using System.Diagnostics;
using System.IO;
using System.IO.Ports;
using System.Text;
using AxiOmron.PcbCheck.Models;
using AxiOmron.PcbCheck.Options;
using AxiOmron.PcbCheck.Services.Interfaces;
using AxiOmron.PcbCheck.Utils;

namespace AxiOmron.PcbCheck.Services.Implementations;

/// <summary>
/// 提供串口扫码枪的触发与读取能力。
/// </summary>
public sealed class SerialScannerService : IScannerService, IDisposable
{
    private readonly ScannerOptions _options;
    private readonly IAppLogger<SerialScannerService> _logger;
    private readonly SemaphoreSlim _ioLock = new(1, 1);
    private SerialPort? _serialPort;
    private bool _disposed;

    /// <summary>
    /// 初始化扫码枪服务。
    /// </summary>
    /// <param name="config">应用根配置。</param>
    /// <param name="logger">日志记录器。</param>
    public SerialScannerService(AppConfig config, IAppLogger<SerialScannerService> logger)
    {
        ArgumentNullException.ThrowIfNull(config);
        _options = config.Scanner;
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <summary>
    /// 触发一次扫码。
    /// </summary>
    /// <param name="cancellationToken">取消令牌。</param>
    /// <returns>扫码结果。</returns>
    public async Task<ScanOperationResult> TriggerScanAsync(CancellationToken cancellationToken)
    {
        var lockTaken = false;
        try
        {
            await _ioLock.WaitAsync(cancellationToken).ConfigureAwait(false);
            lockTaken = true;
            return await TriggerScanInternalAsync(cancellationToken).ConfigureAwait(false);
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "扫码操作失败");
            return new ScanOperationResult
            {
                IsSuccess = false,
                IsSystemError = ex is not OperationCanceledException,
                DeviceConnected = false,
                ErrorMessage = ex.Message
            };
        }
        finally
        {
            if (lockTaken)
            {
                _ioLock.Release();
            }
        }
    }

    /// <summary>
    /// 测试扫码枪连接。
    /// </summary>
    /// <param name="cancellationToken">取消令牌。</param>
    /// <returns>连接正常返回 <see langword="true"/>；否则返回 <see langword="false"/>。</returns>
    public async Task<bool> TestConnectionAsync(CancellationToken cancellationToken)
    {
        var lockTaken = false;
        try
        {
            await _ioLock.WaitAsync(cancellationToken).ConfigureAwait(false);
            lockTaken = true;
            cancellationToken.ThrowIfCancellationRequested();
            EnsurePortOpen();
            return _serialPort is { IsOpen: true };
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "扫码枪连接测试失败");
            ClosePortUnsafe();
            return false;
        }
        finally
        {
            if (lockTaken)
            {
                _ioLock.Release();
            }
        }
    }

    /// <summary>
    /// 主动断开并重建扫码枪连接。
    /// </summary>
    /// <param name="cancellationToken">取消令牌。</param>
    /// <returns>表示重连完成的任务。</returns>
    public async Task ForceReconnectAsync(CancellationToken cancellationToken)
    {
        var lockTaken = false;
        try
        {
            await _ioLock.WaitAsync(cancellationToken).ConfigureAwait(false);
            lockTaken = true;
            cancellationToken.ThrowIfCancellationRequested();
            ClosePortUnsafe();
            EnsurePortOpen();
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "扫码枪强制重连失败");
            ClosePortUnsafe();
        }
        finally
        {
            if (lockTaken)
            {
                _ioLock.Release();
            }
        }
    }

    /// <summary>
    /// 释放扫码枪串口资源。
    /// </summary>
    public void Dispose()
    {
        if (_disposed)
        {
            return;
        }

        _disposed = true;
        ClosePortUnsafe();
        _ioLock.Dispose();
    }

    /// <summary>
    /// 在异步上下文中执行一次扫码流程。
    /// </summary>
    /// <param name="cancellationToken">取消令牌。</param>
    /// <returns>扫码结果。</returns>
    private async Task<ScanOperationResult> TriggerScanInternalAsync(CancellationToken cancellationToken)
    {
        var stopwatch = Stopwatch.StartNew();
        try
        {
            EnsurePortOpen();
            var port = _serialPort ?? throw new InvalidOperationException("扫码枪串口尚未初始化。");
            port.DiscardInBuffer();
            port.DiscardOutBuffer();
            port.Write(StringEscapeHelper.Unescape(_options.TriggerCommand));

