AdventOfCode23/Day5/RangeMapping.cs

namespace Day5;

public record RangeMapping(long SrcIndex, long DstIndex, long Length)
{
    public static RangeMapping Identity { get; } = new RangeMapping(0, 0, long.MaxValue);
    
    public bool IsMatch(long value)
    {
        return SrcIndex <= value && value < SrcIndex + Length;
    }
    
    public bool IsOverlap(Range range)
    {
        return range.Start < SrcIndex + Length && range.Start + range.Length > SrcIndex;
    }
    
    public bool IsWithin(Range range)
    {
        return range.Start >= SrcIndex && range.Start + range.Length <= SrcIndex + Length;
    }

    public IEnumerable<Range> Split(Range range)
    {
        if (range.Start >= SrcIndex + Length || range.Start + range.Length < SrcIndex)
        {
            throw new ArgumentException("Not overlapping");
        }

        if (range.Start >= SrcIndex && range.Start + range.Length < SrcIndex + Length)
        {
            throw new ArgumentException("Already within");
        }

        if (range.Start < SrcIndex)
        {
            yield return new Range(range.Start, SrcIndex - range.Start);
        }

        if (range.Start + range.Length > SrcIndex + Length)
        {
            yield return new Range(SrcIndex + Length, (range.Start + range.Length) - (SrcIndex + Length));
        }
        
        var left = Math.Max(SrcIndex, range.Start);
        var right = Math.Min(SrcIndex + Length, range.Start + range.Length);

        yield return new Range(SrcIndex + (left - SrcIndex), right - left);
    }

    public long Transform(long value)
    {
        return DstIndex + (value - SrcIndex);
    }

    public Range Transform(Range range)
    {
        if (!IsWithin(range))
        {
            throw new ArgumentException("Not in range");
        }
        var left = Math.Max(SrcIndex, range.Start);
        var right = Math.Min(SrcIndex + Length, range.Start + range.Length);

        return new Range(DstIndex + (left - SrcIndex), right - left);
    }
}