/*
 ***************************************************************************************
 *  Copyright (C) 2006 EsperTech, Inc. All rights reserved.                            *
 *  http://www.espertech.com/esper                                                     *
 *  http://www.espertech.com                                                           *
 *  ---------------------------------------------------------------------------------- *
 *  The software in this package is published under the terms of the GPL license       *
 *  a copy of which has been included with this distribution in the license.txt file.  *
 ***************************************************************************************
 */
package com.espertech.esper.collection;

import com.espertech.esper.client.EventBean;

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

/**
 * An iterator over a list of iterables.
 * The IterablesListIterator iterator takes a list of Iterable instances as a parameter. The iterator will
 * Start at the very first Iterable and obtain it's iterator. It then allows iteration over this first iterator
 * until that iterator returns no next value. Then the IterablesListIterator iterator will obtain the next iterable and iterate
 * over this next iterable's iterator until no more values can be obtained. This continues until the last Iterable
 * in the order of the list of Iterables.
 */
public final class IterablesListIterator implements Iterator<EventBean> {
    private final Iterator<Iterable<EventBean>> listIterator;
    private Iterator<EventBean> currentIterator;

    /**
     * Constructor - takes a list of Iterable that supply the iterators to iterate over.
     *
     * @param iteratorOfIterables super-iterate of iterables
     */
    public IterablesListIterator(Iterator<Iterable<EventBean>> iteratorOfIterables) {
        listIterator = iteratorOfIterables;
        nextIterable();
    }


    public EventBean next() {
        if (currentIterator == null) {
            throw new NoSuchElementException();
        }
        if (currentIterator.hasNext()) {
            return currentIterator.next();
        }

        nextIterable();

        if (currentIterator == null) {
            throw new NoSuchElementException();
        }
        return currentIterator.next();
    }

    public boolean hasNext() {
        if (currentIterator == null) {
            return false;
        }

        if (currentIterator.hasNext()) {
            return true;
        }

        nextIterable();

        if (currentIterator == null) {
            return false;
        }

        return true;
    }

    public void remove() {
        throw new UnsupportedOperationException();
    }

    private void nextIterable() {
        while (listIterator.hasNext()) {
            Iterable<EventBean> iterable = listIterator.next();
            currentIterator = iterable.iterator();
            if (currentIterator.hasNext()) {
                return;
            }
        }

        currentIterator = null;
    }
}