package adventofcode;

import adventofcode.utils.Utils;
import java.awt.Point;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class Day10 {
    public static void solve() {
        List<String> input = Utils.getInput(10);

        char[][] map = input.stream().map(String::toCharArray).toArray(char[][]::new);

        List<Point> points = new ArrayList<>();
        for(int y = 0 ; y < map.length ; y++) {
            for(int x = 0 ; x < map[y].length ; x++) {
                if(map[y][x] == '#') {
                    points.add(new Point(x, y));
                }
            }
        }

        Map<Point, Set<Point>> visibleAsteroids = new HashMap<>();

        for(Point point : points) {
            visibleAsteroids.put(point, new HashSet<>());
            for(Point other : points) {
                if(point == other) {
                    continue;
                }

                int dx = other.x - point.x;
                int dy = other.y - point.y;
                int gcd = gcd(dx, dy);
                visibleAsteroids.get(point).add(new Point(dx / gcd, dy / gcd));
            }
        }

        int mostVisible = visibleAsteroids.values().stream()
                .mapToInt(Set::size)
                .max().getAsInt();

        System.out.println(mostVisible);
    }

    private static int gcd(int a, int b) {
        if(a < 0) return gcd(-a, b);
        if(b < 0) return gcd(a, -b);
        if(a == b) return a;
        if(a == 0) return b;
        if(b == 0) return a;
        if((a & 1) == 0 && (b & 1) == 0) return gcd(a >> 1, b >> 1) << 1;
        if((a & 1) == 0) return gcd(a >> 1, b);
        if((b & 1) == 0) return gcd(a, b >> 1);
        if(a > b) return gcd((a - b) >> 1, b);
        return gcd((b - a) >> 1, a);
    }
}