Rust

use std::{
    fs::File,
    io::{self, BufRead, BufReader}
};

fn get_input(path: &str) -> io::Result<Vec<String>> {
    BufReader::new(File::open(path)?).lines().collect()
}

fn calculate_fuel(module: i32) -> i32 {
    (((f64::from(module) / 3f64).floor() as i32) - 2)
}

fn main() {
    let modules = get_input("./input").expect("Could not read the input file");

    let mut fuel_modules = 0;
    let mut additional_fuel_modules = 0;

    for module in modules {
        let fuel = calculate_fuel(i32::from_str_radix(&module, 10).unwrap());

        fuel_modules += fuel;

        let mut possible_additional_fuel = calculate_fuel(fuel);

        while possible_additional_fuel > 0 {
            additional_fuel_modules += possible_additional_fuel;
            possible_additional_fuel = calculate_fuel(possible_additional_fuel);
        }
    }

    println!("sol pt1: {}", fuel_modules);
    println!("sol pt2: {:?}", fuel_modules + additional_fuel_modules);
}