# rc.py - functions for handling Czech birth numbers
# coding: utf-8
#
# Copyright (C) 2012 Arthur de Jong
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA

"""Module for handling Czech birth numbers (RČ, Rodné číslo), the Czech
national identifier. The number can be 9 or 10 digits long. Numbers given
out after January 1st 1954 should have 10 digits. The number includes the
birth date of the person and their gender.

>>> compact('710319/2745')
'7103192745'
>>> is_valid('7103192745')
True
>>> is_valid('991231123')
True
>>> is_valid('7103192746')  # invalid check digit
False
>>> is_valid('1103492745')  # invalid date
False
>>> is_valid('590312/123')  # 9 digit number in 1959
False
>>> format('7103192745')
'710319/2745'
"""

import datetime

from stdnum.util import clean


def compact(number):
    """Convert the number to the minimal representation. This strips the
    number of any valid separators and removes surrounding whitespace."""
    return clean(number, ' /').upper().strip()


def get_birth_date(number):
    """Split the date parts from the number and return the birth date."""
    year = 1900 + int(number[0:2])
    # females have 50 added to the month value, 20 is added when the serial
    # overflows (since 2004)
    month = int(number[2:4]) % 50 % 20
    day = int(number[4:6])
    # 9 digit numbers were used until January 1st 1954
    if len(number) == 9:
        if year >= 1980:
            year -= 100
        if year > 1953:
            raise ValueError('No 9 digit birth numbers after 1953.')
    elif year < 1954:
        year += 100
    return datetime.date(year, month, day)


def is_valid(number):
    """Checks to see if the number provided is a valid birth number. This
    checks the length, formatting, embedded date and check digit."""
    try:
        number = compact(number)
    except:
        return False
    if not number.isdigit() or len(number) not in (9, 10):
        return False
    # check if birth date is valid
    try:
        birth_date = get_birth_date(number)
        # TODO: check that the birth date is not in the future
    except ValueError, e:
        return False
    # check the check digit
    if len(number) == 10:
        check = int(number[:-1]) % 11
        # before 1985 the checksum could be 0 or 10
        if birth_date < datetime.date(1985, 1, 1):
            check = check % 10
        return number[-1] == str(check)
    return True


def format(number):
    """Reformat the passed number to the standard format."""
    number = compact(number)
    return number[:6] + '/' + number[6:]