{ lib, config, pkgs, satnogsDemoDisplayPkgs, ... }:
with lib;
let
  # Shorter name to access final settings a 
  # user of hello.nix module HAS ACTUALLY SET.
  # cfg is a typical convention.
  cfg = config.services.satnogsDemoDisplay;
in
{

  options.services.satnogsDemoDisplay = {
    enable = mkEnableOption "satnogs-demo-display service";

    package = mkOption {
      default = satnogsDemoDisplayPkgs.x86_64-linux.default;
      type = types.package;
      description = "satnogsDemoDisplay packages to use. Needed to fix crosscompilation issues.";
    };

    user = mkOption {
      type = types.str;
      default = "satnogs-demo";
      description = mdDoc "User to run the desktop environment and display script.";
    };

    group = mkOption {
      type = types.str;
      default = "satnogs-demo";
      description = mdDoc "Group for the user.";
    };


    stateDir = mkOption {
      default = "/var/lib/satnogs-demo-display";
      type = types.str;
      description = mdDoc "Demo display data directory.";
    };
  };

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

      unclutter
      xorg.xhost
      xorg.xrandr
      feh
    ];

    users.users = mkIf (cfg.user == "satnogs-demo") {
      satnogs-demo = {
        group = cfg.group;
        isNormalUser = true;
      };
    };

    users.groups = mkIf (cfg.group == "satnogs-demo") {
      satnogs-demo = { };
    };

    systemd.tmpfiles.rules = [
      "d '${cfg.stateDir}' 0750 ${cfg.user} ${cfg.group} - -"
    ];

    systemd.services.satnogsDemoDisplay = {
      wantedBy = [ "multi-user.target" ];
      description = "satnogsDemoDisplay service";
      serviceConfig = {
        Type = "exec";
        User = cfg.user;
        Group = cfg.group;
        Restart = "always";
        RestartSec = "1s";
        StartLimitIntervalSec = "0";
        WorkingDirectory = cfg.stateDir;
      };
      script = ''
        unlink ./satnogs-logo.png
        ln -s ${cfg.package}/satnogs-logo.png ./
        unlink ./Montserrat-Regular.otf
        ln -s ${cfg.package}/Montserrat-Regular.otf ./

        while true; do
          ${cfg.package}/bin/satnogs-demo-display
          sleep 60
        done
      '';
    };

    # Some programs need SUID wrappers, can be configured further or are
    # started in user sessions.
    # programs.mtr.enable = true;
    # programs.gnupg.agent = {
    #   enable = true;
    #   enableSSHSupport = true;
    # };


    services.xserver = {
      enable = true;

      monitorSection = ''
        Option   "NODPMS"
      '';
      serverLayoutSection = ''
        Option   "BlankTime" "0"
        Option   "DPMS" "false"
      '';

      # Let lightdm handle autologin
      displayManager = {
        autoLogin = {
          user = cfg.user;
          enable = true;
        };

        lightdm = {
          enable = true;
        };

        defaultSession = "none+i3";
      };

      # Start i3 after autologin
      windowManager.i3 = {
        enable = true;
        configFile = ./i3config;

        extraSessionCommands = ''
          ${pkgs.xorg.xhost}/bin/xhost +
          ${pkgs.unclutter}/bin/unclutter &
          ${pkgs.feh}/bin/feh --reload 30.0 -F ${cfg.stateDir}/waterfall.png &
        '';
      };
    };

    systemd.services."display-manager".after = [
      "network-online.target"
      "systemd-resolved.service"
    ];

  };
}