/*
 * The contents of this file are subject to the terms of the Common Development and
 * Distribution License (the License). You may not use this file except in compliance with the
 * License.
 *
 * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
 * specific language governing permission and limitations under the License.
 *
 * When distributing Covered Software, include this CDDL Header Notice in each file and include
 * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
 * Header, with the fields enclosed by brackets [] replaced by your own identifying
 * information: "Portions Copyright [year] [name of copyright owner]".
 *
 * Copyright 2013-2016 ForgeRock AS.
 */
package org.opends.server.replication.server.changelog.api;

import org.opends.server.replication.common.CSN;
import org.forgerock.opendj.ldap.DN;

/**
 * This class stores an index of all the changes seen by this server in the form
 * of {@link ChangeNumberIndexRecord}s. The records are sorted by a global
 * ordering as defined in the CSN class. The index links a
 * <code>changeNumber</code> to the corresponding CSN. The CSN then links to a
 * corresponding change in one of the ReplicaDBs.
 *
 * @see <a href=
 * "https://wikis.forgerock.org/confluence/display/OPENDJ/OpenDJ+Domain+Names"
 * >OpenDJ Domain Names</a> for more information about the changelog.
 * @see <a href= "http://tools.ietf.org/html/draft-good-ldap-changelog-04"
 * >OpenDJ Domain Names</a> for more information about the changeNumber.
 */
public interface ChangeNumberIndexDB
{

  /**
   * Returns the last generated change number.
   *
   * @return the last generated change number
   */
  long getLastGeneratedChangeNumber();

  /**
   * Get the oldest record stored in this DB.
   *
   * @return Returns the oldest {@link ChangeNumberIndexRecord} in this DB, null
   *         when the DB is empty or closed
   * @throws ChangelogException
   *           if a database problem occurs.
   */
  ChangeNumberIndexRecord getOldestRecord() throws ChangelogException;

  /**
   * Get the newest record stored in this DB.
   *
   * @return Returns the newest {@link ChangeNumberIndexRecord} in this DB, null
   *         when the DB is empty or closed
   * @throws ChangelogException
   *           if a database problem occurs.
   */
  ChangeNumberIndexRecord getNewestRecord() throws ChangelogException;

  /**
   * Add an update to the list of messages that must be saved to this DB managed
   * by this DB and return the changeNumber associated to this record.
   * <p>
   * Note: this method disregards the changeNumber in the provided record.
   *
   * @param record
   *          The {@link ChangeNumberIndexRecord} to add to this DB.
   * @return the change number associated to this record on adding to this DB
   * @throws ChangelogException
   *           if a database problem occurs.
   */
  long addRecord(ChangeNumberIndexRecord record) throws ChangelogException;

  /**
   * Generate a new {@link DBCursor} that allows to browse the db managed by
   * this object and starting at the position defined by a given changeNumber.
   *
   * @param startChangeNumber
   *          The position where the iterator must start.
   * @return a new DBCursor that allows to browse this DB managed by
   *         this object and starting at the position defined by a given
   *         changeNumber.
   * @throws ChangelogException
   *           if a database problem occurs.
   */
  DBCursor<ChangeNumberIndexRecord> getCursorFrom(long startChangeNumber)
      throws ChangelogException;

  /**
   * Resets ChangeNumber index to the given number and CSN.
   * @param newFirstCN
   *          the new change number to appear as first change in the external changelog
   * @param baseDN
   *          the new record for the first change
   * @param newFirstCSN
   *          the CSN of the new first change
   * @throws ChangelogException
   *          if an error occurs during reset
   */
  void resetChangeNumberTo(long newFirstCN, DN baseDN, CSN newFirstCSN) throws ChangelogException;
}