fodselsnummer.py

"""Functions for validation and generation of Norwegian fødselsnumbers"""

import re
from datetime import date, datetime
from typing import Callable, Literal, Optional

from dateutil.relativedelta import relativedelta

FNR_REGEX = re.compile(r'\d{11}')


class FodselsnummerException(Exception):
    pass


class InvalidControlDigitException(FodselsnummerException):
    pass


def validate_fnr(fnr: str, d_numbers=True, h_numbers=False) -> Literal[True]:
    """
    Check if a number is a valid fødselsnumber.
    Args:
        fnr: A string containing the fodselsnummer to check
        h_numbers: False (the default) if h-numbers should be accepted
        d_numbers: True (the default) if d-numbers should be accepted
    Returns:
        True if it is a valid fodselsnummer, False otherwise.
    """
    if not FNR_REGEX.match(fnr):
        raise ValueError('Fødselsnumber does not match regex \\d{11}')

    individual_number = int(fnr[6:9])
    day, month, year = int(fnr[0:2]), int(fnr[2:4]), int(fnr[4:6])
    if 41 <= day <= 71:  # if D-number
        if not d_numbers:
            raise ValueError('Fødselsnumber is a D-number (or day out of range)')
        day -= 40

    if not (1 <= day <= 31):
        raise ValueError('Day out of range in fødselsnumber')
    if 41 <= month <= 52:  # if H-number
        if h_numbers:
            month -= 40
        else:
            raise ValueError('Fødselsnumber is a H-number (or month out of range)')
    if not 1 <= month <= 12:
        raise ValueError('Month out of range in fødselsnumber')
    if individual_number <= 499:  # individual numbers 000-499 indicate person is born in 19XX
        year += 1900
    else:
        year += 2000
    if individual_number >= 900 and year >= 2040:
        year -= 100
    dob: Optional[date] = None
    try:
        dob = date(year=year, month=month, day=day)
        if dob > date.today():
            raise ValueError('Date of fødselsnumber is larger than current date')
    except ValueError:
        raise ValueError(f'{year}-{month}-{day} is not a valid date')

    try:
        generatedfnr = _generate_control_digits(fnr[0:9])
    except InvalidControlDigitException:
        raise ValueError('Control digit does not match fødselsnumber')

    if not bool(fnr == generatedfnr):
        raise ValueError('Control digit does not match fødselsnumber')
    return True


def check_fnr(fnr: str, d_numbers=True, h_numbers=False, logger: Callable = lambda _x: None) -> bool:
    """
    Check if a number is a valid fødselsnumber.
    Args:
        fnr: A string containing the fodselsnummer to check
        h_numbers: False (the default) if h-numbers should be accepted
        d_numbers: True (the default) if d-numbers should be accepted
        logger: A function used to log things
    Returns:
        True if it is a valid fodselsnummer, False otherwise.
    """
    try:
        return validate_fnr(fnr=fnr, d_numbers=d_numbers, h_numbers=h_numbers)
    except ValueError as e:
        logger(str(e))
        return False


def generate_fnr_for_year(year, d_numbers):
    """
    Generates all the possible fødselsnumbers for a year.

    Args:
        year: The year to generate fodselsnummers for (integer)
        d_numbers: True if you want d-numbers as well, False otherwise.
    Returns:
        A list with all the possible fodselsnummers for that year.
    """
    allfnrs = []
    startdate = date(year, 1, 1)
    enddate = date(year, 12, 31)
    delta = enddate - startdate
    for i in range(delta.days + 1):
        allfnrs += generate_fnr_for_day(startdate + td(days=i), d_numbers)
    return allfnrs


def generate_fnr_for_day(day, d_numbers):
    """
    Generates all the possible fødselsnumbers for a day.

    Args:
        day: The day to generate fodslesnummers for (datetime)
        d_numbers: True if you want d-numbers as well, False otherwise.
    Returns:
        A list with all the possible fodselsnummers for that day.
    """
    thisdaysfnr = []
    stupid1900s = False
    datestring = day.strftime('%d%m%y')
    if d_numbers:
        dnrdatestring = str(int(datestring[0]) + 4) + datestring[1:]
    # ref:
    # http://www.kith.no/upload/5588/KITH1001-2010_Identifikatorer-for-personer_v1.pdf
    # Does not account for the 1800s, since this is for living persons
    # (this means that the 1800s list will be a little longer than necessary)
    if 1900 <= day.year <= 1999:
        individualmin = 000
        individualmax = 499
        if 1940 <= day.year <= 1999:
            stupid1900s = True
    else:
        individualmin = 500
        individualmax = 999
    for x in range(individualmin, individualmax + 1):
        individualnr = str(x).zfill(3)
        try:
            thisdaysfnr.append(_generate_control_digits(datestring + individualnr))
        except InvalidControlDigitException:
            pass
        if d_numbers:
            try:
                thisdaysfnr.append(_generate_control_digits(dnrdatestring + individualnr))
            except InvalidControlDigitException:
                pass
    # Bonus round because of the stupid 1900s
    if stupid1900s:
        for x in range(900, 1000):
            individualnr = str(x).zfill(3)
            try:
                thisdaysfnr.append(_generate_control_digits(datestring + individualnr))
            except InvalidControlDigitException:
                pass
            if d_numbers:
                try:
                    thisdaysfnr.append(_generate_control_digits(dnrdatestring + individualnr))
                except InvalidControlDigitException:
                    pass
    return thisdaysfnr


