"""
Swiss-specific Form helpers
"""

from django.newforms import ValidationError
from django.newforms.fields import Field, RegexField, Select, EMPTY_VALUES
from django.utils.encoding import smart_unicode
from django.utils.translation import ugettext
import re

id_re = re.compile(r"^(?P<idnumber>\w{8})(?P<pos9>(\d{1}|<))(?P<checksum>\d{1})$")
phone_digits_re = re.compile(r'^0([1-9]{1})\d{8}$')

class CHZipCodeField(RegexField):
    def __init__(self, *args, **kwargs):
        super(CHZipCodeField, self).__init__(r'^\d{4}$',
        max_length=None, min_length=None,
        error_message=ugettext('Enter a zip code in the format XXXX.'),
        *args, **kwargs)

class CHPhoneNumberField(Field):
    """
    Validate local Swiss phone number (not international ones)
    The correct format is '0XX XXX XX XX'.
    '0XX.XXX.XX.XX' and '0XXXXXXXXX' validate but are corrected to
    '0XX XXX XX XX'.
    """
    def clean(self, value):
        super(CHPhoneNumberField, self).clean(value)
        if value in EMPTY_VALUES:
            return u''
        value = re.sub('(\.|\s|/|-)', '', smart_unicode(value))
        m = phone_digits_re.search(value)
        if m:
            return u'%s %s %s %s' % (value[0:3], value[3:6], value[6:8], value[8:10])
        raise ValidationError('Phone numbers must be in 0XX XXX XX XX format.')

class CHStateSelect(Select):
    """
    A Select widget that uses a list of CH states as its choices.
    """
    def __init__(self, attrs=None):
        from ch_states import STATE_CHOICES # relative import
        super(CHStateSelect, self).__init__(attrs, choices=STATE_CHOICES)

class CHIdentityCardNumberField(Field):
    """
    A Swiss identity card number.

    Checks the following rules to determine whether the number is valid:

        * Conforms to the X1234567<0 or 1234567890 format.
        * Included checksums match calculated checksums

    Algorithm is documented at http://adi.kousz.ch/artikel/IDCHE.htm
    """
    def has_valid_checksum(self, number):
        given_number, given_checksum = number[:-1], number[-1]
        new_number = given_number
        calculated_checksum = 0
        fragment = ""
        parameter = 7

        first = str(number[:1])
        if first.isalpha():
            num = ord(first.upper()) - 65
            if num < 0 or num > 8:
                return False
            new_number = str(num) + new_number[1:]
            new_number = new_number[:8] + '0'

        if not new_number.isdigit():
            return False

        for i in range(len(new_number)):
          fragment = int(new_number[i])*parameter
          calculated_checksum += fragment

          if parameter == 1:
            parameter = 7
          elif parameter == 3:
            parameter = 1
          elif parameter ==7:
            parameter = 3

        return str(calculated_checksum)[-1] == given_checksum

    def clean(self, value):
        super(CHIdentityCardNumberField, self).clean(value)
        error_msg = ugettext('Enter a valid Swiss identity or passport card number in X1234567<0 or 1234567890 format.')
        if value in EMPTY_VALUES:
            return u''

        match = re.match(id_re, value)
        if not match:
            raise ValidationError(error_msg)

        idnumber, pos9, checksum = match.groupdict()['idnumber'], match.groupdict()['pos9'], match.groupdict()['checksum']

        if idnumber == '00000000' or \
           idnumber == 'A0000000':
            raise ValidationError(error_msg)

        all_digits = "%s%s%s" % (idnumber, pos9, checksum)
        if not self.has_valid_checksum(all_digits):
            raise ValidationError(error_msg)

        return u'%s%s%s' % (idnumber, pos9, checksum)