#![feature(test)]
extern crate test;
use aoc2021::common::*;
use fnv::FnvHashMap;
use itertools::Itertools;
use std::collections::HashMap;

const DAY: usize = 5;
type Parsed = Vec<((usize, usize), (usize, usize))>;

fn parse_input(raw: &str) -> Parsed {
    raw.lines()
        .filter_map(|line| line.split_once(" -> "))
        .filter_map(|(c1, c2)| c1.split_once(',').zip(c2.split_once(',')))
        .map(|((x1, y1), (x2, y2))| ((x1.parse().unwrap(), y1.parse().unwrap()), (x2.parse().unwrap(), y2.parse().unwrap())))
        .collect()
}

fn part1(parsed: &Parsed) -> usize {
    let mut map: HashMap<_, _, _> = FnvHashMap::default();
    parsed
        .iter()
        .flat_map(|cs| match cs {
            ((x1, y1), (x2, y2)) if x1 == x2 => (*y1.min(y2)..=*y1.max(y2)).map(|y| (*x1, y)).collect(),
            ((x1, y1), (x2, y2)) if y1 == y2 => (*x1.min(x2)..=*x1.max(x2)).map(|x| (x, *y1)).collect(),
            _ => vec![],
        })
        .for_each(|c| *map.entry(c).or_insert(0) += 1);
    map.values().filter(|&&n| n > 1).count()
}

fn part2(parsed: &Parsed) -> usize {
    let mut map: HashMap<_, _, _> = FnvHashMap::default();
    parsed
        .iter()
        .flat_map(|cs| match cs {
            ((x1, y1), (x2, y2)) if x1 == x2 => (*y1.min(y2)..=*y1.max(y2)).map(|y| (*x1, y)).collect_vec(),
            ((x1, y1), (x2, y2)) if y1 == y2 => (*x1.min(x2)..=*x1.max(x2)).map(|x| (x, *y1)).collect(),
            ((x1, y1), (x2, y2)) if x1 < x2 && y1 < y2 => (*x1..=*x2).zip(*y1..=*y2).collect(),
            ((x1, y1), (x2, y2)) if x1 < x2 && y1 > y2 => (*x1..=*x2).zip((*y2..=*y1).rev()).collect(),
            ((x1, y1), (x2, y2)) if x1 > x2 && y1 < y2 => (*x2..=*x1).rev().zip(*y1..=*y2).collect(),
            ((x1, y1), (x2, y2)) if x1 > x2 && y1 > y2 => (*x2..=*x1).rev().zip((*y2..=*y1).rev()).collect(),
            _ => unreachable!(),
        })
        .for_each(|c| *map.entry(c).or_insert(0) += 1);
    map.values().filter(|&&n| n > 1).count()
}

fn main() {
    let input = parse_input(&read_file(DAY));
    println!("Part 1: {}", part1(&input));
    println!("Part 2: {}", part2(&input));
}

#[cfg(test)]
mod tests {
    use super::*;
    use aoc2021::*;

    const TEST_INPUT: &str = "0,9 -> 5,9
8,0 -> 0,8
9,4 -> 3,4
2,2 -> 2,1
7,0 -> 7,4
6,4 -> 2,0
0,9 -> 2,9
3,4 -> 1,4
0,0 -> 8,8
5,5 -> 8,2";

    test!(part1() == 5);
    test!(part2() == 12);
    bench!(part1() == 5280);
    bench!(part2() == 16716);
    bench_input!(Vec::len => 500);
}