using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using NLog;

namespace FATrace.OEMApp.Services
{
    /// <summary>
    /// Socket 服务器 - 基于原生 TcpListener 实现的多客户端 TCP 服务器
    /// 功能：接收客户端数据、解析为字符串、触发事件通知外部、支持向客户端发送数据
    /// 协议：使用 CRLF (\r\n) 作为行分隔符的文本协议
    /// 编码：UTF-8
    /// </summary>
    public class SocketService
    {
        #region 私有字段

        /// <summary>
        /// NLog 日志记录器
        /// </summary>
        private static readonly Logger Logger = LogManager.GetCurrentClassLogger();

        /// <summary>
        /// TCP 监听器
        /// </summary>
        private TcpListener _listener;

        /// <summary>
        /// 服务器是否正在运行
        /// </summary>
        private bool _isRunning = false;

        /// <summary>
        /// 取消令牌源，用于停止服务器
        /// </summary>
        private CancellationTokenSource _cts;

        /// <summary>
        /// 已连接的客户端字典（SessionId -> ClientSession）
        /// 使用线程安全的 ConcurrentDictionary
        /// </summary>
        private readonly ConcurrentDictionary<string, ClientSession> _clients = new ConcurrentDictionary<string, ClientSession>();

        /// <summary>
        /// 会话 ID 计数器
        /// </summary>
        private int _sessionIdCounter = 0;

        #endregion

        #region 公共属性

        /// <summary>
        /// 服务器监听 IP 地址
        /// 默认：127.0.0.1（本地回环）
        /// 0.0.0.0 表示监听所有网卡
        /// </summary>
        public string ListenIp { get; set; } = "127.0.0.1";

        /// <summary>
        /// 服务器监听端口
        /// 默认：6001
        /// </summary>
        public int ListenPort { get; set; } = 6001;

        /// <summary>
        /// 接收超时时间（秒）
        /// 默认：30 秒
        /// 如果客户端在此时间内无数据交互，连接将被关闭
        /// </summary>
        public int ReceiveTimeout { get; set; } = 30;

        /// <summary>
        /// 发送超时时间（秒）
        /// 默认：30 秒
        /// </summary>
        public int SendTimeout { get; set; } = 30;

        /// <summary>
        /// 服务器是否正在运行
        /// </summary>
        public bool IsRunning => _isRunning;

        /// <summary>
        /// 当前连接的客户端数量
        /// </summary>
        public int ConnectedClientCount
        {
            get
            {
                return _clients.Count;
            }
        }

        #endregion

        #region 事件定义

        /// <summary>
        /// 数据接收事件参数
        /// </summary>
        public class DataReceivedEventArgs : EventArgs
        {
            /// <summary>
            /// 会话 ID（客户端唯一标识）
            /// </summary>
            public string SessionId { get; set; }

            /// <summary>
            /// 客户端 IP 地址
            /// </summary>
            public string RemoteIp { get; set; }

            /// <summary>
            /// 客户端端口
            /// </summary>
            public int RemotePort { get; set; }

            /// <summary>
            /// 接收到的数据（已解析为字符串）
            /// </summary>
            public string Data { get; set; }

            /// <summary>
            /// 接收时间
            /// </summary>
            public DateTime ReceivedTime { get; set; }
        }

        /// <summary>
        /// 客户端连接事件参数
        /// </summary>
        public class ClientConnectedEventArgs : EventArgs
        {
            /// <summary>
            /// 会话 ID
            /// </summary>
            public string SessionId { get; set; }

            /// <summary>
            /// 客户端 IP 地址
            /// </summary>
            public string RemoteIp { get; set; }

            /// <summary>
            /// 客户端端口
            /// </summary>
            public int RemotePort { get; set; }

            /// <summary>
            /// 连接时间
            /// </summary>
            public DateTime ConnectedTime { get; set; }
        }

        /// <summary>
        /// 客户端断开事件参数
        /// </summary>
        public class ClientDisconnectedEventArgs : EventArgs
        {
            /// <summary>
            /// 会话 ID
            /// </summary>
            public string SessionId { get; set; }

