function orderUnits(titles, groups) {
  const byCode = new Map(titles.filter((title) => title.Code).map((title) => [title.Code, title]));
  const state = new Map(),
    ordered = [];
  for (const title of titles) {
    if (!title.Code || state.has(title.Code)) continue;
    const stack = [{ title, expanded: false }];
    while (stack.length) {
      const item = stack.pop(),
        code = item.title.Code;
      if (item.expanded) {
        state.set(code, 2);
        ordered.push(item.title);
        continue;
      }
      if (state.has(code)) continue;
      state.set(code, 1);
      stack.push({ title: item.title, expanded: true });
      for (const row of groups.get(code) || []) {
        const dependency =
          !(row.JdlSummary && Number(row.CalcIndex) === 1) &&
          Number(row.LinkIndex) === 103 &&
          byCode.get(row.Code);
        if (dependency && !state.has(dependency.Code))
          stack.push({ title: dependency, expanded: false });
      }
    }
  }
  return ordered;
}

module.exports = { orderUnits };