distancefilter.java

Local Lucene ==================== Provide geographical based searching to lucene in an efficent ma

/**
 * Copyright 2007 Patrick O'Leary 
 * Licensed 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.pjaol.search.geo.utils;

import java.io.IOException;
import java.util.BitSet;
import java.util.HashMap;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.IndexReader;

import com.pjaol.lucene.search.ISerialChainFilter;


public class DistanceFilter extends ISerialChainFilter {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	
	private double distance;
	private double lat;
	private double lng;
	
	private HashMap<Integer, Double> distances = new HashMap<Integer, Double>();
	
	/**
	 * Provide a distance filter based from a center point with a radius
	 * in miles
	 * @param lat
	 * @param lng
	 * @param miles
	 */
	public DistanceFilter(double lat, double lng, double miles){
		distance = miles;
		this.lat = lat;
		this.lng = lng;
		
	}
	
	public HashMap<Integer, Double> getDistances(){
		return distances;
	}
	
	
	@Override
	public BitSet bits(IndexReader reader) throws IOException {
		
		int maxdocs = reader.numDocs();
		BitSet bits = new BitSet(maxdocs);
		
		for (int i = 0 ; i < maxdocs; i++) {
			
			Document doc = reader.document(i);
			
			double x = DistanceUtils.stringToLat(doc.get("lat"));
			double y = DistanceUtils.stringToLng(doc.get("lng"));
			
			double d = DistanceUtils.getDistanceMi(lat, lng, x, y);
			distances.put(i, d);
			
			if (d < distance){
				bits.set(i);
			}
			
		}
		
		return bits;
	}

	
	@Override
	public BitSet bits(IndexReader reader, BitSet bits) throws CorruptIndexException, IOException {
		
		int size = bits.cardinality();
		BitSet result = new BitSet(size);
		int i = 0;
		
		while (i >= 0){
			i = bits.nextSetBit(i);
			if (i < 0)
				return result;
			Document doc = reader.document(i);
			
			double x = DistanceUtils.stringToLat(doc.get("lat"));
			double y = DistanceUtils.stringToLng(doc.get("lng"));
			
			double d = DistanceUtils.getDistanceMi(lat, lng, x, y);
			distances.put(i, d);	
			if (d < distance){
				result.set(i);
			}
			i = bits.nextSetBit(i+1);
		}
		return result;
	}

}