{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-24.05";
    unstable.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    numbers.url = "git+https://git.strudelline.net/cascade/numbers";
    interlude.url = "git+https://git.strudelline.net/nix/interlude";
    putex.url = "git+https://git.strudelline.net/james/putex";
    nixos-generators = { url = "github:nix-community/nixos-generators"; inputs.nixpkgs.follows = "nixpkgs"; };
    deploy-rs.url = "github:serokell/deploy-rs";
  };
  outputs = { self, nixpkgs, unstable, numbers, interlude, putex, nixos-generators, deploy-rs }@inputs:
  with builtins;
  with nixpkgs.lib;
  with interlude.lib;
  let
    includableModules =
      let localModules = "${./.}" + "/modules";
          dirContents = readDir (localModules);
          filenames = attrNames (dirContents);
          dirs = (filter (n: dirContents."${n}" == "directory" &&
                             readFileType "${localModules}/${n}/default.nix" == "regular" ) filenames);
          files = concatMap (filterAndStripSuffix ".nix") (filter (n: dirContents."${n}" == "regular") filenames);
      in
        foldl recursiveUpdate {} (
             (map (x: { nixosModules."${x}" = import (trace "importing ${localModules}/${x}" "${localModules}/${x}"); }) (trace "dirs: ${toJSON dirs}" dirs))
          ++ (map (x: { nixosModules."${x}" = import (trace "importing ${localModules}/${x}.nix" "${localModules}/${x}.nix"); }) (trace "files: ${toJSON files}" files))
        );
    buildMachine' = name: mods: cfg: {
      # the evaluated machine
      nixosConfigurations."${name}" =
      let
        pkgs = import nixpkgs { config = { allowUnfree = true; };};
        specialArgs = { basePath = "${toString ./.}"; inherit inputs numbers; };
      in nixosSystem (cfg // {
        inherit pkgs specialArgs;
        modules = [
          self.nixosModules.vmFormats
          numbers.nixosModules.users
          self.nixosModules.session
          putex.nixosModules.default
          {
            # global fixed values.
            networking.hostName = mkForce name;
            system.stateVersion = mkForce "24.05";
            nix.settings.require-sigs = mkForce false;
          }
        ] ++ mods;
      });
    };
    buildMachine = name:
      # the evaluated machine
      with numbers.api;
      let
        modules = [
          self.nixosModules.fixFlakeRegistry
          numbers.nixosModules.networking
          self.nixosModules.packages
          self.nixosModules.luks
          self.nixosModules.systemd-efi
          numbers.nixosModules.users
        ] ++ (map (x: self.nixosModules."${x}") (hostModules name));
        arch = hostSystem name;
      in
        (buildMachine' name modules { system = arch; })
          //
        {
          deploy.nodes."${name}" = {
            hostname = "172.16.19.1";
            profiles.system = {
              user = "root";
              path = deploy-rs.lib."${arch}".activate.nixos self.nixosConfigurations."${name}";
            };
          };
          
          # This is highly advised, and will prevent many possible mistakes
          checks = deploy-rs.lib."${arch}".deployChecks self.deploy;
        };
  in
  foldl recursiveUpdate {
    nixosModules = {
      vmFormats = { config, ... }: {
        imports = [
          nixos-generators.nixosModules.all-formats
        ];

        nixpkgs.hostPlatform = "x86_64-linux";

        formatConfigs.iso = { ... }: {
          isoImage.squashfsCompression = "zstd";
        };

        # the sample format from nixos-generators
        # formatConfigs.my-custom-format = { config, modulesPath, ... }: {
        #   imports = [ "${toString modulesPath}/installer/cd-dvd/installation-cd-base.nix" ];
        #   formatAttr = "isoImage";
        #   fileExtension = ".iso";
        #   networking.wireless.networks = {
        #     # ...
        #   };
        # };
      };
      fixFlakeRegistry = { ... }: { nix.registry = {
        nixpkgs.flake = inputs.nixpkgs;
        unstable.flake = inputs.unstable;
      };};
    };
  } ( # lists to recursively merge into the config.
         [ includableModules ]
      ++ (with numbers.api; map (h: buildMachine h) deployableHosts)
      ++ [(buildMachine' "cascade-installer" [self.nixosModules.installer] {} )]
  );
}