use crate::solvers::Solver;
use memchr::{memchr, memchr_iter};
use std::io::BufRead;

pub struct Laboratories {}

impl Laboratories {
    const START_CHAR: u8 = b'S';
    const SPLITTER_CHAR: u8 = b'^';

    fn start_beam(line: &str) -> Vec<u64> {
        let mut beams = vec![0; line.len()];
        if let Some(s) = memchr(Self::START_CHAR, line.as_bytes()) {
            beams[s] = 1;
        }
        beams
    }

    fn split_beams(line: &str, mut beams: Vec<u64>, mut splits: u64) -> (Vec<u64>, u64) {
        for s in memchr_iter(Self::SPLITTER_CHAR, line.as_bytes()) {
            if beams[s] > 0 {
                splits += 1;
                beams[s - 1] += beams[s];
                beams[s + 1] += beams[s];
                beams[s] = 0;
            }
        }
        (beams, splits)
    }
}

impl Solver for Laboratories {
    const PUZZLE_INDEX: u8 = 7;
    const PUZZLE_NAME: &'static str = "Laboratories";

    fn process_data<R: BufRead>(&self, mut reader: R) -> (u64, u64) {
        let line = reader.by_ref().lines().next().unwrap().unwrap();
        let mut beams = Self::start_beam(&line);
        let mut splits = 0;
        for line in reader.lines().map_while(Result::ok) {
            (beams, splits) = Self::split_beams(&line, beams, splits);
        }
        (splits, beams.iter().sum())
    }
}