use rand::Rng;
pub fn generate(rng: &mut rand::rngs::ThreadRng) -> String {
let len = rng.gen_range(2..=9);
let mut body: Vec<u8> = (0..len).map(|_| rng.gen_range(0..=9)).collect();
if body[0] == 0 {
body[0] = rng.gen_range(1..=9);
}
let mut padded = vec![0u8; 9 - body.len()];
padded.extend_from_slice(&body);
let weights = [7u32, 5, 3, 2, 1, 7, 5, 3, 2];
let sum: u32 = padded
.iter()
.zip(weights.iter())
.map(|(&d, &w)| d as u32 * w)
.sum();
let check = ((10 * sum) % 11 % 10) as u8;
body.push(check);
body.iter().map(|d| (b'0' + d) as char).collect()
}
pub fn validate(code: &str) -> bool {
let clean: String = if let Some(stripped) = code.strip_prefix("RO") {
stripped.to_string()
} else {
code.chars().filter(|c| c.is_ascii_digit()).collect()
};
if clean.len() < 2 || clean.len() > 10 || !clean.chars().all(|c| c.is_ascii_digit()) {
return false;
}
let digits: Vec<u8> = clean.bytes().map(|b| b - b'0').collect();
if digits[0] == 0 {
return false;
}
let len = digits.len();
let body = &digits[..len - 1];
let mut padded = vec![0u8; 9 - body.len()];
padded.extend_from_slice(body);
let weights = [7u32, 5, 3, 2, 1, 7, 5, 3, 2];
let sum: u32 = padded
.iter()
.zip(weights.iter())
.map(|(&d, &w)| d as u32 * w)
.sum();
let expected = ((10 * sum) % 11 % 10) as u8;
expected == digits[len - 1]
}