use std::io::{self, Read};

type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;

fn get_input_string() -> io::Result<String> {
    let mut buffer = String::new();
    io::stdin().read_to_string(&mut buffer)?;
    Ok(buffer)
}

fn main() -> Result<()> {
    let program: Vec<_> = get_input_string()?
        .trim()
        .split(",")
        .filter(|s| !s.is_empty())
        .map(|n| n.parse::<usize>().unwrap())
        .collect();
    part1(&program);
    part2(&program);
    Ok(())
}

fn part1(program: &Vec<usize>) {
    let data = run_program(12, 2, program.clone());
    println!("Part 1: {}", data[0]);
}

fn part2(program: &Vec<usize>) {
    const GOAL: usize = 19690720;
    for noun in 0..=99 {
        for verb in 0..=99 {
            let data = run_program(noun, verb, program.clone());
            if data[0] == GOAL {
                println!("Part 2: noun: {} verb: {} answer: {}", noun, verb, (noun * 100) + verb);
                return;
            }
        }
    }
    println!("could not find a solution");
}

fn run_program(noun: usize, verb: usize, mut program: Vec<usize>) -> Vec<usize> {
    let mut pc = 0;
    program[1] = noun;
    program[2] = verb;

    loop {
        match program[pc] {
            op @ 1 | op @ 2 => {
                let in1 = program[program[pc + 1]];
                let in2 = program[program[pc + 2]];
                let out = program[pc + 3];

                let value = if op == 1 {
                    in1 + in2
                } else {
                    in1 * in2
                };
                program[out] = value;
            }
            99 => break,
            _ => panic!("bad opcode: {}", program[pc]),
        }
        pc += 4;
    }

    program
}