use itertools::Itertools;

pub fn process_part_1(input: &str) -> usize {
    let trees = parse_trees(input);

    let rows = trees.len();
    let cols = trees[0].len();
    (0..rows)
        .cartesian_product(0..cols)
        .filter(|&(row, col)| {
            let height = trees[row][col];
            (0..row).all(|i| trees[i][col] < height) // up
                || (row + 1..rows).all(|i| trees[i][col] < height) // down
                || (0..col).all(|i| trees[row][i] < height) // left
                || (col + 1..cols).all(|i| trees[row][i] < height) // right
        })
        .count()
}

pub fn process_part_2(input: &str) -> usize {
    let trees = parse_trees(input);
    let rows = trees.len();
    let cols = trees[0].len();
    (0..rows)
        .cartesian_product(0..cols)
        .map(|(row, col)| {
            let height = trees[row][col];

            let up = match (0..row).rev().position(|i| trees[i][col] >= height) {
                Some(n) => n + 1,
                None => row,
            };
            let down = match (row + 1..rows).position(|i| trees[i][col] >= height) {
                Some(n) => n + 1,
                None => rows - row - 1,
            };
            let left = match (0..col).rev().position(|i| trees[row][i] >= height) {
                Some(n) => n + 1,
                None => col,
            };
            let right = match (col + 1..cols).position(|i| trees[row][i] >= height) {
                Some(n) => n + 1,
                None => cols - col - 1,
            };

            up * down * left * right
        })
        .max()
        .unwrap()
}

fn parse_trees(input: &str) -> Vec<Vec<u8>> {
    input
        .trim()
        .split('\n')
        .map(|i| i.chars().map(|c| c.to_digit(10).unwrap() as u8).collect())
        .collect()
}

#[cfg(test)]
mod tests {
    use super::*;

    const INPUT: &str = "30373
25512
65332
33549
35390";

    #[test]
    fn day1() {
        assert_eq!(process_part_1(INPUT), 21);
    }

    #[test]
    fn day2() {
        assert_eq!(process_part_2(INPUT), 8);
    }
}