/*
 * Copyright 2012  Research Studios Austria Forschungsges.m.b.H.
 *
 *    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 won.bot.framework.eventbot.listener;

import won.bot.framework.eventbot.event.Event;
import won.bot.framework.eventbot.EventListenerContext;
import won.bot.framework.eventbot.filter.EventFilter;

/**
 * Base class for listeners that eventually stop listening. When the decision is made to finish,
 * a FinishedEvent is published and the listener is unsubscribed from all further events.
 */
public abstract class AbstractFinishingListener extends BaseEventListener implements FinishingListener
{
  private Object monitor = new Object();
  private boolean finished = false;

  protected AbstractFinishingListener(final EventListenerContext context) {
    super(context);
  }

  protected AbstractFinishingListener(final EventListenerContext context, final EventFilter eventFilter) {
    super(context, eventFilter);
  }

  protected AbstractFinishingListener(final EventListenerContext context, final String name) {
    super(context, name);
  }

  protected AbstractFinishingListener(final EventListenerContext context, final String name, final EventFilter eventFilter) {
    super(context, name, eventFilter);
  }

  @Override
  public void doOnEvent(final Event event) throws Exception
  {
    boolean doRun = true;
    synchronized (monitor){
      if (finished){
        logger.debug("not executing handleEvent() as listener is finished: {}",this);
        return;
      }
      if (isFinished()) {
        logger.debug("not executing handleEvent() as listener's finishing condition is met: {}",this);
        doRun = false;
      }
    }
    if (doRun) {
      handleEvent(event);
    }
    if (isFinished()) {
      logger.debug("performing finishing actions for listener: {}",this);
      performFinish();
    }
  }

  /**
   * Performs all finishing actions and sets the finished flag
   */
  protected void performFinish() {
    synchronized (monitor){
      if (finished) return;
      unsubscribe();
      publishFinishedEvent();
      finished = true;
    }
  }

  protected abstract void unsubscribe();

  protected abstract void handleEvent(final Event event) throws Exception;

  @Override
  public abstract boolean isFinished();

  @Override
  public String toString()
  {
    return getClass().getSimpleName() +
        "{name='" + name +
        ", finished=" + finished +
        '}';
  }
}