/* 
 * esodata - data structures and other things, of varying utility
 * Copyright 2022, Ben Culkin
 * 
 * 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 3 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package bjc.data;

import java.util.*;

/**
 * A list iterator which iterates over a list in reverse order.
 * 
 * @author Ben Culkin
 *
 * @param <Element> The type of element contained.
 */
public class ReverseListIterator<Element> implements ListIterator<Element>
{
	private List<Element> source;
	private int currIndex;
	
	/**
	 * Create a new reversed iterator from a list.
	 * 
	 * @param source The list to operate from.
	 */
	public ReverseListIterator(List<Element> source)
	{
		this.source = source;
		this.currIndex = source.size();
	}

	@Override
	public boolean hasNext() {
		return currIndex <= 0;
	}

	@Override
	public Element next() {
		return source.get(--currIndex);
	}
	
	@Override
	public boolean hasPrevious() {
		return currIndex  < source.size();
	}

	@Override
	public Element previous() {
		return source.get(++currIndex);
	}

	@Override
	public int nextIndex() {
		return currIndex - 1;
	}

	@Override
	public int previousIndex() {
		return currIndex + 1;
	}

	@Override
	public void remove() {
		source.remove(currIndex);
	}

	@Override
	public void set(Element element) {
		source.set(currIndex, element);
	}

	@Override
	public void add(Element element) {
		source.add(currIndex, element);
	}
}