package org.apache.lucene.facet.util;

/*
 * 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.
 */

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.apache.lucene.facet.encoding.IntDecoder;
import org.apache.lucene.facet.encoding.IntEncoder;
import org.apache.lucene.facet.params.CategoryListParams;
import org.apache.lucene.facet.params.FacetIndexingParams;
import org.apache.lucene.facet.taxonomy.directory.DirectoryTaxonomyWriter.OrdinalMap;
import org.apache.lucene.index.AtomicReader;
import org.apache.lucene.index.BinaryDocValues;
import org.apache.lucene.index.FilterAtomicReader;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.IntsRef;

/**
 * A {@link FilterAtomicReader} for updating facets ordinal references,
 * based on an ordinal map. You should use this code in conjunction with merging
 * taxonomies - after you merge taxonomies, you receive an {@link OrdinalMap}
 * which maps the 'old' ordinals to the 'new' ones. You can use that map to
 * re-map the doc values which contain the facets information (ordinals) either
 * before or while merging the indexes.
 * <p>
 * For re-mapping the ordinals during index merge, do the following:
 * 
 * <pre class="prettyprint">
 * // merge the old taxonomy with the new one.
 * OrdinalMap map = DirectoryTaxonomyWriter.addTaxonomies();
 * int[] ordmap = map.getMap();
 * 
 * // Add the index and re-map ordinals on the go
 * DirectoryReader reader = DirectoryReader.open(oldDir);
 * IndexWriterConfig conf = new IndexWriterConfig(VER, ANALYZER);
 * IndexWriter writer = new IndexWriter(newDir, conf);
 * List&lt;AtomicReaderContext&gt; leaves = reader.leaves();
 *   AtomicReader wrappedLeaves[] = new AtomicReader[leaves.size()];
 *   for (int i = 0; i < leaves.size(); i++) {
 *     wrappedLeaves[i] = new OrdinalMappingAtomicReader(leaves.get(i).reader(), ordmap);
 *   }
 * writer.addIndexes(new MultiReader(wrappedLeaves));
 * writer.commit();
 * </pre>
 * 
 * @lucene.experimental
 */
public class OrdinalMappingAtomicReader extends FilterAtomicReader {
  
  private final int[] ordinalMap;
  
  private final Map<String,CategoryListParams> dvFieldMap = new HashMap<String,CategoryListParams>();
  
  /**
   * Wraps an AtomicReader, mapping ordinals according to the ordinalMap.
   * Calls {@link #OrdinalMappingAtomicReader(AtomicReader, int[], FacetIndexingParams)
   * OrdinalMappingAtomicReader(in, ordinalMap, new DefaultFacetIndexingParams())}
   */
  public OrdinalMappingAtomicReader(AtomicReader in, int[] ordinalMap) {
    this(in, ordinalMap, FacetIndexingParams.DEFAULT);
  }
  
  /**
   * Wraps an AtomicReader, mapping ordinals according to the ordinalMap,
   * using the provided indexingParams.
   */
  public OrdinalMappingAtomicReader(AtomicReader in, int[] ordinalMap, FacetIndexingParams indexingParams) {
    super(in);
    this.ordinalMap = ordinalMap;
    for (CategoryListParams params: indexingParams.getAllCategoryListParams()) {
      dvFieldMap.put(params.field, params);
    }
  }

  @Override
  public BinaryDocValues getBinaryDocValues(String field) throws IOException {
    BinaryDocValues inner = super.getBinaryDocValues(field);
    if (inner == null) {
      return inner;
    }
    
    CategoryListParams clp = dvFieldMap.get(field);
    if (clp == null) {
      return inner;
    } else {
      return new OrdinalMappingBinaryDocValues(clp, inner);
    }
  }
  
  private class OrdinalMappingBinaryDocValues extends BinaryDocValues {

    private final IntEncoder encoder;
    private final IntDecoder decoder;
    private final IntsRef ordinals = new IntsRef(32);
    private final BinaryDocValues delegate;
    private final BytesRef scratch = new BytesRef();
    
    protected OrdinalMappingBinaryDocValues(CategoryListParams clp, BinaryDocValues delegate) {
      this.delegate = delegate;
      encoder = clp.createEncoder();
      decoder = encoder.createMatchingDecoder();
    }
    
    @SuppressWarnings("synthetic-access")
    @Override
    public void get(int docID, BytesRef result) {
      // NOTE: this isn't quite koscher, because in general
      // multiple threads can call BinaryDV.get which would
      // then conflict on the single scratch instance, but
      // because this impl is only used for merging, we know
      // only 1 thread calls us:
      delegate.get(docID, scratch);
      if (scratch.length > 0) {
        // We must use scratch (and not re-use result) here,
        // else encoder may overwrite the DV provider's
        // private byte[]:
        decoder.decode(scratch, ordinals);
        
        // map the ordinals
        for (int i = 0; i < ordinals.length; i++) {
          ordinals.ints[i] = ordinalMap[ordinals.ints[i]];
        }
        
        encoder.encode(ordinals, result);
      }
    }
  }
}

@@ -2049,16 +2049,43 @@
 ap map =
+ new MemoryOrdinalMap();%0A *
  Directo
@@ -2115,12 +2115,25 @@
 onom
-ies(
+y(srcTaxoDir, map
 );%0A 

fix code example in jdoc