using DeviceCommand.Base;
using Logger;
using Model.Models;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;

namespace UIShare.GlobalVariable
{
    /// <summary>
    /// 设备健康监控器：独立于监控采样的心跳重连机制。
    /// <para>
    /// 设计原则——与检测值零冲突：
    /// <list type="bullet">
    ///   <item>健康检查平时只读 <see cref="IBaseInterface.IsConnected"/>（纯本地属性，零网络开销，不碰通信锁）</item>
    ///   <item>仅在 IsConnected==false 时才获取 _commLock 执行重连，与监控采样天然串行化</item>
    ///   <item>ModbusTcp 的 ConnectAsync 是幂等的（已连接时直接返回），不会中断正在进行的监控</item>
    ///   <item>TCP 的 ConnectAsync 会重置连接，但监控的 catch 容忍单次失败，下次 tick 自动恢复</item>
    /// </list>
    /// </para>
    /// </summary>
    public class DeviceHealthMonitor : IDisposable
    {
        private readonly IDictionary<string, IBaseInterface> _deviceMap;
        private readonly SystemConfig _systemConfig;
        private readonly string _scopeName;

        /// <summary>健康检查定时器</summary>
        private Timer? _healthCheckTimer;

        /// <summary>每个设备的连续失败计数</summary>
        private readonly ConcurrentDictionary<string, int> _failureCounts = new();

        /// <summary>每个设备的重连尝试次数（用于计算退避阈值）</summary>
        private readonly ConcurrentDictionary<string, int> _reconnectAttempts = new();

        /// <summary>基础失败阈值（首次重连触发值）</summary>
        private const int BaseFailureThreshold = 3;

        /// <summary>退避上限（最大阈值）</summary>
        private const int MaxBackoffThreshold = 15;

        /// <summary>健康检查间隔（毫秒）</summary>
        private readonly int _checkIntervalMs;

        private bool _disposed;
        private readonly object _startStopLock = new();

        /// <summary>
        /// 创建健康监控器实例。
        /// </summary>
        /// <param name="deviceMap">当前作用域的设备字典</param>
        /// <param name="systemConfig">当前作用域的系统配置（用于更新 DeviceInfoVM.IsConnected）</param>
        /// <param name="scopeName">作用域名称（日志标识）</param>
        /// <param name="checkIntervalMs">健康检查间隔，默认 5000ms</param>
        public DeviceHealthMonitor(
            IDictionary<string, IBaseInterface> deviceMap,
            SystemConfig systemConfig,
            string scopeName,
            int checkIntervalMs = 5000)
        {
            _deviceMap = deviceMap;
            _systemConfig = systemConfig;
            _scopeName = scopeName;
            _checkIntervalMs = checkIntervalMs;
        }

        /// <summary>启动健康监控（幂等：多次调用只启动一次）</summary>
        public void Start()
        {
            lock (_startStopLock)
            {
                if (_disposed || _healthCheckTimer != null) return;
                _healthCheckTimer = new Timer(
                    OnHealthCheckTick,
                    null,
                    TimeSpan.FromSeconds(10),     // 首次检查延迟 10 秒，避免启动时设备尚未连接完成
                    TimeSpan.FromMilliseconds(_checkIntervalMs));
                LoggerHelper.Info($"[{_scopeName}] 设备健康监控已启动，检查间隔={_checkIntervalMs}ms，基础重连阈值={BaseFailureThreshold}次（指数退避上限={MaxBackoffThreshold}）");
            }
        }

        /// <summary>停止健康监控</summary>
        public void Stop()
        {
            lock (_startStopLock)
            {
                _healthCheckTimer?.Change(Timeout.Infinite, Timeout.Infinite);
                _healthCheckTimer?.Dispose();
                _healthCheckTimer = null;
                _failureCounts.Clear();
                _reconnectAttempts.Clear();
            }
        }

        /// <summary>
        /// 健康检查核心逻辑：遍历设备，检查连接状态，失败计数超阈值则重连。
        /// <para>TCP 设备额外进行主动探活（*IDN?），以检测死连接（对端崩溃但 TCP 未收到 FIN）。</para>
        /// </summary>
        private async void OnHealthCheckTick(object? state)
        {
            if (_disposed || _deviceMap.Count == 0) return;

            // 快照避免枚举期间字典被修改
            var snapshot = _deviceMap.ToArray();

            foreach (var kvp in snapshot)
            {
                if (_disposed) return;

                string deviceName = kvp.Key;
                var device = kvp.Value;

                try
                {
                    bool alive = device.IsConnected;

                    // TCP 设备主动探活：IsConnected 只反映上次操作状态，无法检测死连接
                    if (alive && device is Tcp tcpDevice)
                    {
                        alive = await ProbeTcpDeviceAsync(tcpDevice);
                    }

                    if (alive)
                    {
                        // 连接正常：清零失败计数与退避
                        _failureCounts.TryRemove(deviceName, out _);
                        _reconnectAttempts.TryRemove(deviceName, out _);
                        continue;
                    }

