/*************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

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- Redistributions of source code must retain the above copyright
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- Neither  the name  of Rice  University (RICE) nor  the names  of its
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This software is provided by RICE and the contributors on an "as is"
basis, without any representations or warranties of any kind, express
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********************************************************************************/

package rice.p2p.past.gc;

import rice.*;
import rice.p2p.commonapi.*;
import rice.p2p.past.*;

/**
 * @(#) GCPast.java This interface represents an extension to the Past
 * interface, which adds support for garbage collection and versionsing.
 * Individual objects are each given versions and timeout times. Version numbers
 * are used to keep different replicas in sync, and the timeout times are used
 * to determine when space can be reclaimed. Applications must periodically
 * invoke the refresh() operation on all objects which they are interested in.
 * Otherwise, objects may be reclaimed and will be no longer available.
 *
 * @version $Id: GCPast.java 2372 2005-03-21 18:56:11Z amislove $
 * @author Alan Mislove
 * @author Andreas Haeberlen
 */
public interface GCPast extends Past {

  /**
   * Timeout value which indicates that the object should never expire. Note
   * that objects with this timeout value _will_ be deleted in the year
   * 292473178. If this is a problem, applications should check for this value
   * explicitly.
   */
  public static final long INFINITY_EXPIRATION = Long.MAX_VALUE;

  /**
   * Inserts an object with the given ID into this instance of Past.
   * Asynchronously returns a PastException to command, if the operation was
   * unsuccessful. If the operation was successful, a Boolean[] is returned
   * representing the responses from each of the replicas which inserted the
   * object. This method is equivalent to insert(obj, INFINITY_EXPIRATION,
   * command) as it inserts the object with a timeout value of infinity. This is
   * done for simplicity, as well as backwards-compatibility for applications.
   *
   * @param obj the object to be inserted
   * @param command Command to be performed when the result is received
   */
  public void insert(PastContent obj, Continuation command);

  /**
   * Inserts an object with the given ID into this instance of Past.
   * Asynchronously returns a PastException to command, if the operation was
   * unsuccessful. If the operation was successful, a Boolean[] is returned
   * representing the responses from each of the replicas which inserted the
   * object. The contract for this method is that the provided object will be
   * stored until the provided expiration time. Thus, if the application
   * determines that it is still interested in this object, it must refresh the
   * object via the refresh() method.
   *
   * @param obj the object to be inserted
   * @param expiration the time until which the object must be stored
   * @param command Command to be performed when the result is received
   */
  public void insert(PastContent obj, long expiration, Continuation command);

  /**
   * Updates the objects stored under the provided keys id to expire no earlier
   * than the provided expiration time. Asyncroniously returns the result to the
   * caller via the provided continuation. The result of this operation is an
   * Object[], which is the same length as the input array of Ids. Each element
   * in the array is either Boolean(true), representing that the refresh
   * succeeded for the cooresponding Id, or an Exception describing why the
   * refresh failed. Specifically, the possible exceptions which can be returned
   * are: ObjectNotFoundException - if no object was found under the given key
   * RefreshFailedException - if the refresh operation failed for any other
   * reason (the getMessage() will describe the failure)
   *
   * @param ids DESCRIBE THE PARAMETER
   * @param expiration The time to extend the lifetime to
   * @param command Command to be performed when the result is received
   */
  public void refresh(Id[] ids, long[] expiration, Continuation command);

  /**
   * Updates the objects stored under the provided keys id to expire no earlier
   * than the provided expiration time. Asyncroniously returns the result to the
   * caller via the provided continuation. The result of this operation is an
   * Object[], which is the same length as the input array of Ids. Each element
   * in the array is either Boolean(true), representing that the refresh
   * succeeded for the cooresponding Id, or an Exception describing why the
   * refresh failed. Specifically, the possible exceptions which can be returned
   * are: ObjectNotFoundException - if no object was found under the given key
   * RefreshFailedException - if the refresh operation failed for any other
   * reason (the getMessage() will describe the failure)
   *
   * @param ids DESCRIBE THE PARAMETER
   * @param expiration The time to extend the lifetime to (applies to all keys)
   * @param command Command to be performed when the result is received
   */
  public void refresh(Id[] ids, long expiration, Continuation command);

}

