use std::fs;

fn read_file(file : &str) -> String {
    fs::read_to_string(file).unwrap()
}

fn required_fuel(mass : u32) -> u32 {
    (mass / 3).saturating_sub(2)
}

fn required_fuel_with_fuel(mass : u32) -> u32 {
    let mut total = 0;
    let mut current = mass;
    loop {
        current = required_fuel(current);
        total += current;
        if current == 0 {
            break;
        }
    }
    total
}

fn day1() {
    let input = read_file("input1");
    let sum : u32 = input.split('\n')
                      .filter(|x| !x.is_empty())
                      .map(|x| x.parse::<u32>().unwrap())
                      .map(|x| required_fuel(x))
                      .sum();
    println!("1a: {}", sum);

    let sum2 : u32 = input.split('\n')
                         .filter(|x| !x.is_empty())
                         .map(|x| x.parse::<u32>().unwrap())
                         .map(|x| required_fuel_with_fuel(x))
                         .sum();
    println!("1b: {}", sum2);
}

fn main() {
    day1();
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_day1() {
        assert_eq!(required_fuel(12), 2);
        assert_eq!(required_fuel(14), 2);
        assert_eq!(required_fuel(1969), 654);
        assert_eq!(required_fuel(100756), 33583);

        assert_eq!(required_fuel_with_fuel(14), 2);
        assert_eq!(required_fuel_with_fuel(1969), 966);
        assert_eq!(required_fuel_with_fuel(100756), 50346);
    }
}