nixos/options/copySysConf.nix

{
  config,
  pkgs,
  lib,
  ...
}:
with lib; let
  cfg = config.system.copySysConf;
  cfgPath = ../.;
  copySysConf =
    if !(isStorePath cfgPath)
    then
      pkgs.stdenv.mkDerivation rec {
        name = "NixOS_Configuration-${version}";
        version = commitIdFromGitRepo (cfgPath + "/.git");

        src = cleanSource cfgPath;

        installPhase = ''
          cp -R ./. $out
        '';
      }
    else (builtins.toPath ../.);
in {
  options.system.copySysConf = {
    enable = mkOption {
      type = types.bool;
      description = ''
        Wether to copy the systems configuration.
      '';
    };
    addToNixPath = mkOption {
      type = types.bool;
      description = ''
        Use backup for nixos-rebuild.
      '';
    };
  };

  config = mkIf cfg.enable {
    environment.variables = {
      NIXOS_CONFIG_PATH = "${copySysConf}";
    };
    nix = mkIf cfg.addToNixPath {
      # Do not use lib.optionals as it would override the default nixPath
      nixPath = [
        "nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos"
        "nixos-config=${copySysConf}/configuration.nix"
        "/nix/var/nix/profiles/per-user/root/channels"
      ];
    };
  };
}