import re

from django.core.validators import RegexValidator
from django.core.exceptions import ValidationError
from django.utils.translation import gettext_lazy as _
from django.conf import settings

from .common import (
    validate_first_letter_not_number,
    end_with_letter_or_number,
    MinLengthValidator,
    MaxLengthValidator,
    NoDoubleSpecialValidator,
    DoesNotEndWithConfusingSuffixValidator
)


class UsernameCharacterValidator(RegexValidator):
    regex = re.compile(r'^[a-zA-Z0-9-_\u4e00-\u9fa5]+$')
    message = _('should only contains: number、letter、chinese character、hyphen or underline.')


class UsernameFirstCharacterValidator(RegexValidator):
    regex = re.compile(r'^[a-zA-Z_\u4e00-\u9fa5]')
    message = _('first letter should only be: letter、chinese character or underline.')


def does_not_reserverd_usernames(username):
    if username.lower() in settings.RESERVED_USERNAMES:
        raise ValidationError(_('already used'))


def validate_username(username, username_validators=None):
    errors = []
    if username_validators is None:
        username_validators = [
            MinLengthValidator(4),
            MaxLengthValidator(20),
            UsernameCharacterValidator(),
            UsernameFirstCharacterValidator(),
            NoDoubleSpecialValidator(),
            DoesNotEndWithConfusingSuffixValidator(),
            validate_first_letter_not_number,
            end_with_letter_or_number,
            does_not_reserverd_usernames
        ]

    for validator in username_validators:
        try:
            validator(username)
        except ValidationError as error:
            errors.append(error)
    if errors:
        raise ValidationError(errors)