package org.springblade.common.utils;

import java.awt.geom.Point2D;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;

/**
 * 根据经纬度计算面积工具类
 *
 * @author hwl
 * @version 1.0.0 2018-01-17
 */
public class PolyginArea {

	// 地球半径 - 米
	// 源码中使用半径为 6367460.0;
	private static double earthRadiusMeters = 6371000.0;
	private static double metersPerDegree = 2.0 * Math.PI * earthRadiusMeters / 360.0;
	private static double radiansPerDegree = Math.PI / 180.0;
	private static double degreesPerRadian = 180.0 / Math.PI;

//	/**
//	 * 传入经纬度集合计算面积
//	 * @param points
//	 */
//	private void calculateArea(List<double[]> points) {
//		if (points.size() > 2) {
//			double areaMeters2 = PlanarPolygonAreaMeters2(points);
//			// if (areaMeters2 > 1000000.0) {
//			areaMeters2 = SphericalPolygonAreaMeters2(points);
//			System.out.println("面积为：" + areaMeters2 + "（平方米）");
//			// }
//
//		}
//	}

	/**
	 * 球面多边形面积计算
	 *
	 * @param points
	 * @return
	 */
	private double SphericalPolygonAreaMeters2(List<double[]> points) {
		double totalAngle = 0.0;
		for (int i = 0; i < points.size(); i++) {
			int j = (i + 1) % points.size();
			int k = (i + 2) % points.size();
			totalAngle += Angle(points.get(i), points.get(j), points.get(k));
		}

		double planarTotalAngle = (points.size() - 2) * 180.0;
		double sphericalExcess = totalAngle - planarTotalAngle;

		if (sphericalExcess > 420.0) {
			totalAngle = points.size() * 360.0 - totalAngle;
			sphericalExcess = totalAngle - planarTotalAngle;
		} else if (sphericalExcess > 300.0 && sphericalExcess < 420.0) {
			sphericalExcess = Math.abs(360.0 - sphericalExcess);
		}

		return sphericalExcess * radiansPerDegree * earthRadiusMeters
				* earthRadiusMeters;
	}

	/**
	 * 角度
	 *
	 * @param p1
	 * @param p2
	 * @param p3
	 * @return
	 */
	private double Angle(double[] p1, double[] p2, double[] p3) {
		double bearing21 = Bearing(p2, p1);
		double bearing23 = Bearing(p2, p3);
		double angle = bearing21 - bearing23;
		if (angle < 0.0) {
			angle += 360.0;
		}
		return angle;
	}

	/**
	 * 方向
	 *
	 * @param from
	 * @param to
	 * @return
	 */
	private double Bearing(double[] from, double[] to) {
		double lat1 = from[1] * radiansPerDegree;
		double lon1 = from[0] * radiansPerDegree;
		double lat2 = to[1] * radiansPerDegree;
		double lon2 = to[0] * radiansPerDegree;
		double angle = -Math.atan2(
				Math.sin(lon1 - lon2) * Math.cos(lat2),
				Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1)
						* Math.cos(lat2) * Math.cos(lon1 - lon2));
		if (angle < 0.0) {
			angle += Math.PI * 2.0;
		}
		angle = angle * degreesPerRadian;
		return angle;
	}

	/***
	 * 平面多边形面积
	 *
	 * @param points
	 *            Point2D.Double
	 * @return
	 * */
	public static double getAreaByxy(List<Point2D.Double> points) {
		double a = 0.0;
		if(points.size() > 2){
			for (int i = 0; i < points.size(); ++i) {
				int j = (i + 1) % points.size();
				double xi = points.get(i).x * metersPerDegree
						* Math.cos(points.get(i).y * radiansPerDegree);
				double yi = points.get(i).y * metersPerDegree;
				double xj = points.get(j).x * metersPerDegree
						* Math.cos(points.get(j).y * radiansPerDegree);
				double yj = points.get(j).y * metersPerDegree;
				a += xi * yj - xj * yi;
			}
		}
		a = BigDecimal.valueOf(Math.abs(a / 2.0)).setScale(1,BigDecimal.ROUND_DOWN).doubleValue();
		return a;
	}

	public static void main(String[] args) {
		List<Point2D.Double> points = new ArrayList<Point2D.Double>();

		/**
		 * x1 = 84.86258; y1 = 44.46333;
		 *
		 * x2 = 84.86075; y2 = 44.45999;
		 *
		 * x3 = 84.86229; y3 = 44.45971;
		 *
		 * x4 = 84.86414; y4 = 44.46309;
		 */
		// String s = "112.5293197631836,37.868892669677734;" +
		// "112.5170669555664,37.8605842590332;" +
		// "112.52099609375,37.849857330322266;" +
		// "112.54137420654297,37.85125732421875;" +
		// "112.53511810302734,37.858699798583984";
		String s = "114.917883,25.816108;114.917207,25.815577;114.918162,25.815519;114.917883,25.816108";
		String[] s1 = s.split(";");
		for (String ss : s1) {
			String[] temp = ss.split(",");
			Point2D.Double point = new Point2D.Double(Double.parseDouble(temp[0]),
					Double.parseDouble(temp[1]));
			points.add(point);
			System.out.println(temp[1] + "," + temp[0]);
		}
		PolyginArea tp = new PolyginArea();
		double area = tp.getAreaByxy(points);
		System.out.println("面积是: " + area);
	}

}