"""

Czech-specific form helpers

"""

from django.forms import ValidationError

from django.forms.fields import Select, RegexField, Field, EMPTY_VALUES

from django.utils.translation import ugettext_lazy as _

import re

birth_number = re.compile(r'^(?P<birth>\d{6})/?(?P<id>\d{3,4})$')

ic_number = re.compile(r'^(?P<number>\d{7})(?P<check>\d)$')

class CZRegionSelect(Select):

    """

    A select widget widget with list of Czech regions as choices.

    """

    def __init__(self, attrs=None):

        from cz_regions import REGION_CHOICES

        super(CZRegionSelect, self).__init__(attrs, choices=REGION_CHOICES)

class CZPostalCodeField(RegexField):

    """

    A form field that validates its input as Czech postal code.

    Valid form is XXXXX or XXX XX, where X represents integer.

    """

    default_error_messages = {

        'invalid': _(u'Enter a postal code in the format XXXXX or XXX XX.'),

    }

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

        super(CZPostalCodeField, self).__init__(r'^\d{5}$|^\d{3} \d{2}$',

            max_length=None, min_length=None, *args, **kwargs)

    def clean(self, value):

        """

        Validates the input and returns a string that contains only numbers.

        Returns an empty string for empty values.

        """

        v = super(CZPostalCodeField, self).clean(value)

        return v.replace(' ', '')

class CZBirthNumberField(Field):

    """

    Czech birth number field.

    """

    default_error_messages = {

        'invalid_format': _(u'Enter a birth number in the format XXXXXX/XXXX or XXXXXXXXXX.'),

        'invalid_gender': _(u'Invalid optional parameter Gender, valid values are \'f\' and \'m\''),

        'invalid': _(u'Enter a valid birth number.'),

    }

    def clean(self, value, gender=None):

        super(CZBirthNumberField, self).__init__(value)

        if value in EMPTY_VALUES:

            return u''

        match = re.match(birth_number, value)

        if not match:

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

        birth, id = match.groupdict()['birth'], match.groupdict()['id']

        # Three digits for verificatin number were used until 1. january 1954

        if len(id) == 3:

            return u'%s' % value

        # Birth number is in format YYMMDD. Females have month value raised by 50.

        # In case that all possible number are already used (for given date),

        #  the month field is raised by 20.

        if gender is not None:

            if gender == 'f':

                female_const = 50

            elif gender == 'm':

                female_const = 0

            else:

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

            month = int(birth[2:4]) - female_const

            if (not 1 <= month <= 12):

                if (not 1 <= (month - 20) <= 12):

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

        day = int(birth[4:6])

        if not (1 <= day <= 31):

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

        # Fourth digit has been added since 1. January 1954.

        # It is modulo of dividing birth number and verification number by 11.

        # If the modulo were 10, the last number was 0 (and therefore, the whole

        # birth number wasn't divisable by 11. These number are no longer used (since 1985)

        # and the condition 'modulo == 10' can be removed in 2085.

        modulo = int(birth + id[:3]) % 11

        if (modulo == int(id[-1])) or (modulo == 10 and id[-1] == '0'):

            return u'%s' % value

        else:

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

class CZICNumberField(Field):

    """

    Czech IC number field.

    """

    default_error_messages = {

        'invalid': _(u'Enter a valid IC number.'),

    }

    def clean(self, value):

        super(CZICNumberField, self).__init__(value)

        if value in EMPTY_VALUES:

            return u''

        match = re.match(ic_number, value)

        if not match:

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

        number, check = match.groupdict()['number'], int(match.groupdict()['check'])

        sum = 0

        weight = 8

        for digit in number:

            sum += int(digit)*weight

            weight -= 1

        remainder = sum % 11

        # remainder is equal:

        #  0 or 10: last digit is 1

        #  1: last digit is 0

        # in other case, last digin is 11 - remainder

        if (not remainder % 10 and check == 1) or \

        (remainder == 1 and check == 0) or \

        (check == (11 - remainder)):

            return u'%s' % value

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