MO Plate Checker

MO Plate Checker is a learning project built with Elm, with an OCaml backend in progress. It is not affiliated with the Missouri Department of Revenue and cannot determine whether a plate is available or whether an application will be approved.

Reference

https://github.com/mo-plate-web https://github.com/mo-custom-plate-finder

Current status

The Elm code currently includes:

• A basic interface for entering a seed plate
• Plate normalization and validation
• Candidate variation generation
• Automated tests for the plate and variation logic
• UI displays variations
• Checks a fake API endpoint using the fixed AHMED query

The OCaml backend is still in progress. The application does not currently query the Missouri DOR.

OPAM requirements

Install the required packages:

opam install dune cohttp-eio eio_main alcotest

Server

Build and test the server:

cd server
opam exec -- dune build
opam exec -- dune runtest

Run it on port 8080:

cd server
PORT=8080 opam exec -- dune exec bin/main.exe

The server provides a GET /api/health endpoint and returns structured JSON errors for unknown paths and unsupported methods.

Implemented API contract

GET /api/health
-> 200  Content-Type: application/json
   {"status":"ok"}

GET /missing
-> 404  Content-Type: application/json
   {"error":"not_found"}

POST /api/health
-> 405  Content-Type: application/json
        Allow: GET
   {"error":"method_not_allowed"}

Planned availability API contract

GET /api/check?plate=AHMED
-> 200  {"plate":"AHMED","available":true}
-> 200  {"plate":"AHMED","available":false}
-> 400  {"error":"invalid_plate"}
-> 429  {"error":"rate_limited"}
-> 502  {"error":"upstream_failure"}

/api/check is not yet implemented.

Background

Elm rewrite of an existing OCaml project.

Running locally

You will need Elm 0.19.1 and elm-test installed.

Compile the Elm application:

elm make src/Main.elm --output=public/app.js

Serve the public directory:

python3 -m http.server 8000 --directory public

Then open http://localhost:8000.

Tests

Run the Elm test suite with:

elm-test

License

This project is available under the MIT License. See LICENSE for details.