notifications: add notification manager

This commit adds a generic notification manager
that can be used to subscribe to different types
of notifications.

notifications/log.go

@@ -0,0 +1,26 @@
+package notifications
+
+import (
+	"github.com/btcsuite/btclog"
+	"github.com/lightningnetwork/lnd/build"
+)
+
+// Subsystem defines the sub system name of this package.
+const Subsystem = "NTFNS"
+
+// log is a logger that is initialized with no output filters.  This
+// means the package will not perform any logging by default until the caller
+// requests it.
+var log btclog.Logger
+
+// The default amount of logging is none.
+func init() {
+	UseLogger(build.NewSubLogger(Subsystem, nil))
+}
+
+// UseLogger uses a specified Logger to output package logging info.
+// This should be used in preference to SetLogWriter if the caller is also
+// using btclog.
+func UseLogger(logger btclog.Logger) {
+	log = logger
+}

notifications/manager.go

@@ -0,0 +1,205 @@
+package notifications
+
+import (
+	"context"
+	"time"
+
+	"github.com/lightninglabs/loop/swapserverrpc"
+	"google.golang.org/grpc"
+)
+
+type NotificationType int
+
+const (
+	NotificationTypeUnknown NotificationType = iota
+	NotificationTypeReservation
+)
+
+type NotificationsClient interface {
+	SubscribeNotifications(ctx context.Context,
+		in *swapserverrpc.SubscribeNotificationsRequest,
+		opts ...grpc.CallOption) (
+		swapserverrpc.SwapServer_SubscribeNotificationsClient, error)
+}
+
+// Config contains all the services that the notification manager needs to
+// operate.
+type Config struct {
+	// Client is the client used to communicate with the swap server.
+	Client NotificationsClient
+
+	// FetchL402 is the function used to fetch the l402 token.
+	FetchL402 func(context.Context) error
+}
+
+// Manager is a manager for notifications that the swap server sends to the
+// client.
+type Manager struct {
+	cfg *Config
+
+	hasL402 bool
+
+	subscribers map[NotificationType][]subscriber
+}
+
+// NewManager creates a new notification manager.
+func NewManager(cfg *Config) *Manager {
+	return &Manager{
+		cfg:         cfg,
+		subscribers: make(map[NotificationType][]subscriber),
+	}
+}
+
+type subscriber struct {
+	subCtx   context.Context
+	recvChan interface{}
+}
+
+// SubscribeReservations subscribes to the reservation notifications.
+func (m *Manager) SubscribeReservations(ctx context.Context,
+) <-chan *swapserverrpc.ServerReservationNotification {
+
+	// We'll create a channel that we'll use to send the notifications to the
+	// caller.
+	notifChan := make(
+		chan *swapserverrpc.ServerReservationNotification, //nolint:lll
+	)
+	sub := subscriber{
+		subCtx:   ctx,
+		recvChan: notifChan,
+	}
+
+	m.subscribers[NotificationTypeReservation] = append(
+		m.subscribers[NotificationTypeReservation],
+		sub,
+	)
+
+	return notifChan
+}
+
+// Run starts the notification manager.
+func (n *Manager) Run(ctx context.Context) error {
+	err := n.registerNotifications(ctx)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// registerNotifications registers a new server notification stream.
+func (n *Manager) registerNotifications(mainCtx context.Context) error {
+	// In order to create a valid l402 we first are going to call
+	// the FetchL402 method. As a client might not have outbound capacity
+	// yet, we'll retry until we get a valid response.
+	if !n.hasL402 {
+		n.fetchL402(mainCtx)
+	}
+
+	callCtx, cancel := context.WithCancel(mainCtx)
+
+	// We'll now subscribe to the swap server notifications.
+	notifStream, err := n.cfg.Client.SubscribeNotifications(
+		callCtx, &swapserverrpc.SubscribeNotificationsRequest{},
+	)
+	if err != nil {
+		cancel()
+		return err
+	}
+
+	log.Debugf("Successfully subscribed to server notifications")
+
+	// We'll now start a goroutine that will handle all the incoming
+	// notifications.
+	go func() {
+		for {
+			notification, err := notifStream.Recv()
+			if err == nil && notification != nil {
+				log.Debugf("Received notification: %v", notification)
+				n.handleNotification(notification)
+				continue
+			}
+			log.Errorf("Error receiving "+
+				"notification: %v", err)
+
+			cancel()
+
+			// If we encounter an error, we'll
+			// try to reconnect.
+			for {
+				select {
+				case <-mainCtx.Done():
+					return
+
+				case <-time.After(time.Second * 10):
+					log.Debugf("Reconnecting to server notifications")
+					err = n.registerNotifications(mainCtx)
+					if err != nil {
+						log.Errorf("Error reconnecting: %v", err)
+						continue
+					}
+
+					// If we were able to reconnect, we'll
+					// return.
+					return
+				}
+			}
+		}
+	}()
+
+	return nil
+}
+
+// fetchL402 fetches the L402 from the server. This method will keep on
+// retrying until it gets a valid response.
+func (m *Manager) fetchL402(ctx context.Context) {
+	// Add a 0 timer so that we initially fetch the L402 immediately.
+	timer := time.NewTimer(0)
+	for {
+		select {
+		case <-ctx.Done():
+			return
+
+		case <-timer.C:
+			err := m.cfg.FetchL402(ctx)
+			if err != nil {
+				log.Warnf("Error fetching L402: %v", err)
+				timer.Reset(time.Second * 10)
+				continue
+			}
+			m.hasL402 = true
+
+			return
+		}
+	}
+}
+
+// handleNotification handles an incoming notification from the server,
+// forwarding it to the appropriate subscribers.
+func (n *Manager) handleNotification(notification *swapserverrpc.
+	SubscribeNotificationsResponse) {
+
+	switch notification.Notification.(type) {
+	case *swapserverrpc.SubscribeNotificationsResponse_ReservationNotification:
+		// We'll forward the reservation notification to all subscribers.
+		// Cleaning up any subscribers that have been canceled.
+		newSubs := []subscriber{}
+		for _, sub := range n.subscribers[NotificationTypeReservation] {
+			recvChan := sub.recvChan.(chan *swapserverrpc.
+				ServerReservationNotification)
+
+			select {
+			case <-sub.subCtx.Done():
+				continue
+			case recvChan <- notification.GetReservationNotification():
+				newSubs = append(newSubs, sub)
+			}
+		}
+
+		n.subscribers[NotificationTypeReservation] = newSubs
+
+	default:
+		log.Warnf("Received unknown notification type: %v",
+			notification)
+	}
+}

