use crate::days::Solution;

pub struct Day01;

impl Solution for Day01 {
    type Input = Vec<i16>;

    fn parse(&self, data: &str) -> Self::Input {
        data.split("\n")
            .filter_map(|l| {
                let mut chars = l.chars();
                let first = chars.next();
                let num = chars.collect::<String>().parse::<i16>();

                match (first, num) {
                    (Some('L'), Ok(n)) => Some(-1 * n),
                    (Some('R'), Ok(n)) => Some(n),
                    _ => None,
                }
            })
            .collect()
    }

    fn part1(&self, input: &Self::Input) -> usize {
        input
            .iter()
            .fold((50, 0), |(sum, res), x| match (sum + x) % 100 {
                0 => (0, res + 1),
                newsum => (newsum, res),
            })
            .1
    }

    fn part2(&self, input: &Self::Input) -> usize {
        input
            .iter()
            .fold((50, 0), |(pointer, res), x| {
                let new_pointer = (pointer + x).rem_euclid(100);
                let rem_x = x % 100;
                (
                    (pointer + x).rem_euclid(100),
                    res + (x / 100).abs()
                        + if (pointer != 0 && pointer + rem_x != new_pointer)
                            || pointer + rem_x == 0
                        {
                            1
                        } else {
                            0
                        },
                )
            })
            .1 as usize
    }
}