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 * may not use this file except in compliance with the License. You can obtain
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 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
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package com.sun.hk2.component;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.logging.Level;

import org.jvnet.hk2.component.ComponentException;
import org.jvnet.hk2.component.Inhabitant;
import org.jvnet.hk2.component.PreDestroy;

/**
 * Enables lifecycle controls surrounding and inhabitant's get() and release().
 * 
 * 
 * Resembles LazyInhabitant is some ways, but varies by caching the result of get()
 * and keeping it cached while ref count >= 1.
 * 
 * @author Jeff Trent
 * @since 3.1
 */
@SuppressWarnings("unchecked")
public class ReferenceCountedLazyInhabitant extends EventPublishingInhabitant {

  private volatile T object;
  private volatile Inhabitant onBehalfOf;
  private final AtomicInteger refCount;
  
  public ReferenceCountedLazyInhabitant(Inhabitant delegate) {
    this(delegate, 0);
  }
  
  public ReferenceCountedLazyInhabitant(Inhabitant delegate, int startingRefCount) {
    super(delegate);
    refCount = new AtomicInteger(startingRefCount);
  }
  
  int getRefCount() {
    return refCount.get();
  }

  @Override
  public T get(Inhabitant onBehalfOf) {
    T object = this.object; 
    int val = refCount.incrementAndGet();
    if (1 == val || null == this.onBehalfOf) {
      try {
        object = this.object = super.get(onBehalfOf);
      } catch (RuntimeException e) {
        logger.log(Level.FINE, "error encountered", new ComponentException(e));
        refCount.decrementAndGet(); // ignore result
        throw e;
      }
      this.onBehalfOf = onBehalfOf;
    }
    assert (onBehalfOf == this.onBehalfOf) : "wrong onBehalfOf context";
    return object;
  }

  @Override
  public void release() {
    int val = refCount.decrementAndGet();
    if (val < 0) {  // somebody go too far in release()?
      refCount.set(0);
      val = 0;
    }
    
    if (0 == val) {
      try {
        if (PreDestroy.class.isInstance(object)) {
          PreDestroy.class.cast(object).preDestroy();
        }
      } catch (RuntimeException e) {
        logger.log(Level.FINE, "error encountered", new ComponentException(e));
        throw e;
      } finally {
        this.object = null;
        this.onBehalfOf = null;
        super.release();
      }
    }
  }
  
  @Override
  public Inhabitant scopedClone() {
    if (null == real) {
      fetch();
    }
    Inhabitant real = this.real;
    return real.scopedClone();
  }
}