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The repeated implementation of the listener pattern for Java is a boring task which cannot be easily abstracted. Events-On-Fire is a way to get rid of this. Events-On-Fire offers a simple mechanism to fire events across your application without the need for any configuration and without the danger of memory leaks.

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/*
 * Copyright (c) 2011, 2012 events-on-fire Team
 * 
 * This file is part of Events-On-Fire (http://code.google.com/p/events-on-fire), licensed under the terms of the MIT
 * License (MIT).
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 * Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
package com.google.code.eventsonfire;

import java.lang.ref.Reference;
import java.util.LinkedHashSet;
import java.util.Set;

/**
 * Bindings of a producer with its consumers
 * 
 * @author Manfred Hantschel
 */
class ProducerInfo
{

    /**
     * The set of references to consumers. The set it not synchronized. All calls are made by the {@link Events} thread.
     */
    private final Set> consumerReferences;

    public ProducerInfo()
    {
        super();

        consumerReferences = new LinkedHashSet>();
    }

    /**
     * Adds the reference to the consumer to this producer.
     * 
     * @param consumerReference the reference to the consumer
     * @throws IllegalArgumentException if the consumer does not contain at least one method annotated with the
     *             {@link EventHandler} annotation
     */
    public void add(final Reference consumerReference) throws IllegalArgumentException
    {
        Object consumer = consumerReference.get();

        if (consumer == null)
        {
            return;
        }

        // ensure validity
        ConsumerClassInfo.getInstance(consumer.getClass());

        consumerReferences.add(consumerReference);
    }

    /**
     * Returns true, if the reference to the consumer was already added to the producer
     * 
     * @param consumerReference the reference to the consume
     * @return true if the producer contains the reference to the consumer
     */
    public boolean contains(final Reference consumerReference)
    {
        return consumerReferences.contains(consumerReference);
    }

    /**
     * Removes the reference to the consumer from this producer
     * 
     * @param consumerReference the reference to the consumer
     */
    public void remove(final Reference consumerReference)
    {
        consumerReferences.remove(consumerReference);
    }

    /**
     * Returns true if the set of consumers is empty
     * 
     * @return true if empty
     */
    public boolean isEmpty()
    {
        return consumerReferences.isEmpty();
    }

    /**
     * Fires an event to all consumers
     * 
     * @param event the event
     * @param tags the tags
     */
    public void fire(Object producer, Object event, String[] tags)
    {
        for (Reference consumerReference : consumerReferences)
        {
            Object consumer = consumerReference.get();

            if (consumer != null)
            {
                ConsumerClassInfo consumerClassInfo = ConsumerClassInfo.getInstance(consumer.getClass());

                consumerClassInfo.invoke(producer, consumer, event, tags);
            }
        }
    }

}