class ExamRecord {
  const ExamRecord({
    required this.code,
    required this.name,
    this.assessment = '',
    this.candidate = '',
    this.sequence = '',
    this.room = '',
    this.seat = '',
    this.time = '',
  });
  final String code, name, assessment, candidate, sequence, room, seat, time;
  Map<String, dynamic> toJson() => {
    'code': code,
    'name': name,
    'assessment': assessment,
    'candidate': candidate,
    'sequence': sequence,
    'room': room,
    'seat': seat,
    'time': time,
  };
  factory ExamRecord.fromJson(Map<String, dynamic> json) {
    String field(String key) {
      final value = json[key];
      if (value is! String || value.length > 1000) {
        throw const FormatException('考试信息无效');
      }
      return value;
    }

    final record = ExamRecord(
      code: field('code'),
      name: field('name'),
      assessment: field('assessment'),
      candidate: field('candidate'),
      sequence: field('sequence'),
      room: field('room'),
      seat: field('seat'),
      time: field('time'),
    );
    if (record.code.isEmpty || record.name.isEmpty) {
      throw const FormatException('考试课程无效');
    }
    return record;
  }
}

class ExamSchedule {
  ExamSchedule({
    required this.semesterLabel,
    required this.termId,
    required List<ExamRecord> records,
  }) : records = List.unmodifiable(records);
  final String semesterLabel, termId;
  final List<ExamRecord> records;
  Map<String, dynamic> toJson() => {
    'semesterLabel': semesterLabel,
    'termId': termId,
    'records': records.map((r) => r.toJson()).toList(),
  };
  factory ExamSchedule.fromJson(Map<String, dynamic> json) {
    final label = json['semesterLabel'],
        id = json['termId'],
        rows = json['records'];
    if (label is! String ||
        label.trim().isEmpty ||
        id is! String ||
        !RegExp(r'^\d+$').hasMatch(id) ||
        rows is! List ||
        rows.length > 500) {
      throw const FormatException('考试列表无效');
    }
    final records = rows
        .map((r) => ExamRecord.fromJson(Map<String, dynamic>.from(r as Map)))
        .toList();
    if (records.map((r) => r.code).toSet().length != records.length) {
      throw const FormatException('考试课程重复');
    }
    return ExamSchedule(semesterLabel: label, termId: id, records: records);
  }
}