/**
 * POP3Client.java
 *
 * Copyright (C) 1998-2000 FreeBeans <freebeans@mub.biglobe.ne.jp>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * Copyright (C) 1998-2000? FreeBeans <freebeans@mub.biglobe.ne.jp>
 *
 * ?????????????????????????Free Software Foundation 
 * ?????GNU ??????????????????????????????
 * ?????????????????????????????????????
 * ???????????????????
 * ?????????????????????????????????????
 * ?????????????????????????????????????
 * GNU ??????????????????
 *
 * ???????????????GNU ??????????????????
 * ???????????????Free Software Foundation, Inc., 675 Mass Ave,
 * Cambridge, MA 02139, USA ????????????
 */

package jp.gr.java_conf.roadster.net.pop;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.InterruptedIOException;
import java.io.OutputStream;
import java.io.PushbackInputStream;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;
import java.net.Socket;
import java.net.SocketException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.StringTokenizer;
import java.util.Vector;

import javax.net.ssl.SSLSocketFactory;

/**
 * POP3?????????????????.
 * POP3???????????????????.<BR>
 * ???????javax.mail.* ??????????????????.
 * <BR>
 * ???????????????????.<BR>
 * <OL>
 * <LI>POP3Client????????????????????????
 * ?????.<BR>
 * <UL><CODE>
 *  POP3Client pc = new POP3Client();<BR>
 *  pc.setHost("pop3.host.ne.jp");<BR>
 *  pc.setUser("user");<BR>
 *  pc.setPassword("password");<BR>
 *  pc.setAuthorizationMode(POP3Client.APOP_AUTHORIZATION);<BR>
 * </CODE></UL>
 * <LI>????????.<BR>
 *   <UL><CODE>
 *    pc.connect();<BR>
 *   </CODE></UL>
 * <LI>????????????.<BR>
 *   <UL><CODE>
 *    int count = pc.getMessageCount();<BR>
 *   </CODE></UL>
 * <LI>?????????????????????????.<BR>
 *   <UL><CODE>
 *    InputStream ins = pc.retrieve(i); // i ???????.<BR>
 *    while ((c = ins.read()) != -1) {
 *    <UL>
 *       // ?????????????.
 *    </UL>
 *    }<BR>
 *    ins.close();<BR>
 *   </CODE></UL>
 * <LI>???????????????.
 *   <UL><CODE>
 *    pc.delete(i); // i ???????.<BR>
 *   </CODE></UL>
 * <LI>????????????.<BR>
 *   <UL><CODE>
 *    pc.disconnect();<BR>
 *   </CODE></UL>
 * </OL>
 *
 * ??????????????????????????????.<BR>
 * <OL>
 *  <LI>TCP/IP??????????????(greeting)????????.
 *  <LI>USER?????PASS??????????????.<BR>
 *      ????APOP???????????.
 *  <LI>LIST ??????????????????????????.<BR>
 *      +OK ...<BR>
 *      1 203[CRLF]<BR>
 *      2 345[CRLF]<BR>
 *      (??)<BR>
 *      .[CRLF]<BR>
 *  <LI>????????????????????512 ??????????.<BR>
 *      ????RETR ?????????????????????????????.
 * </OL>
 *
 */
public class POP3Client implements Serializable {
	/**
	 * ???????????.
	 */
	static final long serialVersionUID = -3928372169782263062L;
	
	/**
	 * ??????????( = 512???).
	 * ????????????????????.
	 */
	private static final int MAX_LINE_LENGTH = 512;

	/**
	 * ??????????????????.
	 */
	private static final String ENCODE = "8859_1";

	/**
	 * ??????POP???(=110)
	 */
	protected static final int DEFAULT_POP3_PORT = 110;

	/**
	 * CR???.
	 */
	protected static final byte CR = 0x0d;
	
	/**
	 * LF???.
	 */
	protected static final byte LF = 0x0a;

	/**
	 * USER ????.
	 */
	protected static final String COMMAND_USER = "USER";
	
	/**
	 * PASS ????.
	 */
	protected static final String COMMAND_PASS = "PASS";
	
	/**
	 * QUIT ????.
	 */
	protected static final String COMMAND_QUIT = "QUIT";

	/**
	 * STAT ????.
	 */
	protected static final String COMMAND_STAT = "STAT";

	/**
	 * LIST ????.
	 */
	protected static final String COMMAND_LIST = "LIST";
	
	/**
	 * RETR ????.
	 */
	protected static final String COMMAND_RETR = "RETR";
	
	/**
	 * DELE ????.
	 */
	protected static final String COMMAND_DELE = "DELE";
	
	/**
	 * NOOP ????.
	 */
	protected static final String COMMAND_NOOP = "NOOP";
	
	/**
	 * RSET ????.
	 */
	protected static final String COMMAND_RSET = "RSET";
	
	/**
	 * APOP ????.
	 */
	protected static final String COMMAND_APOP = "APOP";
	
