package org.exolab.castor.mapping.loader.collection.handler;

import java.util.Enumeration;
import java.util.PriorityQueue;
import java.util.Queue;

import org.exolab.castor.mapping.CollectionHandler;
import org.exolab.castor.mapping.loader.CollectionHandlers;
import org.exolab.castor.mapping.loader.J2CollectionHandlers.IteratorEnumerator;

public final class QueueCollectionHandler<T> implements CollectionHandler<T> {

  @SuppressWarnings("unchecked")
  public Object add(Object collection, T object) {
    if (collection == null) {
      collection = new PriorityQueue<T>();
      ((Queue<T>) collection).add(object);
      return collection;
    }
    ((Queue<T>) collection).add(object);
    return null;
  }

  @SuppressWarnings("unchecked")
  public Enumeration<T> elements(Object collection) {
    if (collection == null)
      return new CollectionHandlers.EmptyEnumerator<T>();
    return new IteratorEnumerator<T>(((Queue<T>) collection).iterator());
  }

  @SuppressWarnings("unchecked")
  public int size(Object collection) {
    if (collection == null)
      return 0;
    return ((Queue<T>) collection).size();
  }

  @SuppressWarnings("unchecked")
  public Object clear(Object collection) {
    if (collection != null)
      ((Queue<T>) collection).clear();
    return null;
  }

  public String toString() {
    return "Queue";
  }
}
