const std = @import("std");
const print = std.debug.print;

pub fn solve(part: []u8, reader: *std.Io.Reader, allocator: std.mem.Allocator) !void {
    if (std.mem.eql(u8, part, "1")) {
        try part1(reader, allocator);
    } else {
        try part2(reader, allocator);
    }
}


fn part1(reader: *std.Io.Reader, allocator: std.mem.Allocator) !void {
    var output: usize = 0;
    var list = try std.ArrayList([]u8).initCapacity(allocator, 0);
    defer list.deinit(allocator);

    while (reader.takeDelimiter('\n')) |line| {
        if (line == null){
            break;
        }

        try list.append(allocator, line.?);
    } else |_| {

    }


    for (list.items,0..) |row, y| {
        for (row,0..) |item,x| {
            if (item != '@'){
                continue;
            }

            var adjacent: usize = 0;
            if (y > 0 and x > 0 and list.items[y - 1][x - 1] == '@') adjacent += 1;
            if (y > 0 and list.items[y - 1][x] == '@') adjacent += 1;
            if (y > 0 and x < row.len - 1 and list.items[y - 1][x + 1] == '@') adjacent += 1;
            if (x > 0 and list.items[y][x - 1] == '@') adjacent += 1;
            if (x < row.len - 1 and list.items[y][x + 1] == '@') adjacent += 1;
            if (y < list.items.len - 1 and x > 0 and list.items[y + 1][x - 1] == '@') adjacent += 1;
            if (y < list.items.len - 1 and list.items[y + 1][x] == '@') adjacent += 1;
            if (y < list.items.len - 1 and x < row.len - 1 and list.items[y + 1][x + 1] == '@') adjacent += 1;

            if (adjacent < 4){

                output += 1;
            }
        }
    }

    print("{d}\n", .{output});
}

fn part2(reader: *std.Io.Reader, allocator: std.mem.Allocator) !void {
    var output: usize = 0;
    var list = try std.ArrayList([]u8).initCapacity(allocator, 0);
    defer list.deinit(allocator);

    while (reader.takeDelimiter('\n')) |line| {
        if (line == null){
            break;
        }

        try list.append(allocator, line.?);
    } else |_| {

    }


    var previous_output: usize = 1;
    while (output != previous_output) {
        previous_output = output;
        for (list.items,0..) |row, y| {
            for (row,0..) |item,x| {
                if (item != '@'){
                    continue;
                }

                var adjacent: usize = 0;
                if (y > 0 and x > 0 and list.items[y - 1][x - 1] == '@') adjacent += 1;
                if (y > 0 and list.items[y - 1][x] == '@') adjacent += 1;
                if (y > 0 and x < row.len - 1 and list.items[y - 1][x + 1] == '@') adjacent += 1;
                if (x > 0 and list.items[y][x - 1] == '@') adjacent += 1;
                if (x < row.len - 1 and list.items[y][x + 1] == '@') adjacent += 1;
                if (y < list.items.len - 1 and x > 0 and list.items[y + 1][x - 1] == '@') adjacent += 1;
                if (y < list.items.len - 1 and list.items[y + 1][x] == '@') adjacent += 1;
                if (y < list.items.len - 1 and x < row.len - 1 and list.items[y + 1][x + 1] == '@') adjacent += 1;

                if (adjacent < 4){
                    list.items[y][x] = '.';
                    output += 1;
                }
            }
        }
    }

    print("{d}\n", .{output});
}