/*
 * This file is part of aion-emu <aion-emu.com>.
 *
 * aion-emu 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.
 *
 * aion-emu 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 aion-emu.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.aionemu.commons.utils.collections;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * This class is representing an iterator, that is used to iterate through the collection that has format
 * Iterable<Iterable<V>>.<br>
 * 
 * <pre>
 * <code>
 * Usage:<br>
 * List<List<Integer>> someList = ....
 * IteratorIterator<Integer> iterator = new IteratorIterator<Integer>(someList)
 * 
 * OR:
 * 
 * Map<Integer, Set<SomeClass>> mapOfSets = ....
 * IteratorIterator<SomeCLass> iterator = new IteratorIterator<SomeClass>(mapsOfSets.values());
 * </code>
 * </pre>
 * 
 * This iterator is not thread-safe. <br>
 * This iterator omits null values for first level collection, which means that if we have:
 * 
 * <pre>
 * <code>
 * Set<Set<Integer>> setOfSets = ....
 * setOfSets.add(null);
 * setOfSets.add(someSetOfIntegers); // Where someSetsOfIntegers is a set containing 1 and 2
 * 
 * IteratorIterator<Integer> it = new IteratorIterator<Integer>(setOfSets);
 * </code>
 * </pre>
 * 
 * This <code>it</code> iterator will return only 2 values ( 1 and 2 )
 * 
 * @author Luno
 * 
 * @param <V>
 *            Type of the values over which this iterator iterates
 * 
 */
public class IteratorIterator<V> implements Iterator<V>
{
	/** 1st Level iterator */
	private Iterator<? extends Iterable<V>>	firstLevelIterator;

	/** 2nd level iterator */
	private Iterator<V>						secondLevelIterator;

	/**
	 * Constructor of <tt>IteratorIterator</tt>
	 * 
	 * @param itit
	 *            an Iterator that iterate over Iterable<Value>
	 */
	public IteratorIterator(Iterable<? extends Iterable<V>> itit)
	{
		this.firstLevelIterator = itit.iterator();
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public boolean hasNext()
	{
		if(secondLevelIterator != null && secondLevelIterator.hasNext())
			return true;

		while(firstLevelIterator.hasNext())
		{
			Iterable<V> iterable = firstLevelIterator.next();

			if(iterable != null)
			{
				secondLevelIterator = iterable.iterator();

				if(secondLevelIterator.hasNext())
					return true;
			}
		}
		return false;
	}

	/**
	 * Returns next value of collection.<br>
	 * If there is no next value, then {@link NoSuchElementException} thrown.
	 */
	@Override
	public V next()
	{
		if(secondLevelIterator == null || !secondLevelIterator.hasNext())
			throw new NoSuchElementException();
		return secondLevelIterator.next();
	}

	/**
	 * <font color="red"><b>NOT IMPLEMENTED</b></font>
	 */
	@Override
	public void remove()
	{
		throw new UnsupportedOperationException("This operation is not supported.");
	}
}