{
  config,
  lib,
  pkgs,
  sources,
  ...
}:
let
  inherit (builtins) elemAt;
  inherit (lib.options) mkOption;
  inherit (lib.types) listOf str package;
  inherit (config.meta.mainUser) username;
in
{
  imports = [ (sources.hjem + "/modules/nixos") ];
  options.meta = {
    users = mkOption {
      type = listOf str;
      default = [ "cr" ];
      description = ''
        A list of users on a system.
      '';
    };
    mainUser = {
      username = mkOption {
        type = str;
        default = elemAt config.meta.users 0;
        description = ''
          The main user for each system. This is the first element of the list of users by default.
        '';
      };

      gitSigningKey = mkOption {
        type = str;
        description = ''
          The main user's git signing key, used to automatically sing git commits with this key
        '';
        default = ''
          ecdsa-sha2-nistp521 AAAAE2VjZHNhLXNoYTItbmlzdHA1MjEAAAAIbmlzdHA1MjEAAACFBAAWEDj/Yib6Mqs016jx7rtecWpytwfVl28eoHtPYCM9TVLq81VIHJSN37lbkc/JjiXCdIJy2Ta3A3CVV5k3Z37NbgAu23oKA2OcHQNaRTLtqWlcBf9fk9suOkP1A3NzAqzivFpBnZm3ytaXwU8LBJqxOtNqZcFVruO6fZxJtg2uE34mAw==
        '';
      };

      # TODO: clean this up and move it somewhere else.
      defaultShell = {
        name = mkOption {
          type = str;
          default = "nushell";
          description = ''
            The default shell of a user. This is not the main system shell, but the shell used in terminals.
          '';
        };
        package = mkOption {
          type = package;
          default = pkgs.nushell;
        };
      };
    };
  };
  config = {
    users = {
      mutableUsers = true;
      users = {
        ${username} = {
          isNormalUser = true;
          extraGroups = [
            "wheel"
            "networking"
            "video"
            "networkmanager"
            "audio"
            "nix"
            "docker"
          ];
          shell = pkgs.nushell;
        };
      };
    };
  };
}