using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Configuration;
using NetMQ;
using NetMQ.Sockets;
using Newtonsoft.Json;
using SHH.CameraSdk;
using SHH.Contracts;

namespace SHH.CameraService
{
    /// <summary>
    /// 双模指令总线服务 (Enterprise V2)
    /// <para>核心职责：建立 TCP 指令通道，接收客户端指令并分发给 CameraManager</para>
    /// <para>增强特性：</para>
    /// <para>1. 支持双模：被动监听 (Bind) 与 主动投递 (Connect)</para>
    /// <para>2. 幂等性控制：利用 MemoryCache 防止客户端重试导致的重复执行</para>
    /// <para>3. 顺序一致性：利用时间戳防止指令乱序</para>
    /// </summary>
    public class CommandBusService : BackgroundService
    {
        #region --- 1. 字段与依赖 ---

        private readonly CameraManager _cameraManager;
        private readonly IConfiguration _config;
        private readonly IMemoryCache _cache; // 核心：用于请求去重
        private readonly int _processId;

        // 运行状态标志
        private volatile bool _isRunning = false;

        // 两种模式的 Socket (互斥存在)
        private ResponseSocket? _repSocket;   // 模式A: 被动监听 (Server-Listening)
        private DealerSocket? _dealerSocket;  // 模式B: 主动投递 (Server-Dialing)

        // 顺序一致性锁：记录每个设备最后处理的指令时间戳
        // Key: TargetId (设备ID), Value: Timestamp (最后执行时间)
        private readonly Dictionary<string, DateTime> _deviceLastCmdTime = new();

        #endregion

        #region --- 2. 构造函数 ---

        /// <summary>
        /// 构造函数 (注意：必须在 Program.cs 注册 AddMemoryCache)
        /// </summary>
        public CommandBusService(CameraManager manager, IConfiguration config, IMemoryCache cache)
        {
            _cameraManager = manager;
            _config = config;
            _cache = cache;
            // 获取当前进程 ID (默认为 1)
            _processId = _config.GetValue<int>("ProcessId", 1);
        }

        #endregion

        #region --- 3. 核心生命周期 ---

        protected override Task ExecuteAsync(CancellationToken stoppingToken)
        {
            // 在后台线程启动，避免阻塞 Web 主线程
            return Task.Run(() =>
            {
                _isRunning = true;

                // 1. 读取网络策略
                // 优先读取配置中的主动目标，如果没有则回退到被动监听
                string? activeTargetIp = _config["Network:ActiveTargets:0:Ip"];
                bool isActiveMode = !string.IsNullOrEmpty(activeTargetIp);

                try
                {
                    if (isActiveMode)
                    {
                        // === 模式 B: 主动投递 (Server Connects Client) ===
                        // 场景：服务器在内网，主动连接公网/固定IP的客户端
                        int cmdPort = _config.GetValue<int>("Network:ActiveTargets:0:CmdPort", 7000);
                        string addr = $"tcp://{activeTargetIp}:{cmdPort}";
                        RunActiveMode(addr, stoppingToken);
                    }
                    else
                    {
                        // === 模式 A: 被动监听 (Server Binds Port) ===
                        // 场景：服务器有固定IP，等待客户端连接
                        int basePort = _config.GetValue<int>("Network:Passive:CmdPortBase", 7000);
                        int listenPort = basePort + (_processId - 1);
                        string addr = $"tcp://*:{listenPort}";
                        RunPassiveMode(addr, stoppingToken);
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"[CmdBus] 致命错误停止: {ex.Message}");
                }
                finally
                {
                    _isRunning = false;
                    CleanupSockets();
                }

            }, stoppingToken);
        }

        private void CleanupSockets()
        {
            try
            {
                _repSocket?.Dispose();
                _dealerSocket?.Dispose();
            }
            catch { /* 忽略销毁时的异常 */ }
        }

        #endregion

        #region --- 4. 模式实现：被动监听 (Passive) ---

        private void RunPassiveMode(string address, CancellationToken token)
        {
            using (_repSocket = new ResponseSocket())
            {
                _repSocket.Bind(address);
                Console.WriteLine($"[CmdBus] [被动模式] 指令监听已启动: {address}");

                while (!token.IsCancellationRequested)
                {
                    try
                    {
                        // 1. 阻塞等待请求 (超时1秒以便响应 Cancel 信号)
                        if (!_repSocket.TryReceiveFrameString(TimeSpan.FromSeconds(1), out string reqJson))
                            continue;

                        // 2. 处理业务 (带 去重 + ID回填 逻辑)
                        CommandResult result = this.ProcessRequest(reqJson);

                        // 3. 发送回执
                        // 注意：REP 模式必须发送应答，即使 result 为 null (Fire-and-Forget) 也建议发一个空 ACK 防止 Socket 状态错乱
                        // 但为了协议统一，建议 Passive 模式下总是返回结果
                        string respJson = result != null ? JsonConvert.SerializeObject(result) : "{}";
                        _repSocket.SendFrame(respJson);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine($"[CmdBus-Passive] 异常: {ex.Message}");
                    }
                }
            }
        }

        #endregion

        #region --- 5. 模式实现：主动投递 (Active) ---

        private void RunActiveMode(string address, CancellationToken token)
        {
            // 外层循环：断线重连机制
            while (!token.IsCancellationRequested)
            {
                try
                {
                    using (_dealerSocket = new DealerSocket())
                    {
                        Console.WriteLine($"[CmdBus] [主动模式] 正在连接指令中心: {address}");
                        _dealerSocket.Connect(address);

                        // ★★★ 关键步骤：连接成功后，立即发送【身份注册包】 ★★★
                        // 客户端收到这个包后，才能在界面上显示"设备在线"
                        SendRegistration(_dealerSocket);

