using LibUsbDotNet.LibUsb;
using LibUsbDotNet.Main;

namespace RTCSync.Utils;

public static class I2CUtils
{
    private const int VID = 0x1A86;
    private const int PID = 0x5512; // CH341T

    // Команды CH341 для I2C
    private const byte CH341_CMD_I2C_STREAM = 0xAA;
    private const byte CH341_CMD_I2C_STM_STA = 0x74; // START
    private const byte CH341_CMD_I2C_STM_STO = 0x75; // STOP
    private const byte CH341_CMD_I2C_STM_OUT = 0x80; // write byte (len в младших битах)
    private const byte CH341_CMD_I2C_STM_IN = 0xC0; // read byte
    private const byte CH341_CMD_I2C_STM_END = 0x00; // конец стрима

    public static void ScanDevice(IUsbDevice device)
    {
        var writer = device.OpenEndpointWriter(WriteEndpointID.Ep02);
        var reader = device.OpenEndpointReader(ReadEndpointID.Ep02);

        Console.WriteLine("Сканирование I2C шины (0x03 - 0x77)...");

        for (byte addr = 0x03; addr < 0x78; addr++)
        {
            // Пробуем послать START + адрес + STOP
            // Если устройство есть — придёт ACK, если нет — NACK
            var cmd = new byte[]
            {
                CH341_CMD_I2C_STREAM, // CH341_CMD_I2C_STREAM
                CH341_CMD_I2C_STM_STA, // START
                CH341_CMD_I2C_STM_OUT | 1, // OUT, 1 байт
                (byte)(addr << 1), // адрес + write bit
                CH341_CMD_I2C_STM_STO, // STOP
                CH341_CMD_I2C_STM_END // END
            };

            writer.Write(cmd, 500, out int written);

            var buf = new byte[4];
            reader.Read(buf, 200, out int read);

            // CH341 возвращает статус: 0x00 = ACK получен (устройство есть)
            // Первый байт ответа — статус последней I2C операции
            if (read > 0 && buf[0] == 0x00)
            {
                Console.WriteLine($"  Найдено устройство: 0x{addr:X2}");
            }
        }

        Console.WriteLine("Сканирование завершено.");
    }

    public static void CH341Init(IUsbDevice device)
    {
        Console.WriteLine("Пытаемся инициализировать устройство");
        var writer = device.OpenEndpointWriter(WriteEndpointID.Ep02);

        // Установка скорости I2C: 0x00=20kHz, 0x01=100kHz, 0x02=400kHz, 0x03=750kHz
        var cmd = new byte[]
        {
            CH341_CMD_I2C_STREAM,
            0x60 | 0x01, // CH341_CMD_I2C_STM_SET | 100kHz
            CH341_CMD_I2C_STM_END
        };
        writer.Write(cmd, 1000, out _);
    }

    public static byte[] Read(IUsbDevice device, byte address, byte reg, int length)
    {
        // Формируем пакет: START → write addr+reg → RESTART → read → STOP
        var cmd = new byte[]
        {
            CH341_CMD_I2C_STREAM,
            CH341_CMD_I2C_STM_STA,
            CH341_CMD_I2C_STM_OUT | 2, // 2 байта: адрес + регистр
            (byte)(address << 1), // write
            reg,
            CH341_CMD_I2C_STM_STA, // repeated START
            CH341_CMD_I2C_STM_OUT | 1,
            (byte)((address << 1) | 1), // read
            (byte)(CH341_CMD_I2C_STM_IN | (length - 1)),
            CH341_CMD_I2C_STM_STO,
            CH341_CMD_I2C_STM_END
        };

        var writer = device.OpenEndpointWriter(WriteEndpointID.Ep02);
        var reader = device.OpenEndpointReader(ReadEndpointID.Ep02);

        writer.Write(cmd, 1000, out _);
        var buf = new byte[length];
        reader.Read(buf, 1000, out var transferred);
        return buf;
    }

    public static byte[] ReadWithRetry(IUsbDevice device, byte address, byte reg, int length)
    {
        for (var attempt = 0; attempt < 100; attempt++)
        {
            var result = Read(device, address, reg, length);

            if (result[0] != 0x03)
                return result;

            Thread.Sleep(10);
        }

        throw new Exception("Ошибка чтения CH431 после 100 попыток");
    }

    public static void Write(IUsbDevice device, byte address, byte reg, byte[] data)
    {
        // START → write addr → write reg → write data[0..n] → STOP
        // CH341_CMD_I2C_STM_OUT | N означает "записать N байт"
        // N = 1 (адрес) + 1 (регистр) + data.Length
        var cmd = new byte[5 + data.Length + 2];
        int i = 0;

        cmd[i++] = CH341_CMD_I2C_STREAM;
        cmd[i++] = CH341_CMD_I2C_STM_STA;
        cmd[i++] = (byte)(CH341_CMD_I2C_STM_OUT | (2 + data.Length)); // адрес + регистр + данные
        cmd[i++] = (byte)(address << 1); // write bit = 0
        cmd[i++] = reg;
        foreach (var b in data)
            cmd[i++] = b;
        cmd[i++] = CH341_CMD_I2C_STM_STO;
        cmd[i] = CH341_CMD_I2C_STM_END;

        var writer = device.OpenEndpointWriter(WriteEndpointID.Ep02);
        writer.Write(cmd, 1000, out _);
    }
}