{ self }:
{ scrollsDir }:
let
  allSubDirs = builtins.attrNames (
    builtins.readDir scrollsDir
  );

  directoriesOnly = builtins.filter (name:
    let
      type = (builtins.readDir scrollsDir).${name};
    in type == "directory"
  ) allSubDirs;

  hasScrollNix = dir:
    let
      scrollPath = scrollsDir + "/${dir}/scroll.nix";
    in builtins.pathExists scrollPath;

  scrollDirs = builtins.filter hasScrollNix directoriesOnly;
  missingScrollDirs = builtins.filter (dir: !(hasScrollNix dir)) directoriesOnly;

  warnings =
    if builtins.length missingScrollDirs > 0
    then builtins.trace
      "Warning: Found directories without scroll.nix: ${builtins.toString missingScrollDirs}"
      null
    else null;
in
scrollDirs