notifications/manager_test.go

@@ -0,0 +1,157 @@
+package notifications
+
+import (
+	"context"
+	"io"
+	"testing"
+	"time"
+
+	"github.com/lightninglabs/loop/swapserverrpc"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+)
+
+var (
+	testReservationId  = []byte{0x01, 0x02}
+	testReservationId2 = []byte{0x01, 0x02}
+)
+
+// mockNotificationsClient implements the NotificationsClient interface for testing.
+type mockNotificationsClient struct {
+	mockStream   swapserverrpc.SwapServer_SubscribeNotificationsClient
+	subscribeErr error
+	timesCalled  int
+}
+
+func (m *mockNotificationsClient) SubscribeNotifications(ctx context.Context,
+	in *swapserverrpc.SubscribeNotificationsRequest,
+	opts ...grpc.CallOption) (
+	swapserverrpc.SwapServer_SubscribeNotificationsClient, error) {
+
+	m.timesCalled++
+	if m.subscribeErr != nil {
+		return nil, m.subscribeErr
+	}
+	return m.mockStream, nil
+}
+
+// mockSubscribeNotificationsClient simulates the server stream.
+type mockSubscribeNotificationsClient struct {
+	grpc.ClientStream
+	recvChan    chan *swapserverrpc.SubscribeNotificationsResponse
+	recvErrChan chan error
+}
+
+func (m *mockSubscribeNotificationsClient) Recv() (
+	*swapserverrpc.SubscribeNotificationsResponse, error) {
+
+	select {
+	case err := <-m.recvErrChan:
+		return nil, err
+	case notif, ok := <-m.recvChan:
+		if !ok {
+			return nil, io.EOF
+		}
+		return notif, nil
+	}
+}
+
+func (m *mockSubscribeNotificationsClient) Header() (metadata.MD, error) {
+	return nil, nil
+}
+
+func (m *mockSubscribeNotificationsClient) Trailer() metadata.MD {
+	return nil
+}
+
+func (m *mockSubscribeNotificationsClient) CloseSend() error {
+	return nil
+}
+
+func (m *mockSubscribeNotificationsClient) Context() context.Context {
+	return context.TODO()
+}
+
+func (m *mockSubscribeNotificationsClient) SendMsg(interface{}) error {
+	return nil
+}
+
+func (m *mockSubscribeNotificationsClient) RecvMsg(interface{}) error {
+	return nil
+}
+
+func TestManager_ReservationNotification(t *testing.T) {
+	// Create a mock notification client
+	recvChan := make(chan *swapserverrpc.SubscribeNotificationsResponse, 1)
+	errChan := make(chan error, 1)
+	mockStream := &mockSubscribeNotificationsClient{
+		recvChan:    recvChan,
+		recvErrChan: errChan,
+	}
+	mockClient := &mockNotificationsClient{
+		mockStream: mockStream,
+	}
+
+	// Create a Manager with the mock client
+	mgr := NewManager(&Config{
+		Client: mockClient,
+		FetchL402: func(ctx context.Context) error {
+			// Simulate successful fetching of L402
+			return nil
+		},
+	})
+
+	// Subscribe to reservation notifications.
+	subCtx, subCancel := context.WithCancel(context.Background())
+	subChan := mgr.SubscribeReservations(subCtx)
+
+	// Run the manager.
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	err := mgr.Run(ctx)
+	require.NoError(t, err)
+
+	// Wait a bit to ensure manager is running and has subscribed
+	time.Sleep(100 * time.Millisecond)
+	require.Equal(t, 1, mockClient.timesCalled)
+
+	// Send a test notification
+	testNotif := getTestNotification(testReservationId)
+
+	// Send the notification to the recvChan
+	recvChan <- testNotif
+
+	// Collect the notification in the callback
+	receivedNotification := <-subChan
+
+	// Now, check that the notification received in the callback matches the one sent
+	require.NotNil(t, receivedNotification)
+	require.Equal(t, testReservationId, receivedNotification.ReservationId)
+
+	// Cancel the subscription
+	subCancel()
+
+	// Send another test notification`
+	testNotif2 := getTestNotification(testReservationId2)
+	recvChan <- testNotif2
+
+	// Wait a bit to ensure the notification is not received
+	time.Sleep(100 * time.Millisecond)
+
+	require.Len(t, mgr.subscribers[NotificationTypeReservation], 0)
+
+	// Close the recvChan to stop the manager's receive loop
+	close(recvChan)
+}
+
+func getTestNotification(resId []byte) *swapserverrpc.SubscribeNotificationsResponse {
+	return &swapserverrpc.SubscribeNotificationsResponse{
+		Notification: &swapserverrpc.SubscribeNotificationsResponse_ReservationNotification{
+			ReservationNotification: &swapserverrpc.ServerReservationNotification{
+				ReservationId: resId,
+			},
+		},
+	}
+}