const PHONE_MASK: &str = "(___) ___-____";
const ZERO: u8 = '0' as u8;

fn create_phone_number(numbers: &[u8]) -> String {
    let mut position = 0;
    PHONE_MASK
        .chars()
        .map(|c| match c {
            '_' => {
                let c = (numbers[position] + ZERO) as char;
                position += 1;
                c
            }
            c => c,
        })
        .collect()
}

#[test]
fn returns_expected() {
    assert_eq!(
        create_phone_number(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]),
        "(123) 456-7890"
    );
    assert_eq!(
        create_phone_number(&[1, 1, 1, 1, 1, 1, 1, 1, 1, 1]),
        "(111) 111-1111"
    );
    assert_eq!(
        create_phone_number(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 9]),
        "(123) 456-7899"
    );
}