{ config, lib, pkgs, ... }:
let
  # For GPD Win4’s AMD APU, we assume AMD Vulkan drivers:
  amdPackages = [
    pkgs.amdvlk
    pkgs.driversi686Linux.amdvlk
  ];
in
{
  options.services.steamDeckMode = {
    enable = lib.mkOption {
      type = lib.types.bool;
      default = false;
      description = "Launch Steam in a ‘Deck-like’ session upon login (auto-logins and starts Steam in gamepad UI mode).";
    };
  };

  config = {
    # Enable Steam and Gamescope
    programs.gamescope = {
      enable = true;
      capSysNice = true;
    };
    programs.steam = {
      enable = true;
      # The ‘gamescopeSession’ creates a special session for Steam on Wayland
      gamescopeSession.enable = true;
    };

    # Add some helpful gaming utilities
    environment.systemPackages = with pkgs; [
      mangohud
      steam-tui
      steamcmd
      vulkan-tools
      vulkan-headers
      vulkan-loader
      wlroots
      libdecor
      gamemode
    ];

    # Enable 32-bit support for libraries (often required by Steam)
    hardware.opengl.enable = true;
    hardware.opengl.driSupport32Bit = true;

    # Additional AMD drivers if needed
    hardware.graphics.enable = true;
    hardware.graphics.enable32Bit = true;
    hardware.graphics.extraPackages = amdPackages;

    # Example udev rules for Steam Deck controllers, optional
    environment.etc."udev/rules.d/99-steamdeck-controller.rules".text = ''
      # Valve Controller devices
      SUBSYSTEM=="usb", ATTRS{idVendor}=="28de", MODE="0666"
      KERNEL=="uinput", MODE="0660", GROUP="input", OPTIONS+="static_node=uinput"
    '';

    # Provide a “Steam Deck Mode” session in the display manager
    services.xserver.displayManager.session = {
      "steam-deck-mode" = {
        name = "Steam Deck Mode";
        start = ''
          #!/usr/bin/env bash
          # On X11, you could also remove or adjust the following env variable if you prefer Wayland
          export XDG_SESSION_TYPE=x11

          # Fullscreen + close gamescope on exit, then run Steam in gamepad UI
          exec gamescope -f -e -- steam -gamepadui
        '';
      };
    };
  }
  // lib.mkIf config.services.steamDeckMode.enable {
    # Auto-login to the user of your choice and start in Steam Deck Mode
    services.xserver.displayManager.autoLogin.enable = true;
    services.xserver.displayManager.autoLogin.user = "dominik"; # or your preferred user
    services.xserver.autoRestartXServer = true;
    services.xserver.displayManager.defaultSession = "steam-deck-mode";
  };