using System;

namespace Edu.Common.Plugin
{
    /// <summary>
    /// 地图帮助类
    /// </summary>
    public class MapHelper
    {
        //地球半径，单位米
        private const double EARTH_RADIUS = 6378137;
        /// <summary>
        /// 计算两点位置的距离，返回两点的距离，单位 米
        /// </summary>
        /// <param name="lat1">第一点纬度</param>
        /// <param name="lng1">第一点经度</param>
        /// <param name="lat2">第二点纬度</param>
        /// <param name="lng2">第二点经度</param>
        /// <returns></returns>
        public static double GetDistance(double lat1, double lng1, double lat2, double lng2)
        {
            double radLat1 = Rad(lat1);
            double radLng1 = Rad(lng1);
            double radLat2 = Rad(lat2);
            double radLng2 = Rad(lng2);
            double a = radLat1 - radLat2;
            double b = radLng1 - radLng2;
            double result = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) + Math.Cos(radLat1) * Math.Cos(radLat2) * Math.Pow(Math.Sin(b / 2), 2))) * EARTH_RADIUS;
            return result;
        }

        /// <summary>  
        /// 计算两个坐标点之间的距离  
        /// 计算两点位置的距离，返回两点的距离，单位 米
        /// </summary>
        /// <param name="firstPoint">第一个坐标点的（纬度,经度）</param>  
        /// <param name="secondPoint">第二个坐标点的（纬度,经度）</param>  
        /// <returns>返回两点之间的距离，单位：公里/千米</returns>  
        public static double GetPointDistance(string firstPoint, string secondPoint)
        {
            var firstArray = firstPoint.Split(',');
            var secondArray = secondPoint.Split(',');
            var firstLatitude = Convert.ToDouble(firstArray[0].Trim());
            var firstLongitude = Convert.ToDouble(firstArray[1].Trim());
            var secondLatitude = Convert.ToDouble(secondArray[0].Trim());
            var secondLongitude = Convert.ToDouble(secondArray[1].Trim());
            return GetDistance(firstLatitude, firstLongitude, secondLatitude, secondLongitude);
        }

        /// <summary>
        /// 经纬度转化成弧度
        /// </summary>
        /// <param name="d"></param>
        /// <returns></returns>
        private static double Rad(double d)
        {
            return (double)d * Math.PI / 180d;
        }
    }
}
