use rand::Rng;
pub fn generate(rng: &mut rand::rngs::ThreadRng) -> String {
let prefixes = ["20", "23", "24", "27", "30", "33", "34", "50", "51", "55"];
let prefix = prefixes[rng.gen_range(0..prefixes.len())];
let mut digits: Vec<u8> = prefix.bytes().map(|b| b - b'0').collect();
for _ in 0..8 {
digits.push(rng.gen_range(0..=9));
}
let weights = [5, 4, 3, 2, 7, 6, 5, 4, 3, 2];
let sum: u32 = digits
.iter()
.zip(weights.iter())
.map(|(&d, &w)| d as u32 * w as u32)
.sum();
let rem = sum % 11;
let map_chars = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '9', '0'];
let idx = (11 - rem) as usize;
let check_char = map_chars[idx];
let s: String = digits.iter().skip(2).map(|d| (b'0' + d) as char).collect();
format!("{}-{}-{}", prefix, s, check_char)
}
pub fn validate(code: &str) -> bool {
let clean: String = code.chars().filter(|c| c.is_ascii_digit()).collect();
if clean.len() != 11 {
return false;
}
let prefix = &clean[0..2];
if !["20", "23", "24", "27", "30", "33", "34", "50", "51", "55"].contains(&prefix) {
return false;
}
let digits: Vec<u8> = clean.bytes().map(|b| b - b'0').collect();
let weights = [5, 4, 3, 2, 7, 6, 5, 4, 3, 2];
let sum: u32 = digits[..10]
.iter()
.zip(weights.iter())
.map(|(&d, &w)| d as u32 * w as u32)
.sum();
let rem = sum % 11;
let map_chars = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '9', '0'];
let idx = (11 - rem) as usize;
let expected = map_chars[idx] as u32 - '0' as u32;
expected == digits[10] as u32
}