using System;
using System.Collections.Generic;
using System.Text;

namespace TEAMModelOS.SDK
{
    public static class DateTimeHelper
    {

        public static DateTime FromUnixTimestamp(this long unixtime)
        {
            DateTime sTime = TimeZoneInfo.ConvertTime(new DateTime(1970, 1, 1), TimeZoneInfo.Utc, TimeZoneInfo.Local);
            return sTime.AddMilliseconds(unixtime);
        }

         
        public static long ToUnixTimestamp(this DateTime datetime)
        {
            //DateTime sTime = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
            DateTime sTime = TimeZoneInfo.ConvertTime(new DateTime(1970, 1, 1), TimeZoneInfo.Local, TimeZoneInfo.Local);
            return (long)(datetime - sTime).TotalMilliseconds;
        }
       
        /// <summary>
        /// 获得 GMT+8 时间
        /// </summary>
        /// <returns></returns>
        public static DateTime GetGMTTime(this DateTime dateTime, int GMT = 8)
        {
            //SystemTimeZoneById  :  https://learn.microsoft.com/zh-cn/previous-versions/windows/embedded/ms912391(v=winembedded.11)
            //TimeZoneInfo easternZone = TimeZoneInfo.FindSystemTimeZoneById("China Standard Time");//设置时区
            //DateTime easternTime = TimeZoneInfo.ConvertTimeFromUtc(dateTime, easternZone);
            //return easternTime;


            //处理UTC时差
            TimeZoneInfo localTimezone = TimeZoneInfo.Local;
            var Hours = localTimezone.BaseUtcOffset.Hours;
            dateTime = dateTime.AddHours(GMT-Hours);
            return dateTime;
        }
        /// <summary>
        /// 默认东八区+8
        /// </summary>
        /// <param name="dateTime"></param>
        /// <param name="GMT"></param>
        /// <returns></returns>
        public static DateTimeOffset GetGMTTime(this DateTimeOffset dateTime,int GMT=+8)
        {
            //处理UTC时差
            TimeZoneInfo localTimezone = TimeZoneInfo.Local;
            var Hours = localTimezone.BaseUtcOffset.Hours;
            dateTime = dateTime.AddHours(GMT-Hours);
            return dateTime;
        }
        public static DateTimeOffset GetUTCTime(this DateTimeOffset dateTime, int GMT)
        {
            //处理UTC时差
            TimeZoneInfo localTimezone = TimeZoneInfo.Local;
            var Hours = localTimezone.BaseUtcOffset.Hours;
            dateTime = dateTime.AddHours(Hours - GMT);
            return dateTime;
        }

        public static  int getDays(int year) { 
            int day = 0;
            for (int i = 0;i<=12;i++) {
                int days = 0;
                if (i != 2)
                {
                    switch (i)
                    {
                        case 1:
                        case 3:
                        case 5:
                        case 7:
                        case 8:
                        case 10:
                        case 12:
                            days = 31;
                            break;
                        case 4:
                        case 6:
                        case 9:
                        case 11:
                            days = 30;
                            break;
                    }
                }
                else {
                    if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
                    {
                        days = 29;
                    }
                    else { 
                        days = 28;
                    }
                }
                day += days; 
            }
            return day;
        }

        #region 获取 本周、本月、本季度、本年 的开始时间或结束时间
        /// <summary>
        /// 获取开始时间
        /// </summary>
        /// <param name="TimeType">Week、Month、Season、Year</param>
        /// <param name="now"></param>
        /// <returns></returns>
        public static DateTime? GetTimeStartByType(string TimeType, DateTime now)
        {
            
            switch (TimeType)
            {
                case "Week":
                    return now.AddDays(-(int)now.DayOfWeek + 1);
                case "Month":
                    return now.AddDays(-now.Day + 1);
                case "Season":
                    var time = now.AddMonths(0 - ((now.Month - 1) % 3));
                    return time.AddDays(-time.Day + 1);
                case "Year":
                    return now.AddDays(-now.DayOfYear + 1);
                default:
                    return null;
            }
        }

        /// <summary>
        /// 获取结束时间
        /// </summary>
        /// <param name="TimeType">Week、Month、Season、Year</param>
        /// <param name="now"></param>
        /// <returns></returns>
        public static DateTime? GetTimeEndByType(string TimeType, DateTime now)
        {
            switch (TimeType)
            {
                case "Week":
                    return now.AddDays(7 - (int)now.DayOfWeek);
                case "Month":
                    return now.AddMonths(1).AddDays(-now.AddMonths(1).Day + 1).AddDays(-1);
                case "Season":
                    var time = now.AddMonths((3 - ((now.Month - 1) % 3) - 1));
                    return time.AddMonths(1).AddDays(-time.AddMonths(1).Day + 1).AddDays(-1);
                case "Year":
                    var time2 = now.AddYears(1);
                    return time2.AddDays(-time2.DayOfYear);
                default:
                    return null;
            }
        }
        #endregion


    }
}