                    // 连接断开：累加失败计数
                    int failures = _failureCounts.AddOrUpdate(deviceName, 1, (_, count) => count + 1);

                    // 计算当前退避阈值：基础值 + 重连尝试次数 × 2，上限为 MaxBackoffThreshold
                    int attempts = _reconnectAttempts.GetOrAdd(deviceName, 0);
                    int currentThreshold = Math.Min(BaseFailureThreshold + attempts * 2, MaxBackoffThreshold);

                    if (failures < currentThreshold)
                    {
                        LoggerHelper.Warn(
                            $"[{_scopeName}] 设备 [{deviceName}] 连接断开，等待重连中 ({failures}/{currentThreshold})");
                        continue;
                    }

                    // 达到阈值：执行重连
                    await ReconnectDeviceAsync(deviceName, device);
                }
                catch (Exception ex)
                {
                    LoggerHelper.Error($"[{_scopeName}] 设备 [{deviceName}] 健康检查异常：{ex.Message}");
                }
            }
        }

        /// <summary>
        /// 对 TCP 设备执行轻量级主动探活（SCPI *IDN?），2 秒超时。
        /// <para>通过 WriteReadAsync 内部获取 _commLock，与监控采样天然串行化。</para>
        /// </summary>
        /// <returns>true: 探活成功（连接确实存活）; false: 探活失败（死连接）</returns>
        private async Task<bool> ProbeTcpDeviceAsync(Tcp tcpDevice)
        {
            try
            {
                using var probeCts = new CancellationTokenSource(TimeSpan.FromSeconds(2));
                string resp = await tcpDevice.WriteReadAsync("*IDN?\n", "\n", probeCts.Token);
                return !string.IsNullOrWhiteSpace(resp);
            }
            catch
            {
                return false;
            }
        }

        /// <summary>
        /// 重连单个设备。
        /// <para>
        /// 冲突避免机制：ConnectAsync 内部获取设备的 _commLock，
        /// 如果此时监控采样正在通信，重连会等待锁释放后再执行，
        /// 保证同一时刻只有一个操作在使用通信链路。
        /// </para>
        /// </summary>
        private async Task ReconnectDeviceAsync(string deviceName, IBaseInterface device)
        {
            try
            {
                int attempts = _reconnectAttempts.AddOrUpdate(deviceName, 1, (_, c) => c + 1);
                int nextThreshold = Math.Min(BaseFailureThreshold + attempts * 2, MaxBackoffThreshold);
                LoggerHelper.Info($"[{_scopeName}] 设备 [{deviceName}] 连续失败触发重连（第 {attempts} 次重连，下次阈值={nextThreshold}）...");

                using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
                bool ok = await device.ConnectAsync(cts.Token);

                // 同步更新 DeviceInfoVM 的 UI 状态
                UpdateDeviceInfoState(deviceName, ok);

                if (ok)
                {
                    _failureCounts.TryRemove(deviceName, out _);
                    _reconnectAttempts.TryRemove(deviceName, out _);
                    LoggerHelper.Info($"[{_scopeName}] 设备 [{deviceName}] 重连成功");
                }
                else
                {
                    LoggerHelper.Warn($"[{_scopeName}] 设备 [{deviceName}] 重连失败，将在下次检查时重试");
                }
            }
            catch (OperationCanceledException)
            {
                UpdateDeviceInfoState(deviceName, false);
                LoggerHelper.Warn($"[{_scopeName}] 设备 [{deviceName}] 重连超时（10s），将在下次检查时重试");
            }
            catch (Exception ex)
            {
                UpdateDeviceInfoState(deviceName, false);
                LoggerHelper.Error($"[{_scopeName}] 设备 [{deviceName}] 重连异常：{ex.Message}");
            }
        }

        /// <summary>
        /// 通过 UI 线程更新 SystemConfig.DeviceList 中对应设备的 IsConnected 状态（驱动 UI 刷新）。
        /// <para>Timer 回调运行在线程池线程上，必须切回 UI 线程才能触发 PropertyChanged。</para>
        /// </summary>
        private void UpdateDeviceInfoState(string deviceName, bool isConnected)
        {
            var info = _systemConfig?.DeviceList?
                .FirstOrDefault(d => d != null &&
                    string.Equals(d.DeviceName, deviceName, StringComparison.OrdinalIgnoreCase));
            if (info == null) return;

            var dispatcher = Application.Current?.Dispatcher;
            if (dispatcher == null || dispatcher.CheckAccess())
            {
                // 已在 UI 线程（或无 Dispatcher），直接赋值
                info.IsConnected = isConnected;
            }
            else
            {
                // 切回 UI 线程赋值，避免跨线程 PropertyChanged 异常
                dispatcher.BeginInvoke(() => info.IsConnected = isConnected);
            }
        }

        public void Dispose()
        {
            if (_disposed) return;
            _disposed = true;
            Stop();
        }
    }
}