{
  description = "ZUGFeRD REST API Service";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        pythonPackages = pkgs.python311Packages;

        # factur-x package - not available in nixpkgs, so we package it inline
        factur-x = pythonPackages.buildPythonPackage rec {
          pname = "factur_x";
          version = "3.8";
          format = "wheel";

          src = pythonPackages.fetchPypi {
            inherit pname version format;
            hash = "sha256-alctEgMZw79S2UStnt/bYTigE6h9wqCVpm7i1qc5efs=";
          };

          dependencies = with pythonPackages; [ pypdf lxml ];

          pythonRelaxDeps = true;

          meta = {
            description =
              "Python library to generate and read Factur-X invoices";
            license = pkgs.lib.licenses.mit;
          };
        };

        zugferd-service = pythonPackages.buildPythonApplication {
          pname = "zugferd-service";
          version = "1.0.0";
          pyproject = true;
          src = ./.;

          pythonRelaxDeps = true;

          build-system = [ pythonPackages.hatchling ];

          dependencies = with pythonPackages; [
            fastapi
            uvicorn
            pydantic
            python-multipart
            factur-x
            pypdf
            lxml
          ];

          nativeCheckInputs = with pythonPackages; [
            pytestCheckHook
            pytest-asyncio
            httpx
          ];

          passthru = { mainProgram = "zugferd-service"; };

          meta = {
            description = "REST API for ZUGFeRD invoice extraction";
            license = pkgs.lib.licenses.mit;
          };
        };
      in {
        packages.default = zugferd-service;
        packages.zugferd-service = zugferd-service;

        devShells.default = pkgs.mkShell {
          packages = [
            (pkgs.python311.withPackages (ps:
              with ps; [
                fastapi
                uvicorn
                pydantic
                python-multipart
                pypdf
                lxml
                pytest
                pytest-asyncio
                httpx
                # factur-x - install via pip if not available
              ]))
            pkgs.python311Packages.pip
          ];
        };
      });
}