NixOS module skeleton

gistfile1.nix

{ config, lib, pkgs, ... }:

with builtins;
with lib;

let
  modname = "whatever";

  cfg = config.${modname};

  out = {
    options.${modname} = api // { enable = mkEnableOption modname; };
    config = mkIf cfg.enable imp;
  };

  api = {
    # ...
  };

  imp = {
    # ...
  };

in out