mullvad-vpn: add module

modules/programs/mullvad-vpn.nix

@@ -0,0 +1,52 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+let
+  cfg = config.programs.mullvad-vpn;
+  jsonFormat = pkgs.formats.json { };
+in
+{
+  meta.maintainers = [ lib.maintainers.awwpotato ];
+
+  options.programs.mullvad-vpn = {
+    enable = lib.mkEnableOption "Mullvad VPN";
+    package = lib.mkPackageOption pkgs "mullvad-vpn" { nullable = true; };
+
+    settings = lib.mkOption {
+      inherit (jsonFormat) type;
+      default = { };
+      description = ''
+        Written to {file}`XDG_CONFIG_HOME/Mullvad VPN/gui_settings.json` or
+        {file}`~/Library/Application Support/Mullvad VPN/gui_settings.json`.
+        See <https://github.com/mullvad/mullvadvpn-app/blob/main/desktop/packages/mullvad-vpn/src/main/gui-settings.ts>
+        for options.
+      '';
+      example = {
+        preferredLocale = "system";
+        autoConnect = false;
+        enableSystemNotifications = true;
+        monochromaticIcon = false;
+        startMinimized = false;
+        unpinnedWindow = true;
+        browsedForSplitTunnelingApplications = [ ];
+        changelogDisplayedForVersion = "";
+        updateDismissedForVersion = "";
+        animateMap = true;
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    home.package = lib.mkIf (cfg.package != null) [ cfg.package ];
+
+    home.file."${
+      if pkgs.stdenv.hostPlatform.isDarwin then "Library/Application Support" else config.xdg.configHome
+    }/Mullvad VPN/gui_settings.json" =
+      lib.mkIf (cfg.settings != { }) {
+        source = jsonFormat.generate "mullvad-gui-settings" cfg.settings;
+      };
+  };
+}