use std::fs;
use std::path::Path;
use std::collections::HashSet;

/* AOC21 Day 13: https://adventofcode.com/2021/day/13 */
fn main() {
    let input = Path::new("resources").join("input.txt");
    let content = fs::read_to_string(input).expect("Unable to read input file");
    let (points,instructions) = content.split_once("\n\n").expect("Malformed input");
    let points: HashSet<(u32,u32)> = points.lines().map(|l| {
        let (x,y) = l.split_once(',').expect("Malformed input");
        (x.parse().unwrap(),y.parse().unwrap())
    }).collect();
    let instructions: Vec<(bool,u32)> = instructions.lines().map(|l| {
        let (axis,idx) = l.split_whitespace()
                          .nth(2).expect("Malformed input")
                          .split_once('=').expect("Malformed input");
        (axis=="x", idx.parse().unwrap())
    }).collect();
    ex1(points.clone(), instructions[0]);
    ex2(points, &instructions);
}

fn ex1(points: HashSet<(u32,u32)>, instruction: (bool,u32)) {
    println!("Ex1: The result is {}", fold(points, instruction).len());
}

fn ex2(points: HashSet<(u32,u32)>, instructions: &[(bool,u32)]) {
    let code = instructions.iter().fold(points, |ps,i| fold(ps, *i));
    let code = {
        let x_max = 1 + code.iter().map(|(x,_)| *x).max().unwrap() as usize;
        let y_max = 1 + code.iter().map(|(_,y)| *y).max().unwrap() as usize;
        code.iter().fold(vec![vec![" ";x_max];y_max], |mut c, (x,y)| { c[*y as usize][*x as usize] = "█"; c })
    };
    println!("Ex2: The result is");
    code.iter().for_each(|row| println!("{}", row.join("")));
}

fn fold(mut points: HashSet<(u32,u32)>, instruction: (bool,u32)) -> HashSet<(u32,u32)> {
    let (x_axis, idx) = instruction;
    if x_axis {
        points.drain().map(|(x,y)| if x > idx { (2*idx - x, y) } else { (x,y) }).collect()
    } else {
        points.drain().map(|(x,y)| if y > idx { (x, 2*idx - y) } else { (x,y) }).collect()
    }
}