{ inputs ? import ./npins
, system ? builtins.currentSystem
, pkgs ? import inputs.nixpkgs { config = { }; overlays = [ ]; inherit system; }
, lib ? import "${inputs.nixpkgs}/lib"
    // {
    nixosSystem = args:
      import "${inputs.nixpkgs}/nixos/lib/eval-config.nix"
        (
          {
            inherit lib;
            # Allow system to be set modularly in nixpkgs.system.
            # We set it to null, to remove the "legacy" entrypoint's
            # non-hermetic default.
            system = null;

            modules = args.modules;
          }
          // builtins.removeAttrs args [ "modules" ]
        );
  }
,
}:
rec {
  nixosModules = {
    disko = "${inputs.disko}/module.nix";
    disk-layout = import ./vm/disk-layout.nix;
    interactive-vm = import ./vm/interactive-vm.nix;
    mastodon-vm = import ./vm/mastodon-vm.nix;
    peertube-vm = import ./vm/peertube-vm.nix;
    pixelfed-vm = import ./vm/pixelfed-vm.nix;
  };

  # test with
  #     nix-build -A nixosConfigurations.<config>.installTest
  nixosConfigurations = {
    mastodon = lib.nixosSystem {
      inherit system;
      modules = with nixosModules; [
        disko
        disk-layout
        interactive-vm
        mastodon-vm
      ];
    };

    peertube = lib.nixosSystem {
      inherit system;
      modules = with nixosModules; [
        disko
        disk-layout
        interactive-vm
        peertube-vm
      ];
    };

    pixelfed = lib.nixosSystem {
      inherit system;
      modules = with nixosModules; [
        disko
        disk-layout
        interactive-vm
        pixelfed-vm
      ];
    };

    all = lib.nixosSystem {
      inherit system;
      modules = with nixosModules; [
        interactive-vm
        disko
        disk-layout
        peertube-vm
        pixelfed-vm
        mastodon-vm
      ];
    };
  };

  # build with
  #     nix-build -A installers.<config>
  installers =
    let
      installer = (import ./installer.nix) { inherit lib; outPath = inputs.nixpkgs; };
    in
    lib.mapAttrs (_: config: installer config) nixosConfigurations;

  # run with
  #     $(nix-build -A deploy.<machine> --no-out-link)/bin/deploy
  deploy =
    let
      deployCommand = (pkgs.callPackage ./deploy.nix { });
    in
    lib.mapAttrs (name: config: deployCommand name config) nixosConfigurations;

  tests = {
    mastodon-garage = import ./tests/mastodon-garage.nix { inherit pkgs; };
    pixelfed-garage = import ./tests/pixelfed-garage.nix { inherit pkgs; };
  };

  shell = pkgs.mkShell {
    packages = with pkgs; [
      nil
    ];
  };
}