/*
 * 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.lucene.codecs.lucene53;


import java.io.IOException;

import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.codecs.NormsConsumer;
import org.apache.lucene.codecs.NormsFormat;
import org.apache.lucene.codecs.NormsProducer;
import org.apache.lucene.index.SegmentReadState;
import org.apache.lucene.index.SegmentWriteState;
import org.apache.lucene.store.DataOutput;

/**
 * Lucene 5.3 Score normalization format.
 * <p>
 * Encodes normalization values by encoding each value with the minimum
 * number of bytes needed to represent the range (which can be zero).
 * <p>
 * Files:
 * <ol>
 *   <li><tt>.nvd</tt>: Norms data</li>
 *   <li><tt>.nvm</tt>: Norms metadata</li>
 * </ol>
 * <ol>
 *   <li><a name="nvm"></a>
 *   <p>The Norms metadata or .nvm file.</p>
 *   <p>For each norms field, this stores metadata, such as the offset into the 
 *      Norms data (.nvd)</p>
 *   <p>Norms metadata (.dvm) --> Header,<Entry><sup>NumFields</sup>,Footer</p>
 *   <ul>
 *     <li>Header --> {@link CodecUtil#writeIndexHeader IndexHeader}</li>
 *     <li>Entry --> FieldNumber,BytesPerValue, Address</li>
 *     <li>FieldNumber --> {@link DataOutput#writeVInt vInt}</li>
 *     <li>BytesPerValue --> {@link DataOutput#writeByte byte}</li>
 *     <li>Offset --> {@link DataOutput#writeLong Int64}</li>
 *     <li>Footer --> {@link CodecUtil#writeFooter CodecFooter}</li>
 *   </ul>
 *   <p>FieldNumber of -1 indicates the end of metadata.</p>
 *   <p>Offset is the pointer to the start of the data in the norms data (.nvd), or the singleton value 
 *      when BytesPerValue = 0</p>
 *   <li><a name="nvd"></a>
 *   <p>The Norms data or .nvd file.</p>
 *   <p>For each Norms field, this stores the actual per-document data (the heavy-lifting)</p>
 *   <p>Norms data (.nvd) --> Header,< Data ><sup>NumFields</sup>,Footer</p>
 *   <ul>
 *     <li>Header --> {@link CodecUtil#writeIndexHeader IndexHeader}</li>
 *     <li>Data --> {@link DataOutput#writeByte(byte) byte}<sup>MaxDoc * BytesPerValue</sup></li>
 *     <li>Footer --> {@link CodecUtil#writeFooter CodecFooter}</li>
 *   </ul>
 * </ol>
 * @lucene.experimental
 */
public class Lucene53NormsFormat extends NormsFormat {

  /** Sole Constructor */
  public Lucene53NormsFormat() {}
  
  @Override
  public NormsConsumer normsConsumer(SegmentWriteState state) throws IOException {
    throw new UnsupportedOperationException("This format can only be used for reading");
  }

  @Override
  public NormsProducer normsProducer(SegmentReadState state) throws IOException {
    return new Lucene53NormsProducer(state, DATA_CODEC, DATA_EXTENSION, METADATA_CODEC, METADATA_EXTENSION);
  }
  
  static final String DATA_CODEC = "Lucene53NormsData";
  static final String DATA_EXTENSION = "nvd";
  static final String METADATA_CODEC = "Lucene53NormsMetadata";
  static final String METADATA_EXTENSION = "nvm";
  static final int VERSION_START = 0;
  static final int VERSION_CURRENT = VERSION_START;
}