/**
 * 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.tier;

import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Filter;
import org.apache.lucene.search.FieldComparator;
import org.apache.lucene.search.FieldComparatorSource;

/**
 * <p><font color="red"><b>NOTE:</b> This API is still in
 * flux and might change in incompatible ways in the next
 * release.</font>
 */
public class DistanceFieldComparatorSource extends FieldComparatorSource {

	private static final long serialVersionUID = 1L;

	private DistanceFilter distanceFilter;
	private DistanceScoreDocLookupComparator dsdlc;

	public DistanceFieldComparatorSource(Filter distanceFilter) {

		this.distanceFilter = (DistanceFilter) distanceFilter;

	}

	public void cleanUp() {
		distanceFilter = null;

		if (dsdlc != null)
			dsdlc.cleanUp();

		dsdlc = null;
	}

	@Override
	public FieldComparator newComparator(String fieldname, int numHits,
			int sortPos, boolean reversed) throws IOException {
		dsdlc = new DistanceScoreDocLookupComparator(numHits);
		return dsdlc;
	}

	private class DistanceScoreDocLookupComparator extends FieldComparator {

		private double[] values;
		private double bottom;
		private int offset =0;
		
		public DistanceScoreDocLookupComparator(int numHits) {
			values = new double[numHits];
			return;
		}

		@Override
		public int compare(int slot1, int slot2) {
			double a = values[slot1];
			double b = values[slot2];
			if (a > b)
				return 1;
			if (a < b)
				return -1;

			return 0;
		}

		public void cleanUp() {
			distanceFilter = null;
		}

		@Override
		public int compareBottom(int doc) {
			double v2 = distanceFilter.getDistance(doc+ offset);
			
			if (bottom > v2) {
				return 1;
			} else if (bottom < v2) {
				return -1;
			}
			return 0;
		}

		@Override
		public void copy(int slot, int doc) {
			values[slot] = distanceFilter.getDistance(doc + offset);
		}

		@Override
		public void setBottom(int slot) {
			this.bottom = values[slot];

		}

		@Override
                  public void setNextReader(IndexReader reader, int docBase)
                  throws IOException {
			
			// each reader in a segmented base
			// has an offset based on the maxDocs of previous readers
			offset = docBase;
		}

		@Override
		public Comparable<Double> value(int slot) {
			return values[slot];
		}
	}

}