Connect 4

Exemplary event sourcing and CQRS implementation of the game Connect 4 using

• Haskell
• PureScript
• Elm
• Postgres
• Redis
• GraphQL/Hasura
• No ES/CQRS framework
• No bullshit

Overview

Components:

• Command API (Haskell, Postgres)
• Read Model/Query API (Haskell, Hasura, Postgres)
• Event Publisher (PureScript, Redis)
• UI (Elm)

Two player games

The player identity is tied to a browser instance. So to play a two player game ideally you should play on two different devices. If played on the same device make sure to use different browser instances.

Prerequisites

• Make sure you also clone the git submodules e.g. with git clone --recursive git@github.com:battermann/connect-4.git
• Docker Compose
• Task

Run with docker

Run

task up

Note that if this task is run for the first time it will take a very very long time to build the Haskell containers.

Then browse to http://localhost:3000/.

Run locally

Prerequisites for running locally

• Elm
• create-elm-app
• node/npm
• stack
• ...

Go to ./ui and run npm install.

Start services locally

To run the application locally, run:

task db

Then run each of these commands in a separate terminal window:

task pub

task read-model

task cmd-api

task ui

Todos

• Elm UI: Use one out and one in port