using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace UVC.Util
{
    public static class DateTimeUtil
    {
        //헝가리 서버에서 NQTT 시간이 UTC 시간으로 전송되서 Greenwich Standard Time 로 변경
        private static TimeZoneInfo hungaryInfo = TimeZoneInfo.FindSystemTimeZoneById("Central Europe Standard Time");
        private static TimeZoneInfo koreadInfo = TimeZoneInfo.FindSystemTimeZoneById("Korea Standard Time");//korea

        /// <summary>
        /// 헝가리 시간
        /// </summary>
        public static DateTime HungaryNow { get => TimeZoneInfo.ConvertTime(DateTime.Now, TimeZoneInfo.Local, hungaryInfo); }

        public static string HungaryNowString { get => FormatTime(HungaryNow); }

        public static DateTime UtcNow { get => DateTime.UtcNow; }
        public static string UtcNowString { get => FormatTime(UtcNow); }


        private static TimeSpan utcHungaryGap = TimeSpan.Zero;

        private static TimeSpan utcKoreaGap = TimeSpan.Zero;

        /// <summary>
        /// hungary - utc 시간 차이
        /// </summary>
        public static TimeSpan UtcHungaryGap { get => (utcHungaryGap == TimeSpan.Zero) ? ToHungaryDateTime(DateTime.UtcNow) - DateTime.UtcNow : utcHungaryGap; }

        /// <summary>
        /// korea - utc 시간 차이
        /// </summary>
        public static TimeSpan UtcKoreaGap { get => (utcKoreaGap == TimeSpan.Zero) ? ToKoreaDateTime(DateTime.UtcNow) - DateTime.UtcNow : utcKoreaGap; }

        /// <summary>
        /// UTC string을 UTC DateTime으로 변환. yyyy-MM-ddTHH:mm:ss.fffZ 포맷이라 제대로 변환 됨
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public static DateTime UtcParse(string s) { return DateTime.Parse(s).ToUniversalTime(); }

        /// <summary>
        /// string을 DateTime으로 변환
        /// </summary>
        /// <param name="s"></param>
        /// <param name="format"></param>
        /// <returns></returns>
        public static DateTime Parse(string s, string format) { return DateTime.ParseExact(s, format, CultureInfo.InvariantCulture); }


        /// <summary>
        /// UTC DateTime을 헝가리 DateTime으로 변환
        /// </summary>
        /// <param name="utcDateTime"></param>
        /// <returns></returns>
        public static DateTime ToHungaryDateTime(DateTime utcDateTime)
        {
            return TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, hungaryInfo);
        }

        /// <summary>
        /// UTC string을 헝가리 DateTime으로 변환
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public static DateTime UtcStringToHungaryDateTime(string s)
        {
            return ToHungaryDateTime(UtcParse(s));
        }

        /// <summary>
        /// UTC string을 헝가리 Time String으로 변환
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public static string UtcStringToHungaryTimeString(string s)
        {
            return FormatTime(UtcStringToHungaryDateTime(s));
        }


        /// <summary>
        /// UTC DateTime을 한국 DateTime으로 변환
        /// </summary>
        /// <param name="utcDateTime"></param>
        /// <returns></returns>
        public static DateTime ToKoreaDateTime(DateTime utcDateTime)
        {
            return TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, koreadInfo);
        }

        /// <summary>
        /// UTC string을 한국 DateTime으로 변환
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public static DateTime UtcStringToKoreaDateTime(string s)
        {
            return ToKoreaDateTime(UtcParse(s));
        }


        /// <summary>
        /// UTC string을 한국 Time String으로 변환
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public static string UtcStringToKoreaTimeString(string s)
        {
            return FormatTime(UtcStringToKoreaDateTime(s));
        }

        public static string FormatTime(DateTime dateTime)
        {
            return dateTime.ToString("yyyy-MM-ddTHH:mm:ss.fffZ");
        }
    }
}