            var rawMessage = await ReadUntilTerminatorAsync(
                port,
                StringEscapeHelper.Unescape(_options.ResponseTerminator),
                _options.ReadTimeoutMs,
                cancellationToken).ConfigureAwait(false);
            var barcode = BarcodeCleaner.Clean(rawMessage);
            if (string.IsNullOrEmpty(barcode))
            {
                return new ScanOperationResult
                {
                    IsSuccess = false,
                    DeviceConnected = true,
                    RawMessage = rawMessage,
                    ErrorMessage = "扫码返回空字符串或仅包含控制字符。",
                    DurationMs = stopwatch.ElapsedMilliseconds
                };
            }

            return new ScanOperationResult
            {
                IsSuccess = true,
                DeviceConnected = true,
                Barcode = barcode,
                RawMessage = rawMessage,
                DurationMs = stopwatch.ElapsedMilliseconds
            };
        }
        catch (TimeoutException ex)
        {
            _logger.LogWarning(ex, "扫码等待超时");
            return new ScanOperationResult
            {
                IsSuccess = false,
                DeviceConnected = true,
                ErrorMessage = "扫码超时。",
                DurationMs = stopwatch.ElapsedMilliseconds
            };
        }
        catch (OperationCanceledException)
        {
            throw;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "扫码枪执行失败");
            ClosePortUnsafe();
            return new ScanOperationResult
            {
                IsSuccess = false,
                IsSystemError = true,
                DeviceConnected = false,
                ErrorMessage = ex.Message,
                DurationMs = stopwatch.ElapsedMilliseconds
            };
        }
    }

    /// <summary>
    /// 确保串口已打开并按当前配置初始化。
    /// </summary>
    private void EnsurePortOpen()
    {
        if (_serialPort is { IsOpen: true })
        {
            return;
        }

        ClosePortUnsafe();

        var availablePorts = SerialPort.GetPortNames();
        if (!availablePorts.Contains(_options.PortName, StringComparer.OrdinalIgnoreCase))
        {
            _logger.LogWarning("本地不存在串口 {PortName}，可用串口: {AvailablePorts}", false, _options.PortName, string.Join(", ", availablePorts));
            throw new IOException($"串口 {_options.PortName} 不存在。可用串口: {string.Join(", ", availablePorts)}");
        }

        var parity = Enum.Parse<Parity>(_options.Parity, true);
        var stopBits = Enum.Parse<StopBits>(_options.StopBits, true);
        var serialPort = new SerialPort(_options.PortName, _options.BaudRate, parity, _options.DataBits, stopBits)
        {
            ReadTimeout = 200,
            WriteTimeout = 1000,
            Encoding = Encoding.ASCII,
            DtrEnable = true,
            RtsEnable = true,
            NewLine = StringEscapeHelper.Unescape(_options.ResponseTerminator)
        };

        try
        {
            serialPort.Open();
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "打开串口 {PortName} 失败", false, _options.PortName);
            serialPort.Dispose();
            throw;
        }

        _serialPort = serialPort;
        _logger.LogInformation("已连接扫码枪串口 {PortName}", false, _options.PortName);
    }

    /// <summary>
    /// 从串口读取直到遇到终止符或超时。
    /// </summary>
    /// <param name="port">串口实例。</param>
    /// <param name="terminator">终止符。</param>
    /// <param name="timeoutMs">总超时时间，单位为毫秒。</param>
    /// <param name="cancellationToken">取消令牌。</param>
    /// <returns>读取到的原始字符串。</returns>
    private static async Task<string> ReadUntilTerminatorAsync(SerialPort port, string terminator, int timeoutMs, CancellationToken cancellationToken)
    {
        var stopwatch = Stopwatch.StartNew();
        var buffer = new StringBuilder();

        while (stopwatch.ElapsedMilliseconds < timeoutMs)
        {
            cancellationToken.ThrowIfCancellationRequested();
            var fragment = port.ReadExisting();
            if (!string.IsNullOrEmpty(fragment))
            {
                buffer.Append(fragment);
                if (string.IsNullOrEmpty(terminator) || buffer.ToString().Contains(terminator, StringComparison.Ordinal))
                {
                    return buffer.ToString();
                }
            }

            await Task.Delay(20, cancellationToken).ConfigureAwait(false);
        }

        throw new TimeoutException("扫码枪在规定时间内未返回完整报文。");
    }

    /// <summary>
    /// 关闭当前串口并释放资源。
    /// </summary>
    private void ClosePortUnsafe()
    {
        try
        {
            if (_serialPort?.IsOpen == true)
            {
                _serialPort.Close();
            }
        }
        catch
        {
            // 忽略关闭异常。
        }
        finally
        {
            _serialPort?.Dispose();
            _serialPort = null;
        }
    }
}