using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using HidSharp;
using LibUsbDotNet.LibUsb;
using LibUsbDotNet.Main;
using RGB.NET.Core;

namespace RGB.NET.Devices.PicoPi
{
    public class PicoPiSDK : IDisposable
    {
        #region Constants

        public const int VENDOR_ID = 0x1209;
        public const int HID_BULK_CONTROLLER_PID = 0x2812;

        private const byte COMMAND_CHANNEL_COUNT = 0x01;
        private const byte COMMAND_LEDCOUNTS = 0x0A;
        private const byte COMMAND_PINS = 0x0B;
        private const byte COMMAND_ID = 0x0E;
        private const byte COMMAND_VERSION = 0x0F;
        private const byte COMMAND_UPDATE = 0x01;
        private const byte COMMAND_UPDATE_BULK = 0x02;

        #endregion

        #region Properties & Fields

        private readonly HidDevice _hidDevice;
        private readonly HidStream _hidStream;

        private UsbContext? _usbContext;
        private IUsbDevice? _bulkDevice;
        private UsbEndpointWriter? _bulkWriter;

        private readonly byte[] _hidSendBuffer;
        private readonly byte[] _bulkSendBuffer;

        private int _bulkTransferLength;

        public bool IsBulkSupported { get; private set; }

        public string Id { get; }
        public int Version { get; }
        public IReadOnlyList<(int channel, int ledCount, int pin)> Channels { get; }

        #endregion

        #region Constructors

        public PicoPiSDK(HidDevice device)
        {
            this._hidDevice = device;

            _hidSendBuffer = new byte[_hidDevice.GetMaxOutputReportLength() - 1];

            _hidStream = _hidDevice.Open();
            LoadBulkDevice();

            Id = GetId();
            Version = GetVersion();
            Channels = new ReadOnlyCollection<(int channel, int ledCount, int pin)>(GetChannels().ToList());

            _bulkSendBuffer = new byte[(Channels.Sum(c => c.ledCount + 1) * 3) + 5];
        }

        #endregion

        #region Methods

        public void SetLedCounts(params (int channel, int ledCount)[] ledCounts)
        {
            byte[] data = new byte[Channels.Count + 2];
            data[1] = COMMAND_LEDCOUNTS;
            foreach ((int channel, int ledCount, _) in Channels)
                data[channel + 1] = (byte)ledCount;

            foreach ((int channel, int ledCount) in ledCounts)
                data[channel + 1] = (byte)ledCount;

            SendHID(data);
        }

        public void SetPins(params (int channel, int pin)[] pins)
        {
            byte[] data = new byte[Channels.Count + 2];
            data[1] = COMMAND_PINS;
            foreach ((int channel, _, int pin) in Channels)
                data[channel + 1] = (byte)pin;

            foreach ((int channel, int pin) in pins)
                data[channel + 1] = (byte)pin;

            SendHID(data);
        }

        private void LoadBulkDevice()
        {
            try
            {
                _usbContext = new UsbContext();
                // DarthAffe 24.04.2021: Not using .Find as it's not returning the device :(
                IEnumerable<IUsbDevice> devices = _usbContext.List().Where(d => (d.VendorId == _hidDevice.VendorID) && (d.ProductId == _hidDevice.ProductID));
                foreach (IUsbDevice device in devices)
                {
                    try
                    {
                        device.Open();
                        if (device.Info.SerialNumber == _hidDevice.GetSerialNumber())
                        {
                            _bulkDevice = device;
                            break;
                        }
                        device.Dispose();
                    }
                    catch { /**/ }
                }

                if (_bulkDevice != null)
                {
                    _bulkDevice.ClaimInterface(1);
                    _bulkWriter = _bulkDevice.OpenEndpointWriter(WriteEndpointID.Ep02, EndpointType.Bulk);

                    IsBulkSupported = true;
                }
            }
            catch
            {
                _bulkWriter = null;
                try { _bulkDevice?.Dispose(); } catch { /**/ }
                try { _usbContext?.Dispose(); } catch { /**/ }
                _bulkDevice = null;
            }
        }

        private string GetId()
        {
            SendHID(0x00, COMMAND_ID);
            return ConversionHelper.ToHex(Read().Skip(1).Take(8).ToArray());
        }

        private int GetVersion()
        {
            SendHID(0x00, COMMAND_VERSION);
            return Read()[1];
        }

        private IEnumerable<(int channel, int ledCount, int pin)> GetChannels()
        {
            SendHID(0x00, COMMAND_CHANNEL_COUNT);
            int channelCount = Read()[1];

            for (int i = 1; i <= channelCount; i++)
            {
                SendHID(0x00, (byte)((i << 4) | COMMAND_LEDCOUNTS));
                int ledCount = Read()[1];

                SendHID(0x00, (byte)((i << 4) | COMMAND_PINS));
                int pin = Read()[1];

                yield return (i, ledCount, pin);
            }
        }

        public void SendHidUpdate(in Span<byte> data, int channel, int chunk, bool update)
        {
            if (data.Length == 0) return;

            Span<byte> sendBuffer = _hidSendBuffer;
            sendBuffer[0] = 0x00;
            sendBuffer[1] = (byte)((channel << 4) | COMMAND_UPDATE);
            sendBuffer[2] = update ? (byte)1 : (byte)0;
            sendBuffer[3] = (byte)chunk;
            data.CopyTo(sendBuffer.Slice(4, data.Length));
            SendHID(_hidSendBuffer);
        }

        public void SendBulkUpdate(in Span<byte> data, int channel)
        {
            if ((data.Length == 0) || !IsBulkSupported) return;

            Span<byte> sendBuffer = new Span<byte>(_bulkSendBuffer)[2..];
            int payloadSize = data.Length;

            sendBuffer[_bulkTransferLength++] = (byte)((channel << 4) | COMMAND_UPDATE_BULK);
            sendBuffer[_bulkTransferLength++] = (byte)((payloadSize >> 8) & 0xFF);
            sendBuffer[_bulkTransferLength++] = (byte)(payloadSize & 0xFF);
            data.CopyTo(sendBuffer.Slice(_bulkTransferLength, payloadSize));
            _bulkTransferLength += payloadSize;
        }

        public void FlushBulk()
        {
            if (_bulkTransferLength == 0) return;

            _bulkSendBuffer[0] = (byte)((_bulkTransferLength >> 8) & 0xFF);
            _bulkSendBuffer[1] = (byte)(_bulkTransferLength & 0xFF);
            SendBulk(_bulkSendBuffer, _bulkTransferLength + 2);

            _bulkTransferLength = 0;
        }

        private void SendHID(params byte[] data) => _hidStream.Write(data);
        private void SendBulk(byte[] data, int count) => _bulkWriter!.Write(data, 0, count, 1000, out int _);

        private byte[] Read() => _hidStream.Read();

        public void Dispose()
        {
            _hidStream.Dispose();
            _bulkDevice?.Dispose();
            _usbContext?.Dispose();

            GC.SuppressFinalize(this);
        }

        #endregion
    }
}