Source code for localflavor.kw.forms

"""
Kuwait-specific Form helpers
"""
from __future__ import unicode_literals

import re
from datetime import date

from django.core.validators import EMPTY_VALUES
from django.forms import ValidationError
from django.forms.fields import Field, Select
from django.utils.translation import gettext_lazy as _

from .kw_governorates import GOVERNORATE_CHOICES

id_re = re.compile(r'''^(?P<initial>\d{1})
                       (?P<yy>\d\d)
                       (?P<mm>\d\d)
                       (?P<dd>\d\d)
                       (?P<mid>\d{4})
                       (?P<checksum>\d{1})''', re.VERBOSE)


class KWCivilIDNumberField(Field):
    """
    Kuwaiti Civil ID numbers are 12 digits, second to seventh digits
    represents the person's birthdate.

    Checks the following rules to determine the validty of the number:
        * The number consist of 12 digits.
        * The birthdate of the person is a valid date.
        * The calculated checksum equals to the last digit of the Civil ID.
    """
    default_error_messages = {
        'invalid': _('Enter a valid Kuwaiti Civil ID number'),
    }

    def has_valid_checksum(self, value):
        weight = (2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2)
        calculated_checksum = 0
        for i in range(11):
            calculated_checksum += int(value[i]) * weight[i]

        remainder = calculated_checksum % 11
        checkdigit = 11 - remainder
        if checkdigit != int(value[11]):
            return False
        return True

    def clean(self, value):
        super(KWCivilIDNumberField, self).clean(value)
        if value in EMPTY_VALUES:
            return ''

        match = re.match(id_re, value)

        if not match:
            raise ValidationError(self.error_messages['invalid'])

        gd = match.groupdict()

        # Fix the dates so that those born
        # in 2000+ pass the validation check
        if int(value[0]) == 3:
            gd['yy'] = '20{}'.format(gd['yy'])
        elif int(value[0]) == 2:
            gd['yy'] = '19{}'.format(gd['yy'])

        try:
            date(int(gd['yy']), int(gd['mm']), int(gd['dd']))
        except ValueError:
            raise ValidationError(self.error_messages['invalid'])

        if not self.has_valid_checksum(value):
            raise ValidationError(self.error_messages['invalid'])

        return value


class KWGovernorateSelect(Select):
    """
    A Select widget that uses a list of Kuwait governorates
    as its choices.
    """
    def __init__(self, attrs=None):
        super(KWGovernorateSelect, self).__init__(attrs,
                                                  choices=GOVERNORATE_CHOICES)