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/*******************************************************************************
 * Copyright (c) 2015 Eclipse RDF4J contributors, Aduna, and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Distribution License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *******************************************************************************/

package org.eclipse.rdf4j.common.iteration;

/**
 * Abstract superclass for Iterations that wrap other Iterations. The abstract class IterationWrapper
 * itself provides default methods that forward method calls to the wrapped Iteration. Subclasses of
 * IterationWrapper should override some of these methods and may also provide additional methods and
 * fields.
 */
public class IterationWrapper extends AbstractCloseableIteration {

	/*-----------*
	 * Variables *
	 *-----------*/

	/**
	 * The wrapped Iteration.
	 */
	protected final Iteration wrappedIter;

	/*--------------*
	 * Constructors *
	 *--------------*/

	/**
	 * Creates a new IterationWrapper that operates on the supplied Iteration.
	 * 
	 * @param iter
	 *        The wrapped Iteration for this IterationWrapper, must not be null.
	 */
	public IterationWrapper(Iteration iter) {
		assert iter != null;
		wrappedIter = iter;
	}

	/*---------*
	 * Methods *
	 *---------*/

	/**
	 * Checks whether the wrapped Iteration contains more elements, closing this Iteration when this is not
	 * the case.
	 * 
	 * @return true if the wrapped Iteration contains more elements, false otherwise.
	 */
	public boolean hasNext()
		throws X
	{
		return wrappedIter.hasNext();
	}

	/**
	 * Returns the next element from the wrapped Iteration.
	 * 
	 * @throws java.util.NoSuchElementException
	 *         If all elements have been returned.
	 * @throws IllegalStateException
	 *         If the Iteration has been closed.
	 */
	public E next()
		throws X
	{
		return wrappedIter.next();
	}

	/**
	 * Removes the last element that has been returned from the wrapped Iteration.
	 * 
	 * @throws UnsupportedOperationException
	 *         If the wrapped Iteration does not support the remove operation.
	 * @throws IllegalStateException
	 *         if the Iteration has been closed, or if {@link #next} has not yet been called, or
	 *         {@link #remove} has already been called after the last call to {@link #next}.
	 */
	public void remove()
		throws X
	{
		wrappedIter.remove();
	}

	/**
	 * Closed this Iteration and also closes the wrapped Iteration if it is a {@link CloseableIteration}.
	 */
	@Override
	protected void handleClose()
		throws X
	{
		super.handleClose();
		Iterations.closeCloseable(wrappedIter);
	}
}