use crate::solvers::Solver;
use std::io::BufRead;

pub struct Lobby {}

impl Lobby {
    const PART1_MAX_BATTERIES: usize = 2;
    const PART2_MAX_BATTERIES: usize = 12;

    fn largest_joltage(bank: &str, max_batteries: usize) -> u64 {
        let mut best = vec![0_u8; max_batteries];
        for (i, d) in bank.bytes().map(|c| c - '0' as u8).enumerate() {
            let mut fill_index = max_batteries;
            let skip = (max_batteries + i).saturating_sub(bank.len());
            for (j, b) in best.iter_mut().skip(skip).enumerate() {
                if *b < d {
                    *b = d;
                    fill_index = j + 1 + skip;
                    break;
                }
            }
            best[fill_index..].fill(0);
        }
        u64::from(best.iter().fold(0, |acc: u64, &x| acc * 10 + u64::from(x)))
    }
}

impl Solver for Lobby {
    const PUZZLE_INDEX: u8 = 3;
    const PUZZLE_NAME: &'static str = "Lobby";

    fn process_data<R: BufRead>(&self, reader: R) -> (u64, u64) {
        let mut joltages = (0, 0);
        for line in reader.lines().map_while(Result::ok) {
            joltages.0 += Self::largest_joltage(&line, Self::PART1_MAX_BATTERIES);
            joltages.1 += Self::largest_joltage(&line, Self::PART2_MAX_BATTERIES);
        }
        joltages
    }
}