using System.Text.RegularExpressions;

namespace Day2;

public partial class GameParser
{
    [GeneratedRegex(@"^Game (\d+):(.*)$")]
    private partial Regex GameMatcher();

    [GeneratedRegex(@"(\d+)\s+(\w+)")]
    private partial Regex ItemMatcher();
    
    public GameParser()
    {
    }

    public IEnumerable<GameSamples> Parse(string inputFile)
    {
        using var reader = File.OpenText(inputFile);
        while (!reader.EndOfStream)
        {
            var line = reader.ReadLine()!;
            var match = GameMatcher().Match(line);
            if (!match.Success)
            {
                throw new Exception($"Line not matching expected Game format: {line}");
            }

            var id = int.Parse(match.Groups[1].Value);
            var samples = new List<SampleSet>();
            foreach (var set in match.Groups[2].Value.Split(';', StringSplitOptions.TrimEntries))
            {
                var map = new Dictionary<string, int>();
                foreach (var item in set.Split(',', StringSplitOptions.TrimEntries))
                {
                    var itemMatch = ItemMatcher().Match(item);
                    if (!itemMatch.Success)
                    {
                        throw new Exception($"Item content is invalid: {item}");
                    }
                    map[itemMatch.Groups[2].Value.ToLower()] = int.Parse(itemMatch.Groups[1].Value);
                }
                
                samples.Add(new SampleSet(
                    map.GetValueOrDefault("red"),
                    map.GetValueOrDefault("green"),
                    map.GetValueOrDefault("blue")));
            }

            yield return new GameSamples(id, samples);
        }
    }
}