using NetMQ;
using NetMQ.Sockets;
using System.Diagnostics; // 用于 Debug 输出

namespace SHH.CameraDashboard.Services;

public class StreamReceiverService : IDisposable
{
    // 单例模式
    public static StreamReceiverService Instance { get; } = new StreamReceiverService();

    public event Action<string, byte[]>? OnFrameReceived;

    private SubscriberSocket? _subSocket;
    private Task? _receiveTask;

    // 【修复1】不要在这里初始化，改为在 Start 中初始化
    private CancellationTokenSource? _cts;

    public int ListenPort { get; private set; }

    // 增加运行状态标记
    public bool IsRunning => _receiveTask != null && !_receiveTask.IsCompleted;

    private StreamReceiverService() { }

    public void Start(int port = 6000)
    {
        // 1. 防止重复启动
        if (IsRunning) return;

        ListenPort = port;

        // 【修复1】每次启动时创建新的 TokenSource
        _cts = new CancellationTokenSource();

        try
        {
            // 2. 初始化 Socket
            _subSocket = new SubscriberSocket();

            // 【优化】设置高水位限制 (HWM)
            // 如果 UI 处理不过来，积压超过 1000 帧直接丢弃，防止内存爆炸
            _subSocket.Options.ReceiveHighWatermark = 1000;

            string bindAddr = $"tcp://*:{ListenPort}";
            _subSocket.Bind(bindAddr);
            _subSocket.Subscribe("");

            Console.WriteLine($"[Dashboard] 视频流接收服务启动: {bindAddr}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"[Dashboard] 致命错误 - 端口绑定失败: {ex.Message}");

            // 清理资源
            _subSocket?.Dispose();
            _subSocket = null;

            // 【修复4】抛出异常让上层知道启动失败了
            throw new Exception($"端口 {port} 绑定失败，可能被占用。", ex);
        }

        // 3. 启动任务
        _receiveTask = Task.Run(ReceiveLoop, _cts.Token);
    }

    private void ReceiveLoop()
    {
        var token = _cts?.Token ?? CancellationToken.None;

        while (!token.IsCancellationRequested)
        {
            try
            {
                // 【修复2】线程安全检查
                if (_subSocket == null) break;

                // 接收 Topic
                if (!_subSocket.TryReceiveFrameString(TimeSpan.FromMilliseconds(500), out string cameraId))
                    continue;

                // 接收 Payload
                if (!_subSocket.TryReceiveFrameBytes(TimeSpan.FromMilliseconds(100), out byte[] jpgBytes))
                    continue;

                // 触发事件
                OnFrameReceived?.Invoke(cameraId, jpgBytes);
            }
            catch (ObjectDisposedException)
            {
                // 【修复2】这是正常的退出流程（Socket被Dispose了），优雅退出循环
                break;
            }
            catch (Exception ex)
            {
                // 记录日志，但不崩溃
                Debug.WriteLine($"[ReceiverLoop Error] {ex.Message}");
            }
        }
        Console.WriteLine("[Dashboard] 接收循环已停止");
    }

    /// <summary>
    /// 停止服务（支持停止后重新 Start）
    /// </summary>
    public void Stop()
    {
        // 1. 发出取消信号
        if (_cts != null && !_cts.IsCancellationRequested)
        {
            _cts.Cancel();
        }

        // 2. 销毁 Socket (这会触发 ReceiveLoop 中的 ObjectDisposedException 从而退出循环)
        if (_subSocket != null)
        {
            try { _subSocket.Dispose(); } catch { }
            _subSocket = null;
        }

        // 3. 清理 Token
        _cts?.Dispose();
        _cts = null;

        _receiveTask = null;
    }

    public void Dispose()
    {
        Stop();
    }
}