Simple Todo App API in Haskell

Just a RESTful API representing a simple todo app backend written in Haskell using scotty and postgresql-simple. A simple docker-compose is used to spin up the database. Written by beginners so it might be helpful to other beginners 🤞.

Prerequisites

• Ensure you have ghc and cabal installed. We used ghcup to get these and used ghc 9.2.7 and cabal version 3.6.2.0.
• dbmate installed for raw SQL migrations
  • install docs
• docker and docker-compose installed
• libpq-dev installed (for ubuntu 20.04 run apt install libpq-dev) I think this was required to be able to build postgresql-simple..?

Quickstart

• Set up environment variables cp env.local .env
• Start postgresql/database docker-compose up -d
• Create the database dbmate create
• Create the table for our todo-app and fill it with 3 sample todos dbmate up
• Install dependencies and build the app cabal build
• Run the app cabal run todo-app
• Send requests to the API, an easy way is to just use the hosted OpenAPI specification within the swagger editor here
• For development it might be useful to run bash watch-and-rebuild.sh if you have inotify-watch installed it will then automatically rebuild whenever you make and save changes to the app.
• You can run dbmate down followed by dbmate up to 're-seed' the database.

OpenAPI specification

The Openapi specification is hosted via github pages and is available here.

Managing the database

• dbmate is used for migrations, check their docu there if in doubt.
• Run dbmate to create migrations. Use snake_case since this is the default for postgres and dbmate. E.g. dbmate new add_origin_created_at_to_recipes
• A file will created which looks like this

-- migrate:up


-- migrate:down

Improvements

Happy about suggestions and improvements to the small code base.

Further ToDos

These are just some possibly next steps one could do in order to improve the app. They are not strictly planned since we both have other priorities.

• Create frontend for the app ..? Perhaps adapt to use an html templating library to implement it as server rendered web app? blaze-html seems like it could be used, but that was just a quick search. lucid does also seem to be a va valid choice.
• Read db connection via environment variables. Probably use System.Environment from base..?
• Add users and implement basic/simple authZ and authN.
  • Perhaps implement via "log in with google" or similar using OAuth2/OIDC.
• Check out nix (or nix-shell?) to provide the dev setup. Did not read to much about it yet, might be a nonsense task.
• Format code with formatter (which one is commonly used in haskell..?) Ormoulu seems to be somewhat known/used, but it was just a quick search again.
  • Perhaps add format check as github action
• Add additional tests (probably integration testst with db setup)

Initially created by @vimpostor and @xddq in between the talks at ZuriHac 23 to at least get our feet wet with some Haskell :p.