using Microsoft.Extensions.Options;
using System.Collections.Concurrent;

namespace RIZO.Admin.WebApi.PLC
{
    public class PlcHostedService : IHostedService, IDisposable
    {
        private readonly ILogger<PlcHostedService> _logger;
        private readonly PlcService _plcService;
        private readonly List<PlcConfig> _plcConfigs;
        private Timer _timer;
        private bool _isRunning;
        private readonly SemaphoreSlim _semaphore;
        private readonly object _timerLock = new();
        // 连接状态缓存：减少短时间内重复连接测试
        private readonly ConcurrentDictionary<string, PlcConnectionState> _connectionStateCache;

        // 可配置参数（建议放到配置文件中）
        private readonly int _parallelDegree = 10;          // 并行度（20+PLC建议8-12）
        private readonly int _pollingIntervalSeconds = 5;   // 轮询间隔
        private readonly int _connectTimeoutSeconds = 3;    // 单个PLC连接超时时间
        private readonly int _stateCacheExpireSeconds = 10; // 连接状态缓存有效期

        /// <summary>
        /// PLC 连接状态缓存对象
        /// </summary>
        private class PlcConnectionState
        {
            public bool IsConnected { get; set; }
            public DateTime LastCheckTime { get; set; }
        }

        public PlcHostedService(
            ILogger<PlcHostedService> logger,
            PlcService plcService,
            IOptions<List<PlcConfig>> plcConfigs)
        {
            _logger = logger;
            _plcService = plcService;
            _plcConfigs = plcConfigs.Value ?? new List<PlcConfig>();

            // 初始化并行控制信号量
            _semaphore = new SemaphoreSlim(_parallelDegree, _parallelDegree);
            // 初始化连接状态缓存
            _connectionStateCache = new ConcurrentDictionary<string, PlcConnectionState>();
            foreach (var config in _plcConfigs)
            {
                _connectionStateCache.TryAdd(config.Ip, new PlcConnectionState
                {
                    IsConnected = false,
                    LastCheckTime = DateTime.MinValue
                });
            }
        }

        public async Task StartAsync(CancellationToken cancellationToken)
        {
            _logger.LogInformation("PLC后台监听服务启动中...");

            if (!_plcConfigs.Any())
            {
                _logger.LogWarning("未配置PLC参数，跳过PLC自动连接");
                return;
            }

            _isRunning = true;

            // 1. 启动时并行测试所有PLC连接
            await BatchConnectPlcAsync(cancellationToken);

            // 2. 启动安全定时器（防重叠执行）
            _timer = new Timer(
                TimerCallback,
                null,
                TimeSpan.Zero,
                TimeSpan.FromSeconds(_pollingIntervalSeconds));

            _logger.LogInformation($"PLC服务启动完成 | 并行度：{_parallelDegree} | 轮询间隔：{_pollingIntervalSeconds}s | 设备总数：{_plcConfigs.Count}");
        }

        /// <summary>
        /// 定时器安全回调（防重叠执行）
        /// </summary>
        private async void TimerCallback(object state)
        {
            if (!_isRunning || !Monitor.TryEnter(_timerLock))
            {
                _logger.LogDebug("前一轮PLC轮询未完成，跳过本次执行");
                return;
            }

            try
            {
                await PollPlcDataAsync();
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "PLC轮询回调异常");
            }
            finally
            {
                Monitor.Exit(_timerLock);
            }
        }

        /// <summary>
        /// 启动时批量并行连接PLC
        /// </summary>
        private async Task BatchConnectPlcAsync(CancellationToken cancellationToken)
        {
            _logger.LogInformation("开始批量连接所有PLC...");

            var tasks = _plcConfigs.Select(async config =>
            {
                await _semaphore.WaitAsync(cancellationToken);
                try
                {
                    // 带超时的连接测试
                    using var timeoutToken = new CancellationTokenSource(TimeSpan.FromSeconds(_connectTimeoutSeconds));
                    var result = await _plcService.TestSinglePlcAsync(config, timeoutToken.Token);

