{ stdenv, pypy3, lib }:

let
  # Needs python interpreter with tkinter support.
  python3' = pypy3;
in
stdenv.mkDerivation {
  pname = "still-awake";
  version = "10-09-2023";

  src = builtins.readFile ./still_awake.py;
  passAsFile = [ "buildCommand" "src" ];

  # Building basically boils down to writing source to a file
  # and making it executable.
  buildCommand = ''
    mkdir -p $out/bin

    echo "#!${python3'.interpreter}" >$out/bin/still-awake

    if [ -e "$srcPath" ]; then
      cat "$srcPath" >>$out/bin/still-awake
    else
      echo -n "$src" >>$out/bin/still-awake
    fi

    chmod +x $out/bin/still-awake
  '';

  # It doesn't make sense to do this remotely.
  preferLocalBuild = true;
  allowSubstitute = false;

  meta = with lib; {
    description = "Small program which shuts down Mac, if user is asleep";
    license = licenses.unlicense;
    platforms = platforms.darwin;
  };
}