static S parseDoubleArrowTreeCI_defaultKey = "<default>";

static Map<S, O> parseDoubleArrowTreeCI(S text) {

  L<S> lines = withoutEmpties(rtrimAll(lines(text)));

  if (empty(lines)) null;

  new L<Map<S, O>> nodes;

  new L<Int> indents; // indent of children

  Map<S, O> tree = ciMap();

  nodes.add(tree);

  indents.add(countIndent(first(lines)));

  for i over lines: {

    S s = lines.get(i);

    int indent = countIndent(s);

    while (indent < last(indents)) {

      removeLast(nodes);

      removeLast(indents);

    }

    L<S> x = splitAtDoubleArrow(s);

    if (l(x) == 2) { // leaf (or tree with default)

      S next = get(lines, i+1);

      if (next != null && countIndent(next) > indent) { // tree with default

        Map<S, O> newTree = ciMap();

        last(nodes).put(first(x), newTree);

        nodes.add(newTree);

        indents.add(indent+1);

        newTree.put(parseDoubleArrowTreeCI_defaultKey, second(x));

      } else // leaf

        last(nodes).put(first(x), second(x));

    } else {

      Map<S, O> newTree = ciMap();

      last(nodes).put(trim(s), newTree);

      nodes.add(newTree);

      indents.add(indent+1);

    }

  }

  ret tree;

}