from django.contrib.auth.models import AbstractUser, UserManager as DjangoUserManager
from django.core import validators
from django.db import models
from django.utils.deconstruct import deconstructible
from django.utils.translation import gettext_lazy as _


@deconstructible
class UnicodeUsernameValidator(validators.RegexValidator):
    regex = r'^[\w.-]+\Z'
    message = _(
        'Enter a valid username. This value may contain only letters, '
        'numbers, and ./-/_ characters.'
    )
    flags = 0


class UserManager(DjangoUserManager):
    def get_by_natural_key(self, username):
        return self.get(**{self.model.USERNAME_FIELD + '__iexact': username})


class User(AbstractUser):
    username_validator = UnicodeUsernameValidator()

    objects = UserManager()

    username = models.CharField(
        _('username'),
        max_length=150,
        unique=True,
        help_text=_('Required. 150 characters or fewer. Letters, digits and ./-/_ only.'),
        validators=[username_validator],
        error_messages={
            'unique': _("A user with that username already exists."),
        },
    )

    @classmethod
    def normalize_username(cls, username):
        return super().normalize_username(username).lower()