#![feature(iterator_try_collect, iter_collect_into)]

use std::collections::HashSet;
use std::fs;
use std::io::{self, BufRead};

fn main() {
    let filename = "etc/p03.txt";
    let file = fs::File::open(filename).expect("Can't open file");
    let reader = io::BufReader::new(file);

    println!("PART ONE ---------------");
    let lines: Vec<String> = reader
        .lines()
        .try_collect()
        .expect("Expected all lines to be valid");
    part1(&lines);

    println!("\n PART TWO ---------------");
    part2(&lines);
}

fn to_priority(c: char) -> Result<u32, &'static str> {
    if c.is_ascii_uppercase() {
        Ok(c as u32 - 'A' as u32 + 26 + 1)
    } else if c.is_ascii_lowercase() {
        Ok(c as u32 - 'a' as u32 + 1)
    } else {
        Err("Can't convert non-alphanumeric")
    }
}

fn part1(lines: &[String]) {
    let mut sum: u32 = 0;
    let mut left_set = HashSet::<char>::new();
    for line in lines {
        let (left, right) = line.split_at(line.len() / 2);
        left.chars().collect_into(&mut left_set);
        let outlier = right
            .chars()
            .find(|c| left_set.contains(c))
            .expect("Expected at least one duplicate item");

        let priority = to_priority(outlier).unwrap();
        dbg!(outlier, priority);
        sum += priority;

        left_set.clear();
    }

    println!("Sum: {}", sum);
}

fn part2(lines: &[String]) {
    const GROUP_SIZE: usize = 3;
    let mut sets = Vec::with_capacity(GROUP_SIZE - 1);
    for _ in 0..GROUP_SIZE - 1 {
        sets.push(HashSet::<char>::new())
    }

    let mut sum: u32 = 0;
    for chunk in lines.chunks(GROUP_SIZE) {
        for i in 0..GROUP_SIZE - 1 {
            sets[i].clear();
            chunk[i].chars().collect_into(&mut sets[i]);
        }

        let outlier = chunk[GROUP_SIZE - 1]
            .chars()
            .find(|c| sets[0..GROUP_SIZE - 1].iter().all(|s| s.contains(c)))
            .expect("Expect at least one outlier");

        let priority = to_priority(outlier).unwrap();
        dbg!(outlier, priority);
        sum += priority;
    }

    println!("Sum: {}", sum);
}