/*
 * 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.UUID;
import java.util.Locale;

import org.apache.commons.lang.StringUtils;
import org.apache.solr.common.SolrException;
import static org.apache.solr.common.SolrException.ErrorCode.*;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;
import org.apache.solr.schema.SchemaField;


/**
 * <p>
 * An update processor that adds a newly generated <code>UUID</code> value
 * 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>id</code> field, a new <code>UUID</code> will be generated
 * and added as the value of that field.
 * <br>
 *
 * <pre class="prettyprint">
 * <processor class="solr.UUIDUpdateProcessorFactory">
 *   <str name="fieldName">id</str>
 * </processor>
 * </pre>
 *
 * <p>
 * If field name is omitted in processor configuration,
 * then  @{link org.apache.solr.schema.IndexSchema#getUniqueKeyField()}
 * is used as field and a new <code>UUID</code> will be generated
 * and added as the value of that field. The field type of the uniqueKeyField
 * must be anything which accepts a string or UUID value.
 * @see UUID
 */
public class UUIDUpdateProcessorFactory extends UpdateRequestProcessorFactory {

  protected String fieldName = null;

  @SuppressWarnings("unchecked")
  public void init(NamedList args) {

    Object obj = args.remove("fieldName");
    if (null != obj) {
      fieldName = obj.toString();
    }

    if (0 < args.size()) {
      throw new SolrException(SERVER_ERROR,
          "Unexpected init param(s): '" +
              args.getName(0) + "'");
    }
  }

  public UpdateRequestProcessor getInstance(SolrQueryRequest req,
                                            SolrQueryResponse rsp,
                                            UpdateRequestProcessor next ) {
    if (StringUtils.isEmpty(fieldName)) {
      SchemaField schemaField = req.getSchema().getUniqueKeyField();
      fieldName = schemaField.getName();
    }

    return new AbstractDefaultValueUpdateProcessorFactory.DefaultValueUpdateProcessor(fieldName, next) {
      @Override
      public Object getDefaultValue() {
        return UUID.randomUUID().toString().toLowerCase(Locale.ROOT);
      }
    };
  }
}