/*
 * Copyright (c) 2012,2013 Big Switch Networks, Inc.
 *
 * Licensed under the Eclipse Public License, Version 1.0 (the
 * "License"); you may not use this file except in compliance with the
 * License. You may obtain a copy of the License at
 *
 *      http://www.eclipse.org/legal/epl-v10.html
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *
 *    Originally created by David Erickson, Stanford University 
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the
 *    License. You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an "AS
 *    IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 *    express or implied. See the License for the specific language
 *    governing permissions and limitations under the License. 
 */

package org.sdnplatform.util;

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

/**
 * Iterator over all values in an iterator of iterators
 *
 * @param <T> the type of elements returned by this iterator
 */
public class MultiIterator<T> implements Iterator<T> {
    Iterator<Iterator<T>> subIterator;
    Iterator<T> current = null;
    
    public MultiIterator(Iterator<Iterator<T>> subIterator) {
        super();
        this.subIterator = subIterator;
    }

    @Override
    public boolean hasNext() {
        if (current == null) {
            if (subIterator.hasNext()) {
                current = subIterator.next();
            } else {
                return false;
            }
        }
        while (!current.hasNext() && subIterator.hasNext()) {
            current = subIterator.next();
        }
        
        return current.hasNext();
    }

    @Override
    public T next() {
        if (hasNext())
            return current.next();
        throw new NoSuchElementException();
    }

    @Override
    public void remove() {
        if (hasNext())
            current.remove();
        throw new NoSuchElementException();
    }
}