	/**
	 * TOP ????.
	 */
	protected static final String COMMAND_TOP = "TOP";
	
	/**
	 * UIDL ????.
	 */
	protected static final String COMMAND_UIDL = "UIDL";

	/**
	 * ????.
	 */
	protected static final String RESPONSE_OK = "+OK";
	
	/**
	 * ?????.
	 */
	protected static final String RESPONSE_ERR = "-ERR";
	
	/**
	 * ????????(USER/PASS ???????????
	 *
	 * @see #setAuthorizationMode(int)
	 */
	public static final int NORMAL_AUTHORIZATION = 1;
	
	/**
	 * APOP?????.
	 *
	 * @see #setAuthorizationMode(int)
	 */
	public static final int APOP_AUTHORIZATION = 2;
	
	/**
	 * @serial	POP????. ????????????????.
	 */
	private String user;
	
	/**
	 * ?????.
	 * ????????????????????? transient ???.
	 */
	private transient String password;
	
	/**
	 * @serial	POP???????.
	 */
	private String host;
	
	/**
	 * @serial	POP????????.
	 */
	private int port = -1;
	
	/**
	 * @serial	?????. ?????? NORMAL_AUTHORIZATION
	 */
	private int authorizationMode = NORMAL_AUTHORIZATION;
	
	/**
	 * ???????.
	 */
	protected transient Socket socket;

	/**
	 * ???????????? Stream.
	 */
	protected transient InputStream in;

	/**
	 * ??????????? Stream.
	 */
	protected transient OutputStream out;

	/**
	 * ????????????????????.
	 */
	protected transient boolean connected = false;
	
	/**
	 * ??????????????????.
	 */
	private transient byte responseBytes[];
	
	/**
	 * ????????????????????????????.
	 */
	private transient String status;
	
	/**
	 * ??????????????????(greeting).
	 */
	private transient String greeting;
	
	/**
	 * LIST ????????????????????.
	 */
	protected transient String messageList[] = null;
	
	/**
	 * UIDL ????????????????????.
	 */
	protected transient String uidList[] = null;
	
	/**
	 * ????????????????????.
	 */
	protected transient POP3MessageInputStream messageInput = null;
	
	/**
	 * @serial ???????.
	 */
	private boolean debug;
	
	/**
	 * @serial	?????????
	 */
	protected int timeout;
	
	/**
	 * @serial	?????????????
	 */
	private String preConnectCommand;
	
	/**
	 * 是否使用ssl
	 */
	private boolean ssl;
	
	/**
	 * ???????????POP3Client????????????.
	 */
	public POP3Client() {
		// ?????.
	}

	/**
	 * ?????????????????????? POP3Client????????????.
	 *
	 * @param	host	????.
	 * @exception	java.lang.IllegalArgumentException	host ? null ???.
	 */
	public POP3Client(String host) {
		this(host, DEFAULT_POP3_PORT);
	}

	/**
	 * ????????????????? POP3Client????????????.
	 *
	 * @param	host	????.
	 * @param	port	?????.
	 * @exception	java.lang.IllegalArgumentException	host ? null ???.
	 */
	public POP3Client(String host, int port) {
		setHost(host);
		setPort(port);
	}
	
	/**
	 * ??????????????.
	 * ???????????????System.err ???.
	 *
	 * @param	msg	???????.
	 */
	protected void debugOut(String msg) {
		if (debug) {
			StringBuffer buff = new StringBuffer("DEBUG:");
			buff.append(msg);
			System.err.println(buff.toString());
		}
	}
	
	public void setDebug(boolean mode) {
		this.debug = mode;
	}
	
	public boolean getDebug() {
		return debug;
	}
	
	/**
	 * ??????????????????.
	 * CRLF ?????????.
	 *
	 * @return	????????????????.<BR>
	 *          ???????CRLF??????????????.
	 * @exception java.io.IOException	IO??????????.
	 */
	protected synchronized String readResponseLine() throws IOException {
		boolean cr = false;
		int i;
		for (i = 0; i < responseBytes.length; ++i) {
			int c = in.read();
			if (c == -1) {
				break;
			}
			responseBytes[i] = (byte) c;
			if (responseBytes[i] == CR) {
				cr = true;
			} else if (responseBytes[i] == LF && cr == true) {
				break;
			} else {
				cr = false;
			}
		}
		if( i== 0)
			return "+OK";
		return new String(responseBytes, 0, i - 1, ENCODE);
	}
	
	/**
	 * ?????TCP/IP???????.
	 * ?????????????????????????????.<BR>
	 *
	 * @exception	java.io.IOException	IO??????????.
	 * @exception	java.lang.IllegalStateException	???????????????.
	 */
	protected synchronized void openConnection() throws IOException {
		if (isConnected()) {
			throw new IllegalStateException("Already connected.");
		}
		String cmd = getPreConnectCommand();
		if (cmd != null) {
			debugOut("Execute preconnect command:" + cmd);