/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

/***
 * Java TelnetD library (embeddable telnet daemon)
 * Copyright (c) 2000-2005 Dieter Wimberger
 * All rights reserved.
 * <p/>
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * <p/>
 * Neither the name of the author nor the names of its contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 * <p/>
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS ``AS
 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 ***/

package org.apache.felix.gogo.jline.telnet;

import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.apache.felix.gogo.jline.telnet.ConnectionEvent.Type;

/**
 * Class that represents the TelnetIO implementation. It contains
 * an inner IACHandler class to handle the telnet protocol level
 * communication.
 * <p/>
 * Although supposed to work full-duplex, we only process the telnet protocol
 * layer communication in case of reading requests from the higher levels.
 * This is the only way to meet the one thread per connection requirement.
 * </p>
 * <p/>
 * The output is done via byte-oriented streams, definately suitable for the
 * telnet protocol. The format of the  output is UTF-8 (Unicode), which is a
 * standard and supported by any telnet client, including the ones included
 * in Microsoft OS's.
 * </p>
 * <em>Notes:</em>
 * <ul>
 * <li>The underlying output is buffered, to ensure that all bytes written
 * are send, the flush() method has to be called.
 * <li>This low-level routines ensure nice multithreading behaviour on I/O.
 * Neither large outputs, nor input sequences excuted by the connection thread
 * can hog the system.
 * </ul>
 *
 * @author Dieter Wimberger
 * @version 2.0 (16/07/2006)
 */
public class TelnetIO {

    /**
     * Interpret As Command
     */
    protected static final int IAC = 255;
    /**
     * Go Ahead <BR> Newer Telnets do not make use of this option
     * that allows a specific communication mode.
     */
    protected static final int GA = 249;
    /**
     * Negotiation: Will do option
     */
    protected static final int WILL = 251;
    /**
     * Negotiation: Wont do option
     */
    protected static final int WONT = 252;
    /**
     * Negotiation: Do option
     */
    protected static final int DO = 253;
    /**
     * Negotiation:  Dont do option
     */
    protected static final int DONT = 254;
    /**
     * Marks start of a subnegotiation.
     */
    protected static final int SB = 250;
    /**
     * Marks end of subnegotiation.
     */
    protected static final int SE = 240;
    /**
     * No operation
     */
    protected static final int NOP = 241;
    /**
     * Data mark its the data part of a SYNCH which helps to clean up the buffers between
     * Telnet Server &lt;-&gt; Telnet Client. <BR>
     * It should work like this we send a TCP urgent package and &lt;IAC&gt; &lt;DM&gt; the receiver
     * should get the urgent package (SYNCH) and just discard everything until he receives
     * our &lt;IAC&gt; &lt;DM&gt;.<BR>
     * <EM>Remark</EM>:
     * <OL>
     * <LI>can we send a TCP urgent package?
     * <LI>can we make use of the thing at all?
     * </OL>
     */
    protected static final int DM = 242;
    /**
     * Break
     */
    protected static final int BRK = 243;
    /**
     * Interrupt Process
     */
    protected static final int IP = 244;
    /**
     * Abort Output
     */
    protected static final int AO = 245;

    /**** Implementation of OutputStream ****************************************************/
    /**
     * Are You There
     */
    protected static final int AYT = 246;
    /**
     * Erase Char
     */
    protected static final int EC = 247;
    /**
     * Erase Line
     */
    protected static final int EL = 248;
    /**
     * Telnet Option: ECHO
     */
    protected static final int ECHO = 1;
    /**
     * Telnet Option: SUPress Go Ahead<br>
     * This will be negotiated, all new telnet protocol implementations are
     * recommended to do this.
     */
    protected static final int SUPGA = 3;
    /**
     * Telnet Option: Negotiate About Window Size<br>
     * <ul>
     * <li>Server request is IAC DO NAWS
     * <li>Client response contains subnegotiation with data (columns, rows).
     * </ul>
     */
    protected static final int NAWS = 31;
    /**
     * Telnet Option: Terminal TYPE <br>
     * <ul>
     * <li>Server request contains subnegotiation SEND
     * <li>Client response contains subnegotiation with data IS,terminal type string
     * </ul>
     */
    protected static final int TTYPE = 24;
    /**
     * TTYPE subnegotiation: IS
     */
    protected static final int IS = 0;
    /**
     * TTYPE subnegotiation: SEND
     */
    protected static final int SEND = 1;

    /**** End implementation of OutputStream ***********************************************/


    /**** Implementation of InputStream ****************************************************/
    /**
     * Telnet Option: Logout<br>
     * This allows nice goodbye to time-outed or unwanted clients.
     */
    protected static final int LOGOUT = 18;
    /**
     * Telnet Option: Linemode
     * <p/>
     * The infamous line mode option.
     */
    protected static final int LINEMODE = 34;
    protected static final int LM_MODE = 1;
    protected static final int LM_EDIT = 1;
    protected static final int LM_TRAPSIG = 2;

    /**** Implementation of InputStream ****************************************************/


    /****
     * Following methods implement init/request/answer procedures for telnet
     * protocol level communication.
     */
    protected static final int LM_MODEACK = 4;
    protected static final int LM_FORWARDMASK = 2;
    protected static final int LM_SLC = 3;
    protected static final int LM_SLC_NOSUPPORT = 0;
    protected static final int LM_SLC_DEFAULT = 3;


    /**** End telnet protocol level communication methods *******************************/
    protected static final int LM_SLC_VALUE = 2;


