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

public class WledDdpClient
{
    private readonly UdpClient _udp;
    private readonly string _ip;
    private const int Port = 4048; // Standard DDP UDP port
    private byte _sequence = 1;

    public WledDdpClient(string ipAddress)
    {
        _ip = ipAddress;
        _udp = new UdpClient();
    }

    public async Task SendFrameAsync(byte[] rgbData)
    {
        // Max payload per packet to stay under standard 1500 byte MTU
        const int maxPixelsPerPacket = 480;
        const int maxBytesPerPacket = maxPixelsPerPacket * 3;

        int totalBytes = rgbData.Length;
        int offset = 0;

        while (offset < totalBytes)
        {
            int chunkLength = Math.Min(maxBytesPerPacket, totalBytes - offset);
            bool isLast = (offset + chunkLength) >= totalBytes;

            byte[] packet = new byte[10 + chunkLength];

            // Byte 0: Flags. 0x40 = Version 1. 0x01 = Push bit.
            // We only "Push" to the display on the final chunk of the frame.
            packet[0] = (byte)(isLast ? 0x41 : 0x40);

            // Byte 1: Sequence (0-15)
            packet[1] = _sequence;

            // Byte 2: Data type (1 = RGB)
            packet[2] = 1;

            // Byte 3: Destination ID (Default 1)
            packet[3] = 1;

            // Bytes 4-7: Data Offset (32-bit Big Endian)
            packet[4] = (byte)(offset >> 24);
            packet[5] = (byte)(offset >> 16);
            packet[6] = (byte)(offset >> 8);
            packet[7] = (byte)(offset);

            // Bytes 8-9: Data Length (16-bit Big Endian)
            packet[8] = (byte)(chunkLength >> 8);
            packet[9] = (byte)(chunkLength);

            // Copy the pixel payload into the packet
            Buffer.BlockCopy(rgbData, offset, packet, 10, chunkLength);
            try
            {
                await _udp.SendAsync(packet, packet.Length, _ip, Port);
            }
            catch
            {
                Console.WriteLine("Connection to matrix failed");
            }

            offset += chunkLength;
        }

        // Increment sequence for the next frame (wrap at 15)
        _sequence = (byte)((_sequence + 1) % 16);
    }
}