# AGENTS.md

## Project

A sidecar for Home Assistant that runs automations using arrowized functional
reactive programming (AFRP). Haskell, built with cabal.

## Code style

- Vertical modules: split by feature/concept, not by layer.
- Comments are minimal. They describe the contract, not the implementation,
  and should stay stable as the implementation changes.

## Build

- Nix-backed project: `flake.nix` provides the devShell, `default.nix` is the
  generated cabal derivation.
- Always run cabal through the devShell: `nix develop -c cabal build`.
- After adding dependencies to the .cabal file, regenerate the derivation:
  `nix run nixpkgs#cabal2nix -- ./. > default.nix`. Do not edit it by hand.
- `secrets.yaml` is sops-encrypted. Never read, print, or commit its contents.

## Tests

- hspec for unit tests, hedgehog for property tests.
- Run with `nix develop -c cabal test`.