message.java

Bluetooth chat Server and Client in j2me

/*
 I BlueTooth You -- Simple BlueTooth talker
 Copyright (C) 2007 Jan Tomka

 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.
 */
package net.sf.btw.ibtu;

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Vector;

import net.sf.btw.tools.Logger;

/**
 * This class defines an IBTU message with sender identification and the message
 * body itself.
 * 
 * @author Jan Tomka TODO Hide and encapsulate the member variables. TODO Line
 *         splitting and line counting should be split apart to separate class,
 *         e.g. HistoryMessage.
 */
public final class Message {
	/**
	 * Sender identificator of system message. TODO Update where needed, to use
	 * this constant.
	 */
	public static final String SYSTEM = null;

	/**
	 * Constructs an empty message with <code>null</code> sender (a system
	 * message). TODO Remove this constructor, don't allow empty messages.
	 */
	public Message() {
		super();
	}

	/**
	 * Constructs a message.
	 * 
	 * @param sender
	 *            Sender of the message. Value <code>null</code> indicates
	 *            system messages.
	 * @param body
	 *            Body of the message. Must not be <code>null</code>. TODO
	 *            Strip sender and body string, don't allow null or empty body.
	 */
	public Message(final String sender, final String body) {
		super();
		this.sender = sender;
		this.body = body;
	}

	/**
	 * Sender of the message. Value <code>null</code> indicates system
	 * messages.
	 */
	public String sender;

	/**
	 * Returns sender of a message.
	 * 
	 * @returns Sender of a message.
	 */
	public String getSender() {
		return sender;
	}

	/**
	 * Body of the message. Must not be <code>null</code>.
	 */
	public String body = "";

	/**
	 * Returns body of a message.
	 * 
	 * @return Body of a message.
	 */
	public String getBody() {
		return body;
	}

	/**
	 * Vector of {@link String}s the message sender string is split to,
	 * depending on the device display width.
	 */
	public transient Vector senderLines;

	/**
	 * Vector of {@link String}s the message body string is split to, depending
	 * on the device display width.
	 */
	public transient Vector bodyLines;

	/**
	 * Splits sender and body strings to individual lines. Does it so that each
	 * of the resulting lines would fit on a line of given width, drawn with
	 * given font.
	 * 
	 * @param f
	 *            Font to use when splitting to individual lines.
	 * @param width
	 *            Horizontal width available for each line.
	 */
	/*
	 * TODO Move HistoryCanvas.splitLines here. public void splitToLines(Font f,
	 * int width) { }
	 */

	/**
	 * Creates communication package from given pair.
	 * 
	 * @param sender
	 *            sender, if <code>null</code> then the message is from the
	 *            system.
	 * @param message
	 *            the message.
	 * @return byte array representation.
	 */
	public byte[] toByteArray() {
		final ByteArrayOutputStream bout = new ByteArrayOutputStream(body
				.length() + 14);
		final DataOutputStream out = new DataOutputStream(bout);
		try {
			out.writeUTF(sender == null ? "" : sender);
			out.writeUTF(body);
			out.close();
		} catch (IOException ex) {
			// shouldn't happen
			Logger.error("Message.toByteArray()", ex);
		}
		return bout.toByteArray();
	}

	/**
	 * Reads message object from given stream.
	 * 
	 * @param stream
	 *            stream to read from. The stream is not closed.
	 * @return message instance
	 * @throws IOException
	 *             if decoding error happens.
	 */
	public static Message fromStream(DataInputStream stream) throws IOException {
		final Message result = new Message();
		result.sender = stream.readUTF();
		if (result.sender.length() == 0)
			result.sender = null;
		result.body = stream.readUTF();
		return result;
	}

	/**
	 * Checks if this message is a system message.
	 * 
	 * @return <code>true</code> if {@link #sender} is <code>null</code>.
	 */
	public boolean isSystemMessage() {
		return sender == null;
	}

	/**
	 * Counts lines in a {@link Vector} of {@link Message}'s.
	 * 
	 * @param msgs
	 *            Vector of Message's.
	 * @return Number of lines. TODO Make splitToLines caluculate this once and
	 *         keep track of current line count, and line index to start sending
	 *         the recent history from, as well.
	 */
	public static int countLines(Vector msgs) {
		int result = 0;
		for (int i = 0; i < msgs.size(); i++) {
			int senderLineCount = ((Message) msgs.elementAt(i)).senderLines
					.size();
			int bodyLineCount = ((Message) msgs.elementAt(i)).bodyLines.size();

			result += ((senderLineCount == 0) ? 0 : (senderLineCount - 1))
					+ bodyLineCount;
		}

		return result;
	}
}