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.List;
  import java.util.ListIterator;
  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;
  
  /**
   * Adds the labels of the preceding block to the current block, optionally adding a prefix.
   */
  public final class AddPrecedingLabelsFilter implements BoilerpipeFilter {
  
    public static final AddPrecedingLabelsFilter INSTANCE = new AddPrecedingLabelsFilter("");
    public static final AddPrecedingLabelsFilter INSTANCE_PRE = new AddPrecedingLabelsFilter("^");
  
    private final String labelPrefix;
  
    /**
     * Creates a new {@link AddPrecedingLabelsFilter} instance.
     * 
     * @param maxBlocksDistance The maximum distance in blocks.
     * @param contentOnly
     */
    public AddPrecedingLabelsFilter(final String labelPrefix) {
      this.labelPrefix = labelPrefix;
    }
  
    public boolean process(TextDocument doc) throws BoilerpipeProcessingException {
      List<TextBlock> textBlocks = doc.getTextBlocks();
      if (textBlocks.size() < 2) {
        return false;
      }
  
      boolean changes = false;
      int remaining = textBlocks.size();
  
      TextBlock blockBelow = null;
      TextBlock block;
      for (ListIterator<TextBlock> it = textBlocks.listIterator(textBlocks.size()); it.hasPrevious();) {
        if (--remaining <= 0) {
          break;
        }
        if (blockBelow == null) {
          blockBelow = it.previous();
          continue;
        }
        block = it.previous();
  
        Set<String> labels = block.getLabels();
        if (labels != null && !labels.isEmpty()) {
          for (String l : labels) {
            blockBelow.addLabel(labelPrefix + l);
          }
          changes = true;
        }
        blockBelow = block;
      }
  
      return changes;
    }
  }
  