using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace JY.Inspection
{
    /// <summary>
    /// 设置电脑时间
    /// </summary>
    public class DateTimeSynchronization
    {
        [StructLayout(LayoutKind.Sequential)]
        private struct Systemtime
        {
            public short year;
            public short month;
            public short dayOfWeek;
            public short day;
            public short hour;
            public short minute;
            public short second;
            public short milliseconds;
        }

        [DllImport("kernel32.dll")]
        private static extern bool SetLocalTime(ref Systemtime time);

        private static uint swapEndian(ulong x)
        {
            return (uint)(((x & 0x000000ff) << 24) +
            ((x & 0x0000ff00) << 8) +
            ((x & 0x00ff0000) >> 8) +
            ((x & 0xff000000) >> 24));
        }

        /// <summary>
        /// 手动设置系统时间
        /// </summary>
        /// <param name="dt">需要设置的时间</param>
        /// <returns>返回系统时间设置状态，true为成功，false为失败</returns>
        public static bool SetLocalDateTime(DateTime dt)
        {
            Systemtime st;
            st.year = (short)dt.Year;
            st.month = (short)dt.Month;
            st.dayOfWeek = (short)dt.DayOfWeek;
            st.day = (short)dt.Day;
            st.hour = (short)dt.Hour;
            st.minute = (short)dt.Minute;
            st.second = (short)dt.Second;
            st.milliseconds = (short)dt.Millisecond;
            bool rt = SetLocalTime(ref st);
            return rt;
        }


        private static IPAddress iPAddress = null;
        /// <summary>
        /// 从NTP获取时间更新本地时间
        /// </summary>
        /// <param name="host"></param>
        /// <param name="syncDateTime"></param>
        /// <param name="message"></param>
        /// <returns></returns>
        public static bool Synchronization(string host, out DateTime syncDateTime, out string message)
        {
            syncDateTime = DateTime.Now;
            try
            {
                message = "";
                if (iPAddress == null)
                {
                    var iphostinfo = Dns.GetHostEntry(host);
                    var ntpServer = iphostinfo.AddressList[0];
                    iPAddress = ntpServer;
                }
                DateTime dtStart = DateTime.Now;
                //NTP消息大小摘要是16字节 (RFC 2030)
                byte[] ntpData = new byte[48];
                //设置跳跃指示器、版本号和模式值
                // LI = 0 (no warning), VN = 3 (IPv4 only), Mode = 3 (Client Mode)
                ntpData[0] = 0x1B;
                IPAddress ip = iPAddress;
                // NTP服务给UDP分配的端口号是123
                IPEndPoint ipEndPoint = new IPEndPoint(ip, 123);
                // 使用UTP进行通讯
                Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
                socket.Connect(ipEndPoint);
                socket.ReceiveTimeout = 3000;
                socket.Send(ntpData);
                socket.Receive(ntpData);
                socket?.Close();
                socket?.Dispose();
                DateTime dtEnd = DateTime.Now;
                //传输时间戳字段偏移量，以64位时间戳格式，应答离开客户端服务器的时间
                const byte serverReplyTime = 40;
                // 获得秒的部分
                ulong intPart = BitConverter.ToUInt32(ntpData, serverReplyTime);
                //获取秒的部分
                ulong fractPart = BitConverter.ToUInt32(ntpData, serverReplyTime + 4);
                //由big-endian 到 little-endian的转换
                intPart = swapEndian(intPart);
                fractPart = swapEndian(fractPart);
                ulong milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000UL);
                // UTC时间
                DateTime webTime = (new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc)).AddMilliseconds(milliseconds);
                //本地时间
                DateTime dt = webTime.ToLocalTime();
                bool isSuccess = SetLocalDateTime(dt);
                syncDateTime = dt;

            }
            catch (Exception ex)
            {
                message = ex.Message;
                return false;
            }
            return true;

        }
    }
}