use cached::proc_macro::cached;
use nom::{
    bytes::complete::tag,
    character::complete::u32 as nom_u32,
    combinator::map,
    sequence::{preceded, tuple},
    IResult,
};
use std::fs;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let input = fs::read_to_string("inputs/day_21.txt")?;
    let player_positions = parse_starting_positions(&input).unwrap().1;
    {
        let mut player_positions = player_positions.clone();
        let mut player_scores = [0, 0];
        let mut dice = (1..=100).cycle().enumerate().peekable();
        let mut player_turn = 0;
        while player_scores[0] < 1000 && player_scores[1] < 1000 {
            let dice_roll: u32 = dice.by_ref().take(3).map(|(_, roll)| roll).sum();
            player_positions[player_turn] = (player_positions[player_turn] + dice_roll) % 10;
            if player_positions[player_turn] == 0 {
                player_positions[player_turn] = 10;
            }
            player_scores[player_turn] += player_positions[player_turn];
            player_turn = (player_turn + 1) % 2;
        }
        let losing_score = player_scores.iter().min().cloned().unwrap_or(0);
        let dice_roll_count = dice.peek().unwrap().0;
        dbg!((losing_score, dice_roll_count));
        dbg!(losing_score * dice_roll_count as u32);
    }

    let win_counts = player_win_counts(player_positions, [0, 0]);
    dbg!(win_counts);
    dbg!(win_counts.into_iter().max().unwrap_or(0));
    Ok(())
}

#[cached]
fn player_win_counts(player_positions: [u32; 2], player_scores: [u32; 2]) -> [u64; 2] {
    let mut win_counts = [0; 2];
    for dice_roll_1 in 1..=3 {
        for dice_roll_2 in 1..=3 {
            for dice_roll_3 in 1..=3 {
                let dice_roll = dice_roll_1 + dice_roll_2 + dice_roll_3;
                let mut new_position = (player_positions[0] + dice_roll) % 10;
                if new_position == 0 {
                    new_position = 10;
                }
                let new_score = player_scores[0] + new_position;
                if new_score >= 21 {
                    win_counts[0] += 1;
                } else {
                    let recursive_wins = player_win_counts(
                        [player_positions[1], new_position],
                        [player_scores[1], new_score],
                    );
                    win_counts[0] += recursive_wins[1];
                    win_counts[1] += recursive_wins[0];
                }
            }
        }
    }
    win_counts
}

fn parse_starting_positions(input: &str) -> IResult<&str, [u32; 2]> {
    map(
        tuple((
            preceded(tag("Player 1 starting position: "), nom_u32),
            preceded(tag("\nPlayer 2 starting position: "), nom_u32),
        )),
        |(a, b)| [a, b],
    )(input)
}