def _generate_control_digits(numbersofar):
    """Generates the magic control digits in a fødselsnumber"""
    staticnumbers1 = [3, 7, 6, 1, 8, 9, 4, 5, 2, 1]
    staticnumbers2 = [5, 4, 3, 2, 7, 6, 5, 4, 3, 2, 1]
    sum1 = 0
    for x in range(0, 9):
        sum1 += int(numbersofar[x]) * staticnumbers1[x]
    rest = sum1 % 11
    if rest == 0:
        control1 = 0
    else:
        if 11 - rest != 10:
            control1 = 11 - rest
        else:
            raise InvalidControlDigitException
    numbersofar += str(control1)
    sum2 = 0
    for x in range(0, 10):
        sum2 += int(numbersofar[x]) * staticnumbers2[x]
    rest = sum2 % 11
    if rest == 0:
        control2 = 0
    else:
        if 11 - rest != 10:
            control2 = 11 - rest
        else:
            raise InvalidControlDigitException
    numbersofar += str(control2)
    return numbersofar

"""
The national identity number consists of 11 digits.
The first six digits represent the date of birth in the order day, month, year.
The next three digits are an individual number, the third digit of which indicates gender
– even numbers for women and odd numbers for men. The last two digits are control digits.

Source: https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Norway-TIN.pdf
"""
def get_age(fnr: str) -> int:
    validate_fnr(fnr=fnr, d_numbers=True, h_numbers=True)

    day, month, year, individual_number = int(fnr[0:2]), int(fnr[2:4]), int(fnr[4:6]), int(fnr[6:9])

    if 41 <= day <= 71:  # if D-number
        day -= 40
    if not (1 <= day <= 31):
        raise ValueError('Day out of range in fødselsnumber')

    if 41 <= month <= 52:  # if H-number
        month -= 40
    if not 1 <= month <= 12:
        raise ValueError('Month out of range in fødselsnumber')

    """
    born 1854-1899: allocated from series 749-500
    born 1900-1999: allocated from series 499-000
    born 1940-1999: also allocated from series 999-900
    born 2000-2039: allocated from series 999-500

    Source: https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Norway-TIN.pdf
    """
    if individual_number <= 499:  # individual numbers 000-499 indicate person is born in 19XX
        year += 1900
    else:
        year += 2000
    if individual_number >= 900 and year >= 2040:
        year -= 100

    birth_date = date(year, month, day)
    now_date = datetime.now().date()

    return relativedelta(now_date, birth_date).years


def get_date_of_birth(fnr: str, d_numbers=True, h_numbers=False) -> date:
    """
    Extracts date of birth from a valid fødselsnumber.
    Args:
        fnr: fodselsnummer to check
        h_numbers: False (the default) if h-numbers should be accepted
        d_numbers: True (the default) if d-numbers should be accepted
    Returns:
        returns date of birth of type date
    """

    validate_fnr(fnr=fnr, d_numbers=d_numbers, h_numbers=h_numbers)

    individual_number = int(fnr[6:9])
    day, month, year = int(fnr[0:2]), int(fnr[2:4]), int(fnr[4:6])
    if 41 <= day <= 71:  # if D-number
        if not d_numbers:
            raise ValueError('Fødselsnumber is a D-number (or day out of range)')
        day -= 40

    if not (1 <= day <= 31):
        raise ValueError('Day out of range in fødselsnumber')

    if 41 <= month <= 52:  # if H-number
        if h_numbers:
            month -= 40
        else:
            raise ValueError('Fødselsnumber is a H-number (or month out of range)')
    if not 1 <= month <= 12:
        raise ValueError('Month out of range in fødselsnumber')
    if individual_number <= 499:  # individual numbers 000-499 indicate person is born in 19XX
        year += 1900
    else:
        year += 2000
    if individual_number >= 900 and year >= 2040:
        year -= 100

    return date(year=year, month=month, day=day)