Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/api4/websocket.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package api4
+
+import (
+	"net/http"
+
+	"github.com/gorilla/websocket"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/server/channels/app/platform"
+	"github.com/mattermost/mattermost-server/v6/server/platform/shared/mlog"
+)
+
+const (
+	connectionIDParam   = "connection_id"
+	sequenceNumberParam = "sequence_number"
+)
+
+func (api *API) InitWebSocket() {
+	// Optionally supports a trailing slash
+	api.BaseRoutes.APIRoot.Handle("/{websocket:websocket(?:\\/)?}", api.APIHandlerTrustRequester(connectWebSocket)).Methods("GET")
+}
+
+func connectWebSocket(c *Context, w http.ResponseWriter, r *http.Request) {
+	upgrader := websocket.Upgrader{
+		ReadBufferSize:  model.SocketMaxMessageSizeKb,
+		WriteBufferSize: model.SocketMaxMessageSizeKb,
+		CheckOrigin:     c.App.OriginChecker(),
+	}
+
+	ws, err := upgrader.Upgrade(w, r, nil)
+	if err != nil {
+		c.Err = model.NewAppError("connect", "api.web_socket.connect.upgrade.app_error", nil, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	// We initialize webconn with all the necessary data.
+	// If the queues are empty, they are initialized in the constructor.
+	cfg := &platform.WebConnConfig{
+		WebSocket: ws,
+		Session:   *c.AppContext.Session(),
+		TFunc:     c.AppContext.T,
+		Locale:    "",
+		Active:    true,
+	}
+
+	cfg.ConnectionID = r.URL.Query().Get(connectionIDParam)
+	if cfg.ConnectionID == "" || c.AppContext.Session().UserId == "" {
+		// If not present, we assume client is not capable yet, or it's a fresh connection.
+		// We just create a new ID.
+		cfg.ConnectionID = model.NewId()
+		// In case of fresh connection id, sequence number is already zero.
+	} else {
+		cfg, err = c.App.Srv().Platform().PopulateWebConnConfig(c.AppContext.Session(), cfg, r.URL.Query().Get(sequenceNumberParam))
+		if err != nil {
+			mlog.Warn("Error while populating webconn config", mlog.String("id", r.URL.Query().Get(connectionIDParam)), mlog.Err(err))
+			ws.Close()
+			return
+		}
+	}
+
+	wc := c.App.Srv().Platform().NewWebConn(cfg, c.App, c.App.Srv().Channels())
+	if c.AppContext.Session().UserId != "" {
+		c.App.Srv().Platform().HubRegister(wc)
+	}
+
+	wc.Pump()
+}