import 'dart:collection';

class PacketLossStatistics {
  static final PacketLossStatistics _instance =
      PacketLossStatistics._internal();
  factory PacketLossStatistics() => _instance;
  PacketLossStatistics._internal();

  // 记录每个messageId的分包信息
  // key: messageId, value: {totalPackets, receivedPackets}
  final Map<int, PacketInfo> _packetsMap = HashMap();

  // 统计信息
  int _totalMessages = 0; // 总消息数
  int _lostMessages = 0; // 丢包的消息数
  int _totalPackets = 0; // 总分包数
  int _lostPackets = 0; // 丢失的分包数

  // 记录分包数据
  void recordPacket(int messageId, int currentIndex, int totalPackets) {
    if (!_packetsMap.containsKey(messageId)) {
      _packetsMap[messageId] = PacketInfo(totalPackets);
      _totalMessages++;
      _totalPackets += totalPackets;
    }

    _packetsMap[messageId]!.receivedPackets.add(currentIndex);

    // 如果收到了该messageId的最后一个包，进行统计
    if (currentIndex == totalPackets) {
      _checkPacketLoss(messageId);
    }
  }

  // 检查丢包情况
  void _checkPacketLoss(int messageId) {
    final info = _packetsMap[messageId]!;

    // 检查是否有丢失的包
    int received = info.receivedPackets.length;
    if (received < info.totalPackets) {
      _lostMessages++;
      _lostPackets += (info.totalPackets - received);
    }

    // 清理该messageId的记录，避免内存泄漏
    _packetsMap.remove(messageId);
  }

  // 获取丢包率统计信息
  PacketLossInfo getStatistics() {
    if (_totalMessages == 0 || _totalPackets == 0) {
      return PacketLossInfo(0.0, 0.0);
    }

    // 计算消息级别的丢包率
    double messageLossRate = (_lostMessages / _totalMessages) * 100;

    // 计算分包级别的丢包率
    double packetLossRate = (_lostPackets / _totalPackets) * 100;

    return PacketLossInfo(messageLossRate, packetLossRate);
  }

  // 重置统计数据
  void reset() {
    _packetsMap.clear();
    _totalMessages = 0;
    _lostMessages = 0;
    _totalPackets = 0;
    _lostPackets = 0;
  }
}

// 分包信息类
class PacketInfo {
  final int totalPackets;
  final Set<int> receivedPackets = HashSet<int>();

  PacketInfo(this.totalPackets);
}

// 丢包统计信息类
class PacketLossInfo {
  final double messageLossRate; // 消息丢失率
  final double packetLossRate; // 分包丢失率

  PacketLossInfo(this.messageLossRate, this.packetLossRate);

  @override
  String toString() {
    return 'Message Loss Rate: ${messageLossRate.toStringAsFixed(2)}%, Packet Loss Rate: ${packetLossRate.toStringAsFixed(2)}%';
  }
}