flake.nix

{
  description = "Flake template for Arduino projects";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.url = "github:NixOS/nixpkgs";
  };

  outputs =
    {
      self,
      nixpkgs,
      flake-utils,
    }:
    flake-utils.lib.eachSystem [ "x86_64-linux" ] (
      system:
      let
        name = "blink";

        pkgs = import nixpkgs { inherit system; };

        python = pkgs.python3;

        pythonWithExtras = python.buildEnv.override { extraLibs = [ ]; };

        # The variables starting with underscores are custom,
        # the ones starting with ARDUINO are used by arduino-cli.
        # See https://arduino.github.io/arduino-cli/1.0/configuration/ .

        # Store everything that arduino-cli downloads in a directory
        # reserved for this project, and following the XDG specification,
        # if the variable is available.

        # The _ARDUINO_PYTHON3 variable is passed to arduino-cli via the Makefile.
        arduinoShellHookPaths = ''
          if [ -z "''${_ARDUINO_PROJECT_DIR:-}" ]; then
            if [ -n "''${_ARDUINO_ROOT_DIR:-}" ]; then
              export _ARDUINO_PROJECT_DIR="''${_ARDUINO_ROOT_DIR}/${name}"
            elif [ -n "''${XDG_CACHE_HOME:-}" ]; then
              export _ARDUINO_PROJECT_DIR="''${XDG_CACHE_HOME}/arduino/${name}"
            else
              export _ARDUINO_PROJECT_DIR="''${HOME}/.arduino/${name}"
            fi
          fi
          # The variables below are respected by arduino-cli
          export ARDUINO_DIRECTORIES_USER=$_ARDUINO_PROJECT_DIR
          export ARDUINO_DIRECTORIES_DATA=$_ARDUINO_PROJECT_DIR
          export ARDUINO_DIRECTORIES_DOWNLOADS=$_ARDUINO_PROJECT_DIR/staging
          # This is used to override Python when invoking the Makefile
          export _ARDUINO_PYTHON3=${python}
        '';

        devShellArduinoCLI = pkgs.mkShell {
          name = "${name}-dev";
          packages = with pkgs; [
            # To compile and upload the sketch
            arduino-cli
            # To embed a version hash into the sketch
            git
            # To provide somewhat standardized commands to compile, upload, and monitor the sketch
            gnumake
            # To monitor the serial output
            picocom
            # So that the python3 wrapper of the esp8266 downloaded code can find a working python interpreter on the path
            pythonWithExtras
          ];
          shellHook = ''
            ${arduinoShellHookPaths}
            echo "==> Using arduino-cli version $(arduino-cli version)"
            echo "    Storing arduino-cli data for this project in '$_ARDUINO_PROJECT_DIR'"
          '';
        };

      in
      {
        devShells = {
          inherit devShellArduinoCLI;
        };

        # Development shell spawned by `nix develop`
        devShells.default = devShellArduinoCLI;

        formatter = pkgs.nixfmt-rfc-style;
      }
    );
}