{ pkgs, lib, ... }:

let
  # Add one entry per program you want to install from a .pkg file
  pkgInstalls = [
    {
      name = "cupsadmin";
      url = "https://github.com/kfattic/cupsadmin/releases/download/v1.4.1/cupsadmin-1.4.1.pkg";
      hash = "sha256-DyIyDYSjAlcU7ivyfldMapIZw5nczEBXfnLicnK6k7Y=";
    }
  ];

  installScript = p:
    let
      src = pkgs.fetchurl { inherit (p) url hash; };
    in ''
      stamp="/usr/local/share/nix-pkg-stamps/${p.name}"
      want="${src}"
      if [ "$(cat "$stamp" 2>/dev/null)" != "$want" ]; then
        echo "installing ${p.name}..."
        if /usr/sbin/installer -pkg "$want" -target /; then
          mkdir -p /usr/local/share/nix-pkg-stamps
          echo "$want" > "$stamp"
        else
          echo "${p.name} install failed, skipping"
        fi
      fi
    '';
in
{
  system.activationScripts.postActivation.text =
    lib.concatMapStringsSep "\n" installScript pkgInstalls;
}