split up the flake better

flake.nix

@@ -20,6 +20,27 @@
     serverProject = inputs.pyproject-nix.lib.project.loadPyproject {
       projectRoot = ./.;
     };
+
+    # Packages
+    script = pkgs.writeShellApplication {
+      name = "scanbuddy";
+
+      runtimeInputs = with pkgs; [sane-backends brscan5 ghostscript];
+
+      text = builtins.readFile ./scanbuddy.bash;
+    };
+
+    # Returns an attribute set that can be passed to `buildPythonPackage`.
+    attrs = serverProject.renderers.buildPythonPackage {inherit python;};
+    server = python.pkgs.buildPythonPackage (attrs
+      // {
+        env.CUSTOM_ENVVAR = "foobar";
+      });
+
+    scanbuddy-pkg = pkgs.symlinkJoin {
+      name = "scanbuddy";
+      paths = [script server];
+    };
   in {
     # devShells.${system}.default = pkgs.mkShell {
     #   packages = with pkgs; [
@@ -33,28 +54,32 @@
     #     exec zsh
     #   '';
     # };
-    packages.${system} = let
-      scanbuddy = pkgs.writeShellApplication {
-        name = "scanbuddy";
-
-        runtimeInputs = with pkgs; [sane-backends brscan5 ghostscript];
-
-        text = builtins.readFile ./scanbuddy.bash;
-      };
-
-      # Returns an attribute set that can be passed to `buildPythonPackage`.
-      attrs = serverProject.renderers.buildPythonPackage {inherit python;};
-      server = python.pkgs.buildPythonPackage (attrs
-        // {
-          env.CUSTOM_ENVVAR = "foobar";
-        });
-    in {
-      default = pkgs.symlinkJoin {
-        name = "scanbuddy";
-        paths = [scanbuddy server];
-      };
-      inherit scanbuddy;
+    packages.${system} = {
+      default = scanbuddy-pkg;
+      inherit script;
       inherit server;
     };
+
+    nixosModules.default = {
+      config,
+      pkgs,
+      lib,
+      ...
+    }: {
+      options = {
+        service.scanbuddy = lib.mkEnableOption "Enable the scanbuddy server";
+      };
+      config = {
+        systemd.services.scanbuddy = lib.mkIf config.service.scanbuddy {
+          description = "The scanbuddy webservice";
+          wantedBy = ["multi-user.target"];
+          serviceConfig = {
+            ExecStart = "${scanbuddy-pkg}/bin/scanbuddy-server";
+            Path = ["${scanbuddy-pkg}/bin"];
+            WorkingDirectory = "/var/lib/scanbuddy";
+          };
+        };
+      };
+    };
   };
 }

pyproject.toml

@@ -6,6 +6,7 @@ description = "A REST server for the scanbuddy shell-script"
 # define any Python dependencies
 dependencies = [
   "flask>3",
+  "waitress"
 ]
 
 # define the CLI executable