From 3025d69c55ca193eef069419fa26ad8e0fc5aa5d Mon Sep 17 00:00:00 2001
From: Jeffrey Linwood <jlinwood@gmail.com>
Date: Fri, 12 Jun 2020 07:31:11 -0500
Subject: [PATCH] Refresh access token when it is expired or about to expire

---
 static/chat/index.js | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/static/chat/index.js b/static/chat/index.js
index da1a816..82acaa9 100755
--- a/static/chat/index.js
+++ b/static/chat/index.js
@@ -41,11 +41,7 @@ $(function() {
   print('Logging in...');
 
   // Get an access token for the current user, passing a username (identity)
-  // and a device ID - for browser-based apps, we'll always just use the
-  // value "browser"
-  $.getJSON('/token', {
-    device: 'browser'
-  }, function(data) {
+  $.getJSON('/token', function(data) {
 
 
     // Initialize the Chat client
@@ -54,6 +50,16 @@ $(function() {
       chatClient = client;
       chatClient.getSubscribedChannels().then(createOrJoinGeneralChannel);
 
+      // when the access token is about to expire, refresh it
+      chatClient.on('tokenAboutToExpire', function() {
+        refreshToken(username);
+      });
+
+      // if the access token already expired, refresh it
+      chatClient.on('tokenExpired', function() {
+        refreshToken(username);
+      });
+
     // Alert the user they have been assigned a random username
     username = data.identity;
     print('You have been assigned a random username of: '
@@ -66,6 +72,16 @@ $(function() {
     });
   });
 
+  function refreshToken(identity) {
+    console.log('Token about to expire');
+    // Make a secure request to your backend to retrieve a refreshed access token.
+    // Use an authentication mechanism to prevent token exposure to 3rd parties.
+    $.getJSON('/token/' + identity, function(data) {
+      console.log('updated token for chat client');          
+      chatClient.updateToken(data.token);
+    });
+  }
+
   function createOrJoinGeneralChannel() {
     // Get the general chat channel, which is where all the messages are
     // sent in this simple application