"""

Iceland specific form helpers.

"""

from django.forms import ValidationError

from django.forms.fields import RegexField, EMPTY_VALUES

from django.forms.widgets import Select

from django.utils.translation import ugettext_lazy as _

from django.utils.encoding import smart_unicode

class ISIdNumberField(RegexField):

    """

    Icelandic identification number (kennitala). This is a number every citizen

    of Iceland has.

    """

    default_error_messages = {

        'invalid': _('Enter a valid Icelandic identification number. The format is XXXXXX-XXXX.'),

        'checksum': _(u'The Icelandic identification number is not valid.'),

    }

    def __init__(self, *args, **kwargs):

        kwargs['min_length'],kwargs['max_length'] = 10,11

        super(ISIdNumberField, self).__init__(r'^\d{6}(-| )?\d{4}$', *args, **kwargs)

    def clean(self, value):

        value = super(ISIdNumberField, self).clean(value)

        if value in EMPTY_VALUES:

            return u''

        value = self._canonify(value)

        if self._validate(value):

            return self._format(value)

        else:

            raise ValidationError(self.error_messages['checksum'])

    def _canonify(self, value):

        """

        Returns the value as only digits.

        """

        return value.replace('-', '').replace(' ', '')

    def _validate(self, value):

        """

        Takes in the value in canonical form and checks the verifier digit. The

        method is modulo 11.

        """

        check = [3, 2, 7, 6, 5, 4, 3, 2, 1, 0]

        return sum([int(value[i]) * check[i] for i in range(10)]) % 11 == 0

    def _format(self, value):

        """

        Takes in the value in canonical form and returns it in the common

        display format.

        """

        return smart_unicode(value[:6]+'-'+value[6:])

class ISPhoneNumberField(RegexField):

    """

    Icelandic phone number. Seven digits with an optional hyphen or space after

    the first three digits.

    """

    def __init__(self, *args, **kwargs):

        kwargs['min_length'], kwargs['max_length'] = 7,8

        super(ISPhoneNumberField, self).__init__(r'^\d{3}(-| )?\d{4}$', *args, **kwargs)

    def clean(self, value):

        value = super(ISPhoneNumberField, self).clean(value)

        if value in EMPTY_VALUES:

            return u''

        return value.replace('-', '').replace(' ', '')

class ISPostalCodeSelect(Select):

    """

    A Select widget that uses a list of Icelandic postal codes as its choices.

    """

    def __init__(self, attrs=None):

        from is_postalcodes import IS_POSTALCODES

        super(ISPostalCodeSelect, self).__init__(attrs, choices=IS_POSTALCODES)