struct Arguments {
    // milli-dollars ( $15 = 15000)
    starting_value: i64,
    // milli-dollars
    contrib: i64,
    // percentage in milli-percent ( 13% = 13_000, 100% = 100_000 )
    apr: i64,
    // deci-cents and milli-percent gives us a maximum balance near 922 billion dollars before we overflow
    contrib_years: usize,
    // deci-cents
    withdraw_amount: i64
}

struct Balance {
    // deci-cents
    value: i64
}

fn main() {
    let args = Arguments {
        starting_value: 16000_00_0,
        contrib: 1200_00_0,
        apr: 5_000,
        contrib_years: 20,
        withdraw_amount: 7100_00_0,
    };

    let months = args.contrib_years * 12;
    let mpr = args.apr/12;
    println!("Final monthly milli percentage is {}", mpr);

    let mut balance = Balance {
        value: args.starting_value
    };

    let mut year = 0;
    for i in 1..months+1 {
        // apply last months percentage first
        let interest = (balance.value * mpr) / 1_00_000;
        // add this months contribution
        let new = balance.value + interest + args.contrib;
        //println!("{}. Increase by {} and contribute {} makes about {}.", i, interest as f64 / 1000f64, args.contrib as f64 / 1000f64, new as f64 / 1000f64);
        balance.value = new;

        if i % 12 == 0 {
            println!("Year {} : ${}.{}", i/12, balance.value / 1000, balance.value%1000);
        }
    }

    println!("Max balance is ${}.{}", balance.value / 1000, balance.value%1000);

    // start burn down
}