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.filters.heuristics;
  
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Set;
  
  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.labels.DefaultLabels;
  
  /**
   * Fuses adjacent blocks if their labels are equal.
   */
  public final class LabelFusion implements BoilerpipeFilter {
  
    public static final LabelFusion INSTANCE = new LabelFusion();
  
    /**
     * Creates a new {@link LabelFusion} instance.
     */
    private LabelFusion() {
    }
  
    public boolean process(TextDocument doc) throws BoilerpipeProcessingException {
      List<TextBlock> textBlocks = doc.getTextBlocks();
      if (textBlocks.size() < 2) {
        return false;
      }
  
      boolean changes = false;
      TextBlock prevBlock = textBlocks.get(0);
      int offset = 1;
  
      for (Iterator<TextBlock> it = textBlocks.listIterator(offset); it.hasNext();) {
        TextBlock block = it.next();
  
        if (equalLabels(prevBlock.getLabels(), block.getLabels())) {
          prevBlock.mergeNext(block);
          it.remove();
          changes = true;
        } else {
          prevBlock = block;
        }
      }
  
      return changes;
    }
  
    private boolean equalLabels(Set<String> labels, Set<String> labels2) {
      if (labels == null || labels2 == null) {
        return false;
      }
      return markupLabelsOnly(labels).equals(markupLabelsOnly(labels2));
    }
  
    private Set<String> markupLabelsOnly(final Set<String> set1) {
      Set<String> set = new HashSet<String>(set1);
      for (Iterator<String> it = set.iterator(); it.hasNext();) {
        final String label = it.next();
        if (!label.startsWith(DefaultLabels.MARKUP_PREFIX)) {
          it.remove();
        }
      }
      return set;
    }
  
  }
  