#define Day5
#define PartTwo
#if Day5
using System.Text.RegularExpressions;
Regex regex = new Regex(@"^(?<x1>\d+),(?<y1>\d+) -> (?<x2>\d+),(?<y2>\d+)$");

var lines = File.ReadAllLines("day5/input")
        .Select(l => {
            var match = regex.Match(l);
            return new Line(
                new Point(
                    int.Parse(match.Groups["x1"].Value),
                    int.Parse(match.Groups["y1"].Value)),
                new Point(
                    int.Parse(match.Groups["x2"].Value),
                    int.Parse(match.Groups["y2"].Value))
            );
        }).ToList();

var vents = new Dictionary<Point, int>();
foreach (var line in lines) {
    IEnumerable<Point> points;
    if (line.start.x == line.end.x) {
        points = Enumerable.Range(Math.Min(line.start.y, line.end.y), Math.Abs(line.start.y - line.end.y) + 1)
            .Select(y => new Point(line.start.x, y));
    } else if (line.start.y == line.end.y) {
        points = Enumerable.Range(Math.Min(line.start.x, line.end.x), Math.Abs(line.start.x - line.end.x) + 1)
            .Select(x => new Point(x, line.start.y));
    } else {
#if PartTwo
        Point smallerX;
        Point largerX;
        bool increasingY;
        if (line.start.x < line.end.x) {
            smallerX = line.start;
            largerX = line.end;
        } else {
            smallerX = line.end;
            largerX = line.start;
        }
        increasingY = smallerX.y < largerX.y;
        points = Enumerable.Range(0, largerX.x - smallerX.x + 1)
            .Select(i => new Point(smallerX.x + i, smallerX.y + (increasingY ? i : (i*(-1)))));
#else
        points = new List<Point>();
#endif
    }

    foreach (var p in points) {
        if (vents.ContainsKey(p)) {
            vents[p] += 1;
        } else {
            vents[p] = 1;
        }
    }
}

Console.WriteLine(vents.Count(v => v.Value > 1));


record Line(Point start, Point end);
record Point(int x, int y);
#endif