namespace Day1;

// Advent of Code 2024
// Day 1
// James Plante (jwplante)

class DayOne
{
    private static async Task PartOne()
    {
        await using FileStream inputStream = File.OpenRead("input/day1.txt");
        PairParser parser = new();
        
        IList<(int, int)> entries = await parser.ParseAsync(inputStream);
        
        // Given the parsed entries, add them to two new lists and sort them
        List<int> leftList = [];
        List<int> rightList = [];
        foreach ((int left, int right) in entries)
        {
            leftList.Add(left);
            rightList.Add(right);
        }
        leftList.Sort();
        rightList.Sort();

        // Convert back into pairs of (smallest, smallest), (secondSmallest, ...
        List<(int, int)> sortedPairs = leftList
            .Zip(rightList, (left, right) => (left, right))
            .ToList();
       
        long totalDistance = 0;
        foreach ((int left, int right) in sortedPairs)
        {
            var lineDistance = Math.Abs(left - right);
            totalDistance += lineDistance;
        }

        Console.WriteLine($"Part 1: The total distance of the lines is {totalDistance}.");
    }
    
    private static async Task PartTwo()
    {
        await using FileStream inputStream = File.OpenRead("input/day1.txt");
        PairParser parser = new();
        
        IList<(int, int)> entries = await parser.ParseAsync(inputStream);
        
        // Get the frequencies for the right list
        Dictionary<int, int> frequencies = [];
        foreach ((_, int right) in entries)
        {
            frequencies[right] = frequencies.GetValueOrDefault(right) + 1;
        }

        long similarityScore = 0;
        foreach ((int left, _) in entries)
        {
            var intermediateScore = left * frequencies.GetValueOrDefault(left);
            similarityScore += intermediateScore;
        }
        Console.WriteLine($"Part 2: The total similarity score is {similarityScore}.");
    }
    
    public static async Task Main(string[] args)
    {
        await PartOne();
        await PartTwo();
    }
}