            /// <summary>
            /// 客户端 IP 地址
            /// </summary>
            public string RemoteIp { get; set; }

            /// <summary>
            /// 客户端端口
            /// </summary>
            public int RemotePort { get; set; }

            /// <summary>
            /// 断开时间
            /// </summary>
            public DateTime DisconnectedTime { get; set; }

            /// <summary>
            /// 断开原因
            /// </summary>
            public string Reason { get; set; }
        }

        /// <summary>
        /// 数据接收事件
        /// 当接收到客户端数据时触发，外部可订阅此事件进行业务处理
        /// </summary>
        public event EventHandler<DataReceivedEventArgs> DataReceived;

        /// <summary>
        /// 客户端连接事件
        /// 当有新客户端连接时触发
        /// </summary>
        public event EventHandler<ClientConnectedEventArgs> ClientConnected;

        /// <summary>
        /// 客户端断开事件
        /// 当客户端断开连接时触发
        /// </summary>
        public event EventHandler<ClientDisconnectedEventArgs> ClientDisconnected;

        /// <summary>
        /// 服务器错误事件
        /// 当服务器发生错误时触发
        /// </summary>
        public event EventHandler<Exception> ServerError;

        #endregion

        #region 公共方法

        /// <summary>
        /// 启动 Socket 服务器
        /// </summary>
        /// <returns>启动是否成功</returns>
        public async Task<bool> StartAsync()
        {
            try
            {
                // 检查是否已经在运行
                if (_isRunning)
                {
                    Logger.Warn("Socket 服务器已经在运行中，无需重复启动");
                    return true;
                }

                Logger.Info($"正在启动 Socket 服务器，监听地址：{ListenIp}:{ListenPort}，超时时间：{ReceiveTimeout}秒");

                // 解析 IP 地址
                IPAddress ipAddress;
                if (!IPAddress.TryParse(ListenIp, out ipAddress))
                {
                    Logger.Error($"无效的 IP 地址：{ListenIp}");
                    return false;
                }

                // 创建 TCP 监听器
                _listener = new TcpListener(ipAddress, ListenPort);
                _listener.Start();

                // 创建取消令牌
                _cts = new CancellationTokenSource();

                _isRunning = true;
                Logger.Info($"Socket 服务器启动成功，监听地址：{ListenIp}:{ListenPort}");

                // 启动接受客户端连接的任务
                _ = Task.Run(() => AcceptClientsAsync(_cts.Token), _cts.Token);

                return true;
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"启动 Socket 服务器时发生异常：{ex.Message}");
                OnServerError(ex);
                return false;
            }
        }

        /// <summary>
        /// 停止 Socket 服务器
        /// </summary>
        /// <returns>停止任务</returns>
        public async Task StopAsync()
        {
            try
            {
                if (!_isRunning || _listener == null)
                {
                    Logger.Warn("Socket 服务器未运行，无需停止");
                    return;
                }

                Logger.Info("正在停止 Socket 服务器...");

                _isRunning = false;

                // 取消所有异步操作
                _cts?.Cancel();

                // 停止监听器
                _listener?.Stop();

                // 断开所有客户端
                foreach (var client in _clients.Values)
                {
                    try
                    {
                        client.TcpClient?.Close();
                    }
                    catch (Exception ex)
                    {
                        Logger.Warn(ex, $"关闭客户端连接时发生异常：SessionId={client.SessionId}");
                    }
                }

                // 清空客户端字典
                _clients.Clear();

                // 释放资源
                _cts?.Dispose();
                _cts = null;
                _listener = null;

                Logger.Info("Socket 服务器已停止");

                await Task.CompletedTask;
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"停止 Socket 服务器时发生异常：{ex.Message}");
                OnServerError(ex);
            }
        }

