using System.Globalization;
using System.Text.Json;
using System.Text.RegularExpressions;

namespace Jellyfin.Plugin.Vanguard.Seasons;

/// <summary>Finds the best "when was this recorded" for a media file.</summary>
public static partial class ItemTimestamp
{
    public enum Source { Sidecar, Filename, FileTime }

    public sealed record Result(DateTimeOffset Utc, Source Source);

    /// <summary>
    /// Precedence: clip.json / &lt;name&gt;.json sidecar "timestamp" (UTC ISO-8601, written by the clip bot)
    /// -> MediaMTX filename yyyy-MM-dd_HH-mm-ss (local time of the server, i.e. <paramref name="tz"/>)
    /// -> file last-write time.
    /// </summary>
    public static Result Resolve(string path, TimeZoneInfo tz)
    {
        var sidecar = TryReadSidecar(path);
        if (sidecar is not null) return new Result(sidecar.Value, Source.Sidecar);

        var fromName = TryParseFilename(Path.GetFileNameWithoutExtension(path), tz);
        if (fromName is not null) return new Result(fromName.Value, Source.Filename);

        var mtime = File.Exists(path) ? File.GetLastWriteTimeUtc(path) : DateTime.UtcNow;
        return new Result(new DateTimeOffset(mtime, TimeSpan.Zero), Source.FileTime);
    }

    // MediaMTX  2026-10-29_21-03-11            Xbox Game Bar  Game 2026-10-29 21-03-11
    [GeneratedRegex(@"(?<y>\d{4})-(?<mo>\d{2})-(?<d>\d{2})[_ T](?<h>\d{2})-(?<mi>\d{2})-(?<s>\d{2})")]
    private static partial Regex DashedName();
    // ShadowPlay / NVIDIA App  Game 2026.10.29 - 21.03.11.05.DVR
    [GeneratedRegex(@"(?<y>\d{4})\.(?<mo>\d{2})\.(?<d>\d{2}) - (?<h>\d{2})\.(?<mi>\d{2})\.(?<s>\d{2})")]
    private static partial Regex ShadowPlayName();
    // Steam Game Recording  clip_730_20261029_210311   (also plain 20261029_210311 / 20261029-210311)
    [GeneratedRegex(@"(?<![\d])(?<y>20\d{2})(?<mo>\d{2})(?<d>\d{2})[_-](?<h>\d{2})(?<mi>\d{2})(?<s>\d{2})(?![\d])")]
    private static partial Regex CompactName();

    public static DateTimeOffset? TryParseFilename(string stem, TimeZoneInfo tz)
    {
        var m = DashedName().Match(stem);
        if (!m.Success) m = ShadowPlayName().Match(stem);
        if (!m.Success) m = CompactName().Match(stem);
        if (!m.Success) return null;
        try
        {
            var local = new DateTime(
                int.Parse(m.Groups["y"].Value, CultureInfo.InvariantCulture), int.Parse(m.Groups["mo"].Value, CultureInfo.InvariantCulture), int.Parse(m.Groups["d"].Value, CultureInfo.InvariantCulture),
                int.Parse(m.Groups["h"].Value, CultureInfo.InvariantCulture), int.Parse(m.Groups["mi"].Value, CultureInfo.InvariantCulture), int.Parse(m.Groups["s"].Value, CultureInfo.InvariantCulture),
                DateTimeKind.Unspecified);
            var offset = tz.GetUtcOffset(local);
            return new DateTimeOffset(local, offset);
        }
        catch (ArgumentOutOfRangeException) { return null; }
    }

    private static DateTimeOffset? TryReadSidecar(string path)
    {
        var dir = Path.GetDirectoryName(path) ?? string.Empty;
        var stem = Path.GetFileNameWithoutExtension(path);
        foreach (var candidate in new[] { Path.Combine(dir, stem + ".json"), Path.Combine(dir, stem + ".clip.json") })
        {
            if (!File.Exists(candidate)) continue;
            try
            {
                using var doc = JsonDocument.Parse(File.ReadAllText(candidate));
                if (doc.RootElement.TryGetProperty("timestamp", out var ts) && ts.ValueKind == JsonValueKind.String &&
                    DateTimeOffset.TryParse(ts.GetString(), CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal, out var parsed))
                {
                    return parsed;
                }
            }
            catch (JsonException) { /* ignore broken sidecar */ }
        }
        return null;
    }
}