distributor: use service discovery to check gateway (and fallback to demo)

fix #12

distributor/main.go

@@ -61,7 +61,7 @@ func main() {
 	dbus = distributor.NewDBus("org.unifiedpush.Distributor.xmpp")
 	dbus.StartHandling(&config.XMPP)
 
-	log.Info("startup")
+	log.Debug("startup ...")
 	if err := config.XMPP.Run(dbus, store); err != nil {
 		log.Errorf("startup xmpp: %v", err)
 	}

distributor/xmpp.go

@@ -22,10 +22,16 @@ import (
 	"dev.sum7.eu/genofire/unified-push-xmpp/messages"
 )
 
+// Demo Server as fallback
+var (
+	XMPPUPDemoJID = jid.MustParse("up.chat.sum7.eu")
+)
+
 type XMPPService struct {
 	Login    string
 	Password string
 	Gateway  string
+	gateway  jid.JID
 	dbus     *distributor.DBus
 	session  *xmpp.Session
 	store    *storage.Storage
@@ -63,7 +69,27 @@ func (s *XMPPService) Run(dbus *distributor.DBus, store *storage.Storage) error
 	if err != nil {
 		return err
 	}
-	go s.checkServer()
+	go func() {
+		if err := s.checkServer(); err != nil {
+			log.Errorf("check server: %v", err)
+		}
+	}()
+	go func() {
+		if gateway, err := jid.Parse(s.Gateway); err != nil {
+			if err := s.checkGateway(); err != nil {
+				log.Panicf("no gateway found: %v", err)
+			} else {
+				log.Info("using found UnifiedPush")
+			}
+		} else {
+			if err := s.testAndUseGateway(gateway); err != nil {
+				log.Panic(err)
+			} else {
+				log.Info("using configured UnifiedPush")
+			}
+		}
+	}()
+	log.Debug("xmpp client is running")
 	s.session.Serve(mux.New(
 		// disco.Handle(),
 		mux.MessageFunc("", xml.Name{Local: "subject"}, s.message),
@@ -86,7 +112,7 @@ func (s *XMPPService) message(msgHead stanza.Message, t xmlstream.TokenReadEncod
 		return nil
 	}
 	from := msgHead.From.Bare().String()
-	if s.Gateway == "" || from != s.Gateway {
+	if from != s.gateway.String() {
 		log.WithField("from", from).Info("message not from gateway, that is no notification")
 		return nil
 	}
@@ -122,11 +148,13 @@ func (s *XMPPService) message(msgHead stanza.Message, t xmlstream.TokenReadEncod
 // checkServer - background job
 func (s *XMPPService) checkServer() error {
 	domain := s.session.LocalAddr().Domain()
-	log.Infof("your instant is %s - check running", domain)
+	logger := log.WithField("instance", domain)
+	logger.Debug("check running")
 	info, err := disco.GetInfo(context.TODO(), "", domain, s.session)
 	if err != nil {
 		return err
 	}
+
 	// check if server support msgoffline
 	supportMSGOffline := false
 	for _, f := range info.Features {
@@ -138,9 +166,52 @@ func (s *XMPPService) checkServer() error {
 	if !supportMSGOffline {
 		log.Warn("your server does not support offline messages (XEP-0160) - it is need to deliever messages later, if this distributer has current no connection")
 	}
+	logger.Info("your instance checked")
 	return nil
 }
 
+// checkGateway - background job
+func (s *XMPPService) checkGateway() error {
+	domain := s.session.LocalAddr().Domain()
+	log.WithField("instance", domain).Infof("no gateway configured, try to find one on your instance")
+	iter := disco.FetchItemsIQ(context.TODO(), "", stanza.IQ{To: domain}, s.session)
+	if err := iter.Err(); err != nil {
+		iter.Close()
+		return err
+	}
+	addresses := []jid.JID{iter.Item().JID}
+	for iter.Next() {
+		if err := iter.Err(); err != nil {
+			iter.Close()
+			return err
+		}
+		addresses = append(addresses, iter.Item().JID)
+	}
+	iter.Close()
+	for _, j := range addresses {
+		log.Debugf("check for UnifiedPush gateway: %s", j)
+		if err := s.testAndUseGateway(j); err == nil {
+			return nil
+		}
+	}
+	log.WithField("gateway", XMPPUPDemoJID).Infof("no UnifiedPush gateway on your instance - try demo server")
+	return s.testAndUseGateway(XMPPUPDemoJID)
+}
+func (s *XMPPService) testAndUseGateway(address jid.JID) error {
+	info, err := disco.GetInfo(context.TODO(), "", address, s.session)
+	if err != nil {
+		return err
+	}
+	for _, f := range info.Features {
+		if f.Var == messages.Space {
+			s.gateway = address
+			log.WithField("gateway", s.gateway).Debug("tested UnifiedPush XMPP gateway should work")
+			return nil
+		}
+	}
+	return errors.New("this is no UnifiedPush gateway")
+}
+
 // Register handler of DBUS Distribution
 func (s *XMPPService) Register(appID, appToken string) (string, string, error) {
 	publicToken := uuid.New().String()
@@ -152,7 +223,7 @@ func (s *XMPPService) Register(appID, appToken string) (string, string, error) {
 	iq := messages.RegisterIQ{
 		IQ: stanza.IQ{
 			Type: stanza.SetIQ,
-			To:   jid.MustParse(s.Gateway),
+			To:   s.gateway,
 		},
 	}
 	iq.Register.Token = &messages.TokenData{Body: publicToken}