some refactoring and modularizing locale

modules/nixos/gaming/gamemode/default.nix

@@ -0,0 +1,48 @@
+{
+  config,
+  lib,
+  pkgs,
+  inputs,
+  ...
+}: let
+  inherit (lib) mkIf mkEnableOption mkOption;
+  cfg = config.nixos.gaming.gamemode;
+  pipewireLowLatencyModule = inputs.nix-gaming.nixosModules.pipewireLowLatency;
+in {
+  imports = [
+    pipewireLowLatencyModule
+  ];
+  options = {
+    nixos.gaming.gamemode = {
+      enable = mkEnableOption "Enables gamemode";
+      optimizeGpu.enable = mkOption {
+        type = lib.types.bool;
+        default = false;
+        description = "Whether to apply GPU optimizations.";
+      };
+    };
+  };
+  config = mkIf cfg.enable {
+    programs.gamemode = {
+      enable = true;
+      settings = {
+        general = {
+          inhibit_screensaver = 1;
+          softrealtime = "auto";
+          # renice = 15;
+        };
+        gpu = mkIf cfg.optimizeGpu.enable {
+          apply_gpu_optimisations = "accept-responsibility";
+          gpu_device = 0;
+          amd_performance_level = "high";
+        };
+        custom = {
+          start = "${pkgs.libnotify}/bin/notify-send 'GameMode started'";
+          end = "${pkgs.libnotify}/bin/notify-send 'GameMode ended'";
+        };
+      };
+    };
+    # see https://github.com/fufexan/nix-gaming/#pipewire-low-latency
+    services.pipewire.lowLatency.enable = true;
+  };
+}