{ pkgs ? import <nixpkgs> {} }:
let
  configs = "${toString ./.}#nixosConfigurations";
  hostname = pkgs.lib.fileContents /etc/hostname;
  build = "config.system.build";

  rebuild = pkgs.writeShellScriptBin "rebuild" ''
    if [[ -z $1 ]]; then
      echo "Usage: $0 [host] {switch|boot|test|iso}"
    elif [[ $1 == "iso" ]]; then
      nix build ${configs}.niximg.${build}.isoImage
    elif [[ -z $2 ]]; then
      nix run -vv ${configs}.${hostname}.${build}.toplevel -c switch-to-configuration $1
    else
      nix run -vv ${configs}.$1.${build}.toplevel -c switch-to-configuration $2
    fi
  '';
in
pkgs.mkShell {
  nativeBuildInputs = with pkgs; [
    rebuild
    nixFlakes
  ];

  NIX_CONF_DIR = let
    current = pkgs.lib.optionalString (builtins.pathExists /etc/nix/nix.conf)
      (builtins.readFile /etc/nix/nix.conf);

    nixConf = pkgs.writeTextDir "opt/nix.conf" ''
      ${current}
      experimental-features = nix-command flakes ca-references
    '';
  in
    "${nixConf}/opt";
}