/*
 * Copyright (C) 2005-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */
package org.alfresco.repo.domain.locks;

import org.alfresco.repo.lock.LockAcquisitionException;
import org.alfresco.service.namespace.QName;

/**
 * DAO services for <b>alf_lock</b> and related tables
 * 
 * @author Derek Hulley
 * @since 3.2
 */
public interface LockDAO
{
    /**
     * Aquire a given exclusive lock, assigning it (and any implicitly shared locks) a
     * timeout.  All shared locks are implicitly taken as well.
     * <p>
     * A lock can be re-taken if it has expired and if the lock token has not changed
     * 
     * @param lockQName             the unique name of the lock to acquire
     * @param lockToken             the potential lock token (max 36 chars)
     * @param timeToLive            the time (in milliseconds) that the lock must remain 
     * @return                      Returns <tt>true</tt> if the lock was taken, 
     *                              otherwise <tt>false</tt>
     * @throws LockAcquisitionException     on failure
     */
    void getLock(QName lockQName, String lockToken, long timeToLive);

    /**
     * Refresh a held lock.  This is successful if the lock in question still exists
     * and if the lock token has not changed.  Lock expiry does not prevent the lock
     * from being refreshed.
     * 
     * @param lockQName             the unique name of the lock to update
     * @param lockToken             the lock token for the lock held
     * @param timeToLive            the new time to live (in milliseconds)
     * @return                      Returns <tt>true</tt> if the lock was updated,
     *                              otherwise <tt>false</tt>
     * @throws LockAcquisitionException     on failure
     */
    void refreshLock(QName lockQName, String lockToken, long timeToLive);
    
    /**
     * Release a lock.  The lock token must still apply and all the shared and exclusive
     * locks need to still be present, unless the method is optimistic, in which case the
     * unlock is considered to be a success.<br/>
     * Lock expiration does not prevent this operation from succeeding.
     * <p/>
     * Note: Failure to release a lock due to a exception condition is dealt with by
     *       passing the exception out.
     * 
     * @param lockQName             the unique name of the lock to release
     * @param lockToken             the current lock token
     * @param optimistic            <tt>true</tt> if the release attempt is enough even
     *                              if the number of released locks was incorrect.
     * @return                      <tt>true</tt> if the lock was successfully (and completely)
     *                              released or <tt>false</tt> if the lock was no longer valid
     *                              <b>and the method was being called optimistically.</b>
     * @throws LockAcquisitionException     if the number of locks released was incorrect
     *                              and pessimistic release is requested.
     */
    boolean releaseLock(QName lockQName, String lockToken, boolean optimistic);
}