Work in progress refactor.

lib/modules.nix

@@ -0,0 +1,22 @@
+{
+  modulesDir,
+  defaultFile ? "default.nix",
+  importAll ? false
+}:
+
+with builtins;
+
+let
+  filterAttrNamesToList = filter: set: foldl' (a: b: a ++ b) [] (
+    map (e: if (filter e set.${e}) then [ e ] else []) (attrNames set)
+  );
+  nameValuePair = name: value: { inherit name value; };
+  listToAttrs = foldl' (acc: val: acc // { ${val.name} = val.value; }) {};
+  directories = filterAttrNamesToList (_: type: type == "directory") (readDir modulesDir);
+  files = map (dir: nameValuePair dir (modulesDir + "/${dir}/${defaultFile}")) directories;
+  modules = map ({name, value}:
+    # if the file contains a function, assume it to be a module and pass the path
+    # (for dedup and such). if it contains anything else, pass that.
+    let m = import value; in { inherit name; value = if (isFunction m) && !importAll then value else m; }
+  ) files;
+in (listToAttrs modules)