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Java wrapper for the popular chat & VOIP service: Discord https://discord.com

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/*
 * Copyright 2015 Austin Keener, Michael Ritter, Florian Spieß, and the JDA contributors
 *
 * 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 net.dv8tion.jda.internal.utils;

import javax.annotation.Nonnull;
import java.util.*;

public class ClassWalker implements Iterable>
{
    private final Class clazz;
    private final Class end;

    private ClassWalker(Class clazz)
    {
        this(clazz, Object.class);
    }

    private ClassWalker(Class clazz, Class end)
    {
        this.clazz = clazz;
        this.end = end;
    }

    public static ClassWalker range(Class start, Class end)
    {
        return new ClassWalker(start, end);
    }

    public static ClassWalker walk(Class start)
    {
        return new ClassWalker(start);
    }

    @Nonnull
    @Override
    public Iterator> iterator()
    {
        return new Iterator>()
        {
            private final Set> done = new HashSet<>();
            private final Deque> work = new LinkedList<>();

            {
                work.addLast(clazz);
                done.add(end);
            }

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

            @Override
            public Class next()
            {
                Class current = work.removeFirst();
                done.add(current);
                for (Class parent : current.getInterfaces())
                {
                    if (!done.contains(parent))
                        work.addLast(parent);
                }

                Class parent = current.getSuperclass();
                if (parent != null && !done.contains(parent))
                    work.addLast(parent);
                return current;
            }
        };
    }
}