/**
 * Copyright Microsoft Corporation
 * 
 * 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.microsoft.azure.storage;

import java.util.concurrent.CopyOnWriteArrayList;

/**
 * Represents a generic event multi-caster that allows event listeners to be dynamically added and removed.
 * 
 * @param <EVENT_TYPE>
 *            An object that represents the type of the event.
 * @param <EVENT_LISTENER_TYPE>
 *            An object that represents the type of the event listener.
 */
public final class StorageEventMultiCaster<EVENT_TYPE extends BaseEvent, EVENT_LISTENER_TYPE extends StorageEvent<EVENT_TYPE>> {

    /**
     * Holds the list of listeners.
     */
    private final CopyOnWriteArrayList<EVENT_LISTENER_TYPE> listeners = new CopyOnWriteArrayList<EVENT_LISTENER_TYPE>();

    /**
     * Adds a listener to the event chain.
     * 
     * @param listener
     *            An <code>EventListenerType</code> object that represents the listener to add.
     */
    public void addListener(final EVENT_LISTENER_TYPE listener) {
        this.listeners.add(listener);
    }

    /**
     * Fires the event to all subscribed event listeners.
     * 
     * @param event
     *            An <code>EVENTTYPE</code>object that represents the event being multi-casted.
     */
    public void fireEvent(final EVENT_TYPE event) {
        for (final StorageEvent<EVENT_TYPE> listener : this.listeners) {
            listener.eventOccurred(event);
        }
    }

    /**
     * Returns a value that indicates whether any event listeners are registered for events.
     * 
     * @return <code>true</code> if any event listeners are registered; otherwise, <code>false</code>.
     */
    public boolean hasListeners() {
        return this.listeners.size() > 0;
    }

    /**
     * Removes an event listener from the event chain.
     * 
     * @param listener
     *            An <code>EventListenerType</code> object that represents the listener to remove.
     */
    public void removeListener(final EVENT_LISTENER_TYPE listener) {
        this.listeners.remove(listener);
    }
}