using System;

namespace DTS.Common.Utilities
{
    /// <summary>
    /// Public utilty class for manipulating Unix timestamps
    /// Primarily exposed for the SDK
    /// </summary>
    public class PTP1588Timestamps
    {
        private const int MIN_VALID_TIMESTAMP_YEAR = 1990;
        /// <summary>
        /// tests time in seconds since 1,1,1970 to (unix time) to see whether the time should be valid or not
        /// this is used by TestMetaDataList to control whether to show unix time or not for a dataset in a viewer
        /// now it's also used by the CSV export to eliminate timestamps that occur before 1990
        /// this was done because of a dataset in http://manuscript.dts.local/f/cases/33199/
        /// which contained an invalid timestamp
        /// </summary>
        /// <param name="unixTimeStampSeconds">time in seconds since 1970-1-1</param>
        /// <returns>true if the value is valid or not</returns>
        public static bool IsValidTimeStamp(double unixTimeStampSeconds)
        {
            return UnixTimeStampToDateTimeLocal(unixTimeStampSeconds).Year > MIN_VALID_TIMESTAMP_YEAR;
        }
        /// <summary>
        /// Returns DateTime object from Unix timestamp in seconds
        /// </summary>
        /// <param name="unixTimeStampSec"></param>
        /// <returns></returns>
        public static DateTime UnixTimeStampToDateTimeLocal(double unixTimeStampSec)
        {
            return UnixTimeStampToDateTimeLocal((decimal)unixTimeStampSec);
        }
        public static DateTime UnixTimeStampToDateTimeLocal(decimal unixTimeStampSec)
        {
            return UnitTimeStampToDateTimeLocal(unixTimeStampSec, (decimal)0);
        }
        public static DateTime UnitTimeStampToDateTimeLocal(double unixTimeStampSec, double ns)
        {
            var dtDateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
            dtDateTime = dtDateTime.AddSeconds(unixTimeStampSec).AddTicks(Convert.ToInt64(ns / 100));
            return dtDateTime.ToLocalTime();
        }
        public static DateTime UnitTimeStampToDateTimeLocal(decimal unixTimeStampSec, decimal ns)
        {
            var dtDateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
            dtDateTime = dtDateTime.AddSeconds(Convert.ToDouble(unixTimeStampSec)).AddTicks(Convert.ToInt64(ns / 100));
            return dtDateTime.ToLocalTime();
        }
        /// <summary>
        /// String representation in Unix timestamp is seconds past epoch
        /// </summary>
        public static string ToDateTimeString(double unixTimeStampSec, double ns) =>
            ToDateTimeString((decimal)unixTimeStampSec, (decimal)ns);

        public static string ToDateTimeString(decimal unixTimeStampSec, decimal ns) =>
            $"{UnixTimeStampToDateTimeLocal(unixTimeStampSec).ToUniversalTime():yyyy/MM/dd HH:mm:ss}:{ns,9:000000000}";
    }
}