conference: attach stream metadata to offers

Author: daniel-abramov

pkg/conference/processor.go

@@ -185,8 +185,9 @@ func (c *Conference) handleDataChannelMessage(participant *Participant, sfuMessa
 		}
 
 		participant.sendDataChannelMessage(event.SFUMessage{
-			Op:  event.SFUOperationAnswer,
-			SDP: answer.SDP,
+			Op:       event.SFUOperationAnswer,
+			SDP:      answer.SDP,
+			Metadata: c.getAvailableStreamsFor(participant.id),
 		})
 
 	case event.SFUOperationUnpublish:
@@ -196,7 +197,11 @@ func (c *Conference) handleDataChannelMessage(participant *Participant, sfuMessa
 	case event.SFUOperationAlive:
 		// FIXME: Handle the heartbeat message here (updating the last timestamp etc).
 	case event.SFUOperationMetadata:
-		participant.logger.Info("Received metadata over DC")
+		streamIDs := make([]string, 0, len(sfuMessage.Metadata))
+		for streamID := range sfuMessage.Metadata {
+			streamIDs = append(streamIDs, streamID)
+		}
+		participant.logger.Infof("Received metadata over DC: %v", streamIDs)
 
 		participant.streamMetadata = sfuMessage.Metadata
 		c.resendMetadataToAllExcept(participant.id)