/*
 * Copyright (C) 1996, 1997 By Radu Sion 
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by Radu Sion (radus@cs.pub.ro)
 *
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `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 AUTHOR 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.
 *
 * (radus@cs.pub.ro, http://www.dsp.pub.ro/radu.html)
 *
 */


import Message;
import MessageConstants;
import util;

/**
 * A class used in parsing a Message.<br><br>
 * Written: <a href="http://www.dsp.pub.ro/radu.html">Radu Sion</a><br>
 * Version: 0.41<br>
 * Source: <a href="src/MessageParser.java">MessageParser.java</a>
 * @see	Message
 * @see MessageCreator
 * @see MessageConstants
 */
public class
MessageParser
extends Object
{
/**
 * Tests the validity of the Message.
 * Should be used before any other call to a method of this class.
 * The CRC is tested , also the whole header. 
 * @return 	Returns true if valid, false otherwise
 * @param	message	The Message to test for validity
 */
public static boolean
isValid(Message message)
	{
	if (message == null) return false;
	if (message.length() < MessageConstants.MIN_LENGTH) return false;
	char message_id = message.charAt(MessageConstants.ID_INDEX);
	return	( 
		 (message_id == MessageConstants.CTS_ID) ||
		 (message_id == MessageConstants.RESET_ID) ||
		 (message_id == MessageConstants.DATA_STRING_ID) ||
		 (message_id == MessageConstants.DATA_BYTES_ID) ||
		 (message_id == MessageConstants.DNF_ID) ||
		 (message_id == MessageConstants.DOWN_ID) ||
		 (message_id == MessageConstants.INVRQ_ID) ||
		 (message_id == MessageConstants.OK_ID) ||
		 (message_id == MessageConstants.CHGRP_ID) ||
		 (message_id == MessageConstants.NOP_ID)
		);
	}

/**
 * Tries to get a human readable description of the Message.
 * @return	A description String
 * @param	message	The Message to describe
 */
public static String
getDescription(Message message)
	{
	return "Method MessageParser.getDescription() not implemented yet";
	}

/**
 * Gets the sender number of the Message sender.
 * @param	message	The Message to use
 */
public static int
getSender(Message message)
	{
	return message.getInt(MessageConstants.SENDER_ID_INDEX);
	}

/**
 * Gets the destination number of the Message destination.
 * @param	message	The Message to use
 */
public static int
getDestination(Message message)
        {
        return message.getInt(MessageConstants.DESTINATION_ID_INDEX);
        }

/**
 * Gets the sender group number of the Message sender.
 * @param	message The Message to use
 */
public static int
getSenderGroup(Message message)
        {
        return message.getInt(MessageConstants.SENDER_GROUP_ID_INDEX);
        }

/**
 * Gets the destination group number of the Message destination.
 * @param	message	The Message to use 
 */
public static int
getDestinationGroup(Message message)
        {
        return message.getInt(MessageConstants.DESTINATION_GROUP_ID_INDEX);
        }

/**
 * Tests if it's a INVRQ (Invalid Request) Message.
 * The INVRQ is generated by the server only. 
 * @param	message	The Message to use
 * @return	Returns true if INVRQ, false otherwise
 */
public static boolean
isINVRQ(Message message)
        {
        if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.INVRQ_ID)
                return true;
        return false;
        }

/** 
 * Tests if it's a OK Message. 
 * The OK is generated also by the server as a confirmation of a fullfiled request.
 * @param	message	The Message to use
 * @return	Returns true if OK, false otherwise 
 */
public static boolean
isOK(Message message)
	{
	if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.OK_ID)
		return true;
	return false;
	}

/**
 * Test if it's a CHGRP (Change Group) Message.
 * The CHGRP is generated by a client only when it wishes to change it's group
 * @param	message	The Message to use
 * @return	It returns the wanted new group if ok, MessageConstants.INVALID otherwise
 */
public static int
isCHGRP(Message message)
        {
        if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.CHGRP_ID)
                return message.getInt(MessageConstants.DATA_BEGIN_INDEX);
        return MessageConstants.INVALID;
        }

/**
 * Tests if it's a DOWN (client is down) Message.
 * The DOWN is generated by the server when a client is down, in order to notify other clients.
 * Not implemented yet. [SUBJECT TO CHANGE !!!]
 * @param	message	The Message to use
 * @return	It returns the client number that went down if ok, MessageConstants.INVALID otherwise
 */
public static int
isDOWN(Message message)
	{
	if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.DOWN_ID)
	 	return message.getInt(MessageConstants.DATA_BEGIN_INDEX);
	return MessageConstants.INVALID;
	}

