{ lib, writeErofs }:
{
  layers,
  labelLower ? "base",
  labelUpper ? "image",
}:

let
  inherit (lib.lists) toList;
  nLayers = builtins.length layers;
  mkLabel = seq: if seq + 1 < nLayers then labelLower + toString seq else labelUpper;
  f =
    {
      roots ? [ ],
      layers ? [ ],
      seq ? 0,
    }:
    newRoots: {
      seq = seq + 1;
      roots = roots ++ (toList newRoots);
      layers = layers ++ [
        (writeErofs ({
          roots = toList newRoots;
          rootsExclude = roots;
          passthru = {
            inherit seq;
            label = mkLabel seq;
          };
          label = mkLabel seq;
        }))
      ];
    };
  acc = lib.foldl f { } layers;
in
acc.layers