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 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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 * See the License for the specific language governing permissions and
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package org.apache.lucene.search;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.lucene.codecs.lucene60.Lucene60PointsFormat;
import org.apache.lucene.document.LatLonDocValuesField;
import org.apache.lucene.document.LatLonPoint;
import org.apache.lucene.geo.GeoUtils;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.PointValues;
import org.apache.lucene.util.Bits;
import org.apache.lucene.util.bkd.BKDReader;

Holder class for prototype sandboxed queries When the query graduates from sandbox, these static calls should be placed in LatLonPoint 
@lucene.experimental
/**
 * Holder class for prototype sandboxed queries
 *
 * When the query graduates from sandbox, these static calls should be
 * placed in {@link LatLonPoint}
 *
 * @lucene.experimental
 */
public class LatLonPointPrototypeQueries {

    // no instance
    private LatLonPointPrototypeQueries() {
    }

  
Finds the n nearest indexed points to the provided point, according to Haversine distance. 
 This is functionally equivalent to running MatchAllDocsQuery with a LatLonDocValuesField.newDistanceSort, but is far more efficient since it takes advantage of properties the indexed BKD tree. Currently this only works with Lucene60PointsFormat (used by the default codec). Multi-valued fields are currently not de-duplicated, so if a document had multiple instances of the specified field that make it into the top n, that document will appear more than once. 
 Documents are ordered by ascending distance from the location. The value returned in FieldDoc for the hits contains a Double instance with the distance in meters. 
Params:
searcher – IndexSearcher to find nearest points from.
field – field name. must not be null.
latitude – latitude at the center: must be within standard +/-90 coordinate bounds.
longitude – longitude at the center: must be within standard +/-180 coordinate bounds.
n – the number of nearest neighbors to retrieve.
Throws:
IllegalArgumentException – if the underlying PointValues is not a Lucene60PointsReader (this is a current limitation), or if field or searcher is null, or if latitude, longitude or n are out-of-bounds
IOException – if an IOException occurs while finding the points.
Returns:
TopFieldDocs containing documents ordered by distance, where the field value for each FieldDoc is the distance in meters/**
   * Finds the {@code n} nearest indexed points to the provided point, according to Haversine distance.
   * <p>
   * This is functionally equivalent to running {@link MatchAllDocsQuery} with a {@link LatLonDocValuesField#newDistanceSort},
   * but is far more efficient since it takes advantage of properties the indexed BKD tree.  Currently this
   * only works with {@link Lucene60PointsFormat} (used by the default codec).  Multi-valued fields are
   * currently not de-duplicated, so if a document had multiple instances of the specified field that
   * make it into the top n, that document will appear more than once.
   * <p>
   * Documents are ordered by ascending distance from the location. The value returned in {@link FieldDoc} for
   * the hits contains a Double instance with the distance in meters.
   *
   * @param searcher IndexSearcher to find nearest points from.
   * @param field field name. must not be null.
   * @param latitude latitude at the center: must be within standard +/-90 coordinate bounds.
   * @param longitude longitude at the center: must be within standard +/-180 coordinate bounds.
   * @param n the number of nearest neighbors to retrieve.
   * @return TopFieldDocs containing documents ordered by distance, where the field value for each {@link FieldDoc} is the distance in meters
   * @throws IllegalArgumentException if the underlying PointValues is not a {@code Lucene60PointsReader} (this is a current limitation), or
   *         if {@code field} or {@code searcher} is null, or if {@code latitude}, {@code longitude} or {@code n} are out-of-bounds
   * @throws IOException if an IOException occurs while finding the points.
   */
  // TODO: what about multi-valued documents? what happens?
  public static TopFieldDocs nearest(IndexSearcher searcher, String field, double latitude, double longitude, int n) throws IOException {
    GeoUtils.checkLatitude(latitude);
    GeoUtils.checkLongitude(longitude);
    if (n < 1) {
      throw new IllegalArgumentException("n must be at least 1; got " + n);
    }
    if (field == null) {
      throw new IllegalArgumentException("field must not be null");
    }
    if (searcher == null) {
      throw new IllegalArgumentException("searcher must not be null");
    }
    List<BKDReader> readers = new ArrayList<>();
    List<Integer> docBases = new ArrayList<>();
    List<Bits> liveDocs = new ArrayList<>();
    int totalHits = 0;
    for(LeafReaderContext leaf : searcher.getIndexReader().leaves()) {
      PointValues points = leaf.reader().getPointValues(field);
      if (points != null) {
        if (points instanceof BKDReader == false) {
          throw new IllegalArgumentException("can only run on Lucene60PointsReader points implementation, but got " + points);
        }
        totalHits += points.getDocCount();
        BKDReader reader = (BKDReader) points;
        if (reader != null) {
          readers.add(reader);
          docBases.add(leaf.docBase);
          liveDocs.add(leaf.reader().getLiveDocs());
        }
      }
    }

    NearestNeighbor.NearestHit[] hits = NearestNeighbor.nearest(latitude, longitude, readers, liveDocs, docBases, n);

    // Convert to TopFieldDocs:
    ScoreDoc[] scoreDocs = new ScoreDoc[hits.length];
    for(int i=0;i<hits.length;i++) {
      NearestNeighbor.NearestHit hit = hits[i];
      scoreDocs[i] = new FieldDoc(hit.docID, 0.0f, new Object[] {Double.valueOf(hit.distanceMeters)});
    }
    return new TopFieldDocs(new TotalHits(totalHits, TotalHits.Relation.EQUAL_TO), scoreDocs, null);
  }
}