use crate::spatial::*;

pub fn day4_part1(input: &str) -> String {
    let roll_locations = parse(input);
    removable_rolls(&roll_locations).count().to_string()
}
//fixed point algorithm go brrr
pub fn day4_part2(input: &str) -> String {
    let mut prev_roll_locations = vec![vec![]];
    let mut next_roll_locations = parse(input);
    let mut rolls_removed = 0;
    while prev_roll_locations != next_roll_locations {
        prev_roll_locations = next_roll_locations.clone();
        for roll_coords in removable_rolls(&prev_roll_locations) {
            next_roll_locations[roll_coords.row][roll_coords.col] = false;
            rolls_removed += 1;
        }
    }
    rolls_removed.to_string()
}

fn removable_rolls(roll_locations: &[Vec<bool>]) -> impl Iterator<Item = Point> {
    all_coords(roll_locations[0].len(), roll_locations.len())
        .filter(|coords| roll_locations[coords.row][coords.col])
        .filter(|&coords| {
            adjacent_including_diagonals(roll_locations, coords)
                .iter()
                .flatten()
                .filter(|&&neighbour| neighbour)
                .count()
                < 4
        })
}

fn parse(input: &str) -> Vec<Vec<bool>> {
    input
        .lines()
        .map(|line| line.chars().map(|c| c == '@').collect())
        .collect()
}