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package dk.alexandra.fresco.lib.helper;

import dk.alexandra.fresco.framework.ProtocolCollection;
import dk.alexandra.fresco.framework.ProtocolProducer;
import dk.alexandra.fresco.framework.sce.resources.ResourcePool;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;

/**
 * A parallel producer contains a set of protocols producer that are asked to fill the collection
 * eagerly. Given some of the producers are lazy initialized this performs best - and hence does a
 * breadth first search for more protocols. THis skews the evalueration of the protocols in favor of
 * the first, but delivers the best performance in terms of memory.
 */
public class ParallelProtocolProducer implements ProtocolProducer {

  private final Deque subProducers;

  public ParallelProtocolProducer(List protocols) {
    subProducers = new ArrayDeque<>(protocols);
  }

  @Override
  public boolean hasNextProtocols() {
    for (Iterator iterator = subProducers.iterator(); iterator.hasNext(); ) {
      ProtocolProducer producer = iterator.next();
      if (producer.hasNextProtocols()) {
        return true;
      } else {
        iterator.remove();
      }
    }
    return false;
  }

  @Override
  public  void getNextProtocols(
      ProtocolCollection protocolCollection) {
    iterate(subProducers.iterator(), protocolCollection);
  }

  protected  void iterate(
      Iterator iterator, ProtocolCollection protocolCollection) {
    while (iterator.hasNext() && protocolCollection.hasFreeCapacity()) {
      ProtocolProducer producer = iterator.next();
      if (producer.hasNextProtocols()) {
        producer.getNextProtocols(protocolCollection);
      } else {
        iterator.remove();
      }
    }
  }
}