lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/tree/FilterCellIterator.java

/*
 * 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.lucene.spatial.prefix.tree;

import org.locationtech.spatial4j.shape.Shape;
import org.locationtech.spatial4j.shape.SpatialRelation;

import java.util.Iterator;

/**
 * A filtering iterator of Cells. Those not matching the provided shape (disjoint) are
 * skipped. If {@code shapeFilter} is null then all cells are returned.
 *
 * @lucene.internal
 */
class FilterCellIterator extends CellIterator {
  final Iterator<Cell> baseIter;
  final Shape shapeFilter;

  FilterCellIterator(Iterator<Cell> baseIter, Shape shapeFilter) {
    this.baseIter = baseIter;
    this.shapeFilter = shapeFilter;
  }

  @Override
  public boolean hasNext() {
    thisCell = null;
    if (nextCell != null)//calling hasNext twice in a row
      return true;
    while (baseIter.hasNext()) {
      nextCell = baseIter.next();
      if (shapeFilter == null) {
        return true;
      } else {
        SpatialRelation rel = nextCell.getShape().relate(shapeFilter);
        if (rel.intersects()) {
          nextCell.setShapeRel(rel);
          if (rel == SpatialRelation.WITHIN)
            nextCell.setLeaf();
          return true;
        }
      }
    }
    return false;
  }

}