{
  lib,
  nixpkgs,
  inputs,
  self,
  ...
}:
rec {
  getDirs =
    parentDir:
    lib.mapAttrs (n: v: (import "${parentDir}/${n}")) (
      lib.filterAttrs (n: v: v == "directory") (builtins.readDir parentDir)
    );
  loadInstances =
    dir: extraModules: lib.mapAttrs (n: v: loadInstance extraModules v (getDirs dir)) (getDirs dir);
  loadInstance =
    extraModules: instance: instanceConfigs:
    nixpkgs.lib.nixosSystem {
      specialArgs = { inherit inputs instanceConfigs; instanceConfig = instance; };
      modules =
        instance.modules
        ++ extraModules
        ++ [
          {
            nixpkgs.overlays = [ self.overlays.default ];
            nixpkgs.config.allowUnfree = true;
            networking.hostName = instance.hostName;
          }
        ];
    };
}