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use crate::bank_account::checksum::luhn_check_digit;
use rand::Rng;
const FIRST_CHARS: &[u8] = b"ABCDEFGHJNPQRSUVW";
const CHECK_LETTERS: &[u8; 10] = b"JABCDEFGHI";
/// CIF (Spanish company tax number) - 9 chars: letter + 7 digits + check (digit or letter).
/// stdnum: Luhn on digits 1-7, check = both numeric and letter forms accepted.
pub fn generate(rng: &mut rand::rngs::ThreadRng) -> String {
let letter = FIRST_CHARS[rng.gen_range(0..FIRST_CHARS.len())] as char;
let digits: Vec<u8> = (0..7).map(|_| rng.gen_range(0..=9)).collect();
let check = luhn_check_digit(&digits);
// Use letter check for certain entity types, numeric for others
let check_char = if b"NPQRSW".contains(&(letter as u8)) {
CHECK_LETTERS[check as usize] as char
} else {
(b'0' + check) as char
};
let s: String = digits.iter().map(|d| (b'0' + d) as char).collect();
format!("{}{}{}", letter, s, check_char)
}
pub fn validate(code: &str) -> bool {
let clean: String = code.chars().filter(|c| c.is_ascii_alphanumeric()).collect();
if clean.len() != 9 {
return false;
}
let bytes = clean.as_bytes();
let first = bytes[0];
if !FIRST_CHARS.contains(&first) {
return false;
}
// Middle 7 must be digits
let mid = &clean[1..8];
if !mid.chars().all(|c| c.is_ascii_digit()) {
return false;
}
let digits: Vec<u8> = mid.bytes().map(|b| b - b'0').collect();
let check = luhn_check_digit(&digits);
let last = bytes[8];
// Accept either numeric or letter check digit
last == b'0' + check || last == CHECK_LETTERS[check as usize]
}