{ lib, ... }:

with lib;

/*
  Merges list of records, concatenates arrays, if two values can't be merged - the latter is preferred

  Example 1:
    recursiveMerge [
      { a = "x"; c = "m"; list = [1]; }
      { a = "y"; b = "z"; list = [2]; }
    ]

    returns

    { a = "y"; b = "z"; c="m"; list = [1 2] }

  Example 2:
    recursiveMerge [
      {
        a.a = [1];
        a.b = 1;
        a.c = [1 1];
        boot.loader.grub.enable = true;
        boot.loader.grub.device = "/dev/hda";
      }
      {
        a.a = [2];
        a.b = 2;
        a.c = [1 2];
        boot.loader.grub.device = "";
      }
    ]

    returns

    { a = { a = [ 1 2 ]; b = 2; c = [ 1 2 ]; }; boot = { loader = { grub = { device = ""; enable = true; }; }; }; }

*/

let

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;


in

recursiveMerge