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

namespace Mistox.Client {
    public class UDPReceiver : IDisposable {

        private readonly MistoxClient _parent;

        public UDPReceiver( MistoxClient parent) {
            _parent = parent;
            // Start the receive thread
            Task.Run(ReceiveThread);
        }

        async Task ReceiveThread() {
            while( _parent.Alive ) {
                try {
                    // Read the data out of the UDP packet with a buffer that has the maximum possible UDP packet size
                    // As UDP reads the whole next packet then drops. Im guaranteed to receive 1 packet at a time
                    UdpReceiveResult udpPacket = await _parent.ClientSocket.ReceiveAsync();

                    // Try find the user
                    mUDPClient client = null;
                    bool clientExists = _parent.clientConnections.TryGetValue(udpPacket.RemoteEndPoint, out client);
                    if (clientExists) {
                        
                        // Create the data readers
                        ReadOnlyMemory<byte> dataMemory = udpPacket.Buffer.AsMemory();
                        ReadOnlySpan<byte> dataPacket = dataMemory.Span;

                        // Create the packet header
                        DataPacketHeader Header = new DataPacketHeader {
                          Type = (ushort)((dataPacket[0] << 8) | dataPacket[1]),
                          DataLength = (ushort)((dataPacket[2] << 8) | dataPacket[3])
                        };

                        // Slice out the data part of the packet
                        ReadOnlyMemory<byte> data = dataMemory.Slice(DataPacket.HeaderLength, Header.DataLength);

                        // Extract the object
                        dynamic buildObj = DataPacket.Deserialize( Header, data );

                        // Return the object
                        _parent.InvokeOnReceived( buildObj, client );

                    }
                } catch( Exception e ) {
                    Console.WriteLine( "UDP Receive exception : " + e.Message );
                }
            }
        }

        public void Dispose() {
            _parent.Alive = false;
        }
    }
}