    /** Constants declaration ***********************************************/

//Telnet Protocoll Constants
    protected static final int LM_SLC_CANTCHANGE = 1;
    protected static final int LM_SLC_LEVELBITS = 3;
    protected static final int LM_SLC_ACK = 128;
    protected static final int LM_SLC_FLUSHIN = 64;
    protected static final int LM_SLC_FLUSHOUT = 32;
    protected static final int LM_SLC_SYNCH = 1;
    protected static final int LM_SLC_BRK = 2;
    protected static final int LM_SLC_IP = 3;
    protected static final int LM_SLC_AO = 4;
    protected static final int LM_SLC_AYT = 5;
    protected static final int LM_SLC_EOR = 6;

    /**
     * The following implement the NVT (network virtual terminal) which offers the concept
     * of a simple "printer". They are the basical meanings of control possibilities
     * on a standard telnet implementation.
     */
    protected static final int LM_SLC_ABORT = 7;
    protected static final int LM_SLC_EOF = 8;
    protected static final int LM_SLC_SUSP = 9;
    /**
     * Telnet Option: Environment
     */
    protected static final int NEWENV = 39;
    protected static final int NE_INFO = 2;

    /**
     * The following are constants for supported options,
     * which can be negotiated based upon the telnet protocol
     * specification.
     */
    protected static final int NE_VAR = 0;
    protected static final int NE_VALUE = 1;

    /**
     * The following options are options for which we also support subnegotiation
     * based upon the telnet protocol specification.
     */
    protected static final int NE_ESC = 2;
    protected static final int NE_USERVAR = 3;
    protected static final int NE_VAR_OK = 2;
    protected static final int NE_VAR_DEFINED = 1;
    protected static final int NE_VAR_DEFINED_EMPTY = 0;
    protected static final int NE_VAR_UNDEFINED = -1;
    protected static final int NE_IN_ERROR = -2;
    protected static final int NE_IN_END = -3;
    protected static final int NE_VAR_NAME_MAXLENGTH = 50;
    protected static final int NE_VAR_VALUE_MAXLENGTH = 1000;
    /**
     * Unused
     */
    protected static final int EXT_ASCII = 17;        //Defines Extended ASCII
    protected static final int SEND_LOC = 23;        //Defines Send Location
    protected static final int AUTHENTICATION = 37;    //Defines Authentication
    protected static final int ENCRYPT = 38;            //Defines Encryption
    private static final Logger LOG = Logger.getLogger(TelnetIO.class.getName());
    /**
     * Window Size Constants
     */
    private static final int SMALLEST_BELIEVABLE_WIDTH = 20;
    private static final int SMALLEST_BELIEVABLE_HEIGHT = 6;
    private static final int DEFAULT_WIDTH = 80;
    private static final int DEFAULT_HEIGHT = 25;
    private Connection connection;                    //a reference to the connection this instance works for
    private ConnectionData connectionData;            //holds all important information of the connection
    private DataOutputStream out;                    //the byte oriented outputstream
    private DataInputStream in;                        //the byte oriented input stream
    //Aggregations
    private IACHandler iacHandler;                    //holds a reference to the aggregated IACHandler
    //Members
    private InetAddress localAddress;                //address of the host the telnetd is running on
    private boolean noIac = false;                    //describes if IAC was found and if its just processed
    @SuppressWarnings("unused")
    private boolean initializing;
    private boolean crFlag;
    /**
     * Creates a TelnetIO object for the given connection.<br>
     * Input- and OutputStreams are properly set and the primary telnet
     * protocol initialization is carried out by the inner IACHandler class.<BR>
     */
    public TelnetIO() {
    }//constructor

    public void initIO() throws IOException {
        //we make an instance of our inner class
        iacHandler = new IACHandler();
        //we setup underlying byte oriented streams
        in = new DataInputStream(connectionData.getSocket().getInputStream());
        out = new DataOutputStream(new BufferedOutputStream(connectionData.getSocket().getOutputStream()));

        //we save the local address (necessary?)
        localAddress = connectionData.getSocket().getLocalAddress();
        crFlag = false;
        //bootstrap telnet communication
        initTelnetCommunication();
    }//initIO

    public void setConnection(Connection con) {
        connection = con;
        connectionData = connection.getConnectionData();
    }//setConnection

    /**
     * Method to output a byte. Ensures that CR(\r) is never send
     * alone,but CRLF(\r\n), which is a rule of the telnet protocol.
     *
     * @param b Byte to be written.
     */
    public void write(byte b) throws IOException {
        //ensure CRLF(\r\n) is written for LF(\n) to adhere
        //to the telnet protocol.
        if (!crFlag && b == 10) {
            out.write(13);
        }

        out.write(b);

        crFlag = b == 13;
    }//write(byte)

    /**
     * Method to output an int.
     *
     * @param i Integer to be written.
     */
    public void write(int i)
            throws IOException {
        write((byte) i);
    }//write(int)

    /**
     * Method to write an array of bytes.
     *
     * @param sequence byte[] to be written.
     */
    public void write(byte[] sequence) throws IOException {
        for (byte b : sequence) {
            write(b);
        }
    }//write(byte[])

    /**
     * Method to output an array of int' s.
     *
     * @param sequence int [] to write
     */
    public void write(int[] sequence) throws IOException {
        for (int i : sequence) {
            write((byte) i);
        }
    }//write(int[])

    /**
     * Method to write a char.
     *
     * @param ch char to be written.
     */
    public void write(char ch) throws IOException {
        write((byte) ch);
    }//write(char)

    /**
     * Method to output a string.
     *
     * @param str String to be written.
     */
    public void write(String str) throws IOException {
        write(str.getBytes());
    }//write(String)

    /**
     * Method to flush all buffered output.
     */
    public void flush() throws IOException {
        out.flush();
    }//flush

