emby-toolbox/EmbyToolbox/Services/ExtractCommandBuilder.cs

using System.Globalization;
using System.IO;
using System.Text;
using EmbyToolbox.Models;

namespace EmbyToolbox.Services;

/// <summary>Имена выходных файлов и аргументы ffmpeg для извлечения аудио/субтитров/вложений (stream copy).</summary>
public sealed class ExtractCommandBuilder
{
    /// <summary>
    /// Безопасный фрагмент имени без расширения для префикса выходных файлов (<c>Movie</c> из <c>Movie.mkv</c>).
    /// </summary>
    public static string SanitizeSourceFileStem(string? fileNameWithoutExtension)
    {
        if (string.IsNullOrWhiteSpace(fileNameWithoutExtension))
        {
            return "media";
        }

        var sb = new StringBuilder(fileNameWithoutExtension.Trim().Length);
        foreach (var ch in fileNameWithoutExtension.Trim())
        {
            sb.Append(ch is < '\u0020' or '"' or '*' or ':' or '<' or '>' or '?' or '\\' or '/' or '|' ? '_' : ch);
        }

        var s = sb.ToString().Trim('.', ' ');
        return string.IsNullOrEmpty(s) ? "media" : s[..Math.Min(s.Length, 200)];
    }

    /// <summary>Базовое имя файла (без пути): все результаты в общих каталогах, префикс — имя исходника без расширения.</summary>
    public string ResolveOutputBaseFileName(string sourceStemSanitized, MediaStreamInfo stream, int ordinalInKind)
    {
        return stream.Kind switch
        {
            MediaStreamKind.Audio =>
                $"{sourceStemSanitized}_audio_{ordinalInKind:D2}_{SanitizeLangSegment(stream.Language)}.{GetAudioExtension(stream.CodecName)}",
            MediaStreamKind.Subtitle =>
                $"{sourceStemSanitized}_subtitle_{ordinalInKind:D2}_{SanitizeLangSegment(stream.Language)}.{GetSubtitleExtension(stream.CodecName)}",
            MediaStreamKind.Attachment =>
                $"{sourceStemSanitized}_attachment_{ordinalInKind:D2}_{ResolveAttachmentLeafFileName(stream)}",
            MediaStreamKind.Video or MediaStreamKind.Data =>
                throw new InvalidOperationException("Видео и data-потоки не извлекаются."),
            _ =>
                throw new InvalidOperationException($"Неподдерживаемый тип потока: {stream.Kind}"),
        };
    }

    public IReadOnlyList<string> BuildFfmpegArgumentList(string inputPath, MediaStreamInfo stream, string destinationFullPath)
    {
        return new[]
        {
            "-hide_banner",
            "-loglevel",
            "error",
            "-y",
            "-i",
            inputPath,
            "-map",
            $"0:{stream.Index}",
            "-c",
            "copy",
            destinationFullPath,
        };
    }

    private static string GetAudioExtension(string codecRaw)
    {
        var c = NormalizeCodec(codecRaw);
        return c switch
        {
            "aac" => "aac",
            "ac3" => "ac3",
            "dts" => "dts",
            "flac" => "flac",
            "truehd" => "thd",
            "eac3" => "eac3",
            "opus" => "opus",
            "mp3" => "mp3",
            "vorbis" => "ogg",
            _ => "bin",
        };
    }

    private static string GetSubtitleExtension(string codecRaw)
    {
        var c = NormalizeCodec(codecRaw);
        return c switch
        {
            "subrip" or "srt" => "srt",
            "ass" or "ssa" => "ass",
            "mov_text" or "text" or "tx3g" => "txt",
            "hdmv_pgs_subtitle" or "pgssub" => "sup",
            "dvd_subtitle" or "vobsub" => "sub",
            _ => "bin",
        };
    }

    private static string ResolveAttachmentLeafFileName(MediaStreamInfo stream)
    {
        var declared = stream.AttachmentDeclaredFileName?.Trim();
        if (string.IsNullOrEmpty(declared))
        {
            declared = $"blob_{stream.Index}";
        }

        declared = SanitizeDeclaredAttachmentFileName(declared);
        if (!Path.HasExtension(declared))
        {
            var mimeExt = MimeToExtension(stream.AttachmentDeclaredMimeType);
            if (!string.IsNullOrEmpty(mimeExt))
            {
                declared += mimeExt.StartsWith('.') ? mimeExt : "." + mimeExt;
            }
        }

        return declared;
    }

    private static string? MimeToExtension(string? mimeRaw)
    {
        if (string.IsNullOrWhiteSpace(mimeRaw))
        {
            return null;
        }

        var m = mimeRaw.Trim().ToLowerInvariant();
        return m switch
        {
            "font/ttf" or "application/x-truetype-font" => ".ttf",
            "font/otf" or "application/font-sfnt" => ".otf",
            "application/vnd.ms-opentype" => ".otf",
            _ => null,
        };
    }

    private static string SanitizeDeclaredAttachmentFileName(string declared)
    {
        var cleaned = declared.Replace('\\', '_').Replace('/', '_');
        cleaned = Path.GetFileName(cleaned);
        var sb = new StringBuilder(cleaned.Length);
        foreach (var ch in cleaned)
        {
            sb.Append(ch is < '\u0020' or '"' or '*' or ':' or '<' or '>' or '?' or '|' ? '_' : ch);
        }

        cleaned = sb.ToString().Trim('.', '_');
        return string.IsNullOrEmpty(cleaned) ? "attachment" : cleaned;
    }

    private static string SanitizeLangSegment(string? lang)
    {
        if (string.IsNullOrWhiteSpace(lang))
        {
            return "und";
        }

        var s = lang.Trim().ToLowerInvariant();
        Span<char> buffer = stackalloc char[s.Length];
        for (var i = 0; i < s.Length; i++)
        {
            var ch = s[i];
            buffer[i] = ch is '_' or '-' or >= 'a' and <= 'z' ? ch : '_';
        }

        var span = new string(buffer).Trim('_');
        return string.IsNullOrEmpty(span) ? "und" : span[..Math.Min(span.Length, 24)];
    }

    private static string NormalizeCodec(string? codecRaw) =>
        string.IsNullOrWhiteSpace(codecRaw) ? string.Empty : codecRaw.Trim().ToLowerInvariant();
}