import re

import django.core.validators
from django.core.exceptions import ValidationError
from django.core.validators import RegexValidator
from django.utils.translation import gettext_lazy as _, ngettext_lazy


def validate_first_letter_not_number(value):
    if len(value) > 0 and value[0].isdigit():
        raise ValidationError(_('the first letter cannot be a number'))


def end_with_letter_or_number(value):
    if len(value) > 0 and not value[-1].isalnum():
        raise ValidationError(_('must end with a letter or a number'))

class NoDoubleSpecialValidator(RegexValidator):
    regex = re.compile(r'[-_.]{2,}')
    inverse_match = True
    message = _('must not contain a sequence of 2 or more special chars (.-_)')


class DoesNotEndWithConfusingSuffixValidator(RegexValidator):
    regex = re.compile(r'\.(js|json|css|htm|html|xml|jpg|jpeg|png|gif|bmp|ico|tif|tiff|woff)$')
    inverse_match = True
    message = _('must not end with a confusing suffix like .json or .png etc.')


class MinLengthValidator(django.core.validators.MinLengthValidator):
    message = ngettext_lazy(
        'Ensure this value has at least %(limit_value)d character.',
        'Ensure this value has at least %(limit_value)d characters.',
        'limit_value')


class MaxLengthValidator(django.core.validators.MaxLengthValidator):
    message = ngettext_lazy(
        'Ensure this value has at most %(limit_value)d character.',
        'Ensure this value has at most %(limit_value)d characters.',
        'limit_value')