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This is a demonstration & sample application designed to be a simple multi-user web based chat system.
It provides persistent group chats, user to user private chats, a user list, idle (away from keyboard) detection and several other features.

It is built on several Azure technologies, including:Web PubSub, Static Web Apps andTable Storage

👁‍🗨 Note. This was created as a personal project, created to aid learning while building something interesting. The code comes with all the caveats you might expect from such a project.

Goals:

• Learn about using websockets
• Write a 'fun' thing
• Try out the newAzure Web PubSub service
• Use the authentication features ofAzure Static Web Apps
• Deploy everything usingAzure Bicep

Use cases & key features:

• Sign-in with Microsoft, Twitter or GitHub accounts
• Realtime chat with users
• Shared group chats, only the creator can remove the chat
• Detects where users are idle and away from keyboard (default is one minute)
• Private 'user to user' chats, with notifications and popups

This is the main web frontend as used by end users via the browser.

The source for this is found inclient/ and consists of a static standalone pure ES6 JS application, no bundling or Node.js is required. It is written usingVue.js as a supporting framework, andBulma as a CSS framework.

Some notes:

• ES6 modules are used so the various JS files can use import/export without the need to bundle.
• Vue.js is used as a browser side library loaded from CDN as a ESM module, this is an elegant & lightweight approach supported by modern browsers, rather than the usual vue-cli style app which requires Node and webpack etc.
• client/js/app.js shows how to create a Vue.js app with child components using this approach. The majority of client logic is here.
• client/js/components/chat.js is a Vue.js component used to host each chat tab in the application
• The special.auth/ endpoint provided by Static Web Apps is used to sign users in and fetch their user details, such as userId.

This is the backend, handling websocket events to and from Azure Web PubSub, and providing REST API for some operations.

The source for this is found inapi/ and consists of a Node.js Azure Function App. It connects to Azure Table Storage to persist group chat and user data (Table Storage was picked as it's simple & cheap). This is not hosted in a standalone Azure Function App but insteaddeployed into the Static Web App as part of it's serverless API support

There are four HTTP functions all served from the default/api/ path

• eventHandler - Webhook receiver for "upstream" events sent from Azure Web PubSub service, contains the majority of application logic. Not called directly by the client, only Azure WebPub Sub.
• getToken - Called by the client to get an access token and URL to connect via WebSockets to the Azure Web PubSub service. Must be called with userId in the URL query, e.g. GET/api/getToken?userId={user}
• getUsers - Returns a list of signed in users, note the route for this function is/api/users
• getChats - Returns a list of active group chats, note the route for this function is/api/chats

State is handled withstate.js which is an ES6 module exporting functions supporting state CRUD for users and chats. This module carries out all the interaction with Azure Tables, and provides a relatively transparent interface, so a different storage backend could be swapped in.

There is two way message flow between clients and the server viaAzure Web PubSub and event handlers

The json.webpubsub.azure.v1 subprotocol is used rather than basic WebSockets, this provides a number of features: users can be added to groups, clients can send custom events (usingtype: event), and also send messages direct to other clients without going via the server (usingtype: sendToGroup)

Notes:

• Chat IDs are simply randomly generated GUIDs, these correspond to "groups" in the subprotocol.
• Private chats are a special case, they are not persisted in state, and they do not triggerchatCreated events. Also the user doesn't issue ajoinChat event to join them, that is handled by the server as a kind of "push" to the clients.
• User IDs are simply strings which are considered to be unique, this could be improved, e.g. with prefixing.

Events & chat are sent using thejson.webpubsub.azure.v1 subprotocol

Chat messages sent from the client usesendToGroup and a custom JSON payload with three fieldsmessage,fromUserId &fromUserName, these messages are relayed client to client by Azure Web PubSub, the server is never notified of them:

{type: 'sendToGroup',group:<chatId>,dataType: 'json',data: {message:<messagetext>,fromUserId:<userId>,fromUserName:<userName>,  },}

Events destined for the backend server are sent as WebSocket messages from the client via the same subprotocol with theevent type, and an application specific sub-type, e.g.

{type: 'event',event: 'joinChat',dataType: 'text',data:<chatId>,}

The types of events are:

• createChat - Request the server you want to create a group chat
• createPrivateChat - Request the server you want to create a private chat
• joinChat - To join a chat, the server will add user to the group for that chatId
• leaveChat - To leave a group chat
• deleteChat - Called from a chat owner to delete a chat
• userEnterIdle - Let the server know user is now idle
• userExitIdle - Let the server know user is no longer idle

The backend APIeventHandler function has cases for each of these user events, along with handlers for connection & disconnection system events.

