use std::{collections::HashSet, fs::read_to_string};

fn main() {
    let boxes: Vec<Vec<u64>> = read_to_string("../input.txt")
        .expect("failed to open input file")
        .lines()
        .map(|jbox| {
            jbox.split(',')
                .map(|coord| coord.parse().unwrap())
                .collect()
        })
        .collect();
    let mut distances: Vec<(_, u64)> = boxes
        .iter()
        .enumerate()
        .flat_map(|(i, jbox)| {
            boxes.iter().enumerate().skip(i + 1).map(move |(j, other)| {
                (
                    (i, j),
                    jbox.iter()
                        .zip(other)
                        .map(|(from, to)| from.abs_diff(*to).pow(2))
                        .sum(),
                )
            })
        })
        .collect();
    distances.sort_unstable_by_key(|(_, distance)| *distance);

    let mut circuits: Vec<HashSet<usize>> = Vec::new();
    for ((from, to), _) in distances.into_iter() {
        let from_idx = circuits.iter().position(|circuit| circuit.contains(&from));
        let to_idx = circuits.iter().position(|circuit| circuit.contains(&to));
        match (from_idx, to_idx) {
            (Some(from_idx), Some(to_idx)) if from_idx == to_idx => {}
            (Some(from_idx), Some(to_idx)) => {
                let to_circuit: Vec<_> = circuits[to_idx].drain().collect();
                circuits[from_idx].extend(to_circuit);
                circuits.remove(to_idx);
            }
            (Some(from_idx), None) => {
                circuits[from_idx].insert(to);
            }
            (None, Some(to_idx)) => {
                circuits[to_idx].insert(from);
            }
            (None, None) => circuits.push(HashSet::from([from, to])),
        }

        if circuits[0].len() == boxes.len() {
            let result = boxes[from][0] * boxes[to][0];
            println!(
                "The result of multiplying the x co-ordinates of the last two junction boxes is {result}!"
            );
            break;
        }
    }
}