#![feature(iterator_repeat_with)]

use std::iter;

fn rotating_window_sums<'a>(
    values: &'a [i32],
    size: usize,
) -> impl Iterator<Item = (i32, i32)> + 'a {
    let mut numbers = values.iter().cycle();
    let other_size = values.len() - size;

    iter::repeat_with(move || {
        let sum1: i32 = numbers.by_ref().take(size).sum();
        let sum2: i32 = numbers.by_ref().take(other_size).sum();

        // Skip one so the next iteration is offset by one
        numbers.next();

        (sum1, sum2)
    }).take(values.len())
}

fn main() {
    let d = [1, 2, 3, 4, 5, 6, 7, 8];

    let max = rotating_window_sums(&d, 3)
        .map(|(sum1, sum2)| i32::abs(3 * sum1 + 5 * sum2))
        .max();

    println!("{:?}", max);
}