Add currentDirection to RTPTransceiver

add currentDirection to RTPTransceiver, don't reuse
transceiver if its currentDirection is sendrecv or sendonly

rtptransceiver.go

@@ -13,10 +13,11 @@ import (
 
 // RTPTransceiver represents a combination of an RTPSender and an RTPReceiver that share a common mid.
 type RTPTransceiver struct {
-	mid       atomic.Value // string
-	sender    atomic.Value // *RTPSender
-	receiver  atomic.Value // *RTPReceiver
-	direction atomic.Value // RTPTransceiverDirection
+	mid              atomic.Value // string
+	sender           atomic.Value // *RTPSender
+	receiver         atomic.Value // *RTPReceiver
+	direction        atomic.Value // RTPTransceiverDirection
+	currentDirection atomic.Value // RTPTransceiverDirection
 
 	codecs []RTPCodecParameters // User provided codecs via SetCodecPreferences
 
@@ -38,6 +39,7 @@ func newRTPTransceiver(
 	t.setReceiver(receiver)
 	t.setSender(sender)
 	t.setDirection(direction)
+	t.setCurrentDirection(RTPTransceiverDirection(Unknown))
 	return t
 }
 
@@ -160,6 +162,7 @@ func (t *RTPTransceiver) Stop() error {
 	}
 
 	t.setDirection(RTPTransceiverDirectionInactive)
+	t.setCurrentDirection(RTPTransceiverDirectionInactive)
 	return nil
 }
 
@@ -179,6 +182,17 @@ func (t *RTPTransceiver) setDirection(d RTPTransceiverDirection) {
 	t.direction.Store(d)
 }
 
+func (t *RTPTransceiver) setCurrentDirection(d RTPTransceiverDirection) {
+	t.currentDirection.Store(d)
+}
+
+func (t *RTPTransceiver) getCurrentDirection() RTPTransceiverDirection {
+	if v, ok := t.currentDirection.Load().(RTPTransceiverDirection); ok {
+		return v
+	}
+	return RTPTransceiverDirection(Unknown)
+}
+
 func (t *RTPTransceiver) setSendingTrack(track TrackLocal) error {
 	if err := t.Sender().ReplaceTrack(track); err != nil {
 		return err