sclass QAHandler<QA> {

  QA findQAWithTypos(S s, S language) {

    Lowest<QA> qa = findClosestQA(s, language);

    if (!qa.has()) null;

    if (qa.score() > maxTypos) {

      print("Rejecting " + nTypos((int) qa.score()) + ": " + s + " / " + qa->patterns);

      null;

    }

    print("Accepting " + nTypos((int) qa.score()) + ": " + s + " / " + qa->patterns);

    ret qa!;

  }

  QA findMatchingQA(S s, S language, bool allowTypos) {

    try object QA qa = findMatchingQA(s, conceptsWhere(QA, +language));

    try object QA qa = findMatchingQA(s, filter(list(QA), q -> neq(q.language, language)));

    if (allowTypos)

      try object QA qa = findQAWithTypos(s, language);

    null;

  }

  static Lowest<QA> findClosestQA(S s, S language) {

    time "findClosestQA" {

      new Lowest<QA> qa;

      findClosestQA(s, qa, conceptsWhere(QA, +language));

      findClosestQA(s, qa, filter(list(QA), q -> neq(q.language, language)));

    }

    ret qa;

  }

  static L<QA> sortQAs(Cl<QA> qas) {

    Map<S, Int> categoryToIndex = fieldToFieldIndex('name, 'index, list(Category));

    ret sortedByCalculatedField(qas, q -> pair(categoryToIndex.get(q.category), q.index));

  }

  svoid reindexQAs() {

    for (Language lang) {

      int index = 1;

      for (QA qa : sortQAs(conceptsWhere(QA, language := lang.code)))

        cset(qa, index := index++);

    }

  }

  static QA findMatchingQA(S s, Cl<QA> qas) {

    for (QA qa : sortQAs(qas))

      if (mmo2_match(qa.parsedPattern(), s))

        ret qa;

    null;

  }

  svoid findClosestQA(S s, Lowest<QA> best, Cl<QA> qas) {

    for (QA qa : sortQAs(qas)) {

      Int score = mmo2_levenWithSwapsScore(qa.parsedPattern(), s);

      if (score != null)

        best.put(qa, score);

    }

  }

}