Encapsulate signalR hub connection instance (#144)

### Motivation and Context

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  1. Why is this change required?
  2. What problem does it solve?
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The app currently attempts to establish the Signal R connection before
validating the environment file. If the .env file is missing,
the app won't be able to establish the signal R connection since it
needs the backend URL.

### Description

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->
Delay the attempt to establish the signal R connection to only when the
connection is needed. This allows the error of a missing/incorrect .env
file to be shown.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [Contribution
Guidelines](https://github.com/microsoft/copilot-chat/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/copilot-chat/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

webapp/src/redux/app/store.ts

@@ -3,11 +3,7 @@
 import { AnyAction, Dispatch, MiddlewareAPI, MiddlewareArray, ThunkMiddleware, configureStore } from '@reduxjs/toolkit';
 import { AppState } from '../features/app/AppState';
 import { ConversationsState } from '../features/conversations/ConversationsState';
-import {
-    registerSignalREvents,
-    signalRMiddleware,
-    startSignalRConnection,
-} from '../features/message-relay/signalRMiddleware';
+import { signalRMiddleware } from '../features/message-relay/signalRMiddleware';
 import { PluginsState } from '../features/plugins/PluginsState';
 import { UsersState } from '../features/users/UsersState';
 import resetStateReducer, { resetApp } from './rootReducer';
@@ -36,11 +32,6 @@ export const getSelectedChatID = (): string => {
     return store.getState().conversations.selectedId;
 };
 
-// Start the signalR connection to make sure messages are
-// sent to all clients and received by all clients
-startSignalRConnection(store);
-registerSignalREvents(store);
-
 export type AppDispatch = typeof store.dispatch;
 
