using System;

namespace Jellyfin.Plugin.SRFPlay.Utilities;

/// <summary>
/// Converts times into the time zone the plugin writes into text (item names, file names).
/// SRG sends times with an offset, and DateTime deserialisation turns them into server-local
/// values, so without this the text follows whatever zone the server happens to run in.
/// </summary>
public static class DisplayTime
{
    /// <summary>
    /// Converts a time to the configured display time zone (the server's if none is set).
    /// </summary>
    /// <param name="value">The time. Unspecified values are treated as server-local, like deserialised ones.</param>
    /// <returns>The same instant expressed in the display time zone.</returns>
    public static DateTime From(DateTime value)
    {
        return TimeZoneInfo.ConvertTimeFromUtc(value.ToUniversalTime(), GetZone());
    }

    /// <summary>
    /// Gets the current time in the display time zone.
    /// </summary>
    /// <returns>The current time in the display time zone.</returns>
    public static DateTime Now()
    {
        return TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, GetZone());
    }

    private static TimeZoneInfo GetZone()
    {
        var id = Plugin.Instance?.Configuration.DisplayTimeZone;
        if (string.IsNullOrWhiteSpace(id))
        {
            return TimeZoneInfo.Local;
        }

        // An unknown id falls back to the server's zone rather than breaking listings.
        return TimeZoneInfo.TryFindSystemTimeZoneById(id.Trim(), out var zone) ? zone : TimeZoneInfo.Local;
    }
}