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/**
 * 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 com.gh.bmd.jrt.routine;

import java.util.Collection;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

/**
 * Implementation of a nested queue ensuring that data are returned in the same order as they are
 * added, even if added later through a nested queue.
 * 

 * Created by davide on 9/30/14.
 *
 * @param  the element type.
 */
class OrderedNestedQueue implements NestedQueue {

    private final SimpleQueue mQueue;

    private boolean mClosed;

    /**
     * Default constructor.
     */
    OrderedNestedQueue() {

        this(new SimpleQueue());
    }

    /**
     * Constructor.
     *
     * @param queue the internal queue.
     */
    private OrderedNestedQueue(@Nonnull final SimpleQueue queue) {

        mQueue = queue;
    }

    private static void purge(@Nonnull final OrderedNestedQueue queue) {

        final SimpleQueue simpleQueue = queue.mQueue;

        if (simpleQueue.isEmpty()) {

            return;
        }

        Object element = simpleQueue.peekFirst();

        while (element instanceof OrderedNestedQueue) {

            final OrderedNestedQueue nested = ((OrderedNestedQueue) element);

            if (!nested.mClosed) {

                return;
            }

            final SimpleQueue nestedSimpleQueue = nested.mQueue;

            if (!nestedSimpleQueue.isEmpty()) {

                purge(nested);

                if (!nestedSimpleQueue.isEmpty()) {

                    return;
                }
            }

            simpleQueue.removeFirst();

            if (simpleQueue.isEmpty()) {

                return;
            }

            element = simpleQueue.peekFirst();
        }
    }

    @Nonnull
    @Override
    public NestedQueue add(@Nullable final E element) {

        checkOpen();
        mQueue.add(element);
        return this;
    }

    @Nonnull
    @Override
    public NestedQueue addAll(@Nonnull final Iterable elements) {

        checkOpen();
        mQueue.addAll(elements);
        return this;
    }

    @Nonnull
    @Override
    public NestedQueue addNested() {

        checkOpen();
        final OrderedNestedQueue queue = new OrderedNestedQueue();
        mQueue.add(queue);
        return queue;
    }

    @Nonnull
    @Override
    public NestedQueue clear() {

        mQueue.clear();
        return this;
    }

    @Nonnull
    @Override
    public NestedQueue close() {

        mClosed = true;
        return this;
    }

    @Override
    public boolean isEmpty() {

        purge(this);

        final SimpleQueue queue = mQueue;

        if (queue.isEmpty()) {

            return true;
        }

        final Object element = queue.peekFirst();
        return (element instanceof OrderedNestedQueue)
                && ((OrderedNestedQueue) element).isEmpty();
    }

    @Nonnull
    @Override
    @SuppressWarnings("unchecked")
    public NestedQueue moveTo(@Nonnull final Collection collection) {

        purge(this);

        final SimpleQueue queue = mQueue;

        while (!queue.isEmpty()) {

            final Object element = queue.peekFirst();

            if (element instanceof OrderedNestedQueue) {

                final OrderedNestedQueue nested = (OrderedNestedQueue) element;
                nested.moveTo(collection);

                if (!nested.mClosed || !nested.mQueue.isEmpty()) {

                    return this;
                }

                queue.removeFirst();

            } else {

                collection.add((E) queue.removeFirst());
            }
        }

        return this;
    }

    @Nullable
    @Override
    @SuppressWarnings("unchecked")
    public E removeFirst() {

        purge(this);

        final Object element = mQueue.peekFirst();

        if (element instanceof OrderedNestedQueue) {

            return ((OrderedNestedQueue) element).removeFirst();
        }

        return (E) mQueue.removeFirst();
    }

    private void checkOpen() {

        if (mClosed) {

            throw new IllegalStateException("the queue is closed");
        }
    }
}
    

    

    

            

    

            



    
    






    
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