/**
 * Copyright 2004-2016 Riccardo Solmi. All rights reserved.
 * This file is part of the Whole Platform.
 *
 * The Whole Platform is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * The Whole Platform 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the Whole Platform. If not, see <http://www.gnu.org/licenses/>.
 */
package org.whole.lang.queries.iterators;

import org.whole.lang.iterators.IEntityIterator;
import org.whole.lang.model.IEntity;

/**
 * @author Riccardo Solmi
 */
public class CartesianProductIterator extends AbstractTupleProductIterator {
	protected CartesianProductIterator(IEntityIterator<? extends IEntity>... iterators) {
		super(iterators);
	}

	@Override
	public IEntity[] nextTuple() {
		IEntity[] result = super.nextTuple();
		tupleUpdateIndex = iterators.length-1;
		return result;
	}

	@Override
	protected boolean updateIterators() {
		if (tupleUpdateIndex < iterators.length) {
			getBindings().wEnterScope(lookaheadScope(), true);
			lookaheadScope().wClear();
			for (int j=0; j<tupleUpdateIndex; j++)
				lookaheadScope().wAddAll(iterators[j].lookaheadScope());

			for (int i = tupleUpdateIndex; i < iterators.length;) {
				if (iterators[i].hasNext()) {
					tuple[i] = iterators[i].next();
					tupleUpdateIndex = ++i;
				} else if (i == 0) {
					lookaheadScope().wClear();
					getBindings().wExitScope();
					return false;
				} else {
					iterators[i].reset(initialEntity);
					tuple[i] = null;
					tupleUpdateIndex = --i;

					lookaheadScope().wClear();
					for (int j=0; j<i; j++)
						lookaheadScope().wAddAll(iterators[j].lookaheadScope());
				}
			}
			getBindings().wExitScope();
		}
		return true;
	}
}