"""IT-specific Form helpers."""
import re

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

from .it_province import PROVINCE_CHOICES
from .it_region import REGION_CHOICES, REGION_PROVINCE_CHOICES
from .util import ssn_validation, vat_number_validation


class ITZipCodeField(RegexField):
    """
    A form field that validates input as an Italian zip code.

    Valid codes must have five digits.
    """

    default_error_messages = {
        'invalid': _('Enter a valid zip code.'),
    }

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


class ITRegionSelect(Select):
    """A Select widget that uses a list of IT regions as its choices."""

    def __init__(self, attrs=None):
        super().__init__(attrs, choices=REGION_CHOICES)


class ITRegionProvinceSelect(Select):
    """A Select widget that uses a named group list of IT regions mapped to regions as its choices."""

    def __init__(self, attrs=None):
        super().__init__(attrs, choices=REGION_PROVINCE_CHOICES)


class ITProvinceSelect(Select):
    """A Select widget that uses a list of IT provinces as its choices."""

    def __init__(self, attrs=None):
        super().__init__(attrs, choices=PROVINCE_CHOICES)


class ITSocialSecurityNumberField(RegexField):
    """
    A form field that validates Italian Tax code (codice fiscale) for both persons and entities.

    For reference see http://www.agenziaentrate.it/ and search for:

    * 'Informazioni sulla codificazione delle persone fisiche' for persons' SSN
    * 'Codice fiscale Modello AA5/6' for entities' SSN

    .. versionchanged:: 1.1

    The ``ITSocialSecurityNumberField`` now also accepts SSN values for
    entities (numeric-only form).
    """

    default_error_messages = {
        'invalid': _('Enter a valid Tax code.'),
    }

    def __init__(self, **kwargs):
        super().__init__(
            r'^\w{3}\s*\w{3}\s*\w{5}\s*\w{5}$|\d{10}', **kwargs
        )

    def clean(self, value):
        value = super().clean(value)
        if value in self.empty_values:
            return self.empty_value
        value = re.sub(r'\s', '', value).upper()
        # Entities SSN are numeric-only
        if value.isdigit():
            try:
                return vat_number_validation(value)
            except ValueError:
                raise ValidationError(self.error_messages['invalid'], code='invalid')
        # Person SSN
        else:
            try:
                return ssn_validation(value)
            except (ValueError, IndexError):
                raise ValidationError(self.error_messages['invalid'], code='invalid')


class ITVatNumberField(Field):
    """A form field that validates Italian VAT numbers (partita IVA)."""

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

    def clean(self, value):
        value = super().clean(value)
        if value in EMPTY_VALUES:
            return ''
        try:
            return vat_number_validation(value)
        except ValueError:
            raise ValidationError(self.error_messages['invalid'], code='invalid')