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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.common.geo;

import org.elasticsearch.geometry.Rectangle;

/**
 * Utility functions to transforms WGS84 coordinates into spherical mercator.
 */
public class SphericalMercatorUtils {

    public static final double MERCATOR_BOUNDS = 20037508.34;
    private static final double MERCATOR_FACTOR = MERCATOR_BOUNDS / 180.0;
    // latitude lower limit. Below this limit the transformation might result in -Infinity
    private static final double LAT_LOWER_LIMIT = Math.nextUp(-90.0);

    /**
     * Transforms WGS84 longitude to a Spherical mercator longitude
     */
    public static double lonToSphericalMercator(double lon) {
        return lon * MERCATOR_FACTOR;
    }

    /**
     * Transforms WGS84 latitude to a Spherical mercator latitude
     */
    public static double latToSphericalMercator(double lat) {
        double y = Math.log(Math.tan((90 + Math.max(lat, LAT_LOWER_LIMIT)) * Math.PI / 360)) / (Math.PI / 180);
        return y * MERCATOR_FACTOR;
    }

    /**
     * Transforms WGS84 rectangle to a Spherical mercator rectangle
     */
    public static Rectangle recToSphericalMercator(Rectangle r) {
        return new Rectangle(
            lonToSphericalMercator(r.getMinLon()),
            lonToSphericalMercator(r.getMaxLon()),
            latToSphericalMercator(r.getMaxLat()),
            latToSphericalMercator(r.getMinLat())
        );

    }

    private SphericalMercatorUtils() {
        // no instances
    }
}