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package javax.cache.expiry;

import javax.cache.configuration.Factory;
import javax.cache.configuration.FactoryBuilder;
import java.io.Serializable;

/**
 * An {@link ExpiryPolicy} that defines the expiry {@link Duration}
 * of a Cache Entry based on when it was last touched. A touch includes
 * creation, update or access.
 *
 * @author Greg Luck
 * @author Brian Oliver
 * @since 1.0
 * @see ExpiryPolicy
 */
public final class TouchedExpiryPolicy implements ExpiryPolicy, Serializable {

  /**
   * The serialVersionUID required for {@link java.io.Serializable}.
   */
  public static final long serialVersionUID = 201305291023L;

  /**
   * The {@link Duration} a Cache Entry should be available before it expires.
   */
  private Duration expiryDuration;

  /**
   * Constructs an {@link TouchedExpiryPolicy} {@link ExpiryPolicy}.
   *
   * @param expiryDuration the {@link Duration} a Cache Entry should exist be
   *                       before it expires after being modified
   */
  public TouchedExpiryPolicy(Duration expiryDuration) {
    this.expiryDuration = expiryDuration;
  }

  /**
   * Obtains a {@link Factory} for a Touched {@link ExpiryPolicy}.
   *
   * @return a {@link Factory} for a Touched {@link ExpiryPolicy}.
   */
  public static Factory factoryOf(Duration duration) {
    return new FactoryBuilder.SingletonFactory(new TouchedExpiryPolicy(duration));
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Duration getExpiryForCreation() {
    //for newly created entries we use the specified expiry duration.
    return expiryDuration;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Duration getExpiryForAccess() {
    //accessing a cache entry resets the duration.
    return expiryDuration;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Duration getExpiryForUpdate() {
    //updating a cache entry resets the duration.
    return expiryDuration;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((expiryDuration == null) ? 0 : expiryDuration.hashCode());
    return result;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public boolean equals(Object object) {
    if (this == object) {
      return true;
    }
    if (object == null) {
      return false;
    }
    if (!(object instanceof TouchedExpiryPolicy)) {
      return false;
    }
    TouchedExpiryPolicy other = (TouchedExpiryPolicy) object;
    if (expiryDuration == null) {
      if (other.expiryDuration != null) {
        return false;
      }
    } else if (!expiryDuration.equals(other.expiryDuration)) {
      return false;
    }
    return true;
  }
}