namespace Houston.Services;

public class IniParser
{
    public async Task<IniDocument> ParseAsync(TextReader reader, CancellationToken cancellationToken)
    {
        var sections = new Dictionary<string, Dictionary<string, string>>(StringComparer.OrdinalIgnoreCase);
        var current = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        sections[String.Empty] = current;

        while (await reader.ReadLineAsync(cancellationToken) is { } line)
        {
            var trimmed = line.Trim();

            // Skip blank lines and comments
            if (trimmed.Length == 0 || trimmed[0] is ';' or '#')
                continue;

            if (trimmed.StartsWith('[') && trimmed.EndsWith(']'))
            {
                var name = trimmed[1..^1].Trim();
                if (!sections.TryGetValue(name, out current!))
                    sections[name] = current = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
                continue;
            }

            var separator = trimmed.IndexOf('=');
            if (separator < 0)
                continue;

            var key = trimmed[..separator].Trim();
            if (key.Length == 0)
                continue;

            // Last value wins for duplicate keys within a section.
            current[key] = trimmed[(separator + 1)..].Trim();
        }

        return new(sections);
    }

    /// <summary>
    /// Parses INI content from a string.
    /// </summary>
    public Task<IniDocument> ParseAsync(string content, CancellationToken cancellationToken)
    {
        using var reader = new StringReader(content);
        return ParseAsync(reader, cancellationToken);
    }