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/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.search.aggregations.metrics;

import org.apache.lucene.geo.GeoEncodingUtils;
import org.elasticsearch.Version;
import org.elasticsearch.common.geo.GeoPoint;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.search.aggregations.AggregationReduceContext;
import org.elasticsearch.search.aggregations.InternalAggregation;
import org.elasticsearch.xcontent.ParseField;
import org.elasticsearch.xcontent.XContentBuilder;

import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/**
 * Serialization and merge logic for {@link GeoCentroidAggregator}.
 */
public class InternalGeoCentroid extends InternalAggregation implements GeoCentroid {
    private final GeoPoint centroid;
    private final long count;

    public static long encodeLatLon(double lat, double lon) {
        return (Integer.toUnsignedLong(GeoEncodingUtils.encodeLatitude(lat)) << 32) | Integer.toUnsignedLong(
            GeoEncodingUtils.encodeLongitude(lon)
        );
    }

    public static double decodeLatitude(long encodedLatLon) {
        return GeoEncodingUtils.decodeLatitude((int) (encodedLatLon >>> 32));
    }

    public static double decodeLongitude(long encodedLatLon) {
        return GeoEncodingUtils.decodeLongitude((int) (encodedLatLon & 0xFFFFFFFFL));
    }

    public InternalGeoCentroid(String name, GeoPoint centroid, long count, Map metadata) {
        super(name, metadata);
        assert (centroid == null) == (count == 0);
        this.centroid = centroid;
        assert count >= 0;
        this.count = count;
    }

    /**
     * Read from a stream.
     */
    public InternalGeoCentroid(StreamInput in) throws IOException {
        super(in);
        count = in.readVLong();
        if (in.readBoolean()) {
            if (in.getVersion().onOrAfter(Version.V_7_2_0)) {
                centroid = new GeoPoint(in.readDouble(), in.readDouble());
            } else {
                final long hash = in.readLong();
                centroid = new GeoPoint(decodeLatitude(hash), decodeLongitude(hash));
            }

        } else {
            centroid = null;
        }
    }

    @Override
    protected void doWriteTo(StreamOutput out) throws IOException {
        out.writeVLong(count);
        if (centroid != null) {
            out.writeBoolean(true);
            if (out.getVersion().onOrAfter(Version.V_7_2_0)) {
                out.writeDouble(centroid.lat());
                out.writeDouble(centroid.lon());
            } else {
                out.writeLong(encodeLatLon(centroid.lat(), centroid.lon()));
            }
        } else {
            out.writeBoolean(false);
        }
    }

    @Override
    public String getWriteableName() {
        return GeoCentroidAggregationBuilder.NAME;
    }

    @Override
    public GeoPoint centroid() {
        return centroid;
    }

    @Override
    public long count() {
        return count;
    }

    @Override
    public InternalGeoCentroid reduce(List aggregations, AggregationReduceContext reduceContext) {
        double lonSum = Double.NaN;
        double latSum = Double.NaN;
        long totalCount = 0;
        for (InternalAggregation aggregation : aggregations) {
            InternalGeoCentroid centroidAgg = (InternalGeoCentroid) aggregation;
            if (centroidAgg.count > 0) {
                totalCount += centroidAgg.count;
                if (Double.isNaN(lonSum)) {
                    lonSum = centroidAgg.count * centroidAgg.centroid.getLon();
                    latSum = centroidAgg.count * centroidAgg.centroid.getLat();
                } else {
                    lonSum += (centroidAgg.count * centroidAgg.centroid.getLon());
                    latSum += (centroidAgg.count * centroidAgg.centroid.getLat());
                }
            }
        }
        final GeoPoint result = (Double.isNaN(lonSum)) ? null : new GeoPoint(latSum / totalCount, lonSum / totalCount);
        return new InternalGeoCentroid(name, result, totalCount, getMetadata());
    }

    @Override
    protected boolean mustReduceOnSingleInternalAgg() {
        return false;
    }

    @Override
    public Object getProperty(List path) {
        if (path.isEmpty()) {
            return this;
        } else if (path.size() == 1) {
            String coordinate = path.get(0);
            return switch (coordinate) {
                case "value" -> centroid;
                case "lat" -> centroid.lat();
                case "lon" -> centroid.lon();
                case "count" -> count;
                default -> throw new IllegalArgumentException("Found unknown path element [" + coordinate + "] in [" + getName() + "]");
            };
        } else {
            throw new IllegalArgumentException("path not supported for [" + getName() + "]: " + path);
        }
    }

    static class Fields {
        static final ParseField CENTROID = new ParseField("location");
        static final ParseField COUNT = new ParseField("count");
        static final ParseField CENTROID_LAT = new ParseField("lat");
        static final ParseField CENTROID_LON = new ParseField("lon");
    }

    @Override
    public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
        if (centroid != null) {
            builder.startObject(Fields.CENTROID.getPreferredName());
            {
                builder.field(Fields.CENTROID_LAT.getPreferredName(), centroid.lat());
                builder.field(Fields.CENTROID_LON.getPreferredName(), centroid.lon());
            }
            builder.endObject();
        }
        builder.field(Fields.COUNT.getPreferredName(), count);
        return builder;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        if (super.equals(obj) == false) return false;
        InternalGeoCentroid that = (InternalGeoCentroid) obj;
        return count == that.count && Objects.equals(centroid, that.centroid);
    }

    @Override
    public int hashCode() {
        return Objects.hash(super.hashCode(), centroid, count);
    }

    @Override
    public String toString() {
        return "InternalGeoCentroid{" + "centroid=" + centroid + ", count=" + count + '}';
    }
}