using System;
using System.Net;
using System.Net.Sockets;
using System.ServiceProcess;
using System.Threading;
using System.Threading.Tasks;

namespace MyDelayService
{
    public partial class DelayTaskService : ServiceBase
    {
        private Task _udpListenerTask;
        private CancellationTokenSource _cts;

        // UDP 监听端口（可自己改）
        private readonly int _udpPort = 8888;
        private UdpClient _udpServer;

        public DelayTaskService()
        {
            InitializeComponent();
            ServiceName = "MyUdpEchoService";
        }

        protected override void OnStart(string[] args)
        {
            WriteLog("===== UDP 回声服务已启动 =====");

            _cts = new CancellationTokenSource();
            _udpListenerTask = RunUdpEchoServerAsync(_cts.Token);
        }

        protected override void OnStop()
        {
            WriteLog("===== 服务正在停止 =====");
            _cts?.Cancel();
            _udpServer?.Close();
            _udpListenerTask?.Wait();
            WriteLog("===== 服务已停止 =====");
        }

        /// <summary>
        /// UDP 回声服务端：收到什么就原样发回什么
        /// </summary>
        private async Task RunUdpEchoServerAsync(CancellationToken token)
        {
            try
            {
                _udpServer = new UdpClient(_udpPort);
                WriteLog($"UDP 监听端口：{_udpPort}");

                while (!token.IsCancellationRequested)
                {
                    try
                    {
                        // 等待客户端消息
                        var result = await _udpServer.ReceiveAsync();
                        byte[] clientData = result.Buffer;
                        IPEndPoint clientEp = result.RemoteEndPoint;

                        string msg = System.Text.Encoding.UTF8.GetString(clientData);
                        WriteLog($"【接收】{clientEp.Address}：{msg}");

                        // ======================
                        // 关键：原样返回给客户端
                        // ======================
                        await _udpServer.SendAsync(clientData, clientData.Length, clientEp);
                        WriteLog($"【返回】{clientEp.Address}：{msg}");
                    }
                    catch (Exception ex)
                    {
                        if (!token.IsCancellationRequested)
                            WriteLog($"UDP 异常：{ex.Message}");
                    }
                }
            }
            catch (Exception ex)
            {
                WriteLog($"UDP 服务失败：{ex.Message}");
            }
        }

        /// <summary>
        /// 写日志
        /// </summary>
        public void WriteLog(string msg)
        {
            try
            {
                XLog.XTrace.WriteLine(msg);
            }
            catch { }
        }
    }
}