/* 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 org.activiti.engine.delegate.event;

/**
 * Base event listener that can be used when implementing an
 * {@link ActivitiEventListener} to get notified when an entity is created,
 * updated, deleted or if another entity-related event occurs.
 * 
 * Override the <code>onXX(..)</code> methods to respond to entity changes
 * accordingly.
 * 
 * @author Frederik Heremans
 * 
 */
public class BaseEntityEventListener implements ActivitiEventListener {

	protected boolean failOnException = false;
	protected Class<?> entityClass;

	/**
	 * Create a new BaseEntityEventListener, notified when an event that targets
	 * any type of entity is received. Returning true when
	 * {@link #isFailOnException()} is called.
	 */
	public BaseEntityEventListener() {
		this(true, null);
	}

	/**
	 * Create a new BaseEntityEventListener.
	 * 
	 * @param failOnException
	 *          return value for {@link #isFailOnException()}.
	 */
	public BaseEntityEventListener(boolean failOnException) {
		this(failOnException, null);
	}

	public BaseEntityEventListener(boolean failOnException, Class<?> entityClass) {
		this.failOnException = failOnException;
		this.entityClass = entityClass;
	}

	@Override
	public final void onEvent(ActivitiEvent event) {
		if(isValidEvent(event)) {
			// Check if this event
			if (event.getType() == ActivitiEventType.ENTITY_CREATED) {
				onCreate(event);
			} else if (event.getType() == ActivitiEventType.ENTITY_INITIALIZED) {
				onInitialized(event);
			} else if (event.getType() == ActivitiEventType.ENTITY_DELETED) {
				onDelete(event);
			} else if (event.getType() == ActivitiEventType.ENTITY_UPDATED) {
				onUpdate(event);
			} else {
				// Entity-specific event
				onEntityEvent(event);
			}
		}
	}

	@Override
	public boolean isFailOnException() {
		return failOnException;
	}

	/**
	 * @return true, if the event is an {@link ActivitiEntityEvent} and (if needed) the entityClass
	 * set in this instance, is assignable from the entity class in the event. 
	 */
	protected boolean isValidEvent(ActivitiEvent event) {
		boolean valid = false;
		if(event instanceof ActivitiEntityEvent) {
			if(entityClass == null) {
				valid = true;
			} else {
				valid = entityClass.isAssignableFrom(((ActivitiEntityEvent) event).getEntity().getClass());
			}
		}
		return valid;
	}
	/**
	 * Called when an entity create event is received.
	 */
	protected void onCreate(ActivitiEvent event) {
		// Default implementation is a NO-OP
	}
	
	/**
	 * Called when an entity initialized event is received.
	 */
	protected void onInitialized(ActivitiEvent event) {
		// Default implementation is a NO-OP
	}

	/**
	 * Called when an entity delete event is received.
	 */
	protected void onDelete(ActivitiEvent event) {
		// Default implementation is a NO-OP
	}

	/**
	 * Called when an entity update event is received.
	 */
	protected void onUpdate(ActivitiEvent event) {
		// Default implementation is a NO-OP
	}

	/**
	 * Called when an event is received, which is not a create, an update or
	 * delete.
	 */
	protected void onEntityEvent(ActivitiEvent event) {
		// Default implementation is a NO-OP
	}
}