/***************************************************************************
 * Copyright 2001-2007 The eXo Platform SARL         All rights reserved.  *
 * Please look at license.txt in info directory for more license detail.   *
 **************************************************************************/
package org.exoplatform.services.listener;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.exoplatform.services.log.Log;

import org.exoplatform.services.log.ExoLogger;

/**
 * Created by The eXo Platform SAS Author : Nhu Dinh Thuan
 * nhudinhthuan@exoplatform.com Apr 6, 2007
 */
public class ListenerService {

  private Map<String, List<Listener>> listeners_;

  private static Log                  log = ExoLogger.getLogger("kernel.ListenerService");

  /**
   * Construct a listener service.
   */
  public ListenerService() {
    listeners_ = new HashMap<String, List<Listener>>();
  }

  /**
   * This method is used to register a listener with the service. The method
   * should: 1. Check to see if there is a list of listener with the listener
   * name, create one if the listener list doesn't exit 2. Add the new listener
   * to the listener list
   * 
   * @param listener
   */
  public void addListener(Listener listener) {
    String name = listener.getName();
    List<Listener> list = listeners_.get(name);
    if (list == null) {
      list = new ArrayList<Listener>();
      listeners_.put(name, list);
    }
    list.add(listener);
  }

  /**
   * @deprecated use the Listener name as the event name
   * @param eventName
   * @param listener
   */
  public void addListener(String eventName, Listener listener) {
    listener.setName(eventName);
    addListener(listener);
  }

  /**
   * This method is used to broadcast an event. This method should: 1. Check if
   * there is a list of listener that listen to the event name. 2. If there is a
   * list of listener, create the event object with the given name , source and
   * data 3. For each listener in the listener list, invoke the method
   * onEvent(Event)
   * 
   * @param <S> The type of the source that broacast the event
   * @param <D> The type of the data that the source object is working on
   * @param name The name of the event
   * @param source The source object instance
   * @param data The data object instance
   * @throws Exception TODO: Should not delegate to the method broadcast(Event)
   */
  final public <S, D> void broadcast(String name, S source, D data) throws Exception {
    List<Listener> list = listeners_.get(name);
    if (list == null)
      return;
    for (Listener<S, D> listener : list) {
      if (log.isDebugEnabled()) {
        log.debug("broadcasting event " + name + " on " + listener.getName());
      }
      listener.onEvent(new Event<S, D>(name, source, data));
    }
  }

  /**
   * This method is used when a developer want to implement his own event object
   * and broadcast the event. The method should: 1. Check if there is a list of
   * listener that listen to the event name. 2. If there is a list of the
   * listener, ror each listener in the listener list, invoke the method
   * onEvent(Event)
   * 
   * @param <T> The type of the event object, the type of the event object has
   *          to be extended from the Event type
   * @param event The event instance
   * @throws Exception
   */
  final public <T extends Event> void broadcast(T event) throws Exception {
    List<Listener> list = listeners_.get(event.getEventName());
    if (list == null)
      return;
    for (Listener listener : list)
      listener.onEvent(event);
  }
}