Make firefox module compatible with nixos hosts

hosts/darwin/home-default.nix

@@ -22,6 +22,12 @@
 
   nixpkgs.config.allowUnfree = true;
 
+  # Firefox configuration
+  programs.firefox-custom = {
+    enable = true;
+    package = null;  # Use system Firefox on Darwin
+  };
+
   home.username = "yanlin";
   home.homeDirectory = "/Users/yanlin";
   home.stateVersion = "24.05";

modules/firefox.nix

@@ -1,6 +1,24 @@
 { config, pkgs, lib, ... }@args:
 
+with lib;
+
+let
+  cfg = config.programs.firefox-custom;
+in
+
 {
+  options.programs.firefox-custom = {
+    enable = mkEnableOption "Firefox browser configuration";
+
+    package = mkOption {
+      type = types.nullOr types.package;
+      default = null;
+      example = "pkgs.firefox";
+      description = "Firefox package to use. Set to null on Darwin to use system Firefox, or pkgs.firefox on NixOS.";
+    };
+  };
+
+  config = mkIf cfg.enable {
     # Create userChrome.css to hide Firefox View button
     home.file."${config.home.homeDirectory}/.mozilla/firefox/yanlin/chrome/userChrome.css".text = ''
       /* Hide Firefox View button */
@@ -17,7 +35,7 @@
 
     programs.firefox = {
       enable = true;
-    package = null;
+      package = cfg.package;
       
       profiles.yanlin = {
         id = 0;
@@ -159,4 +177,5 @@
         };
       };
     };
+  };
 }