nixos/dux-calendar: add module

nixos/modules/module-list.nix

@@ -210,6 +210,7 @@
   ./programs/dmrconfig.nix
   ./programs/droidcam.nix
   ./programs/dublin-traceroute.nix
+  ./programs/dux-calendar.nix
   ./programs/dux-search.nix
   ./programs/ente-auth.nix
   ./programs/environment.nix

nixos/modules/programs/dux-calendar.nix

@@ -0,0 +1,54 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  cfg = config.programs.dux-calendar;
+in
+{
+  options.programs.dux-calendar = {
+    enable = lib.mkEnableOption "Dux Calendar, a standalone calendar application";
+
+    package = lib.mkPackageOption pkgs "dux-calendar" { };
+
+    quickshell.package = lib.mkPackageOption pkgs "quickshell" {
+      extraDescription = "The Quickshell package used to run the calendar interface.";
+    };
+
+    systemd = {
+      enable = lib.mkEnableOption "starting Dux Calendar with the graphical session";
+
+      target = lib.mkOption {
+        type = lib.types.str;
+        default = "graphical-session.target";
+        example = "wayland-session.target";
+        description = "The systemd user target that starts Dux Calendar.";
+      };
+
+      restartIfChanged = lib.mkOption {
+        type = lib.types.bool;
+        default = true;
+        description = "Whether to restart the Dux Calendar user service when its package or configuration changes.";
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    environment.systemPackages = [
+      cfg.package
+      cfg.quickshell.package
+    ];
+
+    systemd.packages = lib.mkIf cfg.systemd.enable [ cfg.package ];
+    systemd.user.services.dcal = lib.mkIf cfg.systemd.enable {
+      wantedBy = [ cfg.systemd.target ];
+      restartIfChanged = cfg.systemd.restartIfChanged;
+      path = [ cfg.quickshell.package ];
+    };
+  };
+
+  meta.teams = [ lib.teams.duxlabs ];
+}