                        // 内层循环：消息收发
                        while (!token.IsCancellationRequested)
                        {
                            // 1. 接收指令
                            // DealerSocket 是异步全双工的，这里即使没收到消息也不会阻塞发送
                            if (!_dealerSocket.TryReceiveFrameString(TimeSpan.FromSeconds(1), out string reqJson))
                            {
                                // 空闲周期，可在此处添加心跳发送逻辑 (Ping)
                                continue;
                            }

                            // 2. 处理业务 (带 去重 + ID回填 逻辑)
                            CommandResult result = this.ProcessRequest(reqJson);

                            // 3. 发送结果 (QoS控制)
                            // 如果结果为 null，说明指令是 Fire-and-Forget (无需回执)，则不发送网络包节省带宽
                            if (result != null)
                            {
                                _dealerSocket.SendFrame(JsonConvert.SerializeObject(result));
                            }
                        }
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"[CmdBus-Active] 连接中断或异常: {ex.Message}");
                    // 避免死循环狂刷 CPU，等待 3 秒再重连
                    Thread.Sleep(3000);
                }
            }
        }

        /// <summary>
        /// 发送身份注册包 (Active 模式专用)
        /// </summary>
        private void SendRegistration(DealerSocket socket)
        {
            try
            {
                // 计算实际端口信息
                int portOffset = _processId - 1;
                var regInfo = new ServerRegistrationDto
                {
                    ProcessId = _processId,
                    InstanceId = $"Gateway_{_processId}",
                    ServerIp = GetLocalIpAddress(),
                    WebApiPort = 5000 + portOffset,
                    VideoPort = 5555 + portOffset,
                    CmdPort = 7000 + portOffset,
                    StartTime = DateTime.Now,
                    Description = "Active Mode Connection (V2)"
                };

                // 封装信封 (系统级指令)
                var payload = new CommandPayload
                {
                    CmdCode = "SERVER_REGISTER",
                    TargetId = "SYSTEM",
                    JsonParams = JsonConvert.SerializeObject(regInfo),
                    RequestId = Guid.NewGuid().ToString("N"),
                    RequireAck = false // 注册包通常不需要回执，只要连上就行
                };

                socket.SendFrame(JsonConvert.SerializeObject(payload));
                Console.WriteLine($"[CmdBus] 身份注册包已发送 -> {regInfo.ServerIp}:{regInfo.WebApiPort}");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"[CmdBus] 注册包发送失败: {ex.Message}");
            }
        }

        private string GetLocalIpAddress()
        {
            try
            {
                var host = System.Net.Dns.GetHostEntry(System.Net.Dns.GetHostName());
                foreach (var ip in host.AddressList)
                {
                    if (ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
                        return ip.ToString();
                }
            }
            catch { }
            return "127.0.0.1";
        }

        #endregion

        #region --- 6. 协议处理核心 (★★ V2 核心增强 ★★) ---

        /// <summary>
        /// 统一处理请求协议：去重 -> 排序 -> 执行 -> 回填 ID
        /// </summary>
        private CommandResult ProcessRequest(string json)
        {
            if (string.IsNullOrWhiteSpace(json)) return CommandResult.Fail("Empty Request");

            CommandPayload? payload;
            try { payload = JsonConvert.DeserializeObject<CommandPayload>(json); }
            catch { return CommandResult.Fail("Invalid JSON Protocol"); }

            if (payload == null) return CommandResult.Fail("Null Payload");

            // =========================================================
            // A. 【幂等性检查】(Idempotency Check)
            // =========================================================
            // 查缓存：如果这个 RequestId 10秒内处理过，直接返回上次的结果
            // 这样即使客户端重试发了 10 次，业务逻辑也只跑 1 次
            if (_cache.TryGetValue(payload.RequestId, out CommandResult cachedResult))
            {
                Console.WriteLine($"[Dedup] 拦截重复请求: {payload.RequestId} (Retry: {payload.RetryCount})");
                return cachedResult;
            }

            // =========================================================
            // B. 【顺序一致性检查】(Order Guarantee)
            // =========================================================
            // 防止乱序：比如先发的“停止”因为网络卡顿，比后发的“开始”晚到
            if (payload.TargetId != "SYSTEM")
            {
                lock (_deviceLastCmdTime)
                {
                    if (_deviceLastCmdTime.TryGetValue(payload.TargetId, out DateTime lastTime))
                    {
                        if (payload.Timestamp < lastTime)
                        {
                            Console.WriteLine($"[Order] 丢弃乱序指令: {payload.CmdCode}");
                            return CommandResult.Fail("Order Violation: Stale Command Dropped");
                        }
                    }
                    _deviceLastCmdTime[payload.TargetId] = payload.Timestamp;
                }
            }

            // =========================================================
            // C. 【业务执行】
            // =========================================================
            CommandResult result;
            try
            {
                // 调用纯逻辑层
                result = CommandBusProcessor.ProcessBusinessLogic(_cameraManager, payload);
            }
            catch (Exception ex)
            {
                result = CommandResult.Fail($"Internal Logic Error: {ex.Message}");
            }

            // =========================================================
            // D. 【闭环回填】
            // =========================================================
            // 必须把身份证号贴回去，不然客户端不知道这是谁的回执
            result.RequestId = payload.RequestId;

            // =========================================================
            // E. 【存入缓存】
            // =========================================================
            // 缓存 10 秒，覆盖客户端的重试窗口
            _cache.Set(payload.RequestId, result, TimeSpan.FromSeconds(10));

            // =========================================================
            // F. 【QoS 过滤】
            // =========================================================
            // 如果客户端说不需要回信，返回 null
            if (!payload.RequireAck)
            {
                return null;
            }

            return result;
        }

        #endregion
    }
}