From 86bad15337650ca45dfdaad85a3e5686283868d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Calvi=C3=B1o=20S=C3=A1nchez?= <danxuliu@gmail.com>
Date: Thu, 3 Feb 2022 22:56:41 +0100
Subject: [PATCH] Add support for request offers to update subscriber
 connections
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The "sid" parameter of "requestOffer" messages is now checked to update
the current Janus connection when it matches the "sid" of the subscriber
rather than closing it and creating a new one.

Updating a connection is needed for clients to renegotiate their
received media without interrupting the current connection. For example,
to stop receiving video by triggering a new offer from Janus and then
setting the video transceiver direction as inactive before creating the
answer.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>
---
 mcu_janus.go | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/mcu_janus.go b/mcu_janus.go
index fae34e9..1164736 100644
--- a/mcu_janus.go
+++ b/mcu_janus.go
@@ -1245,6 +1245,26 @@ retry:
 	callback(nil, join_response.Jsep)
 }
 
+func (p *mcuJanusSubscriber) update(ctx context.Context, callback func(error, map[string]interface{})) {
+	handle := p.handle
+	if handle == nil {
+		callback(ErrNotConnected, nil)
+		return
+	}
+
+	configure_msg := map[string]interface{}{
+		"request": "configure",
+		"update":  true,
+	}
+	configure_response, err := handle.Message(ctx, configure_msg, nil)
+	if err != nil {
+		callback(err, nil)
+		return
+	}
+
+	callback(nil, configure_response.Jsep)
+}
+
 func (p *mcuJanusSubscriber) SendMessage(ctx context.Context, message *MessageClientMessage, data *MessageClientMessageData, callback func(error, map[string]interface{})) {
 	statsMcuMessagesTotal.WithLabelValues(data.Type).Inc()
 	jsep_msg := data.Payload
@@ -1256,9 +1276,11 @@ func (p *mcuJanusSubscriber) SendMessage(ctx context.Context, message *MessageCl
 			msgctx, cancel := context.WithTimeout(context.Background(), p.mcu.mcuTimeout)
 			defer cancel()
 
-			// TODO Only join the room if there is no sid or it does not match
-			// the subscriber sid; otherwise configure/update the subscriber.
-			p.joinRoom(msgctx, callback)
+			if data.Sid == "" || data.Sid != p.Sid() {
+				p.joinRoom(msgctx, callback)
+			} else {
+				p.update(msgctx, callback)
+			}
 		}
 	case "answer":
 		p.deferred <- func() {