{ config, lib, ... }:

let
  allowed = config.nix.allowedUnfree;
in
{
  options.nix = {
    experimentalFeatures = lib.mkOption {
      type = lib.types.separatedString " ";
      default = "";
      description = ''
        Enables experimental features
      '';
    };

    allowedUnfree = lib.mkOption {
      type = lib.types.listOf lib.types.str;
      default = [ ];
      description = ''
        Allows for  unfree packages by their name.
      '';
    };
  };

  config = lib.mkMerge [
    (lib.mkIf (config.nix.experimentalFeatures != "") { nix.extraOptions = "experimental-features = ${config.nix.experimentalFeatures}"; })
    (lib.mkIf (allowed != [ ]) { nixpkgs.config.allowUnfreePredicate = (pkg: __elem (lib.getName pkg) allowed); })
    { nix.settings.auto-optimise-store = lib.mkDefault true; }
    {
      nix.gc.automatic = lib.mkDefault true;
      nix.gc.options = lib.mkDefault "--delete-older-than 10d";
    }
  ];
}