content: /**
   * 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.analysis;
  
  import org.apache.lucene.analysis.CharArraySet;
  import org.apache.lucene.analysis.TokenFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
  import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
  import org.apache.lucene.util.Version;
  
  import java.io.IOException;
  
  /**
   * A TokenFilter which filters out Tokens at the same position and Term text as the previous token in the stream.
   */
  public final class RemoveDuplicatesTokenFilter extends TokenFilter {
  
    private final CharTermAttribute termAttribute = addAttribute(CharTermAttribute.class);
    private final PositionIncrementAttribute posIncAttribute =  addAttribute(PositionIncrementAttribute.class);
    
    // use a fixed version, as we don't care about case sensitivity.
    private final CharArraySet previous = new CharArraySet(Version.LUCENE_31, 8, false);
  
    /**
     * Creates a new RemoveDuplicatesTokenFilter
     *
     * @param in TokenStream that will be filtered
     */
    public RemoveDuplicatesTokenFilter(TokenStream in) {
      super(in);
    }
  
    /**
     * {@inheritDoc}
     */
    @Override
    public boolean incrementToken() throws IOException {
      while (input.incrementToken()) {
        final char term[] = termAttribute.buffer();
        final int length = termAttribute.length();
        final int posIncrement = posIncAttribute.getPositionIncrement();
        
        if (posIncrement > 0) {
          previous.clear();
        }
        
        boolean duplicate = (posIncrement == 0 && previous.contains(term, 0, length));
        
        // clone the term, and add to the set of seen terms.
        char saved[] = new char[length];
        System.arraycopy(term, 0, saved, 0, length);
        previous.add(saved);
        
        if (!duplicate) {
          return true;
        }
      }
      return false;
    }
  
    /**
     * {@inheritDoc}
     */
    @Override
    public void reset() throws IOException {
      super.reset();
      previous.clear();
    }
  } 
  