/*
 * 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 2009 Sun Microsystems, Inc.
 * Portions Copyright 2011-2016 ForgeRock AS.
 */
package org.opends.server.replication.server;

import org.forgerock.i18n.slf4j.LocalizedLogger;
import org.forgerock.opendj.ldap.ResultCode;
import org.forgerock.opendj.server.config.server.UserDefinedVirtualAttributeCfg;
import org.opends.server.api.VirtualAttributeProvider;
import org.opends.server.core.SearchOperation;
import org.opends.server.types.Attribute;
import org.opends.server.types.Attributes;
import org.opends.server.types.Entry;
import org.opends.server.types.VirtualAttributeRule;

import static org.opends.messages.ExtensionMessages.*;

/**
 * Virtual attribute returning the oldest change number from the changelogDB.
 */
class FirstChangeNumberVirtualAttributeProvider extends VirtualAttributeProvider<UserDefinedVirtualAttributeCfg>
{
  /** The tracer object for the debug logger. */
  private static final LocalizedLogger logger = LocalizedLogger.getLoggerForThisClass();

  private final ReplicationServer replicationServer;

  /**
   * Creates a new instance of this member virtual attribute provider.
   *
   * @param replicationServer
   *          The replication server.
   */
  public FirstChangeNumberVirtualAttributeProvider(ReplicationServer replicationServer)
  {
    this.replicationServer = replicationServer;
  }

  /** {@inheritDoc} */
  @Override
  public boolean isMultiValued()
  {
    return false;
  }

  /** {@inheritDoc} */
  @Override
  public boolean hasValue(Entry entry, VirtualAttributeRule rule)
  {
    // There's only a value for the rootDSE, i.e. the Null DN.
    return entry.getName().isRootDN();
  }

  /** {@inheritDoc} */
  @Override
  public Attribute getValues(Entry entry,VirtualAttributeRule rule)
  {
    String value = "0";
    try
    {
      if (replicationServer != null)
      {
        value = String.valueOf(replicationServer.getOldestChangeNumber());
      }
    }
    catch(Exception e)
    {
      // We got an error computing this change number.
      // Rather than returning 0 which is no change, return -1 to
      // indicate the error.
      value = "-1";
      logger.traceException(e);
    }
    return Attributes.create(rule.getAttributeType(), value);
  }

  /** {@inheritDoc} */
  @Override
  public boolean isSearchable(VirtualAttributeRule rule,
                              SearchOperation searchOperation,
                              boolean isPreIndexed)
  {
    // We do not allow search for this change number. It's a read-only
    // attribute of the RootDSE.
    return false;
  }

  /** {@inheritDoc} */
  @Override
  public void processSearch(VirtualAttributeRule rule, SearchOperation searchOperation)
  {
    searchOperation.setResultCode(ResultCode.UNWILLING_TO_PERFORM);
    searchOperation.appendErrorMessage(ERR_FIRSTCHANGENUMBER_VATTR_NOT_SEARCHABLE.get(
            rule.getAttributeType().getNameOrOID()));
  }

}