    /**
     * Method to close the underlying output stream to free system resources.<br>
     * Most likely only to be called by the ConnectionManager upon clean up of
     * connections that ended or died.
     */
    public void closeOutput() {

        try {
            //sends telnetprotocol logout acknowledgement
            write(IAC);
            write(DO);
            write(LOGOUT);
            //and now close underlying outputstream

            out.close();
        } catch (IOException ex) {
            LOG.log(Level.SEVERE, "closeOutput()", ex);
            //handle?
        }
    }//close

    private void rawWrite(int i) throws IOException {
        out.write(i);
    }//rawWrite

    /**
     * Method to read a byte from the InputStream.
     * Invokes the IACHandler upon IAC (Byte=255).
     *
     * @return int read from stream.
     */
    public int read() throws IOException {
        int c = rawread();
        //if (c == 255) {
        noIac = false;
        while ((c == 255) && (!noIac)) {
            /**
             * Read next, and invoke
             * the IACHandler he is taking care of the rest. Or at least he should :)
             */
            c = rawread();
            if (c != 255) {
                iacHandler.handleC(c);
                c = rawread();
            } else {
                noIac = true;
            }
        }
        return stripCRSeq(c);
    }//read

    /**
     * Method to close the underlying inputstream to free system resources.<br>
     * Most likely only to be called by the ConnectionManager upon clean up of
     * connections that ended or died.
     */
    public void closeInput() {
        try {
            in.close();
        } catch (IOException e) {
            //handle?
        }
    }//closeInput

    /**
     * This method reads an unsigned 16bit Integer from the stream,
     * its here for getting the NAWS Data Values for height and width.
     */
    private int read16int() throws IOException {
        int c = in.readUnsignedShort();
        return c;
    }//read16int

    /**
     * The following options are options which might be of interest, but are not
     * yet implemented or in use.
     */

    /**
     * Method to read a raw byte from the InputStream.<br>
     * Telnet protocol layer communication is filtered and processed here.
     *
     * @return int read from stream.
     */
    private int rawread() throws IOException {
        int b = 0;

        //try {
        b = in.readUnsignedByte();
        connectionData.activity();
        return b;
    }//rawread

    /**
     * Checks for the telnet protocol specified  CR followed by NULL or LF<BR>
     * Subsequently reads for the next byte and forwards
     * only a ENTER represented by LF internally.
     */
    private int stripCRSeq(int input) throws IOException {
        if (input == 13) {
            rawread();
            return 10;
        }
        return input;
    }//stripCRSeq

    /**
     * Method that initializes the telnet communication layer.
     */
    private void initTelnetCommunication() {

        initializing = true;
        try {
            //start out, some clients just wait
            if (connectionData.isLineMode()) {
                iacHandler.doLineModeInit();
                LOG.log(Level.FINE, "Line mode initialized.");
            } else {
                iacHandler.doCharacterModeInit();
                LOG.log(Level.FINE, "Character mode initialized.");
            }
            //open for a defined timeout so we read incoming negotiation
            connectionData.getSocket().setSoTimeout(1000);
            read();

        } catch (Exception e) {
            //handle properly
            //log.error("initTelnetCommunication()",e);
        } finally {
            //this is important, dont ask me why :)
            try {
                connectionData.getSocket().setSoTimeout(0);
            } catch (Exception ex) {
                LOG.log(Level.SEVERE, "initTelnetCommunication()", ex);
            }
        }
        initializing = false;
    }//initTelnetCommunication

    /**
     * Method that represents the answer to the
     * AreYouThere question of the telnet protocol specification
     * <p/>
     * Output of the String [HostAdress:Yes]
     */
    private void IamHere() {
        try {
            write("[" + localAddress.toString() + ":Yes]");
            flush();
        } catch (Exception ex) {
            LOG.log(Level.SEVERE, "IamHere()", ex);
        }
    }//IamHere

    /**
     * Network virtual terminal break.
     */
    private void nvtBreak() {
        connection.processConnectionEvent(new ConnectionEvent(connection, ConnectionEvent.Type.CONNECTION_BREAK));
    }//nvtBreak

    /**
     * Method that checks reported terminal sizes and sets the
     * asserted values in the ConnectionData instance associated with
     * the connection.
     *
     * @param width  Integer that represents the Window width in chars
     * @param height Integer that represents the Window height in chars
     */
    private void setTerminalGeometry(int width, int height) {
        if (width < SMALLEST_BELIEVABLE_WIDTH) {
            width = DEFAULT_WIDTH;
        }
        if (height < SMALLEST_BELIEVABLE_HEIGHT) {
            height = DEFAULT_HEIGHT;
        }
        //DEBUG: write("[New Window Size " + window_width + "x" + window_height + "]");
        connectionData.setTerminalGeometry(width, height);
        connection.processConnectionEvent(new ConnectionEvent(connection,
                Type.CONNECTION_TERMINAL_GEOMETRY_CHANGED));
    }//setTerminalGeometry

