{
  pkgs,
  config,
  lib,
  __findFile,
  ...
}@args:
with lib;
let
  cfg = config.module.package;
  package = import <package> args;
in
{
  options = {
    module.package = {
      common.enable = mkEnableOption "Common Apps.";
      core.enable = mkEnableOption "Core apps.";
      creative.enable = mkEnableOption "Creative Apps.";
      desktop.enable = mkEnableOption "Desktop Apps.";
      dev.enable = mkEnableOption "Dev Apps.";
      extra.enable = mkEnableOption "Extra Apps.";
      gaming.enable = mkEnableOption "Gaming Apps.";
    };
  };

  config = mkMerge [
    # Core apps.
    (mkIf cfg.core.enable {
      environment.systemPackages = package.core;

      programs = {
        adb.enable = true;
        git.enable = true;
        java = {
          enable = true;
          package = pkgs.corretto21;
        };
      };
      services = {
        udisks2.enable = true;
      };
    })

    # Common apps.
    (mkIf cfg.common.enable {
      environment.systemPackages = package.common;

      xdg.mime.defaultApplications = {
        # Use `file -i file.txt` to find file mime type.
        # Use `xdg-mime query default "text/plain"` to find default app.
        "application/pdf" = "org.gnome.Evince.desktop";
        "application/vnd.openxmlformats-officedocument.*" = "onlyoffice-desktopeditors.desktop";
        "audio/*" = "mpv.desktop";
        "image/*" = "org.gnome.Loupe.desktop";
        "text/*" = "nvim.desktop";
        "video/*" = "mpv.desktop";
      };

      services.gvfs.enable = true;
    })

    # Desktop apps.
    (mkIf cfg.desktop.enable { environment.systemPackages = package.desktop; })

    # Gaming.
    (mkIf cfg.gaming.enable {
      hardware.graphics =
        let
          packages = with pkgs; [
            dxvk
            gamescope
            pkgs.mangohud
            vkd3d
          ];
        in
        {
          extraPackages = packages;
          extraPackages32 = packages;
        };

      programs.steam.enable = true;

      environment.systemPackages = package.gaming;
    })

    # Creative.
    (mkIf cfg.creative.enable { environment.systemPackages = package.creative; })

    # Development.
    (mkIf cfg.dev.enable { environment.systemPackages = package.dev; })

    # Extras.
    (mkIf cfg.extra.enable { environment.systemPackages = package.extra; })
  ];
}