use std::error::Error;
use std::fs::File;
use std::io::{self, BufRead};
use std::vec::Vec;

fn flash(x: i32, y: i32, grid: &mut Vec<Vec<u32>>) {
    for dy in [-1, 0, 1] {
        for dx in [-1, 0, 1] {
            if dx == 0 && dy == 0 {
                continue;
            }

            let ax = x + dx;
            let ay = y + dy;
            if ay < 0 || ay as usize >= grid.len() {
                continue;
            }
            if ax < 0 || ax as usize >= grid[ay as usize].len() {
                continue;
            }

            if grid[ay as usize][ax as usize] > 0 {
                grid[ay as usize][ax as usize] += 1;
            }
        }
    }
    grid[y as usize][x as usize] = 0;
}

fn print_grid(grid: &Vec<Vec<u32>>) {
    for y in 0..grid.len() {
        for x in 0..grid[y].len() {
            print!("{}", grid[y][x]);
        }
        println!("");
    }
    println!();
}

fn main() -> Result<(), Box<dyn Error>> {
    let file = File::open("inputs/day11.txt")?;
    let mut grid: Vec<Vec<u32>> = io::BufReader::new(file)
        .lines()
        .map(|l| {
            l.unwrap()
                .chars()
                .map(|c| c.to_digit(10).unwrap())
                .collect()
        })
        .collect();

    let mut answer1 = 0;
    let mut step = 0;
    while grid.iter().any(|r| r.iter().any(|e| e > &0)) {
        let mut next_grid: Vec<Vec<u32>> = grid
            .iter()
            .map(|r| r.iter().map(|e| e + 1).collect())
            .collect();

        while next_grid.iter().any(|r| r.iter().any(|e| e > &9)) {
            for y in 0..next_grid.len() {
                for x in 0..next_grid[y].len() {
                    if next_grid[y][x] > 9 {
                        flash(x as i32, y as i32, &mut next_grid);
                        if step < 100 {
                            answer1 += 1;
                        }
                    }
                }
            }
        }

        grid = next_grid;
        step += 1;

        println!("Step {}", step);
        print_grid(&grid);
    }

    println!("Answer1: {}", answer1);

    println!("Answer2: {}", step);

    Ok(())
}