using System;

using NodaTime;

using NodaTime.TimeZones;

using System.Linq;

using System.Net;

using RestSharp;

using Newtonsoft.Json;

using System.Xml;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

​

    public static List<string> GetOlsonTimeZoneList()

    {

        return new List<string>(TzdbDateTimeZoneSource.Default.ZoneLocations.Select(item => item.ZoneId).OrderBy(item => item));

    }

​

    public static DateTime UTCtoLocal(DateTime dateTime, string timeZoneId)

    {

        var instant = Instant.FromDateTimeUtc(dateTime);

        var timeZoneProvider = DateTimeZoneProviders.Tzdb;

        var usersTimezoneId = timeZoneId;

        var usersTimezone = timeZoneProvider[usersTimezoneId];

        var usersZonedDateTime = instant.InZone(usersTimezone);

        return usersZonedDateTime.ToDateTimeUnspecified();

    }

​

    public static string IanaToWindows(string ianaZoneId)

    {

        var utcZones = new[]

        {

        "Etc/UTC", "Etc/UCT", "Etc/GMT"

        }

​

        ;

        if (utcZones.Contains(ianaZoneId, StringComparer.Ordinal))

            return "UTC";

        var tzdbSource = TzdbDateTimeZoneSource.Default;

        var links = tzdbSource.CanonicalIdMap.Where(x => x.Value.Equals(ianaZoneId, StringComparison.Ordinal)).Select(x => x.Key);

        var possibleZones = tzdbSource.CanonicalIdMap.ContainsKey(ianaZoneId) ? links.Concat(new[]

        {

        tzdbSource.CanonicalIdMap[ianaZoneId], ianaZoneId

        }

​

        ) : links;

        var mappings = tzdbSource.WindowsMapping.MapZones;

        var item = mappings.FirstOrDefault(x => x.TzdbIds.Any(possibleZones.Contains));

        if (item == null)

            return null;

        return item.WindowsId;

    }

​

    public static string WindowsToIana(string windowsZoneId)

    {

        if (windowsZoneId.Equals("UTC", StringComparison.Ordinal))

            return "Etc/UTC";

        var tzdbSource = NodaTime.TimeZones.TzdbDateTimeZoneSource.Default;

        var tzi = TimeZoneInfo.FindSystemTimeZoneById(windowsZoneId);

        if (tzi == null)

            return null;

        var tzid = tzdbSource.MapTimeZoneId(tzi);

        return tzid == null ? null : tzdbSource.CanonicalIdMap[tzid];

    }

​

    public static string LocationToTimeZone(double latitude, double longitude)

    {

        try

        {

            var client = new RestClient("https://maps.googleapis.com/maps/api/timezone/json");

            var request = new RestRequest(Method.GET);

            request.AddParameter("location", latitude + "," + longitude);

            request.AddParameter("timestamp", ToTimestamp(DateTime.UtcNow));

            request.AddParameter("sensor", "false");

            request.AddHeader("cache-control", "no-cache");

            var response = client.Execute<GoogleTimeZoneResult>(request);

            if (response.StatusCode != HttpStatusCode.OK)

                return "America/Chicago";

            return response.Data.Status != "OK" ? "America/Chicago" : response.Data.TimeZoneId;

        }

        catch (Exception)

        {

            return "America/Chicago";

        }

    }

​

    private static readonly DateTime Epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

    public static long ToTimestamp(DateTime value)

    {

        var elapsedTime = value - Epoch;

        return (long)elapsedTime.TotalSeconds;

    }

}

​

public class GoogleTimeZoneResult

{

    [JsonProperty("dstOffset")]

    public double DstOffset

    {

        get;

        set;

    }

​

    [JsonProperty("rawOffset")]

    public double RawOffset

    {

        get;

        set;

    }

​

    [JsonProperty("status")]

    public string Status

    {

        get;

        set;

    }

​

    [JsonProperty("timeZoneId")]

    public string TimeZoneId

    {

        get;

        set;

    }

​

    [JsonProperty("timeZoneName")]

    public string TimeZoneName

    {

        get;

        set;

    }

}