    public void setEcho(boolean b) {
    }//setEcho

    /**
     * An inner class for handling incoming option negotiations implementing the <B>telnet protocol</B>
     * specification based upon following Standards and RFCs:
     * <OL>
     * <LI><A HREF="ftp://ds.internic.net/rfc/rfc854.txt">854 Telnet Protocol Specification</A>
     * <LI><A HREF="ftp://ds.internic.net/rfc/rfc855.txt">855 Telnet Option Specifications</A>
     * <LI><A HREF="ftp://ds.internic.net/rfc/rfc857.txt">857 Telnet Echo Option</A>
     * <LI><A HREF="ftp://ds.internic.net/rfc/rfc858.txt">858 Telnet Supress Go Ahead Option</A>
     * <LI><A HREF="ftp://ds.internic.net/rfc/rfc727.txt">727 Telnet Logout Option</A>
     * <LI><A HREF="ftp://ds.internic.net/rfc/rfc1073.txt">1073 Telnet Window Size Option</A>
     * <LI><A HREF="ftp://ds.internic.net/rfc/rfc1091.txt">1091 Telnet Terminal-Type Option</A>
     * </OL>
     * <p/>
     * Furthermore there are some more, which helped to solve problems, or might be important
     * for future enhancements:<BR>
     * <A HREF="ftp://ds.internic.net/rfc/rfc1143.txt">1143 The Q Method of Implementing Option Negotiation</A><BR>
     * <A HREF="ftp://ds.internic.net/rfc/rfc1416.txt">1416 Telnet Authentication Option</A><BR>
     * <p/>
     * After an intense study of the available material (mainly cryptical written RFCs,
     * a telnet client implementation for the macintosh based upon NCSA telnet, and a server side
     * implementation called key, a mud-like system completely written in Java) I realized
     * the problems we are facing regarding to the telnet protocol:
     * <OL>
     * <LI> a minimal spread of invented options, which means there are a lot of invented options,
     * but rarely they made it through to become a standard.
     * <LI> Dependency on a special type of implementation is dangerous in our case.
     * We are no kind of host that offers the user to run several processes at once,
     * a BBS is intended to be a single process the user is interacting with.
     * <LI> The <B>LAMER</B> has to be expected to log in with the standard Microsoft telnet
     * implementation. This means forget every nice feature and most of the almost-standards.
     * <p/>
     * </OL>
     * <BR>
     *
     * @author Dieter Wimberger
     * @version 1.1 16/06/1998
     * <p/>
     * <p/>
     * <B>To-Do</B>:<UL>
     * <LI>UNIX conform new style TTYPE negotiation. Setting a list and selecting from it...
     * </UL>
     */
    class IACHandler {

        /**
         * Telnet readin buffer
         * Here its implemented guys. Open your eyes upon this solution.
         * The others take a one byte solution :)
         */
        private int[] buffer = new int[2];

        /**
         * DO_ECHO or not
         */
        private boolean DO_ECHO = false;

        /**
         * DO_SUPGA or not
         */
        private boolean DO_SUPGA = false;

        /**
         * DO_NAWS or not
         */
        private boolean DO_NAWS = false;

        /**
         * DO_TTYPE or not
         */
        private boolean DO_TTYPE = false;

        /**
         * DO_LINEMODE or not
         */
        private boolean DO_LINEMODE = false;

        /**
         * DO_NEWENV or not
         */
        private boolean DO_NEWENV = false;

        /**
         * Are we waiting for a DO reply?
         */
        private boolean WAIT_DO_REPLY_SUPGA = false;
        private boolean WAIT_DO_REPLY_ECHO = false;
        private boolean WAIT_DO_REPLY_NAWS = false;
        private boolean WAIT_DO_REPLY_TTYPE = false;
        private boolean WAIT_DO_REPLY_LINEMODE = false;
        private boolean WAIT_LM_MODE_ACK = false;
        private boolean WAIT_LM_DO_REPLY_FORWARDMASK = false;
        private boolean WAIT_DO_REPLY_NEWENV = false;
        @SuppressWarnings("unused")
        private boolean WAIT_NE_SEND_REPLY = false;

        /**
         * Are we waiting for a WILL reply?
         */
        private boolean WAIT_WILL_REPLY_SUPGA = false;
        private boolean WAIT_WILL_REPLY_ECHO = false;
        private boolean WAIT_WILL_REPLY_NAWS = false;
        private boolean WAIT_WILL_REPLY_TTYPE = false;


        public void doCharacterModeInit() throws IOException {
            sendCommand(WILL, ECHO, true);
            sendCommand(DONT, ECHO, true); //necessary for some clients
            sendCommand(DO, NAWS, true);
            sendCommand(WILL, SUPGA, true);
            sendCommand(DO, SUPGA, true);
            sendCommand(DO, TTYPE, true);
            sendCommand(DO, NEWENV, true); //environment variables
        }//doCharacterModeInit

        public void doLineModeInit() throws IOException {
            sendCommand(DO, NAWS, true);
            sendCommand(WILL, SUPGA, true);
            sendCommand(DO, SUPGA, true);
            sendCommand(DO, TTYPE, true);
            sendCommand(DO, LINEMODE, true);
            sendCommand(DO, NEWENV, true);
        }//doLineModeInit


        /**
         * Method to handle a IAC that came in over the line.
         *
         * @param i (int)ed byte that followed the IAC
         */
        public void handleC(int i) throws IOException {
            buffer[0] = i;
            if (!parseTWO(buffer)) {
                buffer[1] = rawread();
                parse(buffer);
            }
            buffer[0] = 0;
            buffer[1] = 0;
        }//handleC

        /**
         * Method that parses for options with two characters.
         *
         * @param buf int [] that represents the first byte that followed the IAC first.
         * @return true when it was a two byte command (IAC OPTIONBYTE)
         */
        private boolean parseTWO(int[] buf) {
            switch (buf[0]) {
                case IAC:
                    //doubled IAC to escape 255 is handled within the
                    //read method.
                    break;
                case AYT:
                    IamHere();
                    break;
                case AO:
                case IP:
                case EL:
                case EC:
                case NOP:
                    break;
                case BRK:
                    nvtBreak();
                    break;
                default:
                    return false;
            }
            return true;
        }//parseTWO

