TextCoordinateSystemComputer.cs

using System.Buffers;

namespace HydraScript.Domain.FrontEnd.Lexer.Impl;

public class TextCoordinateSystemComputer : ITextCoordinateSystemComputer
{
    private readonly SearchValues<char> _sv = SearchValues.Create('\n');

    /// <inheritdoc/>
    public IReadOnlyList<int> GetLines(string text)
    {
        var newText = text.EndsWith(Environment.NewLine)
            ? text
            : text + Environment.NewLine;
        var textLength = newText.Length;

        var indices = new List<int>(capacity: 128) { -1 };
        var textAsSpan = newText.AsSpan();
        while (true)
        {
            var start = indices[^1] + 1;
            if (start == textLength)
                break;
            var index = textAsSpan.Slice(
                start,
                length: textLength - start).IndexOfAny(_sv);
            indices.Add(start + index);
        }

        return indices;
    }

    /// <inheritdoc/>
    public Coordinates GetCoordinates(int absoluteIndex, IReadOnlyList<int> newLineList)
    {
        for (var i = 1; i < newLineList.Count; i++)
            if (absoluteIndex <= newLineList[i])
            {
                var offset = newLineList[i - 1];
                return new Coordinates(Line: i, Column: absoluteIndex - offset);
            }

        return new Coordinates();
    }
}