MkvLang/MkvToolnixWrapper/MkvInfo/Reader/NodeUtils.cs

using MkvPropEditWrapper.Shared;

namespace MkvPropEditWrapper.MkvInfo.Reader;

public static class NodeUtils
{
    public static IEnumerable<MkvNode> Descendants(this MkvNode root)
    {
        var nodes = new Stack<MkvNode>(new[] {root});

        while (nodes.Any())
        {
            var node = nodes.Pop();

            yield return node;

            foreach (var newNode in node.Children)
            {
                nodes.Push(newNode);
            }
        }
    }

    /// <summary>
    /// Generate track info from parsed output, only works on the first root node as it uses absolute depth
    /// </summary>
    /// <param name="root">Node root</param>
    /// <returns>All parseable <see cref="TrackInfo"/></returns>
    public static IEnumerable<TrackInfo> GetTrackInfos(this MkvNodeRoot root)
    {        
        TrackInfo? ParseTrackInfo(MkvNode track)
        {
            ReadOnlySpan<char> audioType = "audio";
            ReadOnlySpan<char> subtitleType = "subtitles";
            
            int number = -1;
            var trackType = TrackType.Unknown;
            string language = "Unknown";
            bool defaultFlag = default;
            bool forcedFlag = default;

            foreach (var child in track.Children)
            {
                if (child is MkvProperty property)
                {
                    ReadOnlySpan<char> span;
                    
                    switch (property.PropertyType)
                    {
                        case PropertyType.TrackType:
                            span = property.Value.Span;

                            if (span.SequenceEqual(audioType))
                            {
                                trackType = TrackType.Audio;
                            }
                            else if (span.SequenceEqual(subtitleType))
                            {
                                trackType = TrackType.Subtitles;
                            }
                            else
                            {
                                return null;
                            }
                            
                            break;
                        case PropertyType.TrackNumber:
                            span = property.Value.Span;
                        
                            number = int.Parse(span[..span.IndexOf(' ')]);
                            break;
                        case PropertyType.Language:
                            language = property.Value.ToString();
                            break;
                        case PropertyType.FlagDefault:
                            defaultFlag = property.Value.Span[0] == '1';
                            break;
                        case PropertyType.FlagForced:
                            forcedFlag = property.Value.Span[0] == '1';
                            break;
                    }
                }
            }
            
            return number == -1 ? null : new TrackInfo(number, trackType, language, defaultFlag, forcedFlag);
        }
    
        var tracks = root.Descendants().Where(n => n is { Depth: 2, NodeType: NodeType.Track });

        foreach (var track in tracks)
        {
            var trackInfo = ParseTrackInfo(track);

            if (trackInfo is not null)
            {
                yield return trackInfo;
            }
        }
    }
    
    public static (IEnumerable<TrackInfo> audio, IEnumerable<TrackInfo> subtitles) SplitByType(this IEnumerable<TrackInfo> trackInfos)
    {
        var lookup = trackInfos.OrderBy(t => t.Number).ToLookup(t => t.TrackType);

        return (lookup[TrackType.Audio], lookup[TrackType.Subtitles]);
    }
}