# 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

"""RČ (Rodné číslo, the Czech birth number).

The birth number (RČ, Rodné číslo) is 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.

This number is identical to the Slovak counterpart.

>>> 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:]