Refactor: Move Signal server and client (#80)

* Move Signal Server

* Move Signal Client

* Cleanup duplicates and unused files

* Moved Signal client tests

signal/server/signal.go

@@ -0,0 +1,105 @@
+package server
+
+import (
+	"context"
+	"fmt"
+	log "github.com/sirupsen/logrus"
+	"github.com/wiretrustee/wiretrustee/signal/peer"
+	"github.com/wiretrustee/wiretrustee/signal/proto"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
+	"io"
+)
+
+// Server an instance of a Signal server
+type Server struct {
+	registry *peer.Registry
+	proto.UnimplementedSignalExchangeServer
+}
+
+// NewServer creates a new Signal server
+func NewServer() *Server {
+	return &Server{
+		registry: peer.NewRegistry(),
+	}
+}
+
+// Send forwards a message to the signal peer
+func (s *Server) Send(ctx context.Context, msg *proto.EncryptedMessage) (*proto.EncryptedMessage, error) {
+
+	if !s.registry.IsPeerRegistered(msg.Key) {
+		return nil, fmt.Errorf("unknown peer %s", msg.Key)
+	}
+
+	if dstPeer, found := s.registry.Get(msg.RemoteKey); found {
+		//forward the message to the target peer
+		err := dstPeer.Stream.Send(msg)
+		if err != nil {
+			log.Errorf("error while forwarding message from peer [%s] to peer [%s]", msg.Key, msg.RemoteKey)
+			//todo respond to the sender?
+		}
+	} else {
+		log.Warnf("message from peer [%s] can't be forwarded to peer [%s] because destination peer is not connected", msg.Key, msg.RemoteKey)
+		//todo respond to the sender?
+	}
+	return &proto.EncryptedMessage{}, nil
+}
+
+// ConnectStream connects to the exchange stream
+func (s *Server) ConnectStream(stream proto.SignalExchange_ConnectStreamServer) error {
+	p, err := s.connectPeer(stream)
+	if err != nil {
+		return err
+	}
+
+	//needed to confirm that the peer has been registered so that the client can proceed
+	header := metadata.Pairs(proto.HeaderRegistered, "1")
+	err = stream.SendHeader(header)
+	if err != nil {
+		return err
+	}
+
+	log.Infof("peer [%s] has successfully connected", p.Id)
+	for {
+		msg, err := stream.Recv()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return err
+		}
+		log.Debugf("received a new message from peer [%s] to peer [%s]", p.Id, msg.RemoteKey)
+		// lookup the target peer where the message is going to
+		if dstPeer, found := s.registry.Get(msg.RemoteKey); found {
+			//forward the message to the target peer
+			err := dstPeer.Stream.Send(msg)
+			if err != nil {
+				log.Errorf("error while forwarding message from peer [%s] to peer [%s]", p.Id, msg.RemoteKey)
+				//todo respond to the sender?
+			}
+		} else {
+			log.Warnf("message from peer [%s] can't be forwarded to peer [%s] because destination peer is not connected", p.Id, msg.RemoteKey)
+			//todo respond to the sender?
+		}
+
+	}
+	<-stream.Context().Done()
+	return stream.Context().Err()
+}
+
+// Handles initial Peer connection.
+// Each connection must provide an ID header.
+// At this moment the connecting Peer will be registered in the peer.Registry
+func (s Server) connectPeer(stream proto.SignalExchange_ConnectStreamServer) (*peer.Peer, error) {
+	if meta, hasMeta := metadata.FromIncomingContext(stream.Context()); hasMeta {
+		if id, found := meta[proto.HeaderId]; found {
+			p := peer.NewPeer(id[0], stream)
+			s.registry.Register(p)
+			return p, nil
+		} else {
+			return nil, status.Errorf(codes.FailedPrecondition, "missing connection header: "+proto.HeaderId)
+		}
+	} else {
+		return nil, status.Errorf(codes.FailedPrecondition, "missing connection stream meta")
+	}
+}