using System;
using System.Diagnostics;
using System.IO.Ports;
using System.Threading;

namespace AutoFocusTool.Serial
{
    /// <summary>
    /// 单舱室串口控制器（马达 + LED）。自包含，无外部实体依赖。
    /// 采用同步请求-响应：写命令帧 → 按该命令固定回复长度阻塞读 → 校验。
    /// 比原工程的事件+环形缓冲简单，适合调试台单线程操作。
    /// 串口参数固定：9600 8N1，读写超时 3000ms。
    /// </summary>
    public class SerialMotor : IDisposable
    {
        private readonly SerialPort _port;
        private readonly object _ioLock = new object();

        /// <summary>日志回调（发送/接收/错误）</summary>
        public Action<string> Log;

        public string PortName { get; }
        public bool IsOpen => _port != null && _port.IsOpen;

        public SerialMotor(string portName)
        {
            PortName = portName;
            _port = new SerialPort
            {
                PortName = portName,
                BaudRate = 9600,
                DataBits = 8,
                StopBits = StopBits.One,
                Parity = Parity.None,
                ReadTimeout = 3000,
                WriteTimeout = 3000,
            };
        }

        public bool Open()
        {
            try
            {
                if (!_port.IsOpen) _port.Open();
                _port.DiscardInBuffer();
                _port.DiscardOutBuffer();
                return true;
            }
            catch (Exception ex)
            {
                Log?.Invoke($"[{PortName}] 打开串口失败: {ex.Message}");
                return false;
            }
        }

        public void Close()
        {
            try { if (_port.IsOpen) _port.Close(); } catch { }
        }

        /// <summary>
        /// 发送命令帧并读取固定长度回复。返回回复字节（失败返回 null）。
        /// </summary>
        /// <param name="frame">完整命令帧（含校验）</param>
        /// <param name="extraWaitMs">读到回复后额外等待（电机到位延时）</param>
        public byte[] Send(byte[] frame, int extraWaitMs = 0)
        {
            if (!IsOpen && !Open()) return null;

            int replyLen = Protocol.ReplyLength(frame[1]);
            lock (_ioLock)
            {
                try
                {
                    _port.DiscardInBuffer();
                    _port.Write(frame, 0, frame.Length);
                    Log?.Invoke($"[{PortName}] 发送: {ToHex(frame)}");

                    byte[] reply = ReadFixed(replyLen, 3000);
                    if (reply == null)
                    {
                        Log?.Invoke($"[{PortName}] 接收超时（期望{replyLen}字节）");
                        return null;
                    }
                    Log?.Invoke($"[{PortName}] 接收: {ToHex(reply)}{(Protocol.CheckChecksum(reply) ? "" : " [校验失败]")}");

                    // 回复 [n-2] 为下位机结果位，非0视为失败（返回null表示操作失败）
                    if (replyLen >= 2 && reply[replyLen - 2] != 0)
                    {
                        Log?.Invoke($"[{PortName}] 下位机结果位非0（操作失败）");
                        return null;
                    }

                    if (extraWaitMs > 0) Thread.Sleep(extraWaitMs);
                    return reply;
                }
                catch (Exception ex)
                {
                    Log?.Invoke($"[{PortName}] 收发异常: {ex.Message}");
                    return null;
                }
            }
        }

        /// <summary>阻塞读取指定字节数，超时返回 null。</summary>
        private byte[] ReadFixed(int count, int timeoutMs)
        {
            byte[] buf = new byte[count];
            int got = 0;
            var sw = Stopwatch.StartNew();
            while (got < count)
            {
                if (sw.ElapsedMilliseconds > timeoutMs) return null;
                try
                {
                    int n = _port.Read(buf, got, count - got);
                    got += n;
                }
                catch (TimeoutException)
                {
                    if (sw.ElapsedMilliseconds > timeoutMs) return null;
                }
            }
            return buf;
        }

        private static string ToHex(byte[] b)
        {
            if (b == null) return "(null)";
            var sb = new System.Text.StringBuilder(b.Length * 3);
            foreach (var x in b) sb.Append(x.ToString("X2")).Append(' ');
            return sb.ToString().TrimEnd();
        }

        public void Dispose()
        {
            Close();
            _port?.Dispose();
        }
    }
}