{ lib, ... }:
let
  inherit (builtins)
    attrNames
    isAttrs
    readDir
    ;


  inherit (lib)
    filterAttrs
    hasSuffix
    mapAttrs'
    nameValuePair
    removeSuffix
    ;

in
rec {
  # mapFilterAttrs ::
  #   (name -> value -> bool )
  #   (name -> value -> { name = any; value = any; })
  #   attrs
  mapFilterAttrs = seive: f: attrs:
    filterAttrs seive (mapAttrs' f attrs);

  vimport = path: name: import (path + "/${name}");

  reqImport = {
    dir,
    _import ? base: vimport dir (base + ".nix")
  }:
    mapFilterAttrs
      (_: v: v != null)
      (
        n: v:
          if
            n != "default.nix"
            && hasSuffix ".nix" n
            && v == "regular"

          then let
            name = removeSuffix ".nix" n;
          in
            nameValuePair (name) (_import name)

          else
            nameValuePair ("") (null)
      )
      (readDir dir);
}