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

namespace Server
{
	class Server
	{
		private readonly int BUFF_SIZE = 1024;

		private TcpListener listener;

		public async void Start()
		{
			listener = new TcpListener(IPAddress.Any, 7000);
			listener.Start();

			while (true)
			{
				TcpClient client = await listener.AcceptTcpClientAsync().ConfigureAwait(false);
				string clientEndPoint = client.Client.RemoteEndPoint.ToString();
				NetworkStream stream = client.GetStream();

				// Receive data size
				byte[] bytes = new byte[4];
				int readSize = await stream.ReadAsync(bytes, 0, bytes.Length).ConfigureAwait(false);
				if (readSize != 4)
					throw new ApplicationException("Invalid size");

				int totalSize = BitConverter.ToInt32(bytes, 0);
				Console.WriteLine($"[{clientEndPoint}] Data size: {totalSize} byte");

				// Receive data
				string fileName = Guid.NewGuid().ToString("N") + ".png";
				using (FileStream fs = new FileStream(fileName, FileMode.CreateNew))
				{
					byte[] buff = new byte[BUFF_SIZE];
					int received = 0;
					while (received < totalSize)
					{
						int size = totalSize - received >= BUFF_SIZE ? BUFF_SIZE : totalSize - received;
						readSize = await stream.ReadAsync(buff, 0, size).ConfigureAwait(false);
						received += readSize;

						await fs.WriteAsync(buff, 0, readSize);

						Console.WriteLine($"[{clientEndPoint}] Receive: {received}/{totalSize}");
					}
				}

				// Send result
				byte[] result = new byte[1];
				result[0] = 1;
				await stream.WriteAsync(result, 0, result.Length).ConfigureAwait(false);

				Console.WriteLine($"[{clientEndPoint}] Result: {(result[0] == 1 ? "success" : "fail")}");

				stream.Close();
				client.Close();
			}
		}
	}
}