using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;

namespace Housing.Services;

public sealed class Ni6501StartSignalWatcher
{
    private readonly StartSignalSettings _settings;

    public Ni6501StartSignalWatcher(StartSignalSettings settings)
    {
        _settings = settings;
    }

    public async Task WaitForStartAsync(CancellationToken cancellationToken = default)
    {
        if (!_settings.Enabled)
        {
            return;
        }

        try
        {
            await Task.Run(() => WaitForStart(cancellationToken), cancellationToken);
        }
        catch (DllNotFoundException ex)
        {
            throw new InvalidOperationException("NI-DAQmx 드라이버(nicaiu.dll)를 찾을 수 없습니다. NI-DAQmx Runtime 설치와 NI-6501 인식 상태를 확인하세요.", ex);
        }
        catch (EntryPointNotFoundException ex)
        {
            throw new InvalidOperationException("NI-DAQmx DLL에서 필요한 함수가 보이지 않습니다. NI-DAQmx Runtime 버전을 확인하세요.", ex);
        }
        catch (BadImageFormatException ex)
        {
            throw new InvalidOperationException("NI-DAQmx DLL 비트 수가 현재 프로그램과 맞지 않습니다. x64/x86 Runtime과 실행 설정을 확인하세요.", ex);
        }
    }

    private void WaitForStart(CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(_settings.PhysicalChannel))
        {
            throw new InvalidOperationException("Hardware.ini [StartSignal] PhysicalChannel 값을 설정하세요.");
        }

        using var input = new DaqmxDigitalInput(_settings.PhysicalChannel);
        var stopwatch = Stopwatch.StartNew();

        if (_settings.RequireInactiveBeforeStart)
        {
            while (_settings.IsActive(input.ReadSingleLine()))
            {
                ThrowIfTimedOut(stopwatch, "기존 신호 해제 대기");
                Delay(cancellationToken);
            }
        }

        while (!_settings.IsActive(input.ReadSingleLine()))
        {
            ThrowIfTimedOut(stopwatch, "시작 신호 대기");
            Delay(cancellationToken);
        }
    }

    private void ThrowIfTimedOut(Stopwatch stopwatch, string state)
    {
        if (_settings.TimeoutMilliseconds <= 0 ||
            stopwatch.ElapsedMilliseconds <= _settings.TimeoutMilliseconds)
        {
            return;
        }

        throw new TimeoutException(
            $"NI-6501 시작 신호 대기 시간 초과: {state}, 채널={_settings.PhysicalChannel}, 제한={_settings.TimeoutMilliseconds}ms");
    }

    private void Delay(CancellationToken cancellationToken)
    {
        if (cancellationToken.WaitHandle.WaitOne(_settings.PollIntervalMilliseconds))
        {
            throw new OperationCanceledException(cancellationToken);
        }
    }

    private sealed class DaqmxDigitalInput : IDisposable
    {
        private const int DaqmxValChanPerLine = 0;
        private const int DaqmxValGroupByChannel = 0;

        private nint _taskHandle;

        public DaqmxDigitalInput(string physicalChannel)
        {
            Check(DaqmxCreateTask("", out _taskHandle), "NI-DAQmx Task 생성 실패");

            try
            {
                Check(DaqmxCreateDIChan(_taskHandle, physicalChannel, "", DaqmxValChanPerLine), "NI-6501 DI 채널 생성 실패");
                Check(DaqmxStartTask(_taskHandle), "NI-6501 DI Task 시작 실패");
            }
            catch
            {
                Dispose();
                throw;
            }
        }

        public bool ReadSingleLine()
        {
            var readArray = new byte[1];
            Check(
                DaqmxReadDigitalLines(
                    _taskHandle,
                    1,
                    1.0,
                    DaqmxValGroupByChannel,
                    readArray,
                    (uint)readArray.Length,
                    out _,
                    out _,
                    nint.Zero),
                "NI-6501 DI 읽기 실패");

            return readArray[0] != 0;
        }

        public void Dispose()
        {
            if (_taskHandle == nint.Zero)
            {
                return;
            }

            DaqmxStopTask(_taskHandle);
            DaqmxClearTask(_taskHandle);
            _taskHandle = nint.Zero;
        }

        private static void Check(int errorCode, string message)
        {
            if (errorCode >= 0)
            {
                return;
            }

            var detail = GetExtendedErrorInfo();
            throw new InvalidOperationException(string.IsNullOrWhiteSpace(detail)
                ? message
                : $"{message}: {detail}");
        }

        private static string GetExtendedErrorInfo()
        {
            var errorMessage = new StringBuilder(2048);
            var errorCode = DaqmxGetExtendedErrorInfo(errorMessage, (uint)errorMessage.Capacity);
            return errorCode == 0 ? errorMessage.ToString().Trim() : string.Empty;
        }

        [DllImport("nicaiu.dll", EntryPoint = "DAQmxCreateTask", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        private static extern int DaqmxCreateTask(string taskName, out nint taskHandle);

        [DllImport("nicaiu.dll", EntryPoint = "DAQmxCreateDIChan", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        private static extern int DaqmxCreateDIChan(nint taskHandle, string lines, string nameToAssignToLines, int lineGrouping);

        [DllImport("nicaiu.dll", EntryPoint = "DAQmxStartTask", CallingConvention = CallingConvention.Cdecl)]
        private static extern int DaqmxStartTask(nint taskHandle);

        [DllImport("nicaiu.dll", EntryPoint = "DAQmxReadDigitalLines", CallingConvention = CallingConvention.Cdecl)]
        private static extern int DaqmxReadDigitalLines(
            nint taskHandle,
            int numSampsPerChan,
            double timeout,
            int fillMode,
            byte[] readArray,
            uint arraySizeInBytes,
            out int sampsPerChanRead,
            out int numBytesPerSamp,
            nint reserved);

        [DllImport("nicaiu.dll", EntryPoint = "DAQmxStopTask", CallingConvention = CallingConvention.Cdecl)]
        private static extern int DaqmxStopTask(nint taskHandle);

        [DllImport("nicaiu.dll", EntryPoint = "DAQmxClearTask", CallingConvention = CallingConvention.Cdecl)]
        private static extern int DaqmxClearTask(nint taskHandle);

        [DllImport("nicaiu.dll", EntryPoint = "DAQmxGetExtendedErrorInfo", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        private static extern int DaqmxGetExtendedErrorInfo(StringBuilder errorString, uint bufferSize);
    }
}