{
  outputs = { nixpkgs, ... }: let
    spond = { rustPlatform, rustfmt, clippy, pkg-config, openssl, ... }: rustPlatform.buildRustPackage {
      pname = "tb-spond-rs";
      version = "0.1.0";

      src = ./.;
      cargoLock.lockFile = ./Cargo.lock;
      nativeBuildInputs = [
        pkg-config
      ];
      propagatedBuildInputs = [
        openssl.dev
      ];
    };

    allpkgs = pkgs: pkgs.extend (_: _: nixpkgs.lib.attrsets.filterAttrs (name: _: name != "default") (packages' pkgs));

    packages = system: packages';
    packages' = pkgs': let
      pkgs = allpkgs pkgs';
    in {
      default = pkgs.spond;
      spond = pkgs.callPackage spond {};
    };

    devShells = system: pkgs': let
      pkgs = allpkgs pkgs';
    in builtins.mapAttrs (devShell pkgs) (packages pkgs');

    devShell = pkgs: name: pkg: pkgs.mkShell {
      buildInputs = with pkgs; [
        cargo
        cargo-bloat
        cargo-machete
        cargo-workspaces
        cargo-unused-features
        cargo-udeps
        cargo-audit
        cargo-diet
        cargo-duplicates
        cargo-expand
        cargo-flamegraph
        clippy
        lldb
        gdb

        (python3.withPackages (py: [ py.pyyaml ]))

        rustc
        rustfmt
        openssl.dev
      ] ++ pkg.buildInputs;

      nativeBuildInputs = pkg.nativeBuildInputs;

      shellHook = ''
        printf 'Dev shell for %s ready!\n' '${pkg.name}'
      '';
    };

    nixosModule = { pkgs, lib, config, ... }: let
      cli = lib.getExe (packages' pkgs).spond;
    in {
      config.systemd.timers."tb-spond-rs" = {
        description = "[TB] choose who is allowed to participate this week.";
        timerConfig.OnCalendar = "Sat 18:00:00";
        wantedBy = [ "timers.target" ];
      };
      config.systemd.services."tb-spond-rs" = {
        description = "[TB] choose who is allowed to participate this week.";
        after = [ "network.target" ];
        wants = [ "network.target" ];

        serviceConfig = {
          Type = "simple";
          ExecStart = lib.escapeShellArgs [
            cli
            "--email" "jonas.rabenstein@web.de"
            "--heading" "Schwimmtraining Donnerstag"
          ];
          EnvironmentFile=[ "%d/environment" ];
          User = "tb-spond-rs";
          Group = "tb-spond-rs";
          DynamicUser = true;
          RuntimeDirectory = "tb-spond-rs";
          StateDirectory = "tb-spond-rs";
          ProtectSystem = "full";
          ProtectHome = true;
          NoNewPrivileges = true;
          PrivateTmp = true;
          PrivateDevices = true;
        };
      };
    };
  in {
    packages = builtins.mapAttrs packages nixpkgs.legacyPackages;
    devShells = builtins.mapAttrs devShells nixpkgs.legacyPackages;

    nixosModules = {
      default = nixosModule;
      spond = nixosModule;
    }
  };
}