use crate::common;
use crate::common::Number;
use std::io::{BufReader, Read};
use std::ops::Rem;

pub(crate) fn run<R: Read>(read: R) {
    let mut reader = BufReader::new(read).bytes().peekable();

    let mut total = 0;
    while let Some((result, parts)) = common::read_input_line(&mut reader) {
        if let Some(ops) = brute(result, &parts) {
            println!("{:?} & {:?} => {}", ops, parts, result);
            total += result;
        }
    }

    println!("Result: {}", total);
}

fn brute(result: Number, parts: &[Number]) -> Option<Vec<char>> {
    match parts.split_last() {
        None => None,
        Some((last, [])) => {
            if result == *last {
                Some(vec![])
            } else {
                None
            }
        }
        Some((cur, parts)) => {
            let test_result = result - cur;
            if let Some(mut ops) = brute(test_result, parts) {
                ops.push('+');
                return Some(ops);
            }
            let test_result = result / cur;
            if result.rem(cur) == 0 && let Some(mut ops) = brute(test_result, parts) {
                ops.push('*');
                return Some(ops);
            }
            None
        }
    }
}