        /**
         * Method that parses further on for options.
         *
         * @param buf that represents the first two bytes that followed the IAC.
         */
        private void parse(int[] buf) throws IOException {
            switch (buf[0]) {
        /* First switch on the Negotiation Option */
                case WILL:
                    if (supported(buf[1]) && isEnabled(buf[1])) {
                        // do nothing
                    } else {
                        if (waitDOreply(buf[1]) && supported(buf[1])) {
                            enable(buf[1]);
                            setWait(DO, buf[1], false);
                        } else {
                            if (supported(buf[1])) {
                                sendCommand(DO, buf[1], false);
                                enable(buf[1]);
                            } else {
                                sendCommand(DONT, buf[1], false);
                            }
                        }
                    }
                    break;
                case WONT:
                    if (waitDOreply(buf[1]) && supported(buf[1])) {
                        setWait(DO, buf[1], false);
                    } else {
                        if (supported(buf[1]) && isEnabled(buf[1])) {
                            // eanable() Method disables an Option that is already enabled
                            enable(buf[1]);
                        }
                    }
                    break;
                case DO:
                    if (supported(buf[1]) && isEnabled(buf[1])) {
                        // do nothing
                    } else {
                        if (waitWILLreply(buf[1]) && supported(buf[1])) {
                            enable(buf[1]);
                            setWait(WILL, buf[1], false);
                        } else {
                            if (supported(buf[1])) {
                                sendCommand(WILL, buf[1], false);
                                enable(buf[1]);
                            } else {
                                sendCommand(WONT, buf[1], false);
                            }
                        }
                    }
                    break;
                case DONT:
                    if (waitWILLreply(buf[1]) && supported(buf[1])) {
                        setWait(WILL, buf[1], false);
                    } else {
                        if (supported(buf[1]) && isEnabled(buf[1])) {
                            // enable() Method disables an Option that is already enabled
                            enable(buf[1]);
                        }
                    }
                    break;

          /* Now about other two byte IACs */
                case DM:    //How do I implement a SYNCH signal?
                    break;
                case SB: //handle subnegotiations
                    if ((supported(buf[1])) && (isEnabled(buf[1]))) {
                        switch (buf[1]) {
                            case NAWS:
                                handleNAWS();
                                break;
                            case TTYPE:
                                handleTTYPE();
                                break;
                            case LINEMODE:
                                handleLINEMODE();
                                break;
                            case NEWENV:
                                handleNEWENV();
                                break;
                            default:
                        }
                    } else {
                        //do nothing
                    }
                    break;
                default:
            }//switch
        }//parse

        /**
         * Method that reads a NawsSubnegotiation that ends up with a IAC SE
         * If the measurements are unbelieveable it switches to the defaults.
         */
        private void handleNAWS() throws IOException {
            int width = read16int();
            if (width == 255) {
                width = read16int(); //handle doubled 255 value;
            }
            int height = read16int();
            if (height == 255) {
                height = read16int(); //handle doubled 255 value;
            }
            skipToSE();
            setTerminalGeometry(width, height);
        }//handleNAWS

        /**
         * Method that reads a TTYPE Subnegotiation String that ends up with a IAC SE
         * If no Terminal is valid, we switch to the dumb "none" terminal.
         */
        private void handleTTYPE() throws IOException {
            String tmpstr = "";
            // The next read should be 0 which is IS by the protocol
            // specs. hmmm?
            rawread(); //that should be the is :)
            tmpstr = readIACSETerminatedString(40);
            LOG.log(Level.FINE, "Reported terminal name " + tmpstr);
            connectionData.setNegotiatedTerminalType(tmpstr);
        }//handleTTYPE

        /**
         * Method that handles LINEMODE subnegotiation.
         */
        public void handleLINEMODE() throws IOException {
            int c = rawread();
            switch (c) {
                case LM_MODE:
                    handleLMMode();
                    break;
                case LM_SLC:
                    handleLMSLC();
                    break;
                case WONT:
                case WILL:
                    handleLMForwardMask(c);
                    break;
                default:
                    //skip to (including) SE
                    skipToSE();
            }
        }//handleLINEMODE

        public void handleLMMode() throws IOException {
            //we sent the default which no client might deny
            //so we only wait the ACK
            if (WAIT_LM_MODE_ACK) {
                int mask = rawread();
                if (mask != (LM_EDIT | LM_TRAPSIG | LM_MODEACK)) {
                    LOG.log(Level.FINE, "Client violates linemodeack sent: " + mask);
                }
                WAIT_LM_MODE_ACK = false;
            }
            skipToSE();
        }//handleLMMode

        public void handleLMSLC() throws IOException {
            int[] triple = new int[3];
            if (!readTriple(triple)) return;

            //SLC will be initiated by the client
            //case 1. client requests set
            //LINEMODE SLC 0 SLC_DEFAULT 0
            if ((triple[0] == 0) && (triple[1] == LM_SLC_DEFAULT) && (triple[2] == 0)) {
                skipToSE();
                //reply with SLC xxx SLC_DEFAULT 0
                rawWrite(IAC);
                rawWrite(SB);
                rawWrite(LINEMODE);
                rawWrite(LM_SLC);
                //triples defaults for all
                for (int i = 1; i < 12; i++) {
                    rawWrite(i);
                    rawWrite(LM_SLC_DEFAULT);
                    rawWrite(0);
                }
                rawWrite(IAC);
                rawWrite(SE);
                flush();
            } else {

