{ lib }:
root: patterns: f:
lib.listToAttrs (
  lib.concatMap (
    dirent:
    let
      fname = dirent.name;
      typ = dirent.value;
      fpath = root + "/${fname}";
      doMatch =
        pat:
        let
          match = pat fpath fname typ;
          value = f match fpath typ;
        in
        if match == null then [ ] else [ (lib.nameValuePair match value) ];
    in
    (lib.take 1 (lib.concatMap (doMatch) patterns))
  ) (lib.attrsToList (builtins.readDir root))
)