Reimplement framework using the module system

builtinModules/nixosConfigurations.nix

@@ -0,0 +1,37 @@
+# flakelite -- Framework for making flakes simple
+# Copyright (C) 2023 Archit Gupta <archit@accelbread.com>
+# SPDX-License-Identifier: MIT
+
+{ config, lib, ... }:
+let
+  inherit (builtins) isAttrs;
+  inherit (lib) foldl mapAttrsToList mergeOneOption mkIf mkOption mkOptionType
+    recursiveUpdate;
+  inherit (lib.types) lazyAttrsOf;
+
+  nixosConfiguration = mkOptionType {
+    name = "nixosConfiguration";
+    description = "nixosConfiguration";
+    descriptionClass = "noun";
+    check = x: isAttrs x
+      && x ? config.nixpkgs.system
+      && x ? config.system.build.toplevel;
+    merge = mergeOneOption;
+  };
+in
+{
+  options.nixosConfigurations = mkOption {
+    type = lazyAttrsOf nixosConfiguration;
+    default = { };
+  };
+
+  config.outputs = mkIf (config.nixosConfigurations != { }) {
+    inherit (config) nixosConfigurations;
+    checks = foldl recursiveUpdate { } (mapAttrsToList
+      (n: v: {
+        ${v.config.nixpkgs.system}."nixos-${n}" =
+          v.config.system.build.toplevel;
+      })
+      config.nixosConfigurations);
+  };
+}