                //case 2: just acknowledge anything we get from the client
                rawWrite(IAC);
                rawWrite(SB);
                rawWrite(LINEMODE);
                rawWrite(LM_SLC);
                rawWrite(triple[0]);
                rawWrite(triple[1] | LM_SLC_ACK);
                rawWrite(triple[2]);
                while (readTriple(triple)) {
                    rawWrite(triple[0]);
                    rawWrite(triple[1] | LM_SLC_ACK);
                    rawWrite(triple[2]);
                }
                rawWrite(IAC);
                rawWrite(SE);
                flush();
            }
        }//handleLMSLC

        public void handleLMForwardMask(int WHAT) throws IOException {
            switch (WHAT) {
                case WONT:
                    if (WAIT_LM_DO_REPLY_FORWARDMASK) {
                        WAIT_LM_DO_REPLY_FORWARDMASK = false;
                    }
                    break;
            }
            skipToSE();
        }//handleLMForward

        public void handleNEWENV() throws IOException {
            LOG.log(Level.FINE, "handleNEWENV()");
            int c = rawread();
            switch (c) {
                case IS:
                    handleNEIs();
                    break;
                case NE_INFO:
                    handleNEInfo();
                    break;
                default:
                    //skip to (including) SE
                    skipToSE();
            }
        }//handleNEWENV

        /*
          The characters following a "type" up to the next "type" or VALUE specify the
          variable name.

          If a "type" is not followed by a VALUE
          (e.g., by another VAR, USERVAR, or IAC SE) then that variable is
          undefined.
         */
        private int readNEVariableName(StringBuffer sbuf) throws IOException {
            LOG.log(Level.FINE, "readNEVariableName()");
            int i = -1;
            do {
                i = rawread();
                if (i == -1) {
                    return NE_IN_ERROR;
                } else if (i == IAC) {
                    i = rawread();
                    if (i == IAC) {
                        //duplicated IAC
                        sbuf.append((char) i);
                    } else if (i == SE) {
                        return NE_IN_END;
                    } else {
                        //Error should have been duplicated
                        return NE_IN_ERROR;
                    }
                } else if (i == NE_ESC) {
                    i = rawread();
                    if (i == NE_ESC || i == NE_VAR || i == NE_USERVAR || i == NE_VALUE) {
                        sbuf.append((char) i);
                    } else {
                        return NE_IN_ERROR;
                    }
                } else if (i == NE_VAR || i == NE_USERVAR) {
                    return NE_VAR_UNDEFINED;
                } else if (i == NE_VALUE) {
                    return NE_VAR_DEFINED;
                } else {
                    //check maximum length to prevent overflow
                    if (sbuf.length() >= NE_VAR_NAME_MAXLENGTH) {
                        //TODO: Log Overflow
                        return NE_IN_ERROR;
                    } else {
                        sbuf.append((char) i);
                    }
                }
            } while (true);
        }//readNEVariableName


        /*
          The characters following a VALUE up to the next
          "type" specify the value of the variable.
          If a VALUE is immediately
          followed by a "type" or IAC, then the variable is defined, but has
          no value.
          If an IAC is contained between the IS and the IAC SE,
          it must be sent as IAC IAC.
        */
        private int readNEVariableValue(StringBuffer sbuf) throws IOException {
            LOG.log(Level.FINE, "readNEVariableValue()");
            //check conditions for first character after VALUE
            int i = rawread();
            if (i == -1) {
                return NE_IN_ERROR;
            } else if (i == IAC) {
                i = rawread();
                if (i == IAC) {
                    //Double IAC
                    return NE_VAR_DEFINED_EMPTY;
                } else if (i == SE) {
                    return NE_IN_END;
                } else {
                    //according to rule IAC has to be duplicated
                    return NE_IN_ERROR;
                }
            } else if (i == NE_VAR || i == NE_USERVAR) {
                return NE_VAR_DEFINED_EMPTY;
            } else if (i == NE_ESC) {
                //escaped value
                i = rawread();
                if (i == NE_ESC || i == NE_VAR || i == NE_USERVAR || i == NE_VALUE) {
                    sbuf.append((char) i);
                } else {
                    return NE_IN_ERROR;
                }
            } else {
                //character
                sbuf.append((char) i);
            }
            //loop until end of value (IAC SE or TYPE)
            do {
                i = rawread();
                if (i == -1) {
                    return NE_IN_ERROR;
                } else if (i == IAC) {
                    i = rawread();
                    if (i == IAC) {
                        //duplicated IAC
                        sbuf.append((char) i);
                    } else if (i == SE) {
                        return NE_IN_END;
                    } else {
                        //Error should have been duplicated
                        return NE_IN_ERROR;
                    }
                } else if (i == NE_ESC) {
                    i = rawread();
                    if (i == NE_ESC || i == NE_VAR || i == NE_USERVAR || i == NE_VALUE) {
                        sbuf.append((char) i);
                    } else {
                        return NE_IN_ERROR;
                    }
                } else if (i == NE_VAR || i == NE_USERVAR) {
                    return NE_VAR_OK;
                } else {
                    //check maximum length to prevent overflow
                    if (sbuf.length() > NE_VAR_VALUE_MAXLENGTH) {
                        //TODO: LOG Overflow
                        return NE_IN_ERROR;
                    } else {
                        sbuf.append((char) i);
                    }
                }
            } while (true);
        }//readNEVariableValue


