sclass NLLogicChecker_v2 {
  S input;
  new L<S> facts;
  StringMatcher matcher = ai_standardMatcher();
  new L<S> posted;
  new ThreadLocal<IfThen> checkingRule;
  VF3<Exp, Matching, O> onExpressionChecked;

  sclass Matching {
    new LinkedHashMap<S> matches; // var -> match
    new L<Exp> output;
    bool verbose;
  }
  
  bool checkRule(IfThen rule, Matching m) {
    if (rule == null) false;
    temp tempSetThreadLocal(checkingRule, rule);
    if (!checkExpression(rule.in, m)) false;
    print("Rewriting output: " + sfu(rule.out));
    m.output.add(apply(rule.out, m));
    true;
  }
  
  Exp apply(Exp e, Matching m) {
    ret apply(e, m.matches);
  }
  
  Exp apply(Exp e, SS m) {
    if (e == null) null;
    if (e cast And)
      ret And(apply(e.a, m), apply(e.b, m));
    if (e cast ExpNot)
      ret ExpNot(apply(e.a, m));
    if (e cast Func)
      ret Func(e.name, apply(e.arg, m));
      
    if (e cast Sentence)
      ret Sentence(javaTok(matcher.apply(e.text(), m)));
    if (e cast Sentence2)
      ret Sentence2(matcher.apply(e.text(), m));
      
    ret e;
  }
  
  final bool checkExpression(Exp e, Matching m) {
    try {
      bool result = checkExpression_impl(e, m);
      recordExpressionCheck(e, m, result);
      ret result;
    } catch e {
      recordExpressionCheck(e, m, e);
      throw rethrow(e);
    }
  }
  
  void recordExpressionCheck(Exp e, Matching m, O result) {
    callF(onExpressionChecked, e, m, result);
  }
  
  bool checkExpression_impl(Exp e, Matching m) {
    if (e cast And)
      ret checkExpression(e.a, m) && checkExpression(e.b, m);
    if (e cast ExpNot) {
      temp tempBackupMatches(m);
      ret !checkExpression(e.a, m);
    }
    if (e cast Func) {
      if (eq(e.name, "input")) {
        S pat = nlLogic_text(e.arg);
        L<S> tok = javaTokPlusBrackets2(pat);
        for (S pat2 : splitAtTokens(tok, ll("|"))) {
          bool result = matcher.match(pat2, input, m.matches);
          if (m.verbose) print("matched " + sfu(e) + " with " + quote(input) + " & " + sfu(m.matches) + " => " + result);
          if (result) true;
        }
      }
      else if (eq(e.name, "fact")) {
        S pat = nlLogic_text(e.arg);
        for (S fact : facts) {
          bool result = matcher.match(pat, fact, m.matches);
          if (m.verbose) print("matched " + sfu(e) + " with " + quote(fact) + " & " + sfu(m.matches) + " => " + result);
          if (result) true;
        }
      }
    }
    false;
  }
  
  AutoCloseable tempBackupMatches(final Matching m) {
    final LinkedHashMap<S> oldMatches = (LinkedHashMap) cloneMap(m.matches);
    ret autocloseable { m.matches = oldMatches; };
  }
}