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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2013 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * http://glassfish.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
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 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
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 */
package org.glassfish.tyrus.container.grizzly.client;

import java.util.Queue;

/**
 * Class responsible for processing {@link Task} queues.
 *
 * @author Pavel Bucek (pavel.bucek at oracle.com)
 */
public class TaskProcessor {

    /**
     * Processes as much tasks from the queue as possible.
     *
     * @param queue     {@link Task} queue.
     * @param condition if present, it will be called before every processed {@link Task}. When {@link org.glassfish.tyrus.container.grizzly.client.TaskProcessor.Condition#isValid()}
     *                  returns {@code false}, processing will be terminated. If the condition is not present (parameter
     *                  is {@code null}, all tasks from the queue will be processed.
     */
    public static void processQueue(Queue queue, Condition condition) {
        if (!queue.isEmpty()) {
            do {
                if (condition != null && !condition.isValid()) {
                    return;
                }

                final Task first = queue.poll();
                if (first == null) {
                    continue;
                }

                first.execute();
            } while (!queue.isEmpty());
        }
    }

    /**
     * Generic task representation.
     */
    public static abstract class Task {
        /**
         * To be overridden.
         */
        public abstract void execute();
    }

    /**
     * Condition used in {@link #processQueue(java.util.Queue, org.glassfish.tyrus.container.grizzly.client.TaskProcessor.Condition)}.
     */
    public interface Condition {

        /**
         * Check the condition.
         *
         * @return {@code true} when condition is valid, {@code false otherwise}.
         */
        public boolean isValid();
    }
}