        public void readNEVariables() throws IOException {
            LOG.log(Level.FINE, "readNEVariables()");
            StringBuffer sbuf = new StringBuffer(50);
            int i = rawread();
            if (i == IAC) {
                //invalid or empty response
                skipToSE();
                LOG.log(Level.FINE, "readNEVariables()::INVALID VARIABLE");
                return;
            }
            boolean cont = true;
            if (i == NE_VAR || i == NE_USERVAR) {
                do {
                    switch (readNEVariableName(sbuf)) {
                        case NE_IN_ERROR:
                            LOG.log(Level.FINE, "readNEVariables()::NE_IN_ERROR");
                            return;
                        case NE_IN_END:
                            LOG.log(Level.FINE, "readNEVariables()::NE_IN_END");
                            return;
                        case NE_VAR_DEFINED:
                            LOG.log(Level.FINE, "readNEVariables()::NE_VAR_DEFINED");
                            String str = sbuf.toString();
                            sbuf.delete(0, sbuf.length());
                            switch (readNEVariableValue(sbuf)) {
                                case NE_IN_ERROR:
                                    LOG.log(Level.FINE, "readNEVariables()::NE_IN_ERROR");
                                    return;
                                case NE_IN_END:
                                    LOG.log(Level.FINE, "readNEVariables()::NE_IN_END");
                                    return;
                                case NE_VAR_DEFINED_EMPTY:
                                    LOG.log(Level.FINE, "readNEVariables()::NE_VAR_DEFINED_EMPTY");
                                    break;
                                case NE_VAR_OK:
                                    //add variable
                                    LOG.log(Level.FINE, "readNEVariables()::NE_VAR_OK:VAR=" + str + " VAL=" + sbuf.toString());
                                    TelnetIO.this.connectionData.getEnvironment().put(str, sbuf.toString());
                                    sbuf.delete(0, sbuf.length());
                                    break;
                            }
                            break;
                        case NE_VAR_UNDEFINED:
                            LOG.log(Level.FINE, "readNEVariables()::NE_VAR_UNDEFINED");
                            break;
                    }
                } while (cont);
            }
        }//readVariables

        public void handleNEIs() throws IOException {
            LOG.log(Level.FINE, "handleNEIs()");
            if (isEnabled(NEWENV)) {
                readNEVariables();
            }
        }//handleNEIs

        public void handleNEInfo() throws IOException {
            LOG.log(Level.FINE, "handleNEInfo()");
            if (isEnabled(NEWENV)) {
                readNEVariables();
            }
        }//handleNEInfo

        /**
         * Method that sends a TTYPE Subnegotiation Request.
         * IAC SB TERMINAL-TYPE SEND
         */
        public void getTTYPE() throws IOException {
            if (isEnabled(TTYPE)) {
                rawWrite(IAC);
                rawWrite(SB);
                rawWrite(TTYPE);
                rawWrite(SEND);
                rawWrite(IAC);
                rawWrite(SE);
                flush();
            }
        }//getTTYPE

        /**
         * Method that sends a LINEMODE MODE Subnegotiation request.
         * IAC LINEMODE MODE MASK SE
         */
        public void negotiateLineMode() throws IOException {
            if (isEnabled(LINEMODE)) {
                rawWrite(IAC);
                rawWrite(SB);
                rawWrite(LINEMODE);
                rawWrite(LM_MODE);
                rawWrite(LM_EDIT | LM_TRAPSIG);
                rawWrite(IAC);
                rawWrite(SE);
                WAIT_LM_MODE_ACK = true;

                //dont forwardmask
                rawWrite(IAC);
                rawWrite(SB);
                rawWrite(LINEMODE);
                rawWrite(DONT);
                rawWrite(LM_FORWARDMASK);
                rawWrite(IAC);
                rawWrite(SE);
                WAIT_LM_DO_REPLY_FORWARDMASK = true;
                flush();
            }
        }//negotiateLineMode

        /**
         * Method that sends a NEW-ENVIRON SEND subnegotiation request
         * for default variables and user variables.
         * IAC SB NEW-ENVIRON SEND VAR USERVAR IAC SE
         */
        private void negotiateEnvironment() throws IOException {
            //log.debug("negotiateEnvironment()");
            if (isEnabled(NEWENV)) {
                rawWrite(IAC);
                rawWrite(SB);
                rawWrite(NEWENV);
                rawWrite(SEND);
                rawWrite(NE_VAR);
                rawWrite(NE_USERVAR);
                rawWrite(IAC);
                rawWrite(SE);
                WAIT_NE_SEND_REPLY = true;
                flush();
            }
        }//negotiateEnvironment

        /**
         * Method that skips a subnegotiation response.
         */
        private void skipToSE() throws IOException {
            while (rawread() != SE) ;
        }//skipSubnegotiation

        private boolean readTriple(int[] triple) throws IOException {
            triple[0] = rawread();
            triple[1] = rawread();
            if ((triple[0] == IAC) && (triple[1] == SE)) {
                return false;
            } else {
                triple[2] = rawread();
                return true;
            }
        }//readTriple

        /**
         * Method that reads a subnegotiation String,
         * one of those that end with a IAC SE combination.
         * A maximum length is observed to prevent overflow.
         *
         * @return IAC SE terminated String
         */
        private String readIACSETerminatedString(int maxlength) throws IOException {
            int where = 0;
            char[] cbuf = new char[maxlength];
            char b = ' ';
            boolean cont = true;

            do {
                int i;
                i = rawread();
                switch (i) {
                    case IAC:
                        i = rawread();
                        if (i == SE) {
                            cont = false;
                        }
                        break;
                    case -1:
                        return "default";
                    default:
                }
                if (cont) {
                    b = (char) i;
                    //Fix for overflow wimpi (10/06/2004)
                    if (b == '\n' || b == '\r' || where == maxlength) {
                        cont = false;
                    } else {
                        cbuf[where++] = b;
                    }
                }
            } while (cont);

            return (new String(cbuf, 0, where));
        }//readIACSETerminatedString

        /**
         * Method that informs internally about the supported Negotiation Options
         *
         * @param i int that represents requested the Option
         * @return Boolean that represents support status
         */
        private boolean supported(int i) {
            switch (i) {
                case SUPGA:
                case ECHO:
                case NAWS:
                case TTYPE:
                case NEWENV:
                    return true;
                case LINEMODE:
                    return connectionData.isLineMode();
                default:
                    return false;
            }
        }//supported

