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

namespace Server_FTP
{
    public class Client
    {
        public String authorizedEmail;
        public Int32 port;

        public Client(String email, Int32 p)
        {
            authorizedEmail = email;
            port = p;
        }
    }
    public class server
    {
        ManualResetEvent tcpClientConnected = new ManualResetEvent(false);
        List<Client> authorizedEmails = new List<Client>();
        void ProcessIncomingData(object obj)
        {
            TcpClient client = (TcpClient)obj;
            StringBuilder sb = new StringBuilder();
            bool userauth = true;
            bool accessgranted = true;
            Directory.SetCurrentDirectory("D:/FTP");
            using (NetworkStream stream = client.GetStream())
            {
                int i;
                while ((i = stream.ReadByte()) != 0)
                {
                    sb.Append((char)i);
                }
                String[] tab = sb.ToString().Split(' ');
                switch (tab[0].ToUpper())
                {
                    case "DELE":
                        {
                            try
                            {
                                File.Delete(tab[1]);
                            }
                            catch (DirectoryNotFoundException)
                            {
                                Console.WriteLine("Proba usuniecia pliku zakonczona niepowodzeniem. Podana sciezka jest nieprawidlowa");
                            }

                            break;
                        }
                    case "USER":
                        {
                            accessgranted = true;
                            userauth = true;
                            Byte[] bytess = new Byte[256];

                            if (tab[1].Equals("anonymous"))
                            {
                                string rep = "331: Password is required to get access." + '\0';
                                stream.Write(Encoding.ASCII.GetBytes(rep), 0, rep.Length);
                            }
                            else
                            {
                                string rep = "530: Access denied" + '\0';
                                stream.Write(Encoding.ASCII.GetBytes(rep), 0, rep.Length);
                            }
                            break;
                        }
                    case "PASS":
                        {

                            if (userauth)
                            {
                                string userpass = tab[1];
                                if (Regex.IsMatch(tab[1], @"^[a-z0-9][-a-z0-9._]+@([-a-z0-9]+\.)+[a-z]{2,5}$", RegexOptions.IgnoreCase))
                                {
                                    string rep = "230: Access granted. " + '\0';
                                    authorizedEmails.Add(new Client(userpass,13000));
                                    stream.Write(Encoding.ASCII.GetBytes(rep), 0, rep.Length);
                                    accessgranted = true;
                                }
                                else
                                {
                                    string rep = "530: Access denied. " + '\0';
                                    stream.Write(Encoding.ASCII.GetBytes(rep), 0, rep.Length);

                                }
                            }
                            else
                            {
                                string rep = "User has not been specified yet. " + '\0';
                                stream.Write(Encoding.ASCII.GetBytes(rep), 0, rep.Length);

                            }
                            break;
                        }
                    case "PASV":
                        {
                            Random rnd = new Random();
                            Int32 portPASV = rnd.Next(1024, 13000);
                            Int32 port1 = portPASV / 256, port2 = portPASV % 256;
                            String fn = "127.0.0.1";
                            fn = fn.Replace('.', ',');
                            String message = fn + "," + (port1.ToString()) + "," + (port2.ToString() + '\0');
                            Byte[] bytes = Encoding.ASCII.GetBytes(message);
                            authorizedEmails[authorizedEmails.FindIndex(x => x.authorizedEmail.Equals(tab[1]))].port = portPASV;
                            Console.WriteLine(authorizedEmails[authorizedEmails.FindIndex(x => x.authorizedEmail.Equals(tab[1]))].authorizedEmail);
                            Console.WriteLine(authorizedEmails[authorizedEmails.FindIndex(x => x.authorizedEmail.Equals(tab[1]))].port);
                            stream.Write(bytes, 0, bytes.Length);
                            break;
                        }
                    case "RETR":
                        {
                            Client klient = authorizedEmails[authorizedEmails.FindIndex(x => x.authorizedEmail.Equals(tab[2]))];
                            Directory.SetCurrentDirectory("D:\\FTP\\");
                            string path = "D:\\FTP\\" + tab[1];
                            FileStream fs = new FileStream(tab[1], FileMode.Open, FileAccess.Read);
                            Console.WriteLine(klient.authorizedEmail);
                            Console.WriteLine(klient.port);
                            IPEndPoint ep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), klient.port);
                            TcpListener fileServer = new TcpListener(ep);
                            fileServer.Start();
                            TcpClient files = fileServer.AcceptTcpClient();
                            NetworkStream fileNetworkStream = files.GetStream();
                            Byte[] data = new Byte[fs.Length + 1];
                            fs.Read(data, 0, data.Length);
                            fileNetworkStream.WriteAsync(data, 0, data.Length);
                            fs.Close();
                            fileServer.Stop();

                            break;
                        }
                    case "PWD":
                        {
                            string dir = Directory.GetCurrentDirectory() + '\0';
                            stream.Write(Encoding.ASCII.GetBytes(dir), 0, dir.Length);
                            break;
                        }
                    case "MLSD":
                        {
                            string[] filePaths = Directory.GetFiles("D:\\FTP\\", @"*", SearchOption.AllDirectories);
                            string awq = "";
                            foreach (var a in filePaths)
                            {
                                awq += a;
                                awq += "\n";
                            }
                            awq += "\0";
                            stream.Write(Encoding.ASCII.GetBytes(awq), 0, awq.Length);
                            break;
                        }
                    case "QUIT":
                        {
                            authorizedEmails.RemoveAt(authorizedEmails.FindIndex(x => x.authorizedEmail.Equals(tab[1])));
                            string rep = "221: Bye. " + '\0';
                            stream.Write(Encoding.ASCII.GetBytes(rep), 0, rep.Length);
                            stream.Close();
                            client.Close();
                            break;
                        }
                }
            }
        }


        byte[] GetFileData(String path)
        {
            using (var sr = new StreamReader(path))
            {
                return ASCIIEncoding.ASCII.GetBytes(sr.ReadToEnd());
            }

        }
        void ProcessIncomingConnection(IAsyncResult ar)
        {
            TcpListener listener = (TcpListener)ar.AsyncState;
            TcpClient client = listener.EndAcceptTcpClient(ar);
            ThreadPool.QueueUserWorkItem(ProcessIncomingData, client);
            tcpClientConnected.Set();
        }

        public void start()
        {
            IPEndPoint endpoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 21);
            TcpListener listener = new TcpListener(endpoint);
            listener.Start();
            while (true)
            {
                tcpClientConnected.Reset();
                listener.BeginAcceptTcpClient(new AsyncCallback(ProcessIncomingConnection), listener);
                tcpClientConnected.WaitOne();
            }
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            server s = new server();
            s.start();
        }
    }
}