/*
 * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.graal.nodes.util;

import java.util.*;

public class TreeIterators {

    public abstract static class PrefixTreeIterator<T> implements Iterator<T> {

        private Deque<T> stack = new LinkedList<>();

        public PrefixTreeIterator(T root) {
            stack.push(root);
        }

        public PrefixTreeIterator(Iterable<T> roots) {
            for (T root : roots) {
                stack.addLast(root);
            }
        }

        @Override
        public boolean hasNext() {
            return !stack.isEmpty();
        }

        @Override
        public T next() {
            T top = stack.pop();
            LinkedList<T> list = new LinkedList<>();
            for (T child : children(top)) {
                list.addFirst(child);
            }
            for (T child : list) {
                stack.push(child);
            }
            return top;
        }

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

        protected abstract Iterable<T> children(T node);
    }
}