Messages sent from the server have a custom Chatr app specific payload as follows:

{chatEvent:<eventType>,data:<JSONobjecttypedependant>}

WhereeventType is one of:

• chatCreated - Let all users know a new group chat has been created
• chatDeleted - Let all users know a group chat has been removed
• userOnline - Let all users know a user has come online
• userOffline - Let all users know a user has left
• joinPrivateChat - Sent to both the initiator and recipient of a private chat
• userIsIdle - Sent to all users when a user enters idle state
• userNotIdle - Sent to all users when a user exits idle state

The client code inclient/js/app.js handles these messages as they are received by the client, and reacts accordingly.

The plan of this project was to useAzure Web PubSub andAzure Static Web Apps, and to host the server side component as a set of serverless functions in theStatic Web Apps API support (which is in factAzure Functions under the hood).Azure Static Web Apps was selected because it hasamazing support for codeless and config-less user sign-in and auth, which I wanted to leverage.

Some comments on this approach:

• API support inStatic Web Apps is quite limited and can't support the new bindings and triggers for Web PubSub.HOWEVER You don't need to use these bindings 😂. You can create a standard HTTP function to act as a webhook event handler instead of using thewebPubSubConnection binding. For sending messages back to Web PubSub, the server SDK can simply be used within the function code rather than using thewebPubSub output binding.
• Table Storage was picked for persisting state as it has a good JS SDK (the new SDK in @azure/data-table was used), it's extremely lightweight and cheap and was good enough for this project, see deails below

State in Azure Tables consists of two tables (collections) namedchats andusers

As each chat contains nested objects inside the members field, each chat is stored as a JSON string in a field calleddata. The PartitionKey is not used and hardcoded to a string "chatr". The RowKey and the id field inside the data object are the same.

• PartitionKey: "chatr"
• RowKey: The chatId (random GUID created client side)
• data: JSON stringified chat entity

Example of a chat data entity

{"id":"eab4b030-1a3d-499a-bd89-191578395910","name":"This is a group chat","members": {"0987654321": {"userId":"0987654321","userName":"Another Guy"    },"1234567890": {"userId":"1234567890","userName":"Ben"    }  },"owner":"1234567890"}

Users are stored as entities with the fields (columns) described below. As there are no nested fields, there is no need to encode as a JSON string. Again the PartitionKey is not used and hardcoded to a string "chatr".

• PartitionKey: "chatr"
• RowKey: TheuserId field returned from Static Web Apps auth endpoint
• userName: The username (could be email address or handle) of the user
• userProvider: Which auth provided the user signed in withtwitter,aad orgithub
• idle: Boolean, indicating if the user us currently idle

See makefile

$ makehelp                 💬 This help messagelint                 🔎 Lint & format, will not fix but sets exit code on errorlint-fix             📜 Lint & format, will try to fix errors and modify coderun                  🏃 Run server locally using Static Web Apps CLIclean                🧹 Clean up projectdeploy               🚀 Deploy everything to Azure using Biceptunnel               🚇 Start loophole tunnel to expose localhost

Deployment is slightly complex due to the number of components and the configuration between them. The makefile targetdeploy should deploy everything for you in a single step using Bicep templates found in thedeploy/ folder

See readme in deploy folder for details and instructions

This is possible but requires a little effort as the Azure Web PubSub service needs to be able call the HTTP endpoint on your location machine, so a tunnel has employed.

When running locally the Static Web Apps CLI is used and this provides a fake user authentication endpoint for us.

A summary of the steps is:

• Deploy anAzure Storage account, get name and access key.
• Deploy anAzure Web Pub Sub instance, get connection string from the 'Keys' page.
• Copyapi/local.settings.sample.json toapi/local.settings.json and edit the required settings values.
• Start a localhost tunnel service such asngrok orloophole. The tunnel should expose port 7071 over HTTP.
  I useloophole as it allows me to set a custom host & DNS name, e.g.
  • loophole http 7071 --hostname chatr
• InAzure Web Pub Sub settings.
  • Add a hub namedchat
  • In the URL template puthttps://{{hostname-of-tunnel-service}}/api/eventHandler
  • In system events tickconnected anddisconnected
• Runmake run
• Openhttp://localhost:4280/index.html

• Won't run in Firefox as top level await is not yet supported