ExChat

This is a simple chat server built in Elixir with the goal to show a real life application of Websockets.

Features roadmap

• As a client I want to create a user so that I can use the chat system
• As a user I can send a private message to an existing user to that I can talk directly without using an existing room

Run tests

$ mix deps.get
$ mix test

Run application

$ mix deps.get
$ iex -S mix

How to use the chat

The web client will be available at http://localhost:4000/chat.html

At the moment there are two users in the system. You can use two different URLs in order to get associated to them:

• http://localhost:4000/chat.html?access_token=foo_token to enter as foo_user
• http://localhost:4000/chat.html?access_token=bar_token to enter as bar_user

Scratchpad

DOING

TODO

• Rename ChatRoom, ChatRooms and Chatroom to Room (basically remove the Chat term)
• Rename session_id or user_session_id to user_id
• Introduce the ping/pong mechanism between client and server in order to unsubscribe and disconnect a client due inactivity
• Find a way to document the websocket API
• Try to split the API, the Server and the Application Logic in the UserSessions and in the ChatRooms module
  • It could be interesting to open a related thread to the ElixirForum, trying to get more feedback
• Think if it could be useful to use Mox instead of Mock (think about the use of Behaviour)
• find a way to distribute the Chat across different nodes, in order to use more than one nodes
  • we have to think to introduce gproc for distribute the lookup processes across different nodes
• improve the way we make assertions on received messages (e.g. assert_receive wants pattern match and not functions or variables) in the websocket_test.exs
• try to write some acceptance test with Wallaby, for the frontend ?
• setup a continuous integration for the project (e.g. using TravisCI)
• Bonus: Let's try to use Websockex for the server too, instead of using the raw cowboy_websocket
• try to expose the chat using the IRC protocol
• it seems that we have some flaky tests for "other clients" scenarios

DONE

• Try to decouple the WebSocketController from the Application Domain by introducing the Use Cases:
• Extract a use case for SubscribeToUserSession
• Extract a use case for JoinChatRoom
• Extract a use case for CreateChatRoom
• Extract a use case for SendMessageToChatRoom
• Extract a use case for ValidateAccessToken
• Should the WebSocketClient be renamed in WebSocketController ?
• As a client I want to be associated to a user so that other clients can see who send messages
• Prepare the system with some initial data:
  • foo_user associated to the token foo_token
  • bar_user associated to the token bar_token
• Maybe the AuthenticationService is a "Repository" instead. Consider to rename it
• Provide a real implementation of the AuthenticationService
• Extract a collaborator for the WebSocketClient that will be responsible to understand if there is an existing user_session for a given access_token
• Update the UI in order to handle the user id
• It seems that we have a websocket idle timeout issue. Increase the idle timeout to 10 minutes
• Handle the connection when the provided access token is empty or not valid (no user session associated)
• what happen when we try to connect to the chat with an invalid access token
  • 1. the token not exist or is not valid [DONE]
  • 2. no token provided [DONE]
• Bump to version 2.4 to fix the issue of cowboy 1.0 about the cowboy_clock badarg
• When I join a chat room as an identified user I want to read my user name in the welcome message
• Extract the websocket chat URL in the WebSocketAcceptanceTests
• Rename ws_client to client in the WebSocketAcceptanceTests
• Try to remove all the setup duplication in the WebSocketAcceptanceTests
• Review all the acceptance tests in order to align it with the User Feature
• Use the access_token to open websocket connection from the UI
• Try to associate a WebSocketClient to a UserSession
• Draw the actual application architecture sketch
• Think about to rename ExChat.Supervisor in ExChat.Application
• Rename ExChat.Init to ExChat.Setup
• Put the user-session-id as a state of WebSocketClient
• Find a better name for the websocket tests
• Rename ExChat.Web.WebSocket to ExChat.Web.Router
• Rename ChatRoomsWebSocketHandler to WebSocketClient
• ChatRooms.send should use the user-session-id
• The module ChatRooms should be reorganized like the UserSessions
• As a ChatRoom I can notify of new messages to all the subscribed UserSessions
• rename the UserSessions.send to UserSessions.notify
• think to rename clients to session_ids in the ChatRoom process
• Rename ExChat.Registry in ExChat.ChatRoomRegistry
• rename user_session_id to session_id
• Maybe the UserSessions and UserSessionSupervisor could be merged in a single module named UserSessions
• Fix the names used for the user sessions in the UserSessionsTest
• Try to find a way to remove the shared state (the UserSessionRegistry) from the UserSessions Tests
• do not start the application when run all the tests
• remove the UserSession.exists? function in favor of the UserSession.find function
• Refactor the UserSessions module in order to achieve the obvious implementation with Supervisors, UserSession Processes, etc, ...
• Start writing test from the point of view of the Client who tries to subscribe to UserSessions
• ExChat.ChatRooms could be a "simple" module and not a process
• remove the empty file ex_chat_test.exs
• Issue during run the tests: It seems that Elixir.ExChat.Supervisor is already started
• handle invalid command
• handle invalid client messages
• rename subscribers to clients in ChatRoom
• bug: avoid that a client can join twice to a room
• add a Supervisor to supervise all the ChatRoom processes
• use a registry to name all the ChatRoom processes
• think to rename the websocket endpoint (ws://localhost:4000/room), maybe /chat or others
• handle the welcome message in the ChatRoom itself and not in the chatroom_websocket_handler
• handle the case when we try to send a message to an unexisting chat room
• update the roadmap features in the readme
• maybe ExChat.Web.Router is not a good name for the web sockets delivery mechanism (maybe Web.WebSocket)
• rename chatroom_websocket_handler.ex to chat_rooms_websocket_handler.ex
• think to separate the two actions create chatroom and join chatroom (at the moment the chatroom creation happens when a client try to join an unexisting chatroom, look at the ChatRooms.create_and_join_chatroom/3 function)
• update the UI so that it can support the create command
• Handle multiple chat rooms
• adapt the UI to handle the room name
• handle the chat room creation when client wants to join to an unexisting chat room
• rename subscriber to client in ChatRooms
• change the format of the response for other tests (add the room name)
• Rename web.http to web.router
• Remove the /echo endpoint just because it is no longer needed
• Allow web clients to receive messages
• Allow web clients to write and send messages
  • We have to create a better web UI to allows user to write and send messages
• Replace the plug-web-socket with the default cowboy_websocket_handler
• Allow web clients to join a chatroom
• How to test the websocket endpoint in Elixir
• Put how to run tests and how to start application in the README.md
• Start the application
• Rename the test folder exchat to ex_chat
• As a client I can subscribe to a chat room so that I can receive all the messages sent