class UndergraduateActivity {
  UndergraduateActivity(
    this.teacher,
    this.name,
    this.courseCode,
    this.room,
    this.indices,
    this.weeks,
  );
  final String teacher, name, courseCode, room;
  final Set<int> indices, weeks;
  bool get cancelled => room == '停课';
}

List<UndergraduateActivity> parseActivityData(
  String script, {
  required int unitCount,
}) {
  if (unitCount != 12) throw const FormatException('本科节次结构无效');
  final matches = RegExp(
    r'new\s+TaskActivity\s*\((.*?)\)\s*;',
    dotAll: true,
  ).allMatches(script).toList();
  if (RegExp(r'\bnew\s+TaskActivity\s*\(').allMatches(script).length !=
      matches.length) {
    throw const FormatException('课程活动声明不完整');
  }
  final result = <UndergraduateActivity>[];
  for (var i = 0; i < matches.length; i++) {
    final m = matches[i], args = _strings(m[1]!);
    if (args.length != 7) throw const FormatException('课程活动字段不完整');
    final suffix = RegExp(r'\(([A-Za-z0-9_.-]+)\)$').firstMatch(args[3]);
    if (suffix == null || args[1].trim().isEmpty || args[5].trim().isEmpty) {
      throw const FormatException('教师、教室或课程序号缺失');
    }
    final bitmap = args[6];
    if (!RegExp(r'^0[01]+$').hasMatch(bitmap) ||
        bitmap.length > 64 ||
        (bitmap.length > 31 && bitmap.substring(31).contains('1'))) {
      throw const FormatException('上课周次超出1–30周');
    }
    final weeks = {
      for (var w = 1; w < bitmap.length && w <= 30; w++)
        if (bitmap[w] == '1') w,
    };
    if (weeks.isEmpty) throw const FormatException('课程周次为空');
    var end = i + 1 < matches.length ? matches[i + 1].start : script.length;
    final finish = script.indexOf('table0.marshalTable', m.end);
    if (finish >= 0 && finish < end) end = finish;
    final body = script.substring(m.end, end);
    final indices = <int>{};
    final assignments = RegExp(r'\bindex\s*=\s*([^;]+);')
        .allMatches(body)
        .toList();
    final appendPattern = RegExp(
      r'table\d+\.activities\[index\]\s*\[[^;]+?\]\s*=\s*activity\s*;',
    );
    final appends = appendPattern.allMatches(body).length;
    final unconsumed = body
        .replaceAll(appendPattern, '')
        .replaceAll(RegExp(r'\bindex\s*=\s*[^;]+;'), '');
    if (RegExp(r'\btable\d+\.activities\s*\[|\bindex\s*=')
        .hasMatch(unconsumed)) {
      throw const FormatException('存在无法识别的课程节次赋值');
    }
    if (assignments.isEmpty || assignments.length != appends) {
      throw const FormatException('课程节次赋值不完整');
    }
    for (final assignment in assignments) {
      final expression = RegExp(r'^\s*(\d+)\s*\*\s*unitCount\s*\+\s*(\d+)\s*$')
          .firstMatch(assignment[1]!);
      if (expression == null) throw const FormatException('不支持的节次表达式');
      final day = int.parse(expression[1]!), period = int.parse(expression[2]!);
      if (day > 6 || period >= unitCount) {
        throw const FormatException('课程星期或节次无效');
      }
      indices.add(day * unitCount + period);
    }
    result.add(
      UndergraduateActivity(
        args[1].trim(),
        args[3].substring(0, suffix.start).trim(),
        suffix[1]!,
        args[5].trim(),
        indices,
        weeks,
      ),
    );
  }
  return result;
}

/// Reads only quoted JS literals; expressions and calls are never evaluated.
List<String> _strings(String input) {
  final out = <String>[];
  var p = 0;
  void spaces() {
    while (p < input.length && RegExp(r'\s').hasMatch(input[p])) {
      p++;
    }
  }

  while (true) {
    spaces();
    if (p >= input.length) break;
    final quote = input[p++];
    if (quote != '"' && quote != "'") throw const FormatException('活动参数必须为字符串');
    final b = StringBuffer();
    var closed = false;
    while (p < input.length) {
      var c = input[p++];
      if (c == quote) {
        closed = true;
        break;
      }
      if (c == '\\') {
        if (p >= input.length) throw const FormatException('字符串转义不完整');
        c = input[p++];
        const escapes = {
          'n': '\n',
          'r': '\r',
          't': '\t',
          'b': '\b',
          'f': '\f',
          'v': '\u000b',
          '0': '\u0000',
        };
        if (c == 'u' || c == 'x') {
          final count = c == 'u' ? 4 : 2;
          if (p + count > input.length) throw const FormatException('字符串转义无效');
          final hex = input.substring(p, p + count);
          if (!RegExp(r'^[0-9a-fA-F]+$').hasMatch(hex)) {
            throw const FormatException('字符串转义无效');
          }
          b.writeCharCode(int.parse(hex, radix: 16));
          p += count;
        } else if (escapes.containsKey(c)) {
          b.write(escapes[c]);
        } else if (const ['"', "'", '\\', '/'].contains(c)) {
          b.write(c);
        } else {
          throw const FormatException('不支持的字符串转义');
        }
      } else {
        if (c == '\n' || c == '\r') throw const FormatException('字符串未闭合');
        b.write(c);
      }
    }
    if (!closed) throw const FormatException('字符串未闭合');
    out.add(b.toString());
    spaces();
    if (p == input.length) break;
    if (input[p++] != ',') throw const FormatException('活动字段分隔无效');
  }
  return out;
}