using System.Text;

namespace CVRManager.Services;

public static class Vdf
{
    public static Dictionary<string, object> Parse(string text, int start = 0)
    {
        var pos = start;
        var root = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
        var key = ReadToken(text, ref pos);
        if (key == null) return root;
        var next = Peek(text, pos);
        if (next == '{')
        {
            pos = text.IndexOf('{', pos) + 1;
            root[key] = ParseBlock(text, ref pos);
        }
        return root;
    }

    public static Dictionary<string, object> ParseDocument(string text)
    {
        var pos = 0;
        return ParseBlock(text, ref pos, true);
    }

    static Dictionary<string, object> ParseBlock(string text, ref int pos, bool toEnd = false)
    {
        var dict = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
        while (true)
        {
            SkipSpace(text, ref pos);
            if (pos >= text.Length) return dict;
            if (text[pos] == '}')
            {
                pos++;
                return dict;
            }
            var key = ReadToken(text, ref pos);
            if (key == null) return dict;
            SkipSpace(text, ref pos);
            if (pos < text.Length && text[pos] == '{')
            {
                pos++;
                dict[key] = ParseBlock(text, ref pos);
            }
            else
            {
                var val = ReadToken(text, ref pos);
                if (val == null) return dict;
                dict[key] = val;
            }
        }
    }

    static char Peek(string text, int pos)
    {
        SkipSpace(text, ref pos);
        return pos < text.Length ? text[pos] : '\0';
    }

    static void SkipSpace(string text, ref int pos)
    {
        while (pos < text.Length)
        {
            if (char.IsWhiteSpace(text[pos])) pos++;
            else if (text[pos] == '/' && pos + 1 < text.Length && text[pos + 1] == '/')
                while (pos < text.Length && text[pos] != '\n') pos++;
            else break;
        }
    }

    static string? ReadToken(string text, ref int pos)
    {
        SkipSpace(text, ref pos);
        if (pos >= text.Length || text[pos] != '"') return null;
        pos++;
        var sb = new StringBuilder();
        while (pos < text.Length && text[pos] != '"')
        {
            if (text[pos] == '\\' && pos + 1 < text.Length)
            {
                pos++;
                sb.Append(text[pos] switch { 'n' => '\n', 't' => '\t', var c => c });
            }
            else sb.Append(text[pos]);
            pos++;
        }
        pos++;
        return sb.ToString();
    }

    public static Dictionary<string, object>? Dict(this Dictionary<string, object> d, string key) =>
        d.TryGetValue(key, out var v) ? v as Dictionary<string, object> : null;

    public static string Str(this Dictionary<string, object> d, string key) =>
        d.TryGetValue(key, out var v) && v is string s ? s : "";
}