AdventOfCode23/Day5/Almanac.cs

using System.Collections.Generic;

namespace Day5;

public class Almanac
{
    public IList<long> Seeds { get; } = new List<long>();

    public IList<(string Source, string Destination)> Mappings { get; } =
        new List<(string Source, string Destination)>();

    public Dictionary<string, IList<Range>> MappingData { get; } =
        new Dictionary<string, IList<Range>>();

    public IList<long> Map(IList<long> start, string source, string destination)
    {
        var result = start;
        var current = source;
        while (current != destination)
        {
            result = MapSingle(result, current);
            current = Mappings.First(m => m.Source == current).Destination;
        }

        return result;
    }

    private IList<long> MapSingle(IList<long> start, string source)
    {
        return start
            .Select(num => MappingData[source].FirstOrDefault(x => x.IsMatch(num), Range.Identity).Transform(num))
            .ToList();
    }
}