use crate::{Problem, Solution};

pub struct Day04;

impl Problem for Day04 {
    const DAY: u8 = 4;

    const INPUT: &'static str = include_str!("../input/day_04.txt");
}

impl Solution for Day04 {
    type Answer1 = usize;

    type Answer2 = usize;

    fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
        let scores = input
            .trim()
            .split('\n')
            .map(parse_score)
            .collect::<Result<Vec<_>, _>>()?;

        Ok(scores
            .into_iter()
            .filter(|n| n > &0)
            .map(|n| 2usize.pow(n as u32 - 1))
            .sum())
    }

    fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
        let scores = input
            .trim()
            .split('\n')
            .map(parse_score)
            .collect::<Result<Vec<_>, _>>()?;

        let cards = &mut vec![0usize; scores.len()];

        for card in 0..scores.len() {
            add_copy(cards, &scores, card)
        }

        Ok(cards.iter().sum())
    }
}

fn add_copy(cards: &mut Vec<usize>, scores: &[usize], card: usize) {
    cards[card] += 1;

    for card in card + 1..cards.len().min(card + scores[card] + 1) {
        add_copy(cards, scores, card);
    }
}

fn parse_score(s: &str) -> anyhow::Result<usize> {
    let (winning, numbers) = s
        .trim()
        .split_once(':')
        .ok_or(anyhow::format_err!("Invalid card format: {s}"))?
        .1
        .trim()
        .split_once('|')
        .ok_or(anyhow::format_err!("Invalid card format: {s}"))?;

    let winning_set = winning
        .split_whitespace()
        .map(std::str::FromStr::from_str)
        .collect::<Result<Vec<usize>, _>>()?;

    Ok(numbers
        .split_whitespace()
        .map(std::str::FromStr::from_str)
        .collect::<Result<Vec<usize>, _>>()?
        .into_iter()
        .filter(|n| winning_set.contains(n))
        .count())
}

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

    #[test]
    fn test_part_1() -> anyhow::Result<()> {
        const INPUT: &str = indoc::indoc! {"
            Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
            Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
            Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
            Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
            Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
            Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
        "};

        Ok(assert_eq!(13, Day04::part_1(INPUT)?))
    }

    #[test]
    fn test_part_2() -> anyhow::Result<()> {
        const INPUT: &str = indoc::indoc! {"
            Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
            Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
            Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
            Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
            Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
            Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
        "};

        Ok(assert_eq!(30, Day04::part_2(INPUT)?))
    }
}