{ lib, config, ... }:

let
  cfg = config.playground.greeter;
in
{
  # One option namespace keeps the example focused.
  options.playground.greeter = {
    enable = lib.mkEnableOption "the playground greeter";

    name = lib.mkOption {
      type = lib.types.str;
      default = "world";
      description = "Name placed in the generated /etc/greeting file.";
    };
  };

  # `mkIf` discards the whole config block when enable is false, so a
  # system that imports the module but leaves it disabled pays nothing.
  config = lib.mkIf cfg.enable {
    environment.etc."greeting".text = "hello, ${cfg.name}";
  };
}