/*
 * Copyright 2009 Google Inc.
 *
 * 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.dragome.forms.bindings.extra.event.shared;

import com.dragome.model.interfaces.EventHandler;
import com.dragome.model.interfaces.GwtEvent;
import com.dragome.model.interfaces.GwtEvent.Type;
import com.dragome.model.interfaces.HandlerRegistration;

/**
 * Manager responsible for adding handlers to event sources and firing those
 * handlers on passed in events. Primitive ancestor of {@link EventBus}, and
 * used at the core of {com.google.gwt.user.client.ui.Widget}.
 * <p>
 * While widget authors should continue to use
 * {@link com.google.gwt.user.client.ui.Widget#addDomHandler(EventHandler, com.google.gwt.event.dom.client.DomEvent.Type)}
 * and
 * {@link com.google.gwt.user.client.ui.Widget#addHandler(EventHandler, Type)},
 * application developers are strongly discouraged from using a HandlerManager
 * instance as a global event dispatch mechanism.
 */
public class HandlerManager implements HasHandlers
{

	private final SimpleEventBus eventBus;

	// source of the events
	private final Object source;

	/**
	 * Creates a handler manager with a source to be set on all events fired via
	 * {@link #fireEvent(GwtEvent)}. Handlers will be fired in the order that they
	 * are added.
	 *
	 * @param source the default event source
	 */
	public HandlerManager(Object source)
	{
		this(source, false);
	}

	/**
	 * Creates a handler manager with the given source, specifying the order in
	 * which handlers are fired.
	 *
	 * @param source the event source
	 * @param fireInReverseOrder true to fire handlers in reverse order
	 */
	@SuppressWarnings("deprecation")
	public HandlerManager(Object source, boolean fireInReverseOrder)
	{
		eventBus= new SimpleEventBus(fireInReverseOrder);
		this.source= source;
	}

	/**
	 * Adds a handler.
	 *
	 * @param <H> The type of handler
	 * @param type the event type associated with this handler
	 * @param handler the handler
	 * @return the handler registration, can be stored in order to remove the
	 *         handler later
	 */
	public <H extends EventHandler> HandlerRegistration addHandler(GwtEvent.Type<H> type, final H handler)
	{
		return eventBus.addHandler(type, handler);
	}

	/**
	 * Fires the given event to the handlers listening to the event's type.
	 * <p>
	 * Any exceptions thrown by handlers will be bundled into a
	 * {@link UmbrellaException} and then re-thrown after all handlers have
	 * completed. An exception thrown by a handler will not prevent other handlers
	 * from executing.
	 * <p>
	 * Note, any subclass should be very careful about overriding this method, as
	 * adds/removes of handlers will not be safe except within this
	 * implementation.
	 *
	 * @param event the event
	 */
	public void fireEvent(GwtEvent<?> event)
	{
		// If it not live we should revive it.
		if (!event.isLive())
		{
			event.revive();
		}
		Object oldSource= event.getSource();
		event.setSource(source);
		try
		{

			// May throw an UmbrellaException.
			eventBus.fireEvent(event);

		}
		finally
		{
			if (oldSource == null)
			{
				// This was my event, so I should kill it now that I'm done.
				event.kill();
			}
			else
			{
				// Restoring the source for the next handler to use.
				event.setSource(oldSource);
			}
		}
	}

	/**
	 * Gets the handler at the given index.
	 *
	 * @param <H> the event handler type
	 * @param index the index
	 * @param type the handler's event type
	 * @return the given handler
	 */
	@SuppressWarnings("deprecation")
	public <H extends EventHandler> H getHandler(GwtEvent.Type<H> type, int index)
	{
		return eventBus.getHandler(type, index);
	}

	/**
	 * Gets the number of handlers listening to the event type.
	 *
	 * @param type the event type
	 * @return the number of registered handlers
	 */
	@SuppressWarnings("deprecation")
	public int getHandlerCount(Type<?> type)
	{
		return eventBus.getHandlerCount(type);
	}

	/**
	 * Does this handler manager handle the given event type?
	 *
	 * @param e the event type
	 * @return whether the given event type is handled
	 */
	@SuppressWarnings("deprecation")
	public boolean isEventHandled(Type<?> e)
	{
		return eventBus.isEventHandled(e);
	}

	/**
	 * Removes the given handler from the specified event type.
	 *
	 * @param <H> handler type
	 *
	 * @param type the event type
	 * @param handler the handler
	 */
	public <H extends EventHandler> void removeHandler(GwtEvent.Type<H> type, final H handler)
	{
		eventBus.doRemove(type, null, handler);
	}
}