package org.apache.maven.shared.dependency.tree;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

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

/**
 * {@link Iterator} for {@link DependencyNode} implementing a traversal from leaves to root.
 * 
 * TODO {@link #DependencyTreeInverseIterator(DependencyNode)} is costly,
 * a better implementation would move the cost to {@link #next()}
 * 
 * @author <a href="mailto:carlos@apache.org">Carlos Sanchez</a>
 * @version $Id$
 */
public class DependencyTreeInverseIterator
    implements Iterator<DependencyNode>
{
    private Stack<DependencyNode> nodesToProcess = new Stack<DependencyNode>();

    public DependencyTreeInverseIterator( DependencyNode rootNode )
    {
        DependencyTreePreorderIterator it = new DependencyTreePreorderIterator( rootNode );
        while ( it.hasNext() )
        {
            nodesToProcess.push( it.next() );
        }
    }

    public boolean hasNext()
    {
        return !nodesToProcess.isEmpty();
    }

    public DependencyNode next()
    {
        if ( !hasNext() )
        {
            throw new NoSuchElementException();
        }
        return nodesToProcess.pop();
    }

    /**
     * @throws UnsupportedOperationException
     */
    public void remove()
    {
        throw new UnsupportedOperationException();
    }
}