demo/src/checksums.py

from __future__ import annotations

from src.normalize import only_digits, strip_iban


def iran_national_id_ok(value: str) -> bool:
    digits = only_digits(value)
    if len(digits) != 10 or not digits.isdigit():
        return False
    if len(set(digits)) == 1:
        return False
    total = sum(int(digits[index]) * (10 - index) for index in range(9))
    remainder = total % 11
    check = remainder if remainder < 2 else 11 - remainder
    return check == int(digits[9])


def luhn_ok(value: str) -> bool:
    digits = [int(ch) for ch in only_digits(value)]
    if len(digits) < 13 or len(digits) > 19:
        return False
    checksum = 0
    for index, digit in enumerate(reversed(digits)):
        if index % 2 == 1:
            digit *= 2
            if digit > 9:
                digit -= 9
        checksum += digit
    return checksum % 10 == 0


def iban_ok(value: str) -> bool:
    compact = strip_iban(value)
    if len(compact) < 15 or len(compact) > 34:
        return False
    if not compact[:2].isalpha() or not compact[2:4].isdigit():
        return False
    rearranged = compact[4:] + compact[:4]
    numbers = []
    for char in rearranged:
        if char.isdigit():
            numbers.append(char)
        elif char.isalpha():
            numbers.append(str(ord(char) - 55))
        else:
            return False
    try:
        return int("".join(numbers)) % 97 == 1
    except ValueError:
        return False


def make_national_id(rng) -> str:
    for _ in range(80):
        body = "".join(str(rng.randint(0, 9)) for _ in range(9))
        if len(set(body)) == 1:
            continue
        total = sum(int(body[index]) * (10 - index) for index in range(9))
        remainder = total % 11
        check = remainder if remainder < 2 else 11 - remainder
        candidate = f"{body}{check}"
        if iran_national_id_ok(candidate):
            return candidate
    raise RuntimeError("national id generation failed")


def make_luhn(rng, prefix: str = "4111", length: int = 16) -> str:
    body_len = length - 1
    while True:
        rest = "".join(str(rng.randint(0, 9)) for _ in range(body_len - len(prefix)))
        partial = prefix + rest
        for check in range(10):
            candidate = partial + str(check)
            if luhn_ok(candidate):
                return candidate


def make_iban(rng, country: str = "IR") -> str:
    bank = f"{rng.randint(10, 99):02d}{rng.randint(1, 9)}"
    account = f"{rng.randint(1, 10**18 - 1):019d}"
    for check in range(100):
        candidate = f"{country}{check:02d}{bank}{account}"
        if iban_ok(candidate):
            return candidate
    raise RuntimeError("iban generation failed")


def break_national_id(valid: str) -> str:
    digits = list(only_digits(valid))
    digits[-1] = str((int(digits[-1]) + 1) % 10)
    broken = "".join(digits)
    if not iran_national_id_ok(broken):
        return broken
    digits[-2] = str((int(digits[-2]) + 1) % 10)
    return "".join(digits)


def break_luhn(valid: str) -> str:
    digits = list(only_digits(valid))
    digits[-1] = str((int(digits[-1]) + 1) % 10)
    return "".join(digits)


def break_iban(valid: str) -> str:
    compact = strip_iban(valid)
    return compact[:4] + "9" + compact[5:]