using System.Collections;
using System.Text;

namespace MkvPropEditWrapper.MkvInfo;

public class MkvNode : IEnumerable<MkvNode>
{
    private static class KnowNodeTypes
    {
        public const string Head = "EBML head";
        public const string Segment = "Segment";
        public const string Chapter = "Chapters";
        public const string Tag = "Tags";
        public const string Track = "Tracks";
        public const string Attachment = "Attachments";
    }

    public MkvNode? Parent { get; }
    public IList<MkvNode> Children { get; }

    public virtual NodeType NodeType { get; }
    public virtual int Depth { get; }

    public ReadOnlyMemory<char> Name { get; }

    public MkvNode(MkvNode? parent, ReadOnlyMemory<char> name)
    {
        Parent = parent;
        Name = name;

        Depth = parent?.Depth + 1 ?? 0;

        NodeType = parent is null ? NodeType.Root : FindNodeType();

        Children = new List<MkvNode>();
    }

    private NodeType FindNodeType()
    {
        var span = Name.Span;

        return Depth switch
        {
            0 when span.SequenceEqual(KnowNodeTypes.Head) => NodeType.Head,
            0 when span.StartsWith(KnowNodeTypes.Segment) => NodeType.Segment,
            1 when span.SequenceEqual(KnowNodeTypes.Chapter) => NodeType.Chapter,
            1 when span.SequenceEqual(KnowNodeTypes.Tag) => NodeType.Tag,
            1 when span.SequenceEqual(KnowNodeTypes.Track) => NodeType.Track,
            1 when span.SequenceEqual(KnowNodeTypes.Attachment) => NodeType.Attachment,
            1 => NodeType.Unknown,
            _ => Parent!.NodeType
        };
    }

    protected virtual void AppendSelf(StringBuilder builder) => builder.AppendLine($"{new string('-', Depth)}> [{NodeType}] {Name}");

    public IEnumerator<MkvNode> GetEnumerator()
    {
        return Children.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    public override string ToString()
    {
        var builder = new StringBuilder();

        AppendSelf(builder);

        foreach (var mkvNode in Children)
        {
            builder.Append(mkvNode);
        }

        return builder.ToString();
    }
}