        /**
         * Method that sends a Telnet IAC String with TelnetIO.write(byte b) method.
         *
         * @param i int that represents requested Command Type (DO,DONT,WILL,WONT)
         * @param j int that represents the Option itself (e.g. ECHO, NAWS)
         */
        private void sendCommand(int i, int j, boolean westarted) throws IOException {
            rawWrite(IAC);
            rawWrite(i);
            rawWrite(j);
            // we started with DO OPTION and now wait for reply
            if ((i == DO) && westarted) setWait(DO, j, true);
            // we started with WILL OPTION and now wait for reply
            if ((i == WILL) && westarted) setWait(WILL, j, true);
            flush();
        }//sendCommand

        /**
         * Method enables or disables a supported Option
         *
         * @param i int that represents the Option
         */
        private void enable(int i) throws IOException {
            switch (i) {
                case SUPGA:
                    DO_SUPGA = !DO_SUPGA;
                    break;
                case ECHO:
                    DO_ECHO = !DO_ECHO;
                    break;
                case NAWS:
                    DO_NAWS = !DO_NAWS;
                    break;
                case TTYPE:
                    if (DO_TTYPE) {
                        DO_TTYPE = false;
                    } else {
                        DO_TTYPE = true;
                        getTTYPE();
                    }
                    break;
                case LINEMODE:
                    if (DO_LINEMODE) {
                        DO_LINEMODE = false;
                        //set false in connection data, so the application knows.
                        connectionData.setLineMode(false);
                    } else {
                        DO_LINEMODE = true;
                        negotiateLineMode();
                    }
                    break;
                case NEWENV:
                    if (DO_NEWENV) {
                        DO_NEWENV = false;
                    } else {
                        DO_NEWENV = true;
                        negotiateEnvironment();
                    }
                    break;
            }
        }//enable

        /**
         * Method that informs internally about the status of the supported
         * Negotiation Options.
         *
         * @param i int that represents requested the Option
         * @return Boolean that represents the enabled status
         */
        private boolean isEnabled(int i) {
            switch (i) {
                case SUPGA:
                    return DO_SUPGA;
                case ECHO:
                    return DO_ECHO;
                case NAWS:
                    return DO_NAWS;
                case TTYPE:
                    return DO_TTYPE;
                case LINEMODE:
                    return DO_LINEMODE;
                case NEWENV:
                    return DO_NEWENV;
                default:
                    return false;
            }
        }//isEnabled

        /**
         * Method that informs internally about the WILL wait status
         * of an option.
         *
         * @param i that represents requested the Option
         * @return Boolean that represents WILL wait status of the Option
         */
        private boolean waitWILLreply(int i) {
            switch (i) {
                case SUPGA:
                    return WAIT_WILL_REPLY_SUPGA;
                case ECHO:
                    return WAIT_WILL_REPLY_ECHO;
                case NAWS:
                    return WAIT_WILL_REPLY_NAWS;
                case TTYPE:
                    return WAIT_WILL_REPLY_TTYPE;
                default:
                    return false;
            }
        }//waitWILLreply

        /**
         * Method that informs internally about the DO wait status
         * of an option.
         *
         * @param i Integer that represents requested the Option
         * @return Boolean that represents DO wait status of the Option
         */
        private boolean waitDOreply(int i) {
            switch (i) {
                case SUPGA:
                    return WAIT_DO_REPLY_SUPGA;
                case ECHO:
                    return WAIT_DO_REPLY_ECHO;
                case NAWS:
                    return WAIT_DO_REPLY_NAWS;
                case TTYPE:
                    return WAIT_DO_REPLY_TTYPE;
                case LINEMODE:
                    return WAIT_DO_REPLY_LINEMODE;
                case NEWENV:
                    return WAIT_DO_REPLY_NEWENV;
                default:
                    return false;
            }
        }//waitDOreply

        /**
         * Method that mutates the wait status of an option in
         * negotiation. We need the wait status to keep track of
         * negotiation in process. So we cant miss if we started out
         * or the other and so on.
         *
         * @param WHAT   Integer values of  DO or WILL
         * @param OPTION Integer that represents the Option
         * @param WAIT   Boolean that represents the status of wait that should be set
         */
        private void setWait(int WHAT, int OPTION, boolean WAIT) {
            switch (WHAT) {
                case DO:
                    switch (OPTION) {
                        case SUPGA:
                            WAIT_DO_REPLY_SUPGA = WAIT;
                            break;
                        case ECHO:
                            WAIT_DO_REPLY_ECHO = WAIT;
                            break;
                        case NAWS:
                            WAIT_DO_REPLY_NAWS = WAIT;
                            break;
                        case TTYPE:
                            WAIT_DO_REPLY_TTYPE = WAIT;
                            break;
                        case LINEMODE:
                            WAIT_DO_REPLY_LINEMODE = WAIT;
                            break;
                        case NEWENV:
                            WAIT_DO_REPLY_NEWENV = WAIT;
                            break;
                    }
                    break;
                case WILL:
                    switch (OPTION) {
                        case SUPGA:
                            WAIT_WILL_REPLY_SUPGA = WAIT;
                            break;
                        case ECHO:
                            WAIT_WILL_REPLY_ECHO = WAIT;
                            break;
                        case NAWS:
                            WAIT_WILL_REPLY_NAWS = WAIT;
                            break;
                        case TTYPE:
                            WAIT_WILL_REPLY_TTYPE = WAIT;
                            break;
                    }
                    break;
            }
        }//setWait

    }//inner class IACHandler

    /** end Constants declaration **************************************************/

}//class TelnetIO