SuperPower Token Positioning

ParserExtensions.cs

using System.Linq;
using Microsoft.Diagnostics.Tracing.Parsers.MicrosoftWindowsTCPIP;
using Superpower;

namespace Netophone.Systems.Plot.Parsers;

public interface ILocated {
    PositionSpan Span { set; }
}

public readonly record struct PositionSpan(int Start = -1, int End = -1) {
    public bool HasValue => Start >= 0 && End >= 0;

    /// <summary>
    /// Apply the position span to acquire a substring of the source string.
    /// </summary>
    /// <param name="source"></param>
    /// <returns></returns>
    public string Substring(string source) {
        if (!HasValue) throw new InvalidOperationException("PositionSpan must have a value to be used.");
        return source.Substring(Start, End - Start);
    }
}

public static class ParserExtensions {
    /// <summary>
    /// When applied, ensures the parser's result embeds the positioning information into the results.
    /// </summary>
    /// <param name="parser"></param>
    /// <typeparam name="T">An ILocated type</typeparam>
    /// <returns></returns>
    public static TextParser<T> WithLocation<T>(this TextParser<T> parser)
        where T : ILocated {
        return i => {
            var inner = parser(i);
            if (!inner.HasValue) return inner;
            inner.Value.Span = new PositionSpan(
                inner.Location.Position.Absolute, inner.Location.Position.Absolute + inner.Location.Length
            );
            return inner;
        };
    }

    /// <summary>
    /// When applied, ensures the parser's result embeds the positioning information into the results.
    /// </summary>
    /// <param name="parser"></param>
    /// <typeparam name="TKind"></typeparam>
    /// <typeparam name="T">An ILocated type</typeparam>
    /// <returns></returns>
    public static TokenListParser<TKind, T> WithLocation<TKind, T>(this TokenListParser<TKind, T> parser)
        where T : ILocated {
        return i => {
            var inner = parser(i);
            if (!inner.HasValue) return inner;


            var last = inner.Remainder.Any()
                // inner.Location contains both tokens used and the remainder, so get the last 'used' token
                ? inner.Location.ElementAt(inner.Location.Count() - inner.Remainder.Count() - 1)
                // inner.Location is 100% used, just grab the last one
                : inner.Location.Last();

            inner.Value.Span = new PositionSpan(inner.Location.First().Position.Absolute,
                last.Position.Absolute + last.Span.Length);

            return inner;
        };
    }
}