/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j 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 <http://www.gnu.org/licenses/>.
 */
package org.neo4j.internal.helpers.collection;

import java.util.Iterator;
import java.util.function.Predicate;

/**
 * An iterator which filters another iterator, only letting items with certain
 * criteria pass through. All iteration/filtering is done lazily.
 *
 * @param <T> the type of items in the iteration.
 */
public class FilteringIterator<T> extends PrefetchingIterator<T> {
    private final Iterator<T> source;
    private final Predicate<T> predicate;

    public FilteringIterator(Iterator<T> source, Predicate<T> predicate) {
        this.source = source;
        this.predicate = predicate;
    }

    @Override
    protected T fetchNextOrNull() {
        while (source.hasNext()) {
            T testItem = source.next();
            if (predicate.test(testItem)) {
                return testItem;
            }
        }
        return null;
    }
}
