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.Iterator;
  import java.util.List;
  
  import com.kohlschutter.boilerpipe.BoilerpipeFilter;
  import com.kohlschutter.boilerpipe.BoilerpipeProcessingException;
  import com.kohlschutter.boilerpipe.document.TextBlock;
  import com.kohlschutter.boilerpipe.document.TextDocument;
  
  /**
   * Fuses adjacent blocks if their distance (in blocks) does not exceed a certain limit. This
   * probably makes sense only in cases where an upstream filter already has removed some blocks.
   */
  public final class BlockProximityFusion implements BoilerpipeFilter {
  
    private final int maxBlocksDistance;
  
    public static final BlockProximityFusion MAX_DISTANCE_1 = new BlockProximityFusion(1, false,
        false);
    public static final BlockProximityFusion MAX_DISTANCE_1_SAME_TAGLEVEL = new BlockProximityFusion(
        1, false, true);
    public static final BlockProximityFusion MAX_DISTANCE_1_CONTENT_ONLY = new BlockProximityFusion(
        1, true, false);
    public static final BlockProximityFusion MAX_DISTANCE_1_CONTENT_ONLY_SAME_TAGLEVEL =
        new BlockProximityFusion(1, true, true);
  
    private final boolean contentOnly;
  
    private final boolean sameTagLevelOnly;
  
    /**
     * Creates a new {@link BlockProximityFusion} instance.
     * 
     * @param maxBlocksDistance The maximum distance in blocks.
     * @param contentOnly
     */
    public BlockProximityFusion(final int maxBlocksDistance, final boolean contentOnly,
        final boolean sameTagLevelOnly) {
      this.maxBlocksDistance = maxBlocksDistance;
      this.contentOnly = contentOnly;
      this.sameTagLevelOnly = sameTagLevelOnly;
    }
  
    public boolean process(TextDocument doc) throws BoilerpipeProcessingException {
      List<TextBlock> textBlocks = doc.getTextBlocks();
      if (textBlocks.size() < 2) {
        return false;
      }
  
      boolean changes = false;
      TextBlock prevBlock;
  
      int offset;
      if (contentOnly) {
        prevBlock = null;
        offset = 0;
        for (TextBlock tb : textBlocks) {
          offset++;
          if (tb.isContent()) {
            prevBlock = tb;
            break;
          }
        }
        if (prevBlock == null) {
          return false;
        }
      } else {
        prevBlock = textBlocks.get(0);
        offset = 1;
      }
  
      for (Iterator<TextBlock> it = textBlocks.listIterator(offset); it.hasNext();) {
        TextBlock block = it.next();
        if (!block.isContent()) {
          prevBlock = block;
          continue;
        }
        int diffBlocks = block.getOffsetBlocksStart() - prevBlock.getOffsetBlocksEnd() - 1;
        if (diffBlocks <= maxBlocksDistance) {
          boolean ok = true;
          if (contentOnly) {
            if (!prevBlock.isContent() || !block.isContent()) {
              ok = false;
            }
          }
          if (ok && sameTagLevelOnly && prevBlock.getTagLevel() != block.getTagLevel()) {
            ok = false;
          }
          if (ok) {
            prevBlock.mergeNext(block);
            it.remove();
            changes = true;
          } else {
            prevBlock = block;
          }
        } else {
          prevBlock = block;
        }
      }
  
      return changes;
    }
  
  }
  