using System;
using System.IO;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace DeviceCommand.Base
{
    public class Tcp : ITcp
    {
        public string IPAddress { get; set; } = "127.0.0.1";
        public int Port { get; set; } = 502;
        public int SendTimeout { get; set; } = 3000;
        public int ReceiveTimeout { get; set; } = 3000;

        private TcpClient _tcpClient;
        public bool IsConnected => _tcpClient?.Connected ?? false;
        protected readonly SemaphoreSlim _commLock = new(1, 1);

        public Tcp()
        {
            _tcpClient = new TcpClient();
        }

        public void ConfigureDevice(string ipAddress, int port, int sendTimeout = 3000, int receiveTimeout = 3000)
        {
            IPAddress = ipAddress;
            Port = port;
            SendTimeout = sendTimeout;
            ReceiveTimeout = receiveTimeout;
        }

        public virtual async Task<bool> ConnectAsync(CancellationToken ct = default)
        {
            await _commLock.WaitAsync(ct);
            try
            {
                if (_tcpClient.Connected) return true;

                // 修复：释放并彻底清空旧的连接实例，否则复用引发异常
                _tcpClient.Close();
                _tcpClient.Dispose();

                _tcpClient = new TcpClient();
                await _tcpClient.ConnectAsync(IPAddress, Port, ct);
                return true;
            }
            finally
            {
                _commLock.Release();
            }
        }

        public virtual void Close()
        {
            if (_tcpClient.Connected) _tcpClient.Close();
        }

        private async Task LoglessSendAsync(byte[] buffer, CancellationToken ct)
        {
            if (!IsConnected) throw new InvalidOperationException("TCP未连接。");

            NetworkStream stream = _tcpClient.GetStream();
            using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
            if (SendTimeout > 0) cts.CancelAfter(SendTimeout);

            await stream.WriteAsync(buffer, 0, buffer.Length, cts.Token);
        }

        public async Task SendAsync(byte[] buffer, CancellationToken ct = default)
        {
            await _commLock.WaitAsync(ct);
            try
            {
                await LoglessSendAsync(buffer, ct);
            }
            finally
            {
                _commLock.Release();
            }
        }

        public async Task SendAsync(string str, CancellationToken ct = default)
        {
            await SendAsync(Encoding.UTF8.GetBytes(str), ct);
        }

        public async Task<byte[]> ReadAsync(int length, CancellationToken ct = default)
        {
            await _commLock.WaitAsync(ct);
            try
            {
                if (!IsConnected) throw new InvalidOperationException("TCP未连接。");

                NetworkStream stream = _tcpClient.GetStream();
                byte[] buffer = new byte[length];
                int offset = 0;

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

                while (offset < length)
                {
                    int read = await stream.ReadAsync(buffer, offset, length - offset, cts.Token);
                    if (read == 0) break;
                    offset += read;
                }

                return offset == 0 ? Array.Empty<byte>() : buffer[..offset];
            }
            finally
            {
                _commLock.Release();
            }
        }

        private async Task<string> LoglessReadAsync(string delimiter, CancellationToken ct)
        {
            if (!IsConnected) throw new InvalidOperationException("TCP未连接。");

            delimiter ??= "\n";
            var sb = new StringBuilder();
            byte[] buffer = new byte[1024];
            NetworkStream stream = _tcpClient.GetStream();

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

            while (!cts.Token.IsCancellationRequested)
            {
                int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length, cts.Token);
                if (bytesRead == 0) throw new IOException("远程主机已关闭连接");

                sb.Append(Encoding.UTF8.GetString(buffer, 0, bytesRead));

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

            throw new TimeoutException("读取数据超时");
        }

        public async Task<string> ReadAsync(string delimiter = "\n", CancellationToken ct = default)
        {
            await _commLock.WaitAsync(ct);
            try
            {
                return await LoglessReadAsync(delimiter, ct);
            }
            finally
            {
                _commLock.Release();
            }
        }

        // 核心优化：确保发送与读取在同一组锁生命周期内
        public async Task<string> WriteReadAsync(string command, string delimiter = "\n", CancellationToken ct = default)
        {
            await _commLock.WaitAsync(ct);
            try
            {
                await LoglessSendAsync(Encoding.UTF8.GetBytes(command), ct);
                return await LoglessReadAsync(delimiter, ct);
            }
            finally
            {
                _commLock.Release();
            }
        }

        public void Dispose()
        {
            _tcpClient?.Dispose();
            _commLock?.Dispose();
        }
    }
}