                    // 更新缓存状态
                    var state = _connectionStateCache[config.Ip];
                    state.IsConnected = result.ConnectSuccess;
                    state.LastCheckTime = DateTime.Now;

                    if (result.ConnectSuccess)
                        _logger.LogInformation($"[{config.PlcName}] 连接成功 | IP：{config.Ip}");
                    else
                        _logger.LogWarning($"[{config.PlcName}] 连接失败 | IP：{config.Ip} | 原因：{result.ConnectMessage}");
                }
                catch (OperationCanceledException)
                {
                    _logger.LogWarning($"[{config.PlcName}] 连接超时 | IP：{config.Ip} | 超时时间：{_connectTimeoutSeconds}s");
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, $"[{config.PlcName}] 连接异常 | IP：{config.Ip}");
                }
                finally
                {
                    _semaphore.Release();
                }
            });

            await Task.WhenAll(tasks);
        }

        /// <summary>
        /// 并行轮询PLC数据（读取前先验证连接状态）
        /// </summary>
        private async Task PollPlcDataAsync()
        {
            _logger.LogInformation("开始轮询PLC数据...");

            var tasks = _plcConfigs.Select(async config =>
            {
                await _semaphore.WaitAsync();
                try
                {
                    // 1. 先从缓存获取连接状态，未过期则直接使用
                    var state = _connectionStateCache[config.Ip];
                    var needRecheck = (DateTime.Now - state.LastCheckTime).TotalSeconds > _stateCacheExpireSeconds;

                    bool isConnected = state.IsConnected;
                    if (needRecheck)
                    {
                        // 缓存过期，重新测试连接（带超时）
                        using var timeoutToken = new CancellationTokenSource(TimeSpan.FromSeconds(_connectTimeoutSeconds));
                        var connectResult = await _plcService.TestSinglePlcAsync(config, timeoutToken.Token);
                        isConnected = connectResult.ConnectSuccess;
                        // 更新缓存
                        state.IsConnected = isConnected;
                        state.LastCheckTime = DateTime.Now;
                    }

                    // 2. 连接失败直接跳过
                    if (!isConnected)
                    {
                        _logger.LogDebug($"[{config.PlcName}] 连接断开，跳过数据读取 | IP：{config.Ip}");
                        return;
                    }

                    // 3. 连接正常，读取数据
                    var (success, value, message) = await _plcService.ReadPlcDataAsync(
                        config.Ip, config.Rack, config.Slot, config.TestReadAddress);

                    if (success)
                    {
                        _logger.LogInformation($"[{config.PlcName}] 数据读取成功 | 地址：{config.TestReadAddress} | 值：{value}");
                        // 数据处理逻辑：入库/推前端/存Redis
                        // await ProcessPlcDataAsync(config, value);
                    }
                    else
                    {
                        _logger.LogWarning($"[{config.PlcName}] 数据读取失败 | 原因：{message}");
                        // 读取失败，标记连接状态为断开
                        state.IsConnected = false;
                    }
                }
                catch (OperationCanceledException)
                {
                    _logger.LogWarning($"[{config.PlcName}] 操作超时 | IP：{config.Ip}");
                    _connectionStateCache[config.Ip].IsConnected = false;
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, $"[{config.PlcName}] 轮询异常 | IP：{config.Ip}");
                    _connectionStateCache[config.Ip].IsConnected = false;
                }
                finally
                {
                    _semaphore.Release();
                }
            });

            await Task.WhenAll(tasks);
            _logger.LogInformation($"PLC数据轮询完成 | 本次轮询设备数：{_plcConfigs.Count}");
        }

        public Task StopAsync(CancellationToken cancellationToken)
        {
            _logger.LogInformation("PLC后台监听服务停止中...");
            _isRunning = false;
            _timer?.Change(Timeout.Infinite, 0);
            return Task.CompletedTask;
        }

        public void Dispose()
        {
            _timer?.Dispose();
            _semaphore?.Dispose();
            _logger.LogInformation("PLC后台监听服务已释放资源");
        }
    }
}