Fix/connection listener (#777)

Fix add/remove connection listener

In case we call the RemoveConnListener from Java then
we lose the reference from the original instance

client/internal/peer/notifier_test.go

@@ -1,9 +1,48 @@
 package peer
 
 import (
+	"sync"
 	"testing"
 )
 
+type mocListener struct {
+	lastState int
+	wg        sync.WaitGroup
+	peers     int
+}
+
+func (l *mocListener) OnConnected() {
+	l.lastState = stateConnected
+	l.wg.Done()
+}
+func (l *mocListener) OnDisconnected() {
+	l.lastState = stateDisconnected
+	l.wg.Done()
+}
+func (l *mocListener) OnConnecting() {
+	l.lastState = stateConnecting
+	l.wg.Done()
+}
+func (l *mocListener) OnDisconnecting() {
+	l.lastState = stateDisconnecting
+	l.wg.Done()
+}
+
+func (l *mocListener) OnAddressChanged(host, addr string) {
+
+}
+func (l *mocListener) OnPeersListChanged(size int) {
+	l.peers = size
+}
+
+func (l *mocListener) setWaiter() {
+	l.wg.Add(1)
+}
+
+func (l *mocListener) wait() {
+	l.wg.Wait()
+}
+
 func Test_notifier_serverState(t *testing.T) {
 
 	type scenario struct {
@@ -30,3 +69,30 @@ func Test_notifier_serverState(t *testing.T) {
 		})
 	}
 }
+
+func Test_notifier_SetListener(t *testing.T) {
+	listener := &mocListener{}
+	listener.setWaiter()
+
+	n := newNotifier()
+	n.lastNotification = stateConnecting
+	n.setListener(listener)
+	listener.wait()
+	if listener.lastState != n.lastNotification {
+		t.Errorf("invalid state: %d, expected: %d", listener.lastState, n.lastNotification)
+	}
+}
+
+func Test_notifier_RemoveListener(t *testing.T) {
+	listener := &mocListener{}
+	listener.setWaiter()
+	n := newNotifier()
+	n.lastNotification = stateConnecting
+	n.setListener(listener)
+	n.removeListener()
+	n.peerListChanged(1)
+
+	if listener.peers != 0 {
+		t.Errorf("invalid state: %d", listener.peers)
+	}
+}