/// <copyright company="JetBrains">
/// Copyright © 2003-2008 JetBrains s.r.o.
/// You may distribute under the terms of the GNU General Public License, as published by the Free Software Foundation, version 2 (see License.txt in the repository root folder).
/// </copyright>

using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Web.Mail;

namespace SMTP
{
  /// <summary>
  /// provides methods to send email via smtp direct to mail server
  /// </summary>
  public class SmtpDirect
  {
    /// <summary>
    /// Get / Set the name of the SMTP mail server
    /// </summary>
    public static string SmtpServer;

    private enum SMTPResponse : int
    {
      CONNECT_SUCCESS = 220,
      GENERIC_SUCCESS = 250,
      DATA_SUCCESS = 354,
      QUIT_SUCCESS = 221
    }

    public static bool Send(MailMessage message)
    {
      IPHostEntry IPhst = Dns.Resolve(SmtpServer);
      IPEndPoint endPt = new IPEndPoint(IPhst.AddressList[0], 25);
      Socket s = new Socket(endPt.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
      s.Connect(endPt);

      if (!Check_Response(s, SMTPResponse.CONNECT_SUCCESS))
      {
        s.Close();
        return false;
      }

      Senddata(s, string.Format("HELO {0}\r\n", Dns.GetHostName()));
      if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
      {
        s.Close();
        return false;
      }

      Senddata(s, string.Format("MAIL From: {0}\r\n", message.From));
      if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
      {
        s.Close();
        return false;
      }

      string _To = message.To;
      string[] Tos = _To.Split(new char[] {';'});
      foreach (string To in Tos)
      {
        Senddata(s, string.Format("RCPT TO: {0}\r\n", To));
        if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
        {
          s.Close();
          return false;
        }
      }

      if (message.Cc != null)
      {
        Tos = message.Cc.Split(new char[] {';'});
        foreach (string To in Tos)
        {
          Senddata(s, string.Format("RCPT TO: {0}\r\n", To));
          if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
          {
            s.Close();
            return false;
          }
        }
      }

      StringBuilder Header = new StringBuilder();
      Header.Append("From: " + message.From + "\r\n");
      Tos = message.To.Split(new char[] {';'});
      Header.Append("To: ");
      for (int i = 0; i < Tos.Length; i++)
      {
        Header.Append(i > 0 ? "," : "");
        Header.Append(Tos[i]);
      }
      Header.Append("\r\n");
      if (message.Cc != null)
      {
        Tos = message.Cc.Split(new char[] {';'});
        Header.Append("Cc: ");
        for (int i = 0; i < Tos.Length; i++)
        {
          Header.Append(i > 0 ? "," : "");
          Header.Append(Tos[i]);
        }
        Header.Append("\r\n");
      }
      Header.Append("Date: ");
      Header.Append(DateTime.Now.ToString("ddd, d MMM yyyy H:m:s z"));
      Header.Append("\r\n");
      Header.Append("Subject: " + message.Subject + "\r\n");
      Header.Append("X-Mailer: SMTPDirect v1\r\n");
      string importance = null;
      if (message.Priority == MailPriority.High)
      {
        importance = "high";
      }
      else if (message.Priority == MailPriority.Low)
      {
        importance = "low";
      }

      if (importance != null)
      {
        Header.Append("Importance: " + importance + "\r\n");
      }
      string MsgBody = message.Body;
      if (!MsgBody.EndsWith("\r\n"))
      {
        MsgBody += "\r\n";
      }
      if (message.Attachments.Count > 0 || message.BodyFormat == MailFormat.Html)
      {
        Header.Append("MIME-Version: 1.0\r\n");
        Header.Append("Content-Type: multipart/mixed; boundary=unique-boundary-1\r\n");
        Header.Append("\r\n");
        Header.Append("This is a multi-part message in MIME format.\r\n");
        StringBuilder sb = new StringBuilder();
        sb.Append("--unique-boundary-1\r\n");
        string type = message.BodyFormat == MailFormat.Text ? "plain" : "html";
        sb.Append(string.Format("Content-Type: text/{0}\r\n", type));
        sb.Append("Content-Transfer-Encoding: 7Bit\r\n");
        sb.Append("\r\n");
        sb.Append(MsgBody + "\r\n");
        sb.Append("\r\n");

        foreach (object o in message.Attachments)
        {
          MailAttachment a = o as MailAttachment;
          byte[] binaryData;
          if (a != null)
          {
            FileInfo f = new FileInfo(a.Filename);
            sb.Append("--unique-boundary-1\r\n");
            sb.Append("Content-Type: application/octet-stream; file=" + f.Name + "\r\n");
            sb.Append("Content-Transfer-Encoding: base64\r\n");
            sb.Append("Content-Disposition: attachment; filename=" + f.Name + "\r\n");
            sb.Append("\r\n");
            FileStream fs = f.OpenRead();
            binaryData = new Byte[fs.Length];
            long bytesRead = fs.Read(binaryData, 0, (int) fs.Length);
            fs.Close();
            string base64String = Convert.ToBase64String(binaryData, 0, binaryData.Length);

            for (int i = 0; i < base64String.Length; )
            {
              int nextchunk = 100;
              if (base64String.Length - (i + nextchunk) < 0)
              {
                nextchunk = base64String.Length - i;
              }
              sb.Append(base64String.Substring(i, nextchunk));
              sb.Append("\r\n");
              i += nextchunk;
            }
            sb.Append("\r\n");
          }
        }
        MsgBody = sb.ToString();
      }

      Senddata(s, ("DATA\r\n"));
      if (!Check_Response(s, SMTPResponse.DATA_SUCCESS))
      {
        s.Close();
        return false;
      }
      Header.Append("\r\n");
      Header.Append(MsgBody);
      Header.Append(".\r\n");
      Header.Append("\r\n");
      Header.Append("\r\n");
      Senddata(s, Header.ToString());
      if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
      {
        s.Close();
        return false;
      }

      Senddata(s, "QUIT\r\n");
      Check_Response(s, SMTPResponse.QUIT_SUCCESS);
      s.Close();
      return true;
    }

    private static void Senddata(Socket s, string msg)
    {
      byte[] _msg = Encoding.ASCII.GetBytes(msg);
      s.Send(_msg, 0, _msg.Length, SocketFlags.None);
    }

    private static bool Check_Response(Socket s, SMTPResponse response_expected)
    {
      string sResponse;
      int response;
      byte[] bytes = new byte[1024];
      while (s.Available == 0)
        Thread.Sleep(100);

      s.Receive(bytes, 0, s.Available, SocketFlags.None);
      sResponse = Encoding.ASCII.GetString(bytes);
      response = Convert.ToInt32(sResponse.Substring(0, 3));
      if (response != (int) response_expected)
      {
        return false;
      }
      return true;
    }
  }
}