using System;
using System.Collections.Generic;
using System.Text;
using System.Net.Sockets;
using System.Security.Cryptography.X509Certificates;
using System.Net.Security;
using System.Security.Authentication;
using System.IO;
using System.Windows.Forms;
using System.Diagnostics;

namespace FilePOP.Source.POP3
{
    public sealed class POP3Mail
    {
        #region Properties/Variables

        private Stream currentStream;
        private StreamReader streamReader;
        private ASCIIEncoding streamEncoding = new ASCIIEncoding();
        private String serverResponse;

        /// <summary>
        /// The name of the POP3 server.
        /// </summary>
        private String server = String.Empty;
        public String Server
        {
            get { return server; }
            set { server = value; }
        }

        /// <summary>
        /// The port number of the POP3 server.
        /// </summary>
        private int port = 0;
        public int Port
        {
            get { return port; }
            set { port = value; }
        }

        /// <summary>
        /// Server requires a secure tunnel.
        /// </summary>
        private bool secureConnection = false;
        public bool SecureConnection
        {
            get { return secureConnection; }
            set { secureConnection = value; }
        }

        /// <summary>
        /// Server connection status.
        /// </summary>
        private bool connected = false;
        public bool Connected
        {
            get { return connected; }
            set { connected = value; }
        }

        private String username = String.Empty;
        public String Username
        {
            get { return username; }
            set { username = value; }
        }

        private String password = String.Empty;
        public String Password
        {
            get { return password; }
            set { password = value; }
        }

        private int messageCount = 0;
        public int MessageCount
        {
            get { return messageCount; }
            private set { messageCount = value; }
        }

        #endregion
        /// <summary>
        /// Creates a POP3 object with no parameters.
        /// </summary>
        public POP3Mail() { }

        /// <summary>
        /// Creates a POP3 object ready to connect to the server with the specified port.
        /// Secure tunnel option is specified as well.
        /// </summary>
        /// <param name="server">POP3 Server to connect to</param>
        /// <param name="port">Port to connect on.</param>
        /// <param name="bSecureConnection">Server requires a secure tunnel.</param>
        public POP3Mail(String server, int port, bool bSecureConnection)
        {
            Server = server;
            Port = port;
            SecureConnection = bSecureConnection;
        }

        /// <summary>
        /// Connects to the POP3 server.
        /// </summary>
        public void Connect()
        {
            try
            {
                TcpClient popClient = new TcpClient(Server, Port);

                if (SecureConnection)
                {
                    SslStream sslStream = new SslStream(popClient.GetStream(), false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);
                    sslStream.AuthenticateAsClient(Server);
                    currentStream = sslStream;

                    streamReader = new StreamReader(currentStream);
                    serverResponse = streamReader.ReadLine();
#if DEBUG
                    Debug.Print(serverResponse);
#endif

                    POP3SendUserData(Username);
                    POP3SendPasswordData(Password);
                    POP3GetMessageCount();

                    Connected = true;

                }
                else
                {

                    currentStream = popClient.GetStream();

                    streamReader = new StreamReader(currentStream);
                    serverResponse = streamReader.ReadLine();
#if DEBUG
                    Debug.Print(serverResponse);
#endif

                    POP3SendUserData(Username);
                    POP3SendPasswordData(Password);
                    POP3GetMessageCount();


                    Connected = true;
                }
            }
            catch (AuthenticationException e)
            {
                currentStream.Close();
                Connected = false;
                throw new Exception("SSL Authentication error.  Please check your settings.");
            }
            catch (Exception e)
            {
                Connected = false;
                throw new Exception(e.Message);
            }

        }

        /// <summary>
        /// Reads a message from the POP3 server.
        /// </summary>
        /// <param name="index">Index of the mail to read.</param>
        /// <returns>Mail message</returns>
        public String ReadMessage(int index)
        {
            POP3SendMessage("retr " + index);
            serverResponse = streamReader.ReadLine();
#if DEBUG
            Debug.Print(serverResponse);
#endif
            if (serverResponse.Contains("-ERR"))
            {
                throw new Exception("Unable to retrieve messages.  The POP3 server may be down.");
            }

            streamReader.ReadLine();
            while (streamReader.Peek() >= 0)
            {
                serverResponse += streamReader.ReadLine() + Environment.NewLine ;

            }

            return serverResponse;
        }
        /// <summary>
        /// Sends the username to the POP3 server.
        /// </summary>MODE_Separator_Paint
        /// <param name="user">Username</param>
        private void POP3SendUserData(String user)
        {
            POP3SendMessage("user " + user);
            serverResponse = streamReader.ReadLine();
#if DEBUG
            Debug.Print(serverResponse);
#endif
            if (serverResponse.Contains("-ERR"))
            {
                throw new Exception("Unable to authenticate.  Please check your settings.");
            }
        }

        /// <summary>
        /// Sends the password to the POP3 server.
        /// </summary>
        /// <param name="password">Password</param>
        private void POP3SendPasswordData(String password)
        {
            POP3SendMessage("pass " + password);
            serverResponse = streamReader.ReadLine();
#if DEBUG
            Debug.Print(serverResponse);
#endif
            if (serverResponse.Contains("-ERR"))
            {
                throw new Exception("Unable to authenticate.  Please check your settings.");
            }
        }

        /// <summary>
        /// Gets the total number of messages on the POP3 server.
        /// </summary>
        private void POP3GetMessageCount()
        {
            POP3SendMessage("stat");
            serverResponse = streamReader.ReadLine();
#if DEBUG
            Debug.Print(serverResponse);
#endif
            if (serverResponse.Contains("-ERR"))
            {
                throw new Exception("Unable to determine messeges. The POP3 server may be down.");
            }

            int responsePosition = serverResponse.IndexOf(" ", 4);
            String messageCount = serverResponse.Substring(4, responsePosition - 4);
            MessageCount = Int32.Parse(messageCount);
#if DEBUG
            Debug.Print("Total Messages: {0}", messageCount);
#endif
        }

        /// <summary>
        /// Sends data to the POP3 server.
        /// </summary>
        /// <param name="message">Message</param>
        private void POP3SendData(String message)
        {
            byte[] byteData = streamEncoding.GetBytes(message);
            currentStream.Write(byteData, 0, byteData.Length);
        }

        /// <summary>
        /// Sends message to the POP3 server.
        /// </summary>
        /// <param name="message">Message</param>
        private void POP3SendMessage(String message)
        {
            POP3SendData(message + "\r\n");
        }

        public void Disconnect()
        {
            POP3SendMessage("quit");

#if DEBUG
            Debug.Print(serverResponse);
#endif
            if (serverResponse.Contains("-ERR"))
            {
                throw new Exception("Unable to disconnect from server.");
            }
        }
        /// <summary>
        /// Deleted the message via the index.
        /// </summary>
        /// <param name="index">Index of the message to delete.</param>
        public void DeleteMessage(int index)
        {
            // NOTE:  Not all POP3 servers send the +OK reply after marking for deletion!!
            POP3SendMessage("dele " + index.ToString());
            serverResponse = streamReader.ReadLine();
#if DEBUG
            Debug.Print(serverResponse);
#endif
            if (serverResponse.Contains("-ERR"))
            {
                throw new Exception("Unable to delete messages.");
            }
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="certificate"></param>
        /// <param name="chain"></param>
        /// <param name="sslPolicyErrors"></param>
        /// <returns></returns>
        private bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
        {
            if (sslPolicyErrors == SslPolicyErrors.None)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }
}