using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;

namespace HZQR.Common
{
    public class Pub
    {
        #region 方法 -> 获取get,post传参的值
        /// <summary>
        /// 获取get,post传参的值
        /// </summary>
        /// <param name="key">参数名</param>
        /// <param name="defaultValue">参数为空时的默认值</param>
        /// <returns></returns>
        public static string Request(string key, string defaultValue = null)
        {

            var v = HttpContext.Current.Request.Form[key];

            if (v == null)
            {
                v = HttpContext.Current.Request.QueryString[key];
            }

            return v ?? (defaultValue ?? string.Empty);
        }
        #endregion

        #region 方法 -> 获取上个月第一天和最后一天
        //获取上个月第一天
        public static DateTime FirstDayOfPreviousMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day).AddMonths(-1);
        }

        //获取上个月的最后一天
        public static DateTime LastDayOfPrdviousMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day).AddDays(-1);
        }
        #endregion

        #region 方法 -> 计算距离
        /// <summary>
        /// 计算两点位置的距离，返回两点的距离，单位：公里或千米
        /// 该公式为GOOGLE提供，误差小于0.2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>返回两点的距离，单位：公里或千米</returns>
        public static double GetDistance(double lat1, double lng1, double lat2, double lng2)
        {
            //地球半径，单位米
            double EARTH_RADIUS = 6378137;
            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 / 1000;
        }

        /// <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;
        }
        #endregion
    }
}