

@@ -0,0 +1,52 @@
+package loop
+
+import (
+	"context"
+
+	"github.com/lightninglabs/loop/swap"
+	"github.com/lightningnetwork/lnd/lntypes"
+)
+
+// subscribeAndLogUpdates subscribes to updates for a swap and logs them. This
+// function will block, so should run as a goroutine. Note that our subscription
+// does not survive server restarts; we will simply not have update logs if the
+// server restarts during swap execution.
+func subscribeAndLogUpdates(ctx context.Context, hash lntypes.Hash,
+	log *swap.PrefixLog, subscribe func(context.Context,
+		lntypes.Hash) (<-chan *ServerUpdate, <-chan error, error)) {
+
+	subscribeChan, errChan, err := subscribe(ctx, hash)
+	if err != nil {
+		log.Errorf("could not get swap subscription: %v", err)
+		return
+	}
+
+	for {
+		select {
+		// Consume any updates and log them.
+		case update := <-subscribeChan:
+			log.Infof("Server update: %v received, "+
+				"timestamp: %v", update.State, update.Timestamp)
+
+		// If we get an error from the server, we check whether it is
+		// due to server exit, or restart, and log this information
+		// for the client. Otherwise, we just log non-nil errors.
+		case err := <-errChan:
+			switch err {
+			case errServerSubscriptionComplete:
+				log.Infof("swap subscription: %v", err)
+
+			case nil:
+
+			default:
+				log.Errorf("swap subscription error: %v", err)
+			}
+
+			return
+
+		// Exit if our context is cancelled.
+		case <-ctx.Done():
+			return
+		}
+	}
+}