{ config, lib, pkgs, ... }:
let
  cfg = config.my.desktop.greetd;
in
{
  options.my.desktop.greetd = {
    user = lib.mkOption {
      type = lib.types.nullOr lib.types.str;
      default = null;
      description = "User account that runs the default session.";
    };

    command = lib.mkOption {
      type = lib.types.nullOr lib.types.str;
      default = null;
      description = "Command to run for the default session (use an absolute path).";
    };
  };

  config = {
    assertions = [
      {
        assertion = cfg.user != null;
        message = "my.desktop.greetd.user must be set.";
      }
      {
        assertion = cfg.command != null;
        message = "my.desktop.greetd.command must be set (use an absolute path like \"${pkgs.sway}/bin/sway\").";
      }
    ];

    services.greetd = {
      enable = true;
      settings.default_session = {
        user = cfg.user;
        command = cfg.command;
      };
    };
  };
}