using System.Collections.Concurrent;
using System.Diagnostics;
using System.Text;
using ClientTester.Packet;
using LiteNetLib;
using LiteNetLib.Utils;
using Serilog;

namespace ClientTester.EchoDummyService;

public class EchoDummyClients
{
    private NetManager manager;
    private EventBasedNetListener listener;
    private NetDataWriter? writer;
    public NetPeer? peer;
    public int clientId;

    // seq → 송신 타임스탬프 (Stopwatch tick)
    private ConcurrentDictionary<int, long> pendingPings = new();
    private int seqNumber;
    private const int MAX_PENDING_PINGS = 1000;

    // 유닛 테스트용 (0 = 제한 없음)
    public int TestCount
    {
        get;
        set;
    } = 0;

    // 통계
    public int SentCount
    {
        set;
        get;
    }

    public int ReceivedCount
    {
        set;
        get;
    }

    public double LastRttMs
    {
        set;
        get;
    }

    public double TotalRttMs
    {
        set;
        get;
    }

    public int RttCount
    {
        set;
        get;
    }

    public EchoDummyClients(int clientId, string ip, int port, string key)
    {
        this.clientId = clientId;
        listener = new EventBasedNetListener();
        manager = new NetManager(listener);
        writer = new NetDataWriter();

        listener.PeerConnectedEvent += netPeer =>
        {
            peer = netPeer;
            Log.Information("[Client {ClientId:00}] 연결됨", this.clientId);
        };

        listener.NetworkReceiveEvent += (peer, reader, channel, deliveryMethod) =>
        {
            short code = reader.GetShort();
            short bodyLength = reader.GetShort();
            string? msg = reader.GetString();
            long sentTick;

            if (msg != null && msg.StartsWith("Echo seq:") &&
                int.TryParse(msg.Substring("Echo seq:".Length), out int seq) &&
                pendingPings.TryRemove(seq, out sentTick))
            {
                double rttMs = (Stopwatch.GetTimestamp() - sentTick) * 1000.0 / Stopwatch.Frequency;
                LastRttMs = rttMs;
                TotalRttMs += rttMs;
                RttCount++;
            }

            ReceivedCount++;

            if (TestCount > 0 && ReceivedCount >= TestCount)
            {
                peer.Disconnect();
            }

            reader.Recycle();
        };

        listener.PeerDisconnectedEvent += (peer, info) =>
        {
            Log.Warning("[Client {ClientId:00}] 연결 끊김: {Reason}", this.clientId, info.Reason);
            this.peer = null;
        };

        manager.Start();
        manager.Connect(ip, port, key);
    }

    public void SendPing()
    {
        if (peer == null || writer == null)
        {
            return;
        }

        int seq = seqNumber++;
        pendingPings[seq] = Stopwatch.GetTimestamp();

        // 응답 없는 오래된 ping 정리 (패킷 유실 시 메모리 누수 방지)
        if (pendingPings.Count > MAX_PENDING_PINGS)
        {
            int cutoff = seq - MAX_PENDING_PINGS;
            foreach (int key in pendingPings.Keys)
            {
                if (key < cutoff)
                {
                    pendingPings.TryRemove(key, out _);
                }
            }
        }

        // string → raw bytes (길이 prefix 방지)
        EchoPacket echoPacket = new EchoPacket();
        echoPacket.Str = $"Echo seq:{seq}";

        byte[] data = PacketSerializer.Serialize<EchoPacket>((ushort)PacketCode.ECHO, echoPacket);
        writer.Put(data);
        // 순서보장 안함 HOL Blocking 제거
        peer.Send(writer, DeliveryMethod.ReliableUnordered);
        SentCount++;
        writer.Reset();
    }

    public double AvgRttMs => RttCount > 0 ? TotalRttMs / RttCount : 0.0;

    public void PollEvents()
    {
        manager.PollEvents();
    }

    public void Stop()
    {
        manager.Stop();
    }
}