use std::collections::HashSet;
use std::fs;

pub fn run() {
    println!("Day 4:");
    let input = fs::read_to_string("./inputs/day4.txt").expect("Could not read file");

    println!("\tPart 1: {}", part1(&input));
    println!("\tPart 2: {}", part2(&input));
}

struct SectionAssignment {
    left: HashSet<usize>,
    right: HashSet<usize>,
}

fn deserialize(line: &str) -> SectionAssignment {
    let (left, right) = line.split_once(',').unwrap();
    let left = left
        .split_once('-')
        .map(|(l, r)| l.parse().unwrap()..=r.parse().unwrap())
        .unwrap()
        .collect();
    let right = right
        .split_once('-')
        .map(|(l, r)| l.parse().unwrap()..=r.parse().unwrap())
        .unwrap()
        .collect();

    SectionAssignment { left, right }
}

fn part1(input: &str) -> usize {
    let assignments = input.split_whitespace().map(deserialize);
    let mut sum = 0;
    for assignment in assignments {
        if assignment.left.is_subset(&assignment.right)
            || assignment.right.is_subset(&assignment.left)
        {
            sum += 1;
        }
    }
    sum
}

fn part2(input: &str) -> usize {
    let assignments = input.split_whitespace().map(deserialize);
    let mut sum = 0;
    for assignment in assignments {
        if assignment.left.intersection(&assignment.right).count() >= 1 {
            sum += 1;
        }
    }
    sum
}

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

    #[test]
    fn test_1() {
        let input = "2-4,6-8
2-3,4-5
5-7,7-9
2-8,3-7
6-6,4-6
2-6,4-8";

        assert_eq!(part1(input), 2);
    }

    #[test]
    fn test_2() {
        let input = "2-4,6-8
    2-3,4-5
    5-7,7-9
    2-8,3-7
    6-6,4-6
    2-6,4-8";

        assert_eq!(part2(input), 4);
    }
}