/**
 * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
 */

package net.sourceforge.pmd.util;

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

/**
 * Creates a single compound Iterator from an array of Iterators.
 *
 * @param <T>
 *            The type returned by the Iterator.
 *
 * @see Iterator
 */
public class CompoundIterator<T> implements Iterator<T> {
    private final Iterator<T>[] iterators;
    private int index;

    /**
     *
     * @param iterators
     *            The iterators use.
     */
    public CompoundIterator(Iterator<T>... iterators) {
        this.iterators = iterators;
        this.index = 0;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean hasNext() {
        return getNextIterator() != null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public T next() {
        Iterator<T> iterator = getNextIterator();
        if (iterator != null) {
            return iterator.next();
        } else {
            throw new NoSuchElementException();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void remove() {
        Iterator<T> iterator = getNextIterator();
        if (iterator != null) {
            iterator.remove();
        } else {
            throw new IllegalStateException();
        }
    }

    // Get the next iterator with values, returns null if there is no such
    // iterator
    private Iterator<T> getNextIterator() {
        while (index < iterators.length) {
            if (iterators[index].hasNext()) {
                return iterators[index];
            } else {
                index++;
            }
        }
        return null;
    }
}