package cn.qinys.platform.mobile.util;

/**
 * WGS-84 ↔ GCJ-02 坐标转换工具
 */
public class CoordUtil {

    private static final double PI = 3.14159265358979324;
    private static final double A = 6378245.0;
    private static final double EE = 0.00669342162296594323;

    private static boolean outOfChina(double lng, double lat) {
        return lng < 72.004 || lng > 137.8347 || lat < 0.8293 || lat > 55.8271;
    }

    private static double transformLat(double x, double y) {
        double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
        ret += ((20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0) / 3.0;
        ret += ((20.0 * Math.sin(y * PI) + 40.0 * Math.sin((y / 3.0) * PI)) * 2.0) / 3.0;
        ret += ((160.0 * Math.sin((y / 12.0) * PI) + 320.0 * Math.sin((y * PI) / 30.0)) * 2.0) / 3.0;
        return ret;
    }

    private static double transformLng(double x, double y) {
        double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
        ret += ((20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0) / 3.0;
        ret += ((20.0 * Math.sin(x * PI) + 40.0 * Math.sin((x / 3.0) * PI)) * 2.0) / 3.0;
        ret += ((150.0 * Math.sin((x / 12.0) * PI) + 300.0 * Math.sin((x / 30.0) * PI)) * 2.0) / 3.0;
        return ret;
    }

    /** WGS-84 → GCJ-02 */
    public static double[] wgs84ToGcj02(double lng, double lat) {
        if (outOfChina(lng, lat)) return new double[]{lng, lat};

        double dLat = transformLat(lng - 105.0, lat - 35.0);
        double dLng = transformLng(lng - 105.0, lat - 35.0);
        double radLat = (lat / 180.0) * PI;
        double magic = Math.sin(radLat);
        magic = 1 - EE * magic * magic;
        double sqrtMagic = Math.sqrt(magic);

        double gcjLat = lat + (dLat * 180.0) / (((A * (1 - EE)) / (magic * sqrtMagic)) * PI);
        double gcjLng = lng + (dLng * 180.0) / ((A / sqrtMagic) * Math.cos(radLat) * PI);
        return new double[]{gcjLng, gcjLat};
    }
}
