{
  description = "A webserver to create files for testing purposes";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs?rev=a73246e2eef4c6ed172979932bc80e1404ba2d56";

    microvm = {
      url = "github:astro/microvm.nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = {
    self,
    nixpkgs,
    ...
  } @ inputs: let
    supportedSystems = ["x86_64-linux" "x86_64-darwin" "aarch64-linux" "aarch64-darwin"];
    forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
    pkgs = forAllSystems (system: nixpkgs.legacyPackages.${system}.extend overlay);

    overlay = final: prev: rec {
      python3Packages = prev.python3Packages.overrideScope (pfinal: pprev: {
        packageNameToDrv = x: builtins.getAttr (cleanPythonPackageName x) final.python3Packages;
      });

      cleanPythonPackageName = x: let
        cleanName = builtins.match "([a-z,A-Z,0-9,_,-]+).*" x;
      in
        if cleanName != null
        then builtins.elemAt cleanName 0
        else builtins.warn "Could not determine package name from '${x}'" null;
    };

    pyproject = builtins.fromTOML (builtins.readFile ./pyproject.toml);

    buildDependencies = forAllSystems (system: builtins.map pkgs.${system}.python3Packages.packageNameToDrv pyproject.build-system.requires);
    runtimeDependencies = forAllSystems (system: builtins.map pkgs.${system}.python3Packages.packageNameToDrv pyproject.project.dependencies);
    optionalDependencies = forAllSystems (system: builtins.mapAttrs (name: value: builtins.map pkgs.${system}.python3Packages.packageNameToDrv value) pyproject.project.optional-dependencies);
  in {
    # `nix build`
    packages = forAllSystems (system: let
      buildTestdata = {skipCheck ? false}:
        pkgs.${system}.python3Packages.buildPythonPackage {
          pname = pyproject.project.name;
          version = pyproject.project.version;
          src = ./.;

          pyproject = true;

          build-system = buildDependencies.${system};

          dependencies = runtimeDependencies.${system};

          optional-dependencies = optionalDependencies.${system};

          nativeCheckInputs = optionalDependencies.${system}.dev;

          checkPhase = let
            dev = builtins.map (x: x.pname) optionalDependencies.${system}.dev;
          in ''
            ${
              if builtins.elem "pytest" dev && !skipCheck
              then "pytest src tests"
              else ""
            }
            ${
              if builtins.elem "mypy" dev && !skipCheck
              then "mypy src tests"
              else ""
            }
            ${
              if builtins.elem "pylint" dev && !skipCheck
              then "pylint src tests"
              else ""
            }
          '';
        };
    in rec {
      default = testdata;
      testdata = buildTestdata {skipCheck = false;};
      quick = buildTestdata {skipCheck = true;};
      vm = self.nixosConfigurations.vm.config.microvm.declaredRunner;
    });

    # `nix fmt`
    formatter = forAllSystems (system: pkgs.${system}.alejandra);

    # `nix develop`
    devShells = forAllSystems (system: rec {
      default = venv;

      venv = pkgs.${system}.mkShell {
        shellHook = ''
          if [ ! -d .venv/ ]; then
            echo "Creating Virtual Environment..."
            ${pkgs.${system}.python3}/bin/python3 -m venv .venv
          fi

          alias activate='source .venv/bin/activate'

          echo "Entering Virtual Environment..."
          source .venv/bin/activate
        '';
      };
    });

    # NixOS Module
    nixosModules.default = import ./nix/module.nix inputs;

    # nixos definition for a microvm to test nixosModules
    nixosConfigurations = let
      system = "x86_64-linux";
    in {
      vm = nixpkgs.lib.nixosSystem {
        inherit system;

        modules = [
          inputs.microvm.nixosModules.microvm
          ({config, ...}: {
            system.stateVersion = config.system.nixos.version;

            networking.hostName = "vm";
            users.users.root.password = "";

            microvm = {
              # volumes = [
              #   {
              #     mountPoint = "/var";
              #     image = "var.img";
              #     size = 256;
              #   }
              # ];
              shares = [
                {
                  # use proto = "virtiofs" for MicroVMs that are started by systemd
                  proto = "9p";
                  tag = "ro-store";
                  # a host's /nix/store will be picked up so that no
                  # squashfs/erofs will be built for it.
                  source = "/nix/store";
                  mountPoint = "/nix/.ro-store";
                }
              ];

              interfaces = [
                {
                  type = "user";
                  id = "qemu";
                  mac = "02:00:00:01:01:01";
                }
              ];

              forwardPorts = [
                {
                  host.port = config.services.testdata.port;
                  guest.port = config.services.testdata.port;
                }
              ];

              # "qemu" has 9p built-in!
              hypervisor = "qemu";
              socket = "control.socket";
            };
          })

          self.nixosModules.default
          rec {
            networking.firewall.allowedTCPPorts = [services.testdata.port];
            services.testdata = {
              enable = true;

              host = "0.0.0.0";
              port = 1234;

              settings = {
                keys = ["one" "two" "three"];
                max-size = "1GB";
                max-data = "100GB";
                buffer-size = "12MiB";
                database = "/root/testdata_state.json";
                database-update-interval = 5.0;
                log = "/root/log.jsonl";
              };
            };
          }
        ];
      };
    };
  };
}