using System.Net;
using System.Net.Sockets;
using System.Text;

namespace Server;

internal class Server
{
	private static readonly int BUFFER_SIZE = 256;

	static void Main(string[] args)
	{
		Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
		IPEndPoint endPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 20000);
		serverSocket.Bind(endPoint);
		serverSocket.Listen(100);

		SocketAsyncEventArgs arg = new SocketAsyncEventArgs();
		arg.Completed += AcceptCompleted;
		bool pending = serverSocket.AcceptAsync(arg);
		if (!pending)
			AcceptCompleted(serverSocket, arg);

		while (true)
		{
			Thread.Sleep(1000);
		}
	}

	private static void AcceptCompleted(object? sender, SocketAsyncEventArgs e)
	{
		if (sender == null || e == null || e.AcceptSocket == null)
			return;

		Socket serverSocket = (Socket)sender;
		Socket clientSocket = e.AcceptSocket;
		Console.WriteLine(clientSocket.RemoteEndPoint);

		e.AcceptSocket = null;
		bool pending = serverSocket.AcceptAsync(e);
		if (!pending)
			AcceptCompleted(serverSocket, e);

		SocketAsyncEventArgs arg = new SocketAsyncEventArgs();
		arg.Completed += ReceiveCompleted;
		byte[] buffer = new byte[BUFFER_SIZE];
		arg.SetBuffer(buffer, 0, buffer.Length);

		bool pending2 = clientSocket.ReceiveAsync(arg);
		if (!pending2)
			ReceiveCompleted(clientSocket, arg);
	}

	private static void ReceiveCompleted(object? sender, SocketAsyncEventArgs e)
	{
		if (sender == null || e == null)
			return;

		Socket clientSocket = (Socket)sender;
		if (e.BytesTransferred < 1)
		{
			Console.WriteLine("Client is disconnected...");
			clientSocket.Dispose();
			e.Dispose();
			return;
		}

		Console.WriteLine(Encoding.UTF8.GetString(e.Buffer));

		byte[] buffer = new byte[BUFFER_SIZE];
		e.SetBuffer(buffer, 0, buffer.Length);

		bool pending = clientSocket.ReceiveAsync(e);
		if (!pending)
			ReceiveCompleted(clientSocket, e);
	}
}