EDIT

/**

 * Copyright (C) 2009 EDIT

 * European Distributed Institute of Taxonomy

 * http://www.e-taxonomy.eu

 *

 * The contents of this file are subject to the Mozilla Public License Version 1.1

 * See LICENSE.TXT at the top of this package for the full license terms.

 */

package eu.etaxonomy.cdm.persistence.validation;

import java.util.Collection;

import java.util.Iterator;

import java.util.concurrent.ArrayBlockingQueue;

import java.util.concurrent.TimeUnit;

/**

 * A job queue catering to the needs of the entity validation process. If an

 * entity validation task is submitted to the queue, and the queue already

 * contains tasks validating the exact same entity, those tasks should be

 * removed first, because they are validating a state of the entity that is no

 * longer actual. Note that it is not fatal to validate the entity in those

 * intermediary states, because in the end the final state of the entity does

 * get validated as well. It's just useless and may lead to unnecessary

 * contention of the queue.

 *

 * @author ayco_holleman

 *

 */

@SuppressWarnings("serial")

class EntityValidationTaskQueue extends ArrayBlockingQueue<Runnable> {

    public EntityValidationTaskQueue(int capacity) {

        super(capacity);

    }

    @Override

    public boolean add(Runnable r) {

        cleanup(r);

        return super.add(r);

    }

    @Override

    public boolean offer(Runnable r, long timeout, TimeUnit unit) throws InterruptedException {

        cleanup(r);

        return super.offer(r, timeout, unit);

    }

    @Override

    public boolean offer(Runnable r) {

        cleanup(r);

        return super.offer(r);

    }

    @Override

    public void put(Runnable r) throws InterruptedException {

        cleanup(r);

        super.put(r);

    }

    @Override

    public boolean addAll(Collection<? extends Runnable> c) {

        throw new RuntimeException("Submitting multiple validation tasks at once not supported");

    }

    private void cleanup(Runnable runnable) {

        EntityValidationTaskBase newTask = (EntityValidationTaskBase) runnable;

        Iterator<Runnable> iterator = this.iterator();

        while (iterator.hasNext()) {

            EntityValidationTaskBase oldTask = (EntityValidationTaskBase) iterator.next();

            if (oldTask.equals(newTask)) {

                iterator.remove();

            }

        }

    }

}