use rand::Rng;
pub fn generate(rng: &mut rand::rngs::ThreadRng) -> String {
let mut digits: Vec<u8> = (0..8).map(|_| rng.gen_range(0..=9)).collect();
let weights = [8, 9, 4, 5, 6, 7, 8, 9];
let sum: u32 = digits
.iter()
.zip(weights.iter())
.map(|(&d, &w)| d as u32 * w as u32)
.sum();
let check = (sum % 11) as usize;
let check_digit = "01234567891".chars().nth(check).unwrap() as u8 - b'0';
digits.push(check_digit);
digits.iter().map(|d| (b'0' + d) as char).collect()
}
pub fn validate(code: &str) -> bool {
let clean: String = code.chars().filter(|c| c.is_ascii_digit()).collect();
if clean.len() != 9 {
return false;
}
let digits: Vec<u8> = clean.bytes().map(|b| b - b'0').collect();
let weights = [8, 9, 4, 5, 6, 7, 8, 9];
let sum: u32 = digits[..8]
.iter()
.zip(weights.iter())
.map(|(&d, &w)| d as u32 * w as u32)
.sum();
let check_idx = (sum % 11) as usize;
let expected = "01234567891".chars().nth(check_idx).unwrap() as u8 - b'0';
expected == digits[8]
}