        /// <summary>
        /// 向指定客户端发送数据
        /// </summary>
        /// <param name="sessionId">会话 ID（客户端唯一标识）</param>
        /// <param name="data">要发送的字符串数据</param>
        /// <returns>发送是否成功</returns>
        public async Task<bool> SendToClientAsync(string sessionId, string data)
        {
            try
            {
                // 参数校验
                if (string.IsNullOrWhiteSpace(sessionId))
                {
                    Logger.Warn("发送数据失败：SessionId 为空");
                    return false;
                }

                if (string.IsNullOrEmpty(data))
                {
                    Logger.Warn($"发送数据失败：数据为空，SessionId={sessionId}");
                    return false;
                }

                // 查找会话
                if (!_clients.TryGetValue(sessionId, out var client))
                {
                    Logger.Warn($"发送数据失败：未找到会话，SessionId={sessionId}");
                    return false;
                }

                // 发送数据（自动添加 CRLF 行结束符）
                var dataToSend = data.EndsWith("\r\n") ? data : data + "\r\n";
                var buffer = Encoding.UTF8.GetBytes(dataToSend);

                await client.Stream.WriteAsync(buffer, 0, buffer.Length);
                await client.Stream.FlushAsync();

                Logger.Debug($"向客户端发送数据成功，SessionId={sessionId}，数据长度={buffer.Length}字节，内容={data}");
                return true;
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"向客户端发送数据时发生异常：SessionId={sessionId}，错误={ex.Message}");
                OnServerError(ex);
                return false;
            }
        }

        /// <summary>
        /// 向所有已连接的客户端广播数据
        /// </summary>
        /// <param name="data">要广播的字符串数据</param>
        /// <returns>成功发送的客户端数量</returns>
        public async Task<int> BroadcastAsync(string data)
        {
            try
            {
                if (string.IsNullOrEmpty(data))
                {
                    Logger.Warn("广播数据失败：数据为空");
                    return 0;
                }

                // 获取所有客户端
                var clientList = _clients.Values.ToList();

                if (clientList.Count == 0)
                {
                    Logger.Debug("广播数据：当前无已连接的客户端");
                    return 0;
                }

                // 准备数据
                var dataToSend = data.EndsWith("\r\n") ? data : data + "\r\n";
                var buffer = Encoding.UTF8.GetBytes(dataToSend);

                // 向所有客户端发送
                int successCount = 0;
                foreach (var client in clientList)
                {
                    try
                    {
                        await client.Stream.WriteAsync(buffer, 0, buffer.Length);
                        await client.Stream.FlushAsync();
                        successCount++;
                    }
                    catch (Exception ex)
                    {
                        Logger.Error(ex, $"向客户端广播数据失败：SessionId={client.SessionId}，错误={ex.Message}");
                    }
                }

                Logger.Info($"广播数据完成，成功发送到 {successCount}/{clientList.Count} 个客户端，数据长度={buffer.Length}字节");
                return successCount;
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"广播数据时发生异常：{ex.Message}");
                OnServerError(ex);
                return 0;
            }
        }

        /// <summary>
        /// 断开指定客户端的连接
        /// </summary>
        /// <param name="sessionId">会话 ID</param>
        /// <returns>断开是否成功</returns>
        public async Task<bool> DisconnectClientAsync(string sessionId)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(sessionId))
                {
                    Logger.Warn("断开客户端失败：SessionId 为空");
                    return false;
                }

                if (!_clients.TryGetValue(sessionId, out var client))
                {
                    Logger.Warn($"断开客户端失败：未找到会话，SessionId={sessionId}");
                    return false;
                }

                client.TcpClient?.Close();
                _clients.TryRemove(sessionId, out _);
                Logger.Info($"已主动断开客户端连接，SessionId={sessionId}");
                return true;
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"断开客户端连接时发生异常：SessionId={sessionId}，错误={ex.Message}");
                OnServerError(ex);
                return false;
            }
        }

        /// <summary>
        /// 获取所有已连接客户端的会话 ID 列表
        /// </summary>
        /// <returns>会话 ID 列表</returns>
        public List<string> GetConnectedSessionIds()
        {
            return _clients.Keys.ToList();
        }

