"""Israeli-specific form helpers."""
import re

from django.core.exceptions import ValidationError
from django.core.validators import EMPTY_VALUES
from django.forms.fields import Field, RegexField
from django.utils.translation import gettext_lazy as _
from stdnum import luhn

id_number_re = re.compile(r'^(?P<number>\d{1,8})-?(?P<check>\d)$')


class ILPostalCodeField(RegexField):
    """
    A form field that validates its input as an Israeli postal code.

    Valid form is XXXXX where X represents integer.
    """

    default_error_messages = {
        'invalid': _('Enter a postal code in the format XXXXXXX (or XXXXX) - digits only'),
    }

    def __init__(self, **kwargs):
        super().__init__(r'^\d{5}$|^\d{7}$', **kwargs)

    def clean(self, value):
        if value not in self.empty_values:
            value = value.replace(' ', '')
        return super().clean(value)


class ILIDNumberField(Field):
    """
    A form field that validates its input as an Israeli identification number.

    Valid form is per the Israeli ID specification.

    Israeli ID numbers consist of up to 8 digits followed by a checksum digit.
    Numbers which are shorter than 8 digits are effectively left-zero-padded.
    The checksum digit is occasionally separated from the number by a hyphen,
    and is calculated using the luhn algorithm.

    Relevant references (in Hewbrew):

    http://he.wikipedia.org/wiki/%D7%9E%D7%A1%D7%A4%D7%A8_%D7%96%D7%94%D7%95%D7%AA_(%D7%99%D7%A9%D7%A8%D7%90%D7%9C)
    http://he.wikipedia.org/wiki/%D7%A1%D7%A4%D7%A8%D7%AA_%D7%91%D7%99%D7%A7%D7%95%D7%A8%D7%AA
    http://he.wikipedia.org/wiki/%D7%A7%D7%99%D7%93%D7%95%D7%9E%D7%AA_%D7%98%D7%9C%D7%A4%D7%95%D7%9F_%D7%91%D7%99%D7%A9%D7%A8%D7%90%D7%9C#.D7.A7.D7.99.D7.93.D7.95.D7.9E.D7.95.D7.AA_.D7.91.D7.99.D7.A9.D7.A8.D7.90.D7.9C_.D7.9C.D7.A4.D7.99_.D7.9E.D7.A4.D7.A2.D7.99.D7.9C.D7.99.D7.9D_.D7.95.D7.97.D7.9C.D7.95.D7.A7.D7.94_.D7.92.D7.90.D7.95.D7.92.D7.A8.D7.A4.D7.99.D7.AA
    """

    default_error_messages = {
        'invalid': _('Enter a valid ID number.'),
    }

    def clean(self, value):
        value = super().clean(value)

        if value in EMPTY_VALUES:
            return ''

        match = id_number_re.match(value)
        if not match:
            raise ValidationError(self.error_messages['invalid'], code='invalid')

        value = match.group('number') + match.group('check')
        if not luhn.is_valid(value):
            raise ValidationError(self.error_messages['invalid'], code='invalid')
        return value