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

with lib;

let

  cfg = config.programs.htop;

  fmt = value:
    if isList value then concatStringsSep " " (map fmt value) else
    if isString value then value else
    if isBool value || isInt value then toString value else
    throw "Unrecognized type ${typeOf value} in htop settings";

in

{

  options.programs.htop = {
    package = mkOption {
      type = types.package;
      default = pkgs.htop;
      defaultText = lib.literalExpression "pkgs.htop";
      description = lib.mdDoc ''
        The htop package that should be used.
      '';
    };

    enable = mkEnableOption (lib.mdDoc "htop process monitor");

    settings = mkOption {
      type = with types; attrsOf (oneOf [ str int bool (listOf (oneOf [ str int bool ])) ]);
      default = {};
      example = {
        hide_kernel_threads = true;
        hide_userland_threads = true;
      };
      description = lib.mdDoc ''
        Extra global default configuration for htop
        which is read on first startup only.
        Htop subsequently uses ~/.config/htop/htoprc
        as configuration source.
      '';
    };
  };

  config = mkIf cfg.enable {
    environment.systemPackages = [
      cfg.package
    ];

    environment.etc."htoprc".text = ''
      # Global htop configuration
      # To change set: programs.htop.settings.KEY = VALUE;
    '' + concatStringsSep "\n" (mapAttrsToList (key: value: "${key}=${fmt value}") cfg.settings);
  };

}