        #endregion

        #region 私有方法 - 客户端处理

        /// <summary>
        /// 接受客户端连接的循环
        /// </summary>
        private async Task AcceptClientsAsync(CancellationToken cancellationToken)
        {
            Logger.Info("开始接受客户端连接...");

            while (!cancellationToken.IsCancellationRequested && _isRunning)
            {
                try
                {
                    // 等待客户端连接
                    var tcpClient = await _listener.AcceptTcpClientAsync();

                    // 生成会话 ID
                    var sessionId = $"Session_{Interlocked.Increment(ref _sessionIdCounter)}_{DateTime.Now.Ticks}";

                    // 获取客户端信息
                    var remoteEndPoint = tcpClient.Client.RemoteEndPoint as IPEndPoint;
                    var remoteIp = remoteEndPoint?.Address.ToString() ?? "Unknown";
                    var remotePort = remoteEndPoint?.Port ?? 0;

                    // 创建客户端会话
                    var clientSession = new ClientSession
                    {
                        SessionId = sessionId,
                        TcpClient = tcpClient,
                        Stream = tcpClient.GetStream(),
                        RemoteIp = remoteIp,
                        RemotePort = remotePort,
                        ConnectedTime = DateTime.Now
                    };

                    // 添加到客户端字典
                    if (_clients.TryAdd(sessionId, clientSession))
                    {
                        Logger.Info($"客户端已连接，SessionId={sessionId}，远程地址={remoteIp}:{remotePort}，当前连接数={ConnectedClientCount}");

                        // 触发客户端连接事件
                        OnClientConnected(new ClientConnectedEventArgs
                        {
                            SessionId = sessionId,
                            RemoteIp = remoteIp,
                            RemotePort = remotePort,
                            ConnectedTime = clientSession.ConnectedTime
                        });

                        // 启动处理客户端数据的任务
                        _ = Task.Run(() => HandleClientAsync(clientSession, cancellationToken), cancellationToken);
                    }
                    else
                    {
                        Logger.Warn($"添加客户端会话失败，SessionId={sessionId}");
                        tcpClient.Close();
                    }
                }
                catch (ObjectDisposedException)
                {
                    // 监听器已被释放，正常退出
                    Logger.Info("监听器已关闭，停止接受新连接");
                    break;
                }
                catch (SocketException ex) when (ex.SocketErrorCode == SocketError.Interrupted)
                {
                    // 监听被中断，正常退出
                    Logger.Info("监听被中断，停止接受新连接");
                    break;
                }
                catch (Exception ex)
                {
                    Logger.Error(ex, $"接受客户端连接时发生异常：{ex.Message}");
                    OnServerError(ex);
                    await Task.Delay(1000, cancellationToken); // 等待一秒后重试
                }
            }

            Logger.Info("停止接受客户端连接");
        }

        /// <summary>
        /// 处理单个客户端的数据接收
        /// </summary>
        private async Task HandleClientAsync(ClientSession client, CancellationToken cancellationToken)
        {
            var sessionId = client.SessionId;
            var stream = client.Stream;
            var reader = new StreamReader(stream, Encoding.UTF8);

            Logger.Debug($"开始处理客户端数据，SessionId={sessionId}");

            try
            {
                // 设置读取超时
                stream.ReadTimeout = ReceiveTimeout * 1000;

                while (!cancellationToken.IsCancellationRequested && _isRunning)
                {
                    try
                    {
                        // 读取一行数据（以 CRLF 或 LF 结尾）
                        var line = await reader.ReadLineAsync();

                        // 如果读取到 null，表示连接已关闭
                        if (line == null)
                        {
                            Logger.Info($"客户端连接已关闭，SessionId={sessionId}");
                            break;
                        }

                        // 记录接收日志
                        Logger.Debug($"接收到客户端数据，SessionId={sessionId}，远程地址={client.RemoteIp}:{client.RemotePort}，数据长度={line.Length}字符，内容={line}");

