/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.solr.update.processor;

import java.util.Date;

import org.apache.solr.request.SolrRequestInfo;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;
import org.apache.solr.common.params.CommonParams; // javadoc

/**
 * <p>
 * An update processor that adds a newly generated <code>Date</code> value 
 * of "NOW" to any document being added that does not already have a value 
 * in the specified field.
 * </p>
 *
 * <p>
 * In the example configuration below, if a document does not contain a value 
 * in the <code>timestamp</code> field, a new <code>Date</code> will be 
 * generated and added as the value of that field.
 * <br>
 *
 * <pre class="prettyprint">
 * <processor class="solr.TimestampUpdateProcessorFactory">
 *   <str name="fieldName">timestamp</str>
 * </processor>
 * </pre>
 * 
 * @see Date
 * @see CommonParams#NOW
 */
public class TimestampUpdateProcessorFactory
  extends AbstractDefaultValueUpdateProcessorFactory {

  @Override
  public UpdateRequestProcessor getInstance(SolrQueryRequest req, 
                                            SolrQueryResponse rsp, 
                                            UpdateRequestProcessor next ) {
    return new DefaultValueUpdateProcessor(fieldName, next) {
      @Override
      public Object getDefaultValue() { 
        return SolrRequestInfo.getRequestInfo().getNOW();
      }
    };
  }
}