---cargo
---

static CONTENT: &'static str = include_str!("./inputs/04_1.txt");
static GRID_OFFSETS: [(isize, isize); 8] = [(-1, -1), (0, -1), (1, -1), (-1, 0), (1, 0), (-1, 1), (0, 1), (1, 1)];

#[derive(Debug, PartialEq, Clone)]
enum Cell {
    Empty,
    PRoll,
}

fn main() {
    let mut grid: Vec<_> = CONTENT.lines().map(|l| l.trim()).filter(|l| !l.is_empty()).map(|l| {
        l.chars().map(|c| match c {
            '.' => Cell::Empty,
            '@' => Cell::PRoll,
            other => unreachable!("Unexpected Input {:?}", other),
        }).collect::<Vec<_>>()
    }).collect();

    let mut result = 0;

    loop {
        let mut to_remove = Vec::new();
        for (y, row) in grid.iter().enumerate() {
            for (x, cell) in row.iter().enumerate() {
                if cell != &Cell::PRoll {
                    continue;
                }

                let neighbours = GRID_OFFSETS.iter().filter_map(|(xoff, yoff)| Some((x.checked_add_signed(*xoff)?, y.checked_add_signed(*yoff)?))).filter_map(|(x, y)| {
                    let cell = grid.get(y)?.get(x)?;
                    Some((x, y, cell.clone()))
                }).filter(|(_, _, c)| c == &Cell::PRoll).count();
        

                if neighbours < 4 {
                    result += 1;
                    to_remove.push((x, y));
                }
            }
        }
        if to_remove.is_empty() {
            break;
        }

        for (x, y) in to_remove {
            grid[y][x] = Cell::Empty;
        }
    }


    println!("Result: {}", result);
}