package com.infomancers.collections.iterators;

import com.infomancers.collections.yield.Yielder;

import java.util.Deque;
import java.util.Queue;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.BlockingQueue;

/**
 * Copyright (c) 2007, Aviad Ben Dov
 * <p/>
 * All rights reserved.
 * <p/>
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * <p/>
 * 1. Redistributions of source code must retain the above copyright notice, this list
 * of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice, this
 * list of conditions and the following disclaimer in the documentation and/or other
 * materials provided with the distribution.
 * 3. Neither the name of Infomancers, Ltd. nor the names of its contributors may be
 * used to endorse or promote products derived from this software without specific
 * prior written permission.
 * <p/>
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

public final class QueueIterators {
    public static <T> Iterable<T> pollingQueueIterable(final Queue<T> queue) {
        return new Yielder<T>() {
            @Override
            protected void yieldNextCore() {
                T item;
                while ((item = queue.poll()) != null) {
                    yieldReturn(item);
                }
            }
        };
    }

    public static <T> Iterable<T> pollingDequeDescendingIterable(final Deque<T> deque) {
        return new Yielder<T>() {
            @Override
            protected void yieldNextCore() {
                T item;
                while ((item = deque.pollLast()) != null) {
                    yieldReturn(item);
                }
            }
        };
    }

    public static <T> Iterable<T> blockingQueueIterable(final BlockingQueue<T> queue) {
        return new Yielder<T>() {
            @Override
            protected void yieldNextCore() {
                try {
                    while (true) {
                        yieldReturn(queue.take());
                    }
                } catch (InterruptedException e) {
                    yieldBreak();
                }
            }
        };
    }

    public static <T> Iterable<T> blockingDequeDescendingIterable(final BlockingDeque<T> deque) {
        return new Yielder<T>() {
            @Override
            protected void yieldNextCore() {
                try {
                    while (true) {
                        yieldReturn(deque.takeLast());
                    }
                } catch (InterruptedException e) {
                    yieldBreak();
                }
            }
        };
    }
}