using Common.Attributes;
using System;
using System.IO.Ports;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace DeviceCommand.Flexible
{
    /// <summary>
    /// 灵活型串口通信类（免实例化，每次调用临时创建串口连接）。
    /// 支持只发送指令、发送并读取应答两种最常用操作，
    /// 内部使用通信锁保证同一时刻只有一个串口事务在执行，
    /// 适用于偶发性、无需保持长连接的串口设备通信场景（如示波器、电源的 SCPI 指令）。
    /// </summary>
    [ACPCommand]
    public static class FSerialPort
    {
        // 通信锁：保证同一时刻只有一个串口事务在执行
        private static readonly SemaphoreSlim _commLock = new(1, 1);

        /// <summary>
        /// 创建串口实例并配置 UTF8 编码与超时参数。
        /// </summary>
        private static SerialPort CreatePort(string portName, int baudRate, Parity parity, int dataBits, StopBits stopBits, int sendTimeout,int receiveTimeout)
        {
            return new SerialPort(portName, baudRate, parity, dataBits, stopBits)
            {
                Encoding = Encoding.UTF8,
                WriteTimeout = sendTimeout > 0 ? sendTimeout : SerialPort.InfiniteTimeout,
                ReadTimeout = receiveTimeout > 0 ? receiveTimeout : SerialPort.InfiniteTimeout
            };
        }

        #region 最常用：只发送字符串

        /// <summary>
        /// 向串口发送一条字符串指令（只发送，不等待应答）。
        /// </summary>
        /// <param name="portName">串口名称，如 "COM1"</param>
        /// <param name="baudRate">波特率，如 9600、115200</param>
        /// <param name="parity">校验位</param>
        /// <param name="dataBits">数据位，常用 8</param>
        /// <param name="stopBits">停止位</param>
        /// <param name="sendTimeout">发送超时时间（毫秒）</param>
        /// <param name="receiveTimeout">接收超时时间（毫秒）</param>
        /// <param name="command">要发送的指令字符串</param>
        /// <param name="ct">异步取消令牌</param>
        public static async Task 发送指令(string portName,int baudRate,Parity parity,int dataBits,StopBits stopBits,int sendTimeout,int receiveTimeout,string command,CancellationToken ct = default)
        {
            await _commLock.WaitAsync(ct);
            try
            {
                using var port = CreatePort(
                    portName, baudRate, parity, dataBits, stopBits, sendTimeout, receiveTimeout);

                port.Open();

                using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
                if (sendTimeout > 0)
                    cts.CancelAfter(sendTimeout);

                var bytes = port.Encoding.GetBytes(command);
                await port.BaseStream.WriteAsync(bytes, 0, bytes.Length, cts.Token);
                await port.BaseStream.FlushAsync(cts.Token);
            }
            finally
            {
                _commLock.Release();
            }
        }

        #endregion

        #region 最常用：发送字符串并读取字符串

        /// <summary>
        /// 向串口发送一条字符串指令并读取应答，读取到结束符为止（应答不含结束符）。
        /// </summary>
        /// <param name="portName">串口名称，如 "COM1"</param>
        /// <param name="baudRate">波特率，如 9600、115200</param>
        /// <param name="parity">校验位</param>
        /// <param name="dataBits">数据位，常用 8</param>
        /// <param name="stopBits">停止位</param>
        /// <param name="sendTimeout">发送超时时间（毫秒）</param>
        /// <param name="receiveTimeout">接收超时时间（毫秒），超时未收到结束符抛出超时异常</param>
        /// <param name="command">要发送的指令字符串</param>
        /// <param name="delimiter">应答结束符，默认换行符 "\n"</param>
        /// <param name="ct">异步取消令牌</param>
        /// <returns>去除结束符并去除首尾空白后的应答字符串</returns>
        public static async Task<string> 发送并读取应答(string portName,int baudRate, Parity parity, int dataBits, StopBits stopBits,int sendTimeout, int receiveTimeout,string command,string delimiter = "\n", CancellationToken ct = default)
        {
            await _commLock.WaitAsync(ct);
            try
            {
                using var port = CreatePort(
                    portName, baudRate, parity, dataBits, stopBits, sendTimeout, receiveTimeout);

                port.Open();

                // Send
                var sendBytes = port.Encoding.GetBytes(command);
                await port.BaseStream.WriteAsync(sendBytes, 0, sendBytes.Length, ct);
                await port.BaseStream.FlushAsync(ct);

                // Read
                delimiter ??= "\n";
                var sb = new StringBuilder();
                byte[] buffer = new byte[256];

                using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
                if (receiveTimeout > 0)
                    cts.CancelAfter(receiveTimeout);

                while (!cts.Token.IsCancellationRequested)
                {
                    int read = await port.BaseStream.ReadAsync(
                        buffer, 0, buffer.Length, cts.Token);

                    if (read == 0)
                        break;

                    sb.Append(port.Encoding.GetString(buffer, 0, read));

                    int index = sb.ToString().IndexOf(delimiter, StringComparison.Ordinal);
                    if (index >= 0)
                        return sb.ToString(0, index).Trim();
                }

                throw new TimeoutException("串口读取超时");
            }
            finally
            {
                _commLock.Release();
            }
        }

        #endregion
    }
}