MM-56071: Track multiple threads (#25775)

We can have 2 types of threads open at the same time. One from
the thread view, and another from RHS.

We add another variable to distinguish between the 2 states.

In future, if we have the ability for more than 2 threads, then
we would need to track by threadID.

https://mattermost.atlassian.net/browse/MM-56071

```release-note
NONE
```

server/channels/api4/websocket_test.go

@@ -441,7 +441,12 @@ func TestWebSocketPresence(t *testing.T) {
 	require.Nil(t, resp.Error)
 	require.Equal(t, resp.SeqReply, wsClient.Sequence-1, "bad sequence number")
 
-	wsClient.UpdateActiveThread("threadID")
+	wsClient.UpdateActiveThread(true, "threadID")
+	resp = <-wsClient.ResponseChannel
+	require.Nil(t, resp.Error)
+	require.Equal(t, resp.SeqReply, wsClient.Sequence-1, "bad sequence number")
+
+	wsClient.UpdateActiveThread(false, "threadID")
 	resp = <-wsClient.ResponseChannel
 	require.Nil(t, resp.Error)
 	require.Equal(t, resp.SeqReply, wsClient.Sequence-1, "bad sequence number")

server/channels/app/platform/web_conn.go

@@ -105,16 +105,17 @@ type WebConn struct {
 	// a reused connection.
 	// It's theoretically possible for this number to wrap around. But we
 	// leave that as an edge-case.
-	reuseCount            int
-	sessionToken          atomic.Value
-	session               atomic.Pointer[model.Session]
-	connectionID          atomic.Value
-	activeChannelID       atomic.Value
-	activeTeamID          atomic.Value
-	activeThreadChannelID atomic.Value
-	endWritePump          chan struct{}
-	pumpFinished          chan struct{}
-	pluginPosted          chan pluginWSPostedHook
+	reuseCount                      int
+	sessionToken                    atomic.Value
+	session                         atomic.Pointer[model.Session]
+	connectionID                    atomic.Value
+	activeChannelID                 atomic.Value
+	activeTeamID                    atomic.Value
+	activeRHSThreadChannelID        atomic.Value
+	activeThreadViewThreadChannelID atomic.Value
+	endWritePump                    chan struct{}
+	pumpFinished                    chan struct{}
+	pluginPosted                    chan pluginWSPostedHook
 
 	// These counters are to suppress spammy websocket.slow
 	// and websocket.full logs which happen continuously, if they
@@ -237,7 +238,8 @@ func (ps *PlatformService) NewWebConn(cfg *WebConnConfig, suite SuiteIFace, runn
 	wc.SetConnectionID(cfg.ConnectionID)
 	wc.SetActiveChannelID("")
 	wc.SetActiveTeamID("")
-	wc.SetActiveThreadChannelID("")
+	wc.SetActiveRHSThreadChannelID("")
+	wc.SetActiveThreadViewThreadChannelID("")
 
 	ps.Go(func() {
 		runner.RunMultiHook(func(hooks plugin.Hooks) bool {
@@ -316,14 +318,24 @@ func (wc *WebConn) GetActiveTeamID() string {
 	return wc.activeTeamID.Load().(string)
 }
 
-// GetActiveThreadChannelID returns the channel id of the active thread of the connection.
-func (wc *WebConn) GetActiveThreadChannelID() string {
-	return wc.activeThreadChannelID.Load().(string)
+// GetActiveRHSThreadChannelID returns the channel id of the active thread of the connection.
+func (wc *WebConn) GetActiveRHSThreadChannelID() string {
+	return wc.activeRHSThreadChannelID.Load().(string)
 }
 
-// SetActiveThreadChannelID sets the channel id of the active thread of the connection.
-func (wc *WebConn) SetActiveThreadChannelID(id string) {
-	wc.activeThreadChannelID.Store(id)
+// SetActiveRHSThreadChannelID sets the channel id of the active thread of the connection.
+func (wc *WebConn) SetActiveRHSThreadChannelID(id string) {
+	wc.activeRHSThreadChannelID.Store(id)
+}
+
+// GetActiveThreadViewThreadChannelID returns the channel id of the active thread of the connection.
+func (wc *WebConn) GetActiveThreadViewThreadChannelID() string {
+	return wc.activeThreadViewThreadChannelID.Load().(string)
+}
+
+// SetActiveThreadViewThreadChannelID sets the channel id of the active thread of the connection.
+func (wc *WebConn) SetActiveThreadViewThreadChannelID(id string) {
+	wc.activeThreadViewThreadChannelID.Store(id)
 }
 
 // areAllInactive returns whether all of the connections

server/channels/app/platform/websocket_router.go

@@ -84,7 +84,11 @@ func (wr *WebSocketRouter) ServeWebSocket(conn *WebConn, r *model.WebSocketReque
 		}
 		if thChannelID, ok := r.Data["thread_channel_id"].(string); ok {
 			// Set the channelID of the active thread.
-			conn.SetActiveThreadChannelID(thChannelID)
+			if isThreadView, ok := r.Data["is_thread_view"].(bool); ok && isThreadView {
+				conn.SetActiveThreadViewThreadChannelID(thChannelID)
+			} else {
+				conn.SetActiveRHSThreadChannelID(thChannelID)
+			}
 		}
 
 		resp := model.NewWebSocketResponse(model.StatusOk, r.Seq, nil)