AdventOfCode23/Day4/ScratchParser.cs

namespace Day4;

public class ScratchParser
{
    public IEnumerable<ScratchCard> Parse(string inputFile)
    {
        using var reader = File.OpenText(inputFile);

        while (!reader.EndOfStream)
        {
            var line = reader.ReadLine()!;

            var cardParts = line.Split(':', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
            if (cardParts.Length != 2)
            {
                throw new Exception($"Expecting a single colon in each line but got: {line}");
            }

            var id = int.Parse(cardParts[0].Substring(5));
            var card = new ScratchCard(id);
            
            cardParts = cardParts[1].Split('|', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
            
            if (cardParts.Length != 2)
            {
                throw new Exception($"Expecting a single pipe in each line but got: {line}");
            }

            foreach (var numStr in cardParts[0].Split(' ', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries))
            {
                var num = int.Parse(numStr);
                if (card.Winning.Contains(num))
                {
                    throw new Exception($"Unexpected duplicate in winning numbers in card {id}: {cardParts[0]}");
                }

                card.Winning.Add(num);
            }
            
            foreach (var numStr in cardParts[1].Split(' ', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries))
            {
                var num = int.Parse(numStr);
                if (card.Draw.Contains(num))
                {
                    throw new Exception($"Unexpected duplicate in winning numbers in card {id}: {cardParts[0]}");
                }

                card.Draw.Add(num);
            }

            yield return card;
        }
    }
}