using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace Core
{
	public class PServer
	{
		private Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

		public PServer(string ip, int port, int backlog)
		{
			IPEndPoint endPoint = new IPEndPoint(IPAddress.Parse(ip), port);
			serverSocket.Bind(endPoint);
			serverSocket.Listen(backlog);
		}

		public async Task StartAsync()
		{
			while (true)
			{
				Socket clientSocket = await serverSocket.AcceptAsync();
				Console.WriteLine($"[{DateTime.Now}] Accept client: {clientSocket.RemoteEndPoint}");
				ThreadPool.QueueUserWorkItem(RunAsync, clientSocket);
			}
		}

		private async void RunAsync(object? sender)
		{
			if (sender == null)
				return;

			Socket clientSocket = (Socket)sender;
			byte[] headerBuffer = new byte[2];

			while (true)
			{
				// header buffer
				int n1 = await clientSocket.ReceiveAsync(headerBuffer, SocketFlags.None);
				if (n1 < 1)
				{
					Console.WriteLine($"[{DateTime.Now}] Disconnect client: {clientSocket.RemoteEndPoint}");
					clientSocket.Dispose();
					return;
				}
				else if (n1 == 1)
				{
					await clientSocket.ReceiveAsync(new ArraySegment<byte>(headerBuffer, 1, 1), SocketFlags.None);
				}

				// data buffer
				short dataSize = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(headerBuffer));
				byte[] dataBuffer = new byte[dataSize];

				int totalRecv = 0;
				while (totalRecv < dataSize)
				{
					int n2 = await clientSocket.ReceiveAsync(new ArraySegment<byte>(dataBuffer, totalRecv, dataSize - totalRecv), SocketFlags.None);
					totalRecv += n2;
				}
				Console.WriteLine($"[{DateTime.Now}] {clientSocket.RemoteEndPoint} client: {Encoding.UTF8.GetString(dataBuffer)}");
			}
		}
	}
}