Github user dsmiley commented on a diff in the pull request: https://github.com/apache/lucene-solr/pull/302#discussion_r160768230 --- Diff: lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/tree/S2PrefixTree.java --- @@ -0,0 +1,111 @@ +/* + * 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 java.util.ArrayList; +import java.util.List; + +import com.google.common.geometry.S2CellId; +import com.google.common.geometry.S2LatLng; +import com.google.common.geometry.S2Projections; +import org.apache.lucene.util.BytesRef; +import org.locationtech.spatial4j.context.SpatialContext; +import org.locationtech.spatial4j.distance.DistanceUtils; +import org.locationtech.spatial4j.shape.Point; +import org.locationtech.spatial4j.shape.Shape; + +/** + * Spatial prefix tree for S2 Geometry. Shape factories for the given {@link SpatialContext} must + * implement the interface {@link S2ShapeFactory}. + * + * @lucene.experimental + */ +public class S2PrefixTree extends SpatialPrefixTree { + + /** + * Factory for creating {@link S2PrefixTree} instances with useful defaults + */ + public static class Factory extends SpatialPrefixTreeFactory { + + @Override + protected int getLevelForDistance(double degrees) { + S2PrefixTree grid = new S2PrefixTree(ctx, S2PrefixTree.MAX_LEVELS); + return grid.getLevelForDistance(degrees); + } + + @Override + protected SpatialPrefixTree newSPT() { + return new S2PrefixTree(ctx, + maxLevels != null ? maxLevels : S2PrefixTree.MAX_LEVELS); + } + } + + //factory to generate S2 cell shapes + protected final S2ShapeFactory s2ShapeFactory; + public static final int MAX_LEVELS = S2CellId.MAX_LEVEL + 1; + + public S2PrefixTree(SpatialContext ctx, int maxLevels) { + super(ctx, maxLevels); + if (!(ctx.getShapeFactory() instanceof S2ShapeFactory)) { + throw new IllegalArgumentException("Spatial context does not support S2 spatial index."); + } + this.s2ShapeFactory = (S2ShapeFactory) ctx.getShapeFactory(); + } + + @Override + public int getLevelForDistance(double dist) { + if (dist ==0){ + return maxLevels; + } + return Math.min(maxLevels, S2Projections.MAX_WIDTH.getClosestLevel(dist * DistanceUtils.DEGREES_TO_RADIANS) +1); + } + + @Override + public double getDistanceForLevel(int level) { + return S2Projections.MAX_WIDTH.getValue(level -1) * DistanceUtils.RADIANS_TO_DEGREES; + } + + @Override + public Cell getWorldCell() { + return new S2PrefixTreeCell(this, null); + } + + @Override + public Cell readCell(BytesRef term, Cell scratch) { + S2PrefixTreeCell cell = (S2PrefixTreeCell) scratch; + if (cell == null) + cell = (S2PrefixTreeCell) getWorldCell(); --- End diff -- nitpick: our code style in Lucene/Solr is to always use braces
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