/*
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.net.pop3;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.lang.StringBuffer;
import java.util.Enumeration;
import java.util.Vector;
import org.apache.commons.net.MalformedServerReplyException;
import org.apache.commons.net.ProtocolCommandListener;
import org.apache.commons.net.ProtocolCommandSupport;
import org.apache.commons.net.SocketClient;

/***
 * The POP3 class is not meant to be used by itself and is provided
 * only so that you may easily implement your own POP3 client if
 * you so desire.  If you have no need to perform your own implementation,
 * you should use POP3Client.
 * 

 * Rather than list it separately for each method, we mention here that
 * every method communicating with the server and throwing an IOException
 * can also throw a
 * 
 * MalformedServerReplyException , which is a subclass
 * of IOException.  A MalformedServerReplyException will be thrown when
 * the reply received from the server deviates enough from the protocol
 * specification that it cannot be interpreted in a useful manner despite
 * attempts to be as lenient as possible.
 * 

 * 

 * @author Daniel F. Savarese
 * @see POP3Client
 * @see org.apache.commons.net.MalformedServerReplyException
 ***/

public class POP3 extends SocketClient
{
    /*** The default POP3 port.  Set to 110 according to RFC 1288. ***/
    public static final int DEFAULT_PORT = 110;
    /***
     * A constant representing the state where the client is not yet connected
     * to a POP3 server.
     ***/
    public static final int DISCONNECTED_STATE = -1;
    /***  A constant representing the POP3 authorization state. ***/
    public static final int AUTHORIZATION_STATE = 0;
    /***  A constant representing the POP3 transaction state. ***/
    public static final int TRANSACTION_STATE = 1;
    /***  A constant representing the POP3 update state. ***/
    public static final int UPDATE_STATE = 2;

    static final String _OK = "+OK";
    static final String _ERROR = "-ERR";

    // We have to ensure that the protocol communication is in ASCII
    // but we use ISO-8859-1 just in case 8-bit characters cross
    // the wire.
    private static final String __DEFAULT_ENCODING = "ISO-8859-1";

    private int __popState;
    private BufferedWriter __writer;
    private StringBuffer __commandBuffer;

    BufferedReader _reader;
    int _replyCode;
    String _lastReplyLine;
    Vector _replyLines;

    /***
     * A ProtocolCommandSupport object used to manage the registering of
     * ProtocolCommandListeners and te firing of ProtocolCommandEvents.
     ***/
    protected ProtocolCommandSupport _commandSupport_;

    /***
     * The default POP3Client constructor.  Initializes the state
     * to DISCONNECTED_STATE.
     ***/
    public POP3()
    {
        setDefaultPort(DEFAULT_PORT);
        __commandBuffer = new StringBuffer();
        __popState = DISCONNECTED_STATE;
        _reader = null;
        __writer = null;
        _replyLines = new Vector();
        _commandSupport_ = new ProtocolCommandSupport(this);
    }

    private void __getReply() throws IOException
    {
        String line;

        _replyLines.setSize(0);
        line = _reader.readLine();

        if (line == null)
            throw new EOFException("Connection closed without indication.");

        if (line.startsWith(_OK))
            _replyCode = POP3Reply.OK;
        else if (line.startsWith(_ERROR))
            _replyCode = POP3Reply.ERROR;
        else
            throw new
            MalformedServerReplyException(
                "Received invalid POP3 protocol response from server.");

        if (_commandSupport_.getListenerCount() > 0)
            _commandSupport_.fireReplyReceived(_replyCode, getReplyString());

        _replyLines.addElement(line);
        _lastReplyLine = line;
    }


    /***
     * Performs connection initialization and sets state to
     *  AUTHORIZATION_STATE .
     ***/
    protected void _connectAction_() throws IOException
    {
        super._connectAction_();
        _reader =
          new BufferedReader(new InputStreamReader(_input_,
                                                   __DEFAULT_ENCODING));
        __writer =
          new BufferedWriter(new OutputStreamWriter(_output_,
                                                    __DEFAULT_ENCODING));
        __getReply();
        setState(AUTHORIZATION_STATE);
    }


    /***
     * Adds a ProtocolCommandListener.  Delegates this task to
     *  _commandSupport_ .
     * 

     * @param listener  The ProtocolCommandListener to add.
     ***/
    public void addProtocolCommandListener(ProtocolCommandListener listener)
    {
        _commandSupport_.addProtocolCommandListener(listener);
    }

    /***
     * Removes a ProtocolCommandListener.  Delegates this task to
     *  _commandSupport_ .
     * 

