/*
 * 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.component.needproducer.impl;

import won.bot.framework.component.needproducer.NeedProducer;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * Composite Needproducer that will cycle through needFactories, returning a different one each time.
 * The order of the factories returned may change (implemented based on a Set not a List).
 */
public class RoundRobinCompositeNeedProducer extends AbstractCompositeNeedProducer
{
  private NeedProducer lastFactory = null;
  @Override
  protected synchronized NeedProducer selectActiveNeedFactory()
  {
    //work on a copy of the set to avoid concurrency problems
    Set<NeedProducer> factories = new HashSet<NeedProducer>();
    factories.addAll(getNeedFactories());
    Iterator<NeedProducer> factoryIterator = factories.iterator();
    if (!factoryIterator.hasNext()) {
      return null;
    }
    if (lastFactory == null) {
      lastFactory = factoryIterator.next();
      return lastFactory;
    } else {
      //iterate until we reach the last used factory
      while (factoryIterator.hasNext() && factoryIterator.next() != lastFactory){}
      //then, if the iterator has more factories
      if (factoryIterator.hasNext()){
        //choose the next one after the one we returned last
        this.lastFactory = factoryIterator.next();
        return lastFactory;
      } else {
        // else choose take the first factory returned by the iteraor (we were at the end of the iterators)
        this.lastFactory = factories.iterator().next();
        return this.lastFactory;
      }
    }
  }
}