text: # egn.py - functions for handling Bulgarian national identification numbers
  # coding: utf-8
  #
  # Copyright (C) 2012-2015 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
  
  """EGN (ЕГН, Единен граждански номер, Bulgarian personal identity codes).
  
  It is a 10-digit number of which the first 6 digits denote the person's
  birth date, the next three digits represent a birth order number from
  which the person's gender can be determined and the last digit is a check
  digit.
  
  >>> compact('752316 926 3')
  '7523169263'
  >>> validate('8032056031')
  '8032056031'
  >>> get_birth_date('7542011030')
  datetime.date(2075, 2, 1)
  >>> validate('7552A10004')  # invalid digit
  Traceback (most recent call last):
      ...
  InvalidFormat: ...
  >>> validate('8019010008')  # invalid date
  Traceback (most recent call last):
      ...
  InvalidComponent: ...
  """
  
  import datetime
  
  from stdnum.exceptions import *
  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 calc_check_digit(number):
      """Calculate the check digit. The number passed should not have the
      check digit included."""
      weights = (2, 4, 8, 5, 10, 9, 7, 3, 6)
      return str(sum(w * int(n) for w, n in zip(weights, number)) % 11 % 10)
  
  
  def get_birth_date(number):
      """Split the date parts from the number and return the birth date."""
      year = int(number[0:2]) + 1900
      month = int(number[2:4])
      day = int(number[4:6])
      if month > 40:
          year += 100
          month -= 40
      elif month > 20:
          year -= 100
          month -= 20
      try:
          return datetime.date(year, month, day)
      except ValueError:
          raise InvalidComponent()
  
  
  def validate(number):
      """Check if the number is a valid national identification number. This
      checks the length, formatting, embedded date and check digit."""
      number = compact(number)
      if not number.isdigit():
          raise InvalidFormat()
      if len(number) != 10:
          raise InvalidLength()
      # check if birth date is valid
      get_birth_date(number)
      # TODO: check that the birth date is not in the future
      # check the check digit
      if calc_check_digit(number[:-1]) != number[-1]:
          raise InvalidChecksum()
      return number
  
  
  def is_valid(number):
      """Check if the number is a valid national identification number."""
      try:
          return bool(validate(number))
      except ValidationError:
          return False
  