[lib] implement socket Heartbeats with Tunnelbroker

Summary:
Implements protocol described in D9630.

Depends on D9631

Test Plan:
1. Test if client properly exchange `Heartbeats`
2. Test if timeout works

Reviewers: michal, bartek, varun

Reviewed By: michal

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9632

lib/tunnelbroker/tunnelbroker-context.js

@@ -5,6 +5,8 @@ import * as React from 'react';
 import uuid from 'uuid';
 
 import { tunnnelbrokerURL } from '../facts/tunnelbroker.js';
+import { tunnelbrokerHeartbeatTimeout } from '../shared/timeouts.js';
+import type { Heartbeat } from '../types/tunnelbroker/heartbeat-types.js';
 import type { MessageReceiveConfirmation } from '../types/tunnelbroker/message-receive-confirmation-types.js';
 import type { MessageSentStatus } from '../types/tunnelbroker/message-to-device-request-status-types.js';
 import type { MessageToDeviceRequest } from '../types/tunnelbroker/message-to-device-request-types.js';
@@ -51,6 +53,22 @@ function TunnelbrokerProvider(props: Props): React.Node {
   const listeners = React.useRef<Set<TunnelbrokerSocketListener>>(new Set());
   const socket = React.useRef<?WebSocket>(null);
   const promises = React.useRef<Promises>({});
+  const heartbeatTimeoutID = React.useRef();
+
+  const stopHeartbeatTimeout = React.useCallback(() => {
+    if (heartbeatTimeoutID.current) {
+      clearTimeout(heartbeatTimeoutID.current);
+      heartbeatTimeoutID.current = null;
+    }
+  }, []);
+
+  const resetHeartbeatTimeout = React.useCallback(() => {
+    stopHeartbeatTimeout();
+    heartbeatTimeoutID.current = setTimeout(() => {
+      socket.current?.close();
+      setConnected(false);
+    }, tunnelbrokerHeartbeatTimeout);
+  }, [stopHeartbeatTimeout]);
 
   React.useEffect(() => {
     if (connected || !initMessage) {
@@ -89,6 +107,8 @@ function TunnelbrokerProvider(props: Props): React.Node {
       }
       const message: TunnelbrokerMessage = rawMessage;
 
+      resetHeartbeatTimeout();
+
       for (const listener of listeners.current) {
         listener(message);
       }
@@ -134,11 +154,16 @@ function TunnelbrokerProvider(props: Props): React.Node {
             console.log('Tunnelbroker recorded InvalidRequest');
           }
         }
+      } else if (message.type === tunnelbrokerMessageTypes.HEARTBEAT) {
+        const heartbeat: Heartbeat = {
+          type: tunnelbrokerMessageTypes.HEARTBEAT,
+        };
+        socket.current?.send(JSON.stringify(heartbeat));
       }
     };
 
     socket.current = tunnelbrokerSocket;
-  }, [connected, initMessage]);
+  }, [connected, initMessage, resetHeartbeatTimeout, stopHeartbeatTimeout]);
 
   const sendMessage: (message: ClientMessageToDevice) => Promise<void> =
     React.useCallback(