Messenger.java

/*******************************************************************************
 * Copyright (c) 2015
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
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package jsettlers.graphics.messages;

import java.util.LinkedList;

import jsettlers.common.menu.messages.IMessage;
import jsettlers.common.position.ShortPoint2D;
import jsettlers.common.statistics.IGameTimeProvider;

/**
 * This is a messenger, that lets you display messages on the users screen.
 * 
 * @author Michael Zangl
 */
public class Messenger {

	private final LinkedList<IMessage> messages = new LinkedList<IMessage>();
	private final IGameTimeProvider gameTimeProvider;
	private int latestTickTime;
	private int focusedMessageIndex = 0;

	public Messenger(IGameTimeProvider gameTimeProvider) {
		this.gameTimeProvider = gameTimeProvider;
		this.latestTickTime = (int)System.currentTimeMillis();
	}

	/**
	 * Gets an array of messages that should be displayed to the user at the moment.
	 * <p>
	 * The messages have to be sorted by age, the one with the lowest age first.
	 * 
	 * @return The messages to display.
	 */
	public IMessage[] getMessages() {
		return messages.toArray(new IMessage[messages.size()]);
	}

	/**
	 * Adds a given {@link IMessage} to this messenger's FIFO list, but
	 * only if given message doesn't seem to be a duplicate of any of the
	 * messages that are already contained. Whether its a duplicate or not
	 * is determined by {@link IMessage#duplicates(IMessage)}.
	 * @param message
	 * @return
	 */
	public synchronized boolean addMessage(IMessage message) {
		if (isNews(message)) {
			messages.addFirst(message);
			if (messages.size() > IMessage.MAX_MESSAGES)
				messages.removeLast();
			focusedMessageIndex = 0;
			return true;
		}
		return false;
	}

	/**
	 * Perform perpetual update step, i.e. determine amount of time that has
	 * passed since last call, let all currently active messages age by that
	 * interval, then remove all messages whose age exceed the allowed
	 * time-to-live ({@link IMessage#MESSAGE_TTL}).
	 */
	public synchronized void doTick() {
		int millis = (int)System.currentTimeMillis(); 
		if (!gameTimeProvider.isGamePausing()) {
			// update message ages
			int interval = millis - latestTickTime;
			for (IMessage m : messages) {
				if (m.ageBy(interval) > IMessage.MESSAGE_TTL)
					// remove all remaining messages, assuming they in order
					while (!messages.pollLast().equals(m))
						;
			}
		}
		latestTickTime = millis;
	}

	/**
	 * Determines whether a given message is worth its display, considering nature and 
	 * content of the messages already shown. 
	 * @param msg {@link IMessage} to be inspected.
	 * @return true, if message should be displayed.
	 */
	boolean isNews(IMessage msg) {
		for (IMessage m : messages) {
			if (msg.duplicates(m)) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Returns a position this messenger currently considers noteworthy.
	 * I.e. location of latest incoming message, then that of respectively next,
	 * when repeatedly called.
	 * @return A {@link ShortPoint2D} retrieved from a message.
	 */
	public synchronized ShortPoint2D getPosition() {
		if (!messages.isEmpty()) {
			// retrieve nth message's position and increment n
			return messages.get(focusedMessageIndex++ % messages.size()).getPosition();
		}
		return null;
	}

}