code: /**
   * boilerpipe
   *
   * Copyright (c) 2009, 2014 Christian Kohlschütter
   *
   * The author 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 com.kohlschutter.boilerpipe.extractors;
  
  import java.util.List;
  import java.util.ListIterator;
  
  import com.kohlschutter.boilerpipe.BoilerpipeFilter;
  import com.kohlschutter.boilerpipe.BoilerpipeProcessingException;
  import com.kohlschutter.boilerpipe.document.TextBlock;
  import com.kohlschutter.boilerpipe.document.TextDocument;
  import com.kohlschutter.boilerpipe.estimators.SimpleEstimator;
  
  /**
   * A full-text extractor trained on <a href="http://krdwrd.org/">krdwrd</a> <a href
   * ="https://krdwrd.org/trac/attachment/wiki/Corpora/Canola/CANOLA.pdf">Canola </a>. Works well with
   * {@link SimpleEstimator}, too.
   */
  public class CanolaExtractor extends ExtractorBase {
    public static final CanolaExtractor INSTANCE = new CanolaExtractor();
  
    /**
     * Returns the singleton instance for {@link CanolaExtractor}.
     */
    public static CanolaExtractor getInstance() {
      return INSTANCE;
    }
  
    public boolean process(TextDocument doc) throws BoilerpipeProcessingException {
  
      return CLASSIFIER.process(doc);
    }
  
    /**
     * The actual classifier, exposed.
     */
    public static final BoilerpipeFilter CLASSIFIER = new BoilerpipeFilter() {
  
      public boolean process(TextDocument doc) throws BoilerpipeProcessingException {
        List<TextBlock> textBlocks = doc.getTextBlocks();
        boolean hasChanges = false;
  
        ListIterator<TextBlock> it = textBlocks.listIterator();
        if (!it.hasNext()) {
          return false;
        }
        TextBlock prevBlock = TextBlock.EMPTY_START;
        TextBlock currentBlock = it.next();
        TextBlock nextBlock = it.hasNext() ? it.next() : TextBlock.EMPTY_START;
  
        hasChanges = classify(prevBlock, currentBlock, nextBlock) | hasChanges;
  
        if (nextBlock != TextBlock.EMPTY_START) {
          while (it.hasNext()) {
            prevBlock = currentBlock;
            currentBlock = nextBlock;
            nextBlock = it.next();
            hasChanges = classify(prevBlock, currentBlock, nextBlock) | hasChanges;
          }
          prevBlock = currentBlock;
          currentBlock = nextBlock;
          nextBlock = TextBlock.EMPTY_START;
          hasChanges = classify(prevBlock, currentBlock, nextBlock) | hasChanges;
        }
  
        return hasChanges;
      }
  
      protected boolean classify(final TextBlock prev, final TextBlock curr, final TextBlock next) {
        final boolean isContent =
            (curr.getLinkDensity() > 0 && next.getNumWords() > 11)
                || (curr.getNumWords() > 19 || (next.getNumWords() > 6 && next.getLinkDensity() == 0
                    && prev.getLinkDensity() == 0 && (curr.getNumWords() > 6
                    || prev.getNumWords() > 7 || next.getNumWords() > 19)));
  
        return curr.setIsContent(isContent);
      }
    };
  }
  