update/org.eclipse.update.ui/src/org/eclipse/update/internal/ui/forms/DetailsHistory.java

/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.update.internal.ui.forms;
import java.util.*;

public class DetailsHistory {
	private final static int MAX_SIZE = 50;
	private LinkedList history;
	private int current = -1;
	
	public DetailsHistory() {
		history = new LinkedList();
	}
	
	private void resetIterator() {
		current = history.size() -1;
	}
	
	public void add(DetailsHistoryItem item) {
		if (history.isEmpty() ||
		    history.getLast().equals(item)==false) {
			//System.out.println("Item added: "+item);
			history.addLast(item);
			if (history.size() > MAX_SIZE)
		   		history.removeFirst();
		    }
		resetIterator();
	}
	public void add(String pageId, Object input) {
		this.add(new DetailsHistoryItem(pageId, input));
	}
	public boolean hasNext() {
		//if (iterator==null) return false;
		//return iterator.hasNext();
		if (current== -1) return false;
		if (current == history.size()-1) return false;
		return true;
	}
	public boolean hasPrevious() {
		//if (iterator==null) return false;
		//return iterator.hasPrevious();
		if (current == -1) return false;
		return (current>0);
	}
	public DetailsHistoryItem getNext() {
		if (hasNext()) {
			DetailsHistoryItem item = (DetailsHistoryItem)history.get(++current);
			//System.out.println("Next returned: "+item);
			return item;
		}
		return null;
	}
	public DetailsHistoryItem getPrevious() {
		if (hasPrevious()) {
			DetailsHistoryItem item = (DetailsHistoryItem)history.get(--current);
			//System.out.println("Prev returned: "+item);
			return item;
		}
		return null;
	}
}