using System;
using System.ComponentModel;
using System.Net.Sockets;
using System.IO;
using System.Text;

namespace Pop3Com
{
	/// <summary>
	/// Pop3 的摘要說明:Pop3類完成郵件的接收功能。
	/// </summary>
	public class Pop3: Component
	{
		private string _host = "127.0.0.1";
		private int _port = 110;
		private string _userName;
		private string _passWord;
		private int _numOfMails;
		private double _totalSize;
		private string _body;
		private string _status;
		private Pop3Connection con;
		private const string CRLF = "\r\n";
		private const string serverConfig = "服務器配置";
		private const string reciveEvent = "接收事件";

		public delegate void MailRecivedDelegate();
		[Category(reciveEvent)]    [Description("郵件接收成功觸發的事件")]
		public event MailRecivedDelegate OnMailRecived;
		[Category(serverConfig)]
		public string Host
		{
			get{return _host;}
			set
			{
				if (value == null || value.Trim().Length == 0)
				{
					throw new ArgumentException("無效的主機名");
				}
				_host = value;
			}
		}
		[Category(serverConfig)]
		public int Port
		{
			get{return _port;}
			set
			{
				if (value <= 0)
				{
					throw new ArgumentException("無效的端口");
				}
				_port = value;
			}
		}
		[Category(serverConfig)]
		public string UserName
		{
			get{return _userName;}
			set
			{
				if (value == null || value.Trim().Length == 0)
				{
					throw new ArgumentException("無效的用戶名");
				}
				_userName = value;
			}
		}
		[Category(serverConfig)]
		public string PassWord
		{
			get{return _passWord;}
			set
			{
				if (value == null || value.Trim().Length == 0)
				{
					throw new ArgumentException("無效的密碼");
				}
				_passWord = value;
			}
		}
		[Browsable(false)]
		public int NumOfMails
		{
			get{return _numOfMails;}
		}
		[Browsable(false)]
		public double TotalSize
		{
			get{return _totalSize;}
		}
		[Browsable(false)]
		public string Body
		{
			get{return _body;}
		}
		[Browsable(false)]
		public string Status
		{
			get{return _status;}
		}

		/// <summary>
		/// 接收郵件信息
		/// </summary>
		public void ReciveMessage()
		{
			//避免線程沖突
			lock(this)
			{
				// 設置初始連接
				con = new Pop3Connection();
				if (_port <= 0)
					_port = 110;
				con.Open(_host, _port);
				
				StringBuilder buf = new StringBuilder();
				string response;
				int code;
				
				// 獲取歡迎信息
				con.GetReply(out response,out code);
				_status += response;

				//登錄服務器過程
				buf.Append("USER");
				buf.Append(_userName);
				buf.Append(CRLF);
				con.SendCommand(buf.ToString());
				con.GetReply(out response, out code);
				_status += response;
				
				buf.Length = 0;
				buf.Append("PASS");
				buf.Append(_passWord);
				buf.Append(CRLF);
				con.SendCommand(buf.ToString());
				con.GetReply(out response, out code);
				_status += response;

				//向服務器發送STAT命令，從而取得郵箱的相關信息：郵件數量和大小
				buf.Length = 0;
				buf.Append("STAT");
				buf.Append(CRLF);
				con.SendCommand(buf.ToString());
				con.GetReply(out response, out code);
				_status += response;

				//將總郵件數和郵件大小分離
				string[] totalStat = response.Split(new char[]{' '});
				_numOfMails = Int32.Parse(totalStat[1]);
				_totalSize = (double)Int32.Parse(totalStat[2]);
				
				for(int i = 0; i < _numOfMails; i++)
				{
					//根據郵件編號從服務器獲得相應郵件
					buf.Length = 0;
					buf.Append("RETR");
					buf.Append(i.ToString());
					buf.Append(CRLF);
					con.SendCommand(buf.ToString());
					con.GetReply(out response, out code);

					if (response[0] != '-')
					{
						//不斷地讀取郵件內容，只到結束標志：英文句號
						while(response != ".")
						{
							_body += response;
							con.GetReply(out response, out code);
						}
					}
					else
						_status += response;
				}

				//向服務器發送QUIT命令從而結束和POP3服務器的會話
				buf.Length = 0;
				buf.Append("QUIT");
				buf.Append(CRLF);
				con.SendCommand(buf.ToString());
				con.GetReply(out response, out code);
				_status += response;

				con.Close();
				
				// 郵件接收成功后觸發的事件
				if (OnMailRecived != null)
				{
					OnMailRecived();
				}
			}
		}
	}

	/// <summary>
	/// Pop3Connection 的摘要說明:Pop3Connection類完成了與主機的連接、通訊和關閉連接等功能。
	/// </summary>
	public class Pop3Connection
	{
		private TcpClient socket;
		private StreamReader reader;
		private StreamWriter writer;
		private bool _connected;

		public bool Connected
		{
			get{return _connected;}
		}

		public Pop3Connection()
		{
			//
			// TODO: 在此處添加構造函數邏輯
			//			
			socket = new TcpClient();
		}


		public void Open(string host, int port)
		{
			if (host == null || host.Trim().Length == 0 || port <= 0)
			{
				throw new ArgumentException("參數值無效");
			}
			try
			{
				socket.Connect(host, port);
				reader = new StreamReader(socket.GetStream(),System.Text.Encoding.ASCII);
				writer = new StreamWriter(socket.GetStream(),System.Text.Encoding.ASCII);
				_connected = true;
			}
			catch(ArgumentNullException)
			{
				throw new ArgumentException("主機名為空,無效的主機名");
			}
			catch(ArgumentOutOfRangeException)
			{
				throw new ArgumentException("端口號port不在主機的最大端口號和最小端口號之間");
			}
			catch(ObjectDisposedException)
			{
				throw new ArgumentException("主機TcpClient 被關閉");
			}
		}
		internal void SendCommand(string cmd)
		{
			try
			{
				writer.WriteLine(cmd);
				writer.Flush();
			}
			catch(Exception e)
			{
				throw new ArgumentException(e.Message);
			}
		}
		internal void GetReply(out string reply, out int code)
		{
			try
			{
				reply = reader.ReadLine();
			}
			catch(Exception e)
			{
				throw new ArgumentException(e.Message);
			}
			code = -1;//reply == null ? -1 : Int32.Parse(reply.Substring(0, 3)); 
		}
		internal void Close()
		{
			reader.Close();
			writer.Flush();
			writer.Close();
			reader = null;
			writer = null;
			socket.Close();
			_connected = false;
		}
	}
}