# Recursive skill discovery: one `{ name; src; }` per skill in a source tree.
lib: root:
let
  walk =
    dir:
    let
      subdirs = lib.filterAttrs (_: type: type == "directory") (builtins.readDir dir);
    in
    lib.concatLists (
      lib.mapAttrsToList (
        entryName: _:
        let
          child = dir + "/${entryName}";
        in
        # A directory with a SKILL.md is a skill, and its subdirectories are
        # that skill's assets rather than nested skills, so the walk stops here.
        # A directory without one is a cosmetic container to recurse through.
        if (builtins.readDir child) ? "SKILL.md" then
          [
            {
              name = entryName;
              src = child;
            }
          ]
        else
          walk child
      ) subdirs
    );

  found = walk root;
  names = map (s: s.name) found;
  duplicates = lib.unique (lib.filter (n: lib.count (x: x == n) names > 1) names);
in
if duplicates != [ ] then
  throw ''
    Skill name collision: ${lib.concatStringsSep ", " duplicates}.
    Two or more skills under ${toString root} resolve to the same name.
    A skill's name is its leaf directory name and must be globally unique
    across the whole tree, independent of the cosmetic folders above it.
    Rename one of the colliding skills.''
else
  found