     * @param listener  The ProtocolCommandListener to remove.
     ***/
    public void removeProtocolCommandistener(ProtocolCommandListener listener)
    {
        _commandSupport_.removeProtocolCommandListener(listener);
    }


    /***
     * Sets POP3 client state.  This must be one of the
     * _STATE constants.
     * 

     * @param state  The new state.
     ***/
    public void setState(int state)
    {
        __popState = state;
    }


    /***
     * Returns the current POP3 client state.
     * 

     * @return The current POP3 client state.
     ***/
    public int getState()
    {
        return __popState;
    }


    /***
     * Retrieves the additional lines of a multi-line server reply.
     ***/
    public void getAdditionalReply() throws IOException
    {
        String line;

        line = _reader.readLine();
        while (line != null)
        {
            _replyLines.addElement(line);
            if (line.equals("."))
                break;
            line = _reader.readLine();
        }
    }


    /***
     * Disconnects the client from the server, and sets the state to
     *  DISCONNECTED_STATE .  The reply text information
     * from the last issued command is voided to allow garbage collection
     * of the memory used to store that information.
     * 

     * @exception IOException  If there is an error in disconnecting.
     ***/
    public void disconnect() throws IOException
    {
        super.disconnect();
        _reader = null;
        __writer = null;
        _lastReplyLine = null;
        _replyLines.setSize(0);
        setState(DISCONNECTED_STATE);
    }


    /***
     * Sends a command an arguments to the server and returns the reply code.
     * 

     * @param command  The POP3 command to send.
     * @param args     The command arguments.
     * @return  The server reply code (either POP3Reply.OK or POP3Reply.ERROR).
     ***/
    public int sendCommand(String command, String args) throws IOException
    {
        String message;

        __commandBuffer.setLength(0);
        __commandBuffer.append(command);

        if (args != null)
        {
            __commandBuffer.append(' ');
            __commandBuffer.append(args);
        }
        __commandBuffer.append(SocketClient.NETASCII_EOL);

        __writer.write(message = __commandBuffer.toString());
        __writer.flush();

        if (_commandSupport_.getListenerCount() > 0)
            _commandSupport_.fireCommandSent(command, message);

        __getReply();
        return _replyCode;
    }

    /***
     * Sends a command with no arguments to the server and returns the
     * reply code.
     * 

     * @param command  The POP3 command to send.
     * @return  The server reply code (either POP3Reply.OK or POP3Reply.ERROR).
     ***/
    public int sendCommand(String command) throws IOException
    {
        return sendCommand(command, null);
    }

    /***
     * Sends a command an arguments to the server and returns the reply code.
     * 

     * @param command  The POP3 command to send
     *                  (one of the POP3Command constants).
     * @param args     The command arguments.
     * @return  The server reply code (either POP3Reply.OK or POP3Reply.ERROR).
     ***/
    public int sendCommand(int command, String args) throws IOException
    {
        return sendCommand(POP3Command._commands[command], args);
    }

    /***
     * Sends a command with no arguments to the server and returns the
     * reply code.
     * 

     * @param command  The POP3 command to send
     *                  (one of the POP3Command constants).
     * @return  The server reply code (either POP3Reply.OK or POP3Reply.ERROR).
     ***/
    public int sendCommand(int command) throws IOException
    {
        return sendCommand(POP3Command._commands[command], null);
    }


    /***
     * Returns an array of lines received as a reply to the last command
     * sent to the server.  The lines have end of lines truncated.  If
     * the reply is a single line, but its format ndicates it should be
     * a multiline reply, then you must call
     *  getAdditionalReply()  to
     * fetch the rest of the reply, and then call getReplyStrings
     * again.  You only have to worry about this if you are implementing
     * your own client using the  sendCommand  methods.
     * 

     * @return The last server response.
     ***/
    public String[] getReplyStrings()
    {
        String[] lines;
        lines = new String[_replyLines.size()];
        _replyLines.copyInto(lines);
        return lines;
    }

    /***
     * Returns the reply to the last command sent to the server.
     * The value is a single string containing all the reply lines including
     * newlines.  If the reply is a single line, but its format ndicates it
     * should be a multiline reply, then you must call
     *  getAdditionalReply()  to
     * fetch the rest of the reply, and then call getReplyString
     * again.  You only have to worry about this if you are implementing
     * your own client using the  sendCommand  methods.
     * 

     * @return The last server response.
     ***/
    public String getReplyString()
    {
        Enumeration enum;
        StringBuffer buffer = new StringBuffer(256);

        enum = _replyLines.elements();
        while (enum.hasMoreElements())
        {
            buffer.append((String)enum.nextElement());
            buffer.append(SocketClient.NETASCII_EOL);
        }

        return buffer.toString();
    }

}