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use rand::Rng;
pub fn generate(rng: &mut rand::rngs::ThreadRng) -> String {
loop {
let first = rng.gen_range(1..=9);
let mut digits: Vec<u8> = vec![first];
for _ in 0..6 {
digits.push(rng.gen_range(0..=9));
}
let mut sum: u32 = 0;
for (i, &d) in digits.iter().enumerate() {
sum += (8 - i as u32) * d as u32;
}
let r = sum % 11;
if r == 0 || r == 1 {
continue;
} // Both result in invalid SI numbers according to stdnum
let check = 11 - r;
// check will be 2..9
digits.push(check as u8);
let s: String = digits.iter().map(|d| (b'0' + d) as char).collect();
return format!("SI{}", s);
}
}
pub fn validate(code: &str) -> bool {
let clean: String = if let Some(stripped) = code.strip_prefix("SI") {
stripped.to_string()
} else {
code.chars().filter(|c| c.is_ascii_digit()).collect()
};
if clean.len() != 8 || !clean.chars().all(|c| c.is_ascii_digit()) || clean.starts_with('0') {
return false;
}
let digits: Vec<u8> = clean.bytes().map(|b| b - b'0').collect();
let mut sum: u32 = 0;
for (i, &d) in digits[..7].iter().enumerate() {
sum += (8 - i as u32) * d as u32;
}
let r = sum % 11;
if r == 0 || r == 1 {
return false;
}
let expected = 11 - r;
expected == digits[7] as u32
}