 // Function to reset the app state

webapp/src/redux/features/message-relay/signalRHubConnection.ts

@@ -0,0 +1,202 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+import * as signalR from '@microsoft/signalr';
+import { Constants } from '../../../Constants';
+import { AlertType } from '../../../libs/models/AlertType';
+import { AuthorRoles, ChatMessageType, IChatMessage } from '../../../libs/models/ChatMessage';
+import { IChatUser } from '../../../libs/models/ChatUser';
+import { PlanState } from '../../../libs/models/Plan';
+import { StoreMiddlewareAPI } from '../../app/store';
+import { addAlert } from '../app/appSlice';
+import { ChatState } from '../conversations/ChatState';
+
+/*
+ * This is a module that encapsulates the SignalR connection
+ * to the messageRelayHub on the server.
+ */
+
+// These have to match the callback names used in the backend
+const enum SignalRCallbackMethods {
+    ReceiveMessage = 'ReceiveMessage',
+    ReceiveMessageUpdate = 'ReceiveMessageUpdate',
+    UserJoined = 'UserJoined',
+    ReceiveUserTypingState = 'ReceiveUserTypingState',
+    ReceiveBotResponseStatus = 'ReceiveBotResponseStatus',
+    GlobalDocumentUploaded = 'GlobalDocumentUploaded',
+    ChatEdited = 'ChatEdited',
+}
+
+// Set up a SignalR connection to the messageRelayHub on the server
+const setupSignalRConnectionToChatHub = () => {
+    const connectionHubUrl = new URL('/messageRelayHub', process.env.REACT_APP_BACKEND_URI);
+    const signalRConnectionOptions = {
+        skipNegotiation: true,
+        transport: signalR.HttpTransportType.WebSockets,
+        logger: signalR.LogLevel.Warning,
+    };
+
+    // Create the connection instance
+    // withAutomaticReconnect will automatically try to reconnect and generate a new socket connection if needed
+    const hubConnection = new signalR.HubConnectionBuilder()
+        .withUrl(connectionHubUrl.toString(), signalRConnectionOptions)
+        .withAutomaticReconnect()
+        .withHubProtocol(new signalR.JsonHubProtocol())
+        .configureLogging(signalR.LogLevel.Information)
+        .build();
+
+    // Note: to keep the connection open the serverTimeout should be
+    // larger than the KeepAlive value that is set on the server
+    // keepAliveIntervalInMilliseconds default is 15000 and we are using default
+    // serverTimeoutInMilliseconds default is 30000 and we are using 60000 set below
+    hubConnection.serverTimeoutInMilliseconds = 60000;
+
+    return hubConnection;
+};
+
+const registerCommonSignalConnectionEvents = (hubConnection: signalR.HubConnection, store: StoreMiddlewareAPI) => {
+    // Re-establish the connection if connection dropped
+    hubConnection.onclose((error) => {
+        if (hubConnection.state === signalR.HubConnectionState.Disconnected) {
+            const errorMessage = 'Connection closed due to error. Try refreshing this page to restart the connection';
+            store.dispatch(
+                addAlert({
+                    message: String(errorMessage),
+                    type: AlertType.Error,
+                    id: Constants.app.CONNECTION_ALERT_ID,
+                }),
+            );
+            console.log(errorMessage, error);
+        }
+    });
+
+    hubConnection.onreconnecting((error) => {
+        if (hubConnection.state === signalR.HubConnectionState.Reconnecting) {
+            const errorMessage = 'Connection lost due to error. Reconnecting...';
+            store.dispatch(
+                addAlert({
+                    message: String(errorMessage),
+                    type: AlertType.Info,
+                    id: Constants.app.CONNECTION_ALERT_ID,
+                }),
+            );
+            console.log(errorMessage, error);
+        }
+    });
+
+    hubConnection.onreconnected((connectionId = '') => {
+        if (hubConnection.state === signalR.HubConnectionState.Connected) {
+            const message = 'Connection reestablished. Please refresh the page to ensure you have the latest data.';
+            store.dispatch(addAlert({ message, type: AlertType.Success, id: Constants.app.CONNECTION_ALERT_ID }));
+            console.log(message + ` Connected with connectionId ${connectionId}`);
+        }
+    });
+};
+
+const startSignalRConnection = (hubConnection: signalR.HubConnection, store: StoreMiddlewareAPI) => {
+    registerCommonSignalConnectionEvents(hubConnection, store);
+    hubConnection
+        .start()
+        .then(() => {
+            console.assert(hubConnection.state === signalR.HubConnectionState.Connected);
+            console.log('SignalR connection established');
+        })
+        .catch((err) => {
+            console.assert(hubConnection.state === signalR.HubConnectionState.Disconnected);
+            console.error('SignalR Connection Error: ', err);
+            setTimeout(() => {
+                startSignalRConnection(hubConnection, store);
+            }, 5000);
+        });
+};
+
+const registerSignalREvents = (hubConnection: signalR.HubConnection, store: StoreMiddlewareAPI) => {
+    hubConnection.on(
+        SignalRCallbackMethods.ReceiveMessage,
+        (chatId: string, senderId: string, message: IChatMessage) => {
+            if (message.authorRole === AuthorRoles.Bot) {
+                const loggedInUserId = store.getState().app.activeUserInfo?.id;
+                const responseToLoggedInUser = loggedInUserId === senderId;
+                message.planState =
+                    message.type === ChatMessageType.Plan && responseToLoggedInUser
+                        ? PlanState.PlanApprovalRequired
+                        : PlanState.Disabled;
+            }
+
+            store.dispatch({ type: 'conversations/addMessageToConversationFromServer', payload: { chatId, message } });
+        },
+    );
+
+    hubConnection.on(SignalRCallbackMethods.ReceiveMessageUpdate, (message: IChatMessage) => {
+        const { chatId, id: messageId, content } = message;
+        // If tokenUsage is defined, that means full message content has already been streamed and updated from server. No need to update content again.
+        store.dispatch({
+            type: 'conversations/updateMessageProperty',
+            payload: {
+                chatId,
+                messageIdOrIndex: messageId,
+                property: message.tokenUsage ? 'tokenUsage' : 'content',
+                value: message.tokenUsage ?? content,
+                frontLoad: true,
+            },
+        });
+    });
+
+    hubConnection.on(SignalRCallbackMethods.UserJoined, (chatId: string, userId: string) => {
+        const user: IChatUser = {
+            id: userId,
+            online: false,
+            fullName: '',
+            emailAddress: '',
+            isTyping: false,
+            photo: '',
+        };
+        store.dispatch({ type: 'conversations/addUserToConversation', payload: { user, chatId } });
+    });
+
+    hubConnection.on(
+        SignalRCallbackMethods.ReceiveUserTypingState,
+        (chatId: string, userId: string, isTyping: boolean) => {
+            store.dispatch({
+                type: 'conversations/updateUserIsTypingFromServer',
+                payload: { chatId, userId, isTyping },
+            });
+        },
+    );
+
+    hubConnection.on(SignalRCallbackMethods.ReceiveBotResponseStatus, (chatId: string, status: string) => {
+        store.dispatch({ type: 'conversations/updateBotResponseStatus', payload: { chatId, status } });
+    });
+
+    hubConnection.on(SignalRCallbackMethods.GlobalDocumentUploaded, (fileNames: string, userName: string) => {
+        store.dispatch(addAlert({ message: `${userName} uploaded ${fileNames} to all chats`, type: AlertType.Info }));
+    });
+
+    hubConnection.on(SignalRCallbackMethods.ChatEdited, (chat: ChatState) => {
+        const { id, title } = chat;
+        if (!(id in store.getState().conversations.conversations)) {
+            store.dispatch(
+                addAlert({
+                    message: `Chat ${id} not found in store. Chat edited signal from server is not processed.`,
+                    type: AlertType.Error,
+                }),
+            );
+        }
+        store.dispatch({ type: 'conversations/editConversationTitle', payload: { id, newTitle: title } });
+    });
+};
+
+// This is a singleton instance of the SignalR connection
+let hubConnection: signalR.HubConnection | undefined = undefined;
+
+// This function will return the singleton instance of the SignalR connection
+export const getOrCreateHubConnection = (store: StoreMiddlewareAPI) => {
+    if (hubConnection === undefined) {
+        hubConnection = setupSignalRConnectionToChatHub();
+
+        // Start the signalR connection to make sure messages are
+        // sent to all clients and received by all clients
+        startSignalRConnection(hubConnection, store);
+        registerSignalREvents(hubConnection, store);
+    }
+    return hubConnection;
+};