using EmbyToolbox.Models;

namespace EmbyToolbox.Services;

/// <summary>Правила совместимости субтитров с контейнером MKV/MP4 и codec copy в FFmpeg.</summary>
public static class SubtitleCodecRules
{
    public static string Normalize(string? codec) =>
        string.IsNullOrWhiteSpace(codec) ? string.Empty : codec.Trim().ToLowerInvariant();

    public static bool IsTeletext(string? codec) => Normalize(codec) == "dvb_teletext";

    public static bool IsUnknownSubtitleCodec(string? codec)
    {
        var n = Normalize(codec);
        return n is "" or "?" or "unknown";
    }

    /// <summary>Кодеки, которые можно mux copy в Matroska (без teletext / mov_text и пр.).</summary>
    public static bool IsMkvCopySafe(string? codec)
    {
        return Normalize(codec) switch
        {
            "subrip" or "srt" or "ass" or "ssa" => true,
            "webvtt" or "wvtt" => true,
            "hdmv_pgs_subtitle" or "pgssub" => true,
            "dvd_subtitle" or "dvdsub" => true,
            _ => false
        };
    }

    public static bool IsMp4TextDirectCopy(string? codec) => Normalize(codec) == "mov_text";

    /// <summary>Текстовые дорожки, для MP4 требующие перекодирования в mov_text (не mux copy).</summary>
    public static bool Mp4RequiresSubtitleTranscode(string? codec)
    {
        return Normalize(codec) switch
        {
            "subrip" or "srt" or "ass" or "ssa" => true,
            _ => false
        };
    }

    public static bool TargetsMkv(string? container) =>
        !string.IsNullOrWhiteSpace(container) &&
        (container.Contains("mkv", StringComparison.OrdinalIgnoreCase) ||
         container.Contains("matro", StringComparison.OrdinalIgnoreCase));

    public static bool TargetsMp4(string? container) =>
        !string.IsNullOrWhiteSpace(container) &&
        (container.Contains("mp4", StringComparison.OrdinalIgnoreCase) ||
         container.Contains("m4v", StringComparison.OrdinalIgnoreCase) ||
         container.Contains("mov", StringComparison.OrdinalIgnoreCase));

    /// <summary>Действо по умолчанию для встроенной дорожки субтитров после анализа.</summary>
    public static TrackActionKind DefaultEmbeddedSubtitleAction(string? codecName, string? profileContainer)
    {
        var c = codecName;

        if (IsTeletext(c) || IsUnknownSubtitleCodec(c))
        {
            return TrackActionKind.Remove;
        }

        if (TargetsMkv(profileContainer))
        {
            return IsMkvCopySafe(c) ? TrackActionKind.Keep : TrackActionKind.Remove;
        }

        if (TargetsMp4(profileContainer))
        {
            if (IsMp4TextDirectCopy(c))
            {
                return TrackActionKind.Keep;
            }

            if (Mp4RequiresSubtitleTranscode(c))
            {
                return TrackActionKind.Convert;
            }

            return TrackActionKind.Remove;
        }

        return IsMkvCopySafe(c) ? TrackActionKind.Keep : TrackActionKind.Remove;
    }

    /// <summary>Встроенную субдорожку с этим решением включают в ffmpeg -map только если истина.</summary>
    public static bool ShouldMapEmbeddedSubtitle(
        MediaAnalysisResult media,
        TrackOverrideEntry t,
        string effectiveContainer)
    {
        if (t.Source != SourceKind.Embedded || t.StreamKind != MediaStreamKind.Subtitle)
        {
            return true;
        }

        if (t.Action == TrackActionKind.Remove)
        {
            return false;
        }

        var codec = media.AllStreams.FirstOrDefault(s => s.Index == t.StreamIndex)?.CodecName;

        if (TargetsMkv(effectiveContainer))
        {
            if (!IsMkvCopySafe(codec))
            {
                return false;
            }

            return t.Action is TrackActionKind.Keep or TrackActionKind.Convert;
        }

        if (TargetsMp4(effectiveContainer))
        {
            if (IsMp4TextDirectCopy(codec) && t.Action == TrackActionKind.Keep)
            {
                return true;
            }

            if (Mp4RequiresSubtitleTranscode(codec) &&
                t.Action is TrackActionKind.Convert or TrackActionKind.Keep)
            {
                return true;
            }

            return false;
        }

        return IsMkvCopySafe(codec) ? t.Action != TrackActionKind.Remove : false;
    }

    /// <summary>Строковая подпись Codec для дорожки (субтитры отображать как текстовые / teletext).</summary>
    public static string EmbeddedSubtitleCodecLabel(string? ffprobeCodec) =>
        IsTeletext(ffprobeCodec) ? "dvb_teletext (subtitle)" : ffprobeCodec ?? "?";
}