                        // 触发数据接收事件
                        OnDataReceived(new DataReceivedEventArgs
                        {
                            SessionId = sessionId,
                            RemoteIp = client.RemoteIp,
                            RemotePort = client.RemotePort,
                            Data = line,
                            ReceivedTime = DateTime.Now
                        });
                    }
                    catch (IOException ex) when (ex.InnerException is SocketException socketEx)
                    {
                        // 连接被重置或超时
                        Logger.Warn($"客户端连接异常，SessionId={sessionId}，错误={socketEx.SocketErrorCode}");
                        break;
                    }
                    catch (IOException ex)
                    {
                        // 读取超时或其他 IO 异常
                        Logger.Warn(ex, $"读取客户端数据时发生 IO 异常，SessionId={sessionId}");
                        break;
                    }
                }
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"处理客户端数据时发生异常，SessionId={sessionId}，错误={ex.Message}");
                OnServerError(ex);
            }
            finally
            {
                // 清理客户端连接
                try
                {
                    client.TcpClient?.Close();
                    _clients.TryRemove(sessionId, out _);

                    Logger.Info($"客户端已断开，SessionId={sessionId}，远程地址={client.RemoteIp}:{client.RemotePort}，当前连接数={ConnectedClientCount}");

                    // 触发客户端断开事件
                    OnClientDisconnected(new ClientDisconnectedEventArgs
                    {
                        SessionId = sessionId,
                        RemoteIp = client.RemoteIp,
                        RemotePort = client.RemotePort,
                        DisconnectedTime = DateTime.Now,
                        Reason = "连接关闭"
                    });
                }
                catch (Exception ex)
                {
                    Logger.Warn(ex, $"清理客户端连接时发生异常，SessionId={sessionId}");
                }
            }
        }

        #endregion

        #region 私有方法 - 事件触发

        /// <summary>
        /// 触发数据接收事件
        /// </summary>
        private void OnDataReceived(DataReceivedEventArgs e)
        {
            try
            {
                DataReceived?.Invoke(this, e);
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"触发 DataReceived 事件时发生异常：{ex.Message}");
            }
        }

        /// <summary>
        /// 触发客户端连接事件
        /// </summary>
        private void OnClientConnected(ClientConnectedEventArgs e)
        {
            try
            {
                ClientConnected?.Invoke(this, e);
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"触发 ClientConnected 事件时发生异常：{ex.Message}");
            }
        }

        /// <summary>
        /// 触发客户端断开事件
        /// </summary>
        private void OnClientDisconnected(ClientDisconnectedEventArgs e)
        {
            try
            {
                ClientDisconnected?.Invoke(this, e);
            }
            catch (Exception ex)
            {
                Logger.Error(ex, $"触发 ClientDisconnected 事件时发生异常：{ex.Message}");
            }
        }

        /// <summary>
        /// 触发服务器错误事件
        /// </summary>
        private void OnServerError(Exception ex)
        {
            try
            {
                ServerError?.Invoke(this, ex);
            }
            catch (Exception eventEx)
            {
                Logger.Error(eventEx, $"触发 ServerError 事件时发生异常：{eventEx.Message}");
            }
        }

        #endregion

        #region 内部类 - 客户端会话

        /// <summary>
        /// 客户端会话信息
        /// </summary>
        private class ClientSession
        {
            /// <summary>
            /// 会话 ID
            /// </summary>
            public string SessionId { get; set; }

            /// <summary>
            /// TCP 客户端
            /// </summary>
            public TcpClient TcpClient { get; set; }

            /// <summary>
            /// 网络流
            /// </summary>
            public NetworkStream Stream { get; set; }

            /// <summary>
            /// 远程 IP 地址
            /// </summary>
            public string RemoteIp { get; set; }

            /// <summary>
            /// 远程端口
            /// </summary>
            public int RemotePort { get; set; }

            /// <summary>
            /// 连接时间
            /// </summary>
            public DateTime ConnectedTime { get; set; }
        }

        #endregion
    }
}