/**
 * Tests if it's a NOP (No Operation == ignore) Message.
 * @param	message	The Message to use
 * @return	Returns true if it's NOP, false otherwise
 */
public static boolean
isNOP(Message message)
        {
        if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.NOP_ID)
                return true;
        return false;
        }

/**
 * Tests if it's a CTS (Request to send) Message.
 * CTS is server-generated when the client is free to send <a href="Message.html">Messages</a> again.
 * @param	message	The Message to use
 * @return	Returns true if it's CTS, false otherwise
 */
public static boolean
isCTS(Message message)
	{
	if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.CTS_ID)
		return true;
	return false;
	}

/**
 * Tests if it's a DNF (Destination not found) Message.
 * DFN is some INVRQ and should be obsoleted by it.
 * @param	message	The Message to use
 * @return	Returns the destination client number if it's DNF, MessageConstants.INVALID otherwise
 */
public static int
isDNF(Message message)
        {
        if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.DNF_ID)
                return message.getInt(MessageConstants.DATA_BEGIN_INDEX);
        return MessageConstants.INVALID;
        }

/**
 * Tests if it's a RESET Message.
 * RESET is server generated. On receiving it, the client should efectively reset.
 * @param	message	The Message to test
 * @return 	Returns true if it's RESET, false otherwise
 */
public static boolean
isRESET(Message message)
        {
        if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.RESET_ID)
                return true;
        return false;
        }

/**
 * Tests if it's a DataXXXXX Message.
 * @param	message	The Message to test
 * @return	True if it a data message, false otherwise
 */
public static boolean
isData(Message message)
        {
        if ((message.charAt(MessageConstants.ID_INDEX) == MessageConstants.DATA_STRING_ID) ||
	    (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.DATA_BYTES_ID))
		return true;
        return false;
	}

/**
 * Tests if it's a DataString Message.
 * @param	message	The Message to test
 * @return	The sender number if it's DataString, MessageConstants.INVALID otherwise
 */
public static int
isDataString(Message message)
        {
        if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.DATA_STRING_ID)
                return message.getInt(MessageConstants.SENDER_ID_INDEX);
        return MessageConstants.INVALID;
        }

/**
 * Tests if it's a DataBytes Message.
 * @param	message	The Message to test
 * @return	The sender number if it's DataBytes, MessageConstants.INVALID otherwise
 */
public static int                                                 
isDataBytes(Message message)                                     
        {
        if (message.charAt(MessageConstants.ID_INDEX) == MessageConstants.DATA_BYTES_ID)
                return message.getInt(MessageConstants.SENDER_ID_INDEX);
        return MessageConstants.INVALID;
        }

/**
 * Gets the byte array if it's a DataBytes or DataString Message.
 * @param	message	The Message to use
 * @return	Returns a byte array if it's DataBytes, null otherwise
 */
public static byte[]
getDataBytes(Message message)
	{
	if ((isDataBytes(message) == MessageConstants.INVALID) &&
	    (isDataString(message) == MessageConstants.INVALID))
		return null;
	byte dd[] = message.getBytes();
	return util.bytescut(MessageConstants.DATA_BEGIN_INDEX,dd.length-1,dd);
	}

/**
 * Gets the String if it's a DataString or DataBytes Message.
 * @param	message	The Message to use
 * @return	Returns a String if it's DataString, null otherwise
 */
public static String
getDataString(Message message)
	{
	if ((isDataString(message) == MessageConstants.INVALID) &&
	    (isDataBytes(message) == MessageConstants.INVALID))	    
		return null;
	byte dd[] = message.getBytes();
	return new String(dd,0,MessageConstants.DATA_BEGIN_INDEX,dd.length - MessageConstants.DATA_BEGIN_INDEX);
	}

/**
 * Gets a character from the data area of the Message 
 * Treating the Message as a Data 
 * Message (DataBytes, DataString)
 * (no checkings are done to ensure that it's really a Data Message)
 * @param	message	The Message to use
 * @param	index	Index in the data area of the Message
 * @return	Returns a character from the data area of the Message
 */
public static char
getDataChar(Message message, int index)
	{
	return message.charAt(index+MessageConstants.DATA_BEGIN_INDEX);
	}

/**
 * Gets a byte from the data area of the Message
 * Treating the Message as a Data 
 * Message (DataBytes, DataString etc) !!!
 * (no checkings are done to ensure that it's really a Data Message)
 * @param	message	The Message to use
 * @param	index	Index in the data area of the Message
 * @return	Returns a byte from the data area of the Message
 */
public static byte
getDataByte(Message message, int index)
	{
	return message.byteAt(index+MessageConstants.DATA_BEGIN_INDEX);
	}

}
/*eoc*/