complete rework v2

lib/builder.nix

@@ -0,0 +1,53 @@
+args @ {
+  lib,
+  withSystem,
+  inputs,
+  ...
+}:
+with lib; let
+  inherit (import ./. args) recursiveMerge;
+  mkBase = {system ? "x86_64-linux", ...}:
+    withSystem system (
+      {
+        pkgs,
+        system,
+        ...
+      }: {
+        inherit system;
+        specialArgs = {inherit inputs pkgs;};
+        modules = [
+          inputs.disko.nixosModules.disko
+          inputs.home-manager.nixosModules.home-manager
+        ];
+      }
+    );
+  mkNixos = args:
+    inputs.nixpkgs.lib.nixosSystem (recursiveMerge [
+      (mkBase args)
+      args
+    ]);
+in {
+  mkHosts = root: let
+    hosts = attrNames (filterAttrs (_: type: type == "directory") (builtins.readDir root));
+
+    hostDirs = builtins.listToAttrs (
+      lib.map (hostName: lib.nameValuePair hostName (lib.path.append root hostName)) hosts
+    );
+
+    hostResolved =
+      lib.mapAttrs (
+        _: hostDir: (lib.map (fileName: lib.path.append hostDir fileName) (attrNames (builtins.readDir hostDir)))
+      )
+      hostDirs;
+
+    hostsConfig = mapAttrs (_: configs: mkNixos {modules = configs;}) hostResolved;
+  in
+    hostsConfig;
+
+  mkVm = configs:
+    inputs.nixos-generators.nixosGenerate {
+      modules = configs;
+      format = "qcow";
+      system = "x86_64-linux";
+    };
+}

lib/default.nix

@@ -0,0 +1,4 @@
+args: {
+  inherit (import ./util.nix args) recursiveMerge;
+  inherit (import ./builder.nix args) mkNixos mkHosts mkVm;
+}

lib/util.nix

@@ -0,0 +1,17 @@
+{lib, ...}:
+with lib; {
+  recursiveMerge = attrList: let
+    f = attrPath:
+      zipAttrsWith (
+        n: values:
+          if tail values == []
+          then head values
+          else if all isList values
+          then unique (concatLists values)
+          else if all isAttrs values
+          then f (attrPath ++ [n]) values
+          else last values
+      );
+  in
+    f [] attrList;
+}