from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
from django.contrib.auth.models import PermissionsMixin
from django.contrib.auth.validators import UnicodeUsernameValidator
from django.core.mail import send_mail
from django.db import models
from django.utils import timezone
from django.utils.translation import gettext_lazy as _

from userausfall import ldap


class MissingUserAttribute(Exception):
    """The user object is missing a required attribute."""
    pass


class PasswordMismatch(Exception):
    """The given password does not match the user's password."""
    pass


class UserManager(BaseUserManager):
    use_in_migrations = True

    def _create_user(self, email, password, **extra_fields):
        """
        Create and save a user with the given username, email, and password.
        """
        email = self.normalize_email(email)
        # TODO: username = self.model.normalize_username(username)
        user = self.model(email=email, **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_user(self, email, password=None, **extra_fields):
        extra_fields.setdefault('is_staff', False)
        extra_fields.setdefault('is_superuser', False)
        return self._create_user(email, password, **extra_fields)

    def create_superuser(self, email, password, **extra_fields):
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)

        if extra_fields.get('is_staff') is not True:
            raise ValueError('Superuser must have is_staff=True.')
        if extra_fields.get('is_superuser') is not True:
            raise ValueError('Superuser must have is_superuser=True.')

        return self._create_user(email, password, **extra_fields)


class User(AbstractBaseUser, PermissionsMixin):
    username_validator = UnicodeUsernameValidator()

    username = models.CharField(
        _('username'),
        max_length=150,
        help_text=_('Required. 150 characters or fewer. Letters, digits and @/./+/-/_ only.'),
        validators=[username_validator],
        error_messages={
            'unique': _("A user with that username already exists."),
        },
        blank=True,
    )
    email = models.EmailField(_('email address'), unique=True, blank=True)
    is_staff = models.BooleanField(
        _('staff status'),
        default=False,
        help_text=_('Designates whether the user can log into this admin site.'),
    )
    date_joined = models.DateTimeField(_('date joined'), default=timezone.now)
    confidant = models.ForeignKey("User", on_delete=models.SET_NULL, null=True)

    objects = UserManager()

    EMAIL_FIELD = 'email'
    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = []

    class Meta:
        verbose_name = _('user')
        verbose_name_plural = _('users')

    def clean(self):
        super().clean()
        self.email = self.__class__.objects.normalize_email(self.email)

    def get_confidant_email(self):
        return ""

    def email_user(self, subject, message, from_email=None, **kwargs):
        """Send an email to this user."""
        send_mail(subject, message, from_email, [self.email], **kwargs)

    def create_ldap_account(self, raw_password):
        """Create the LDAP account which corresponds to this user."""
        if not self.username:
            raise MissingUserAttribute("User is missing a username.")
        if not self.confidant:
            raise MissingUserAttribute("User is missing a confirmed confidant.")
        if not self.check_password(raw_password):
            raise PasswordMismatch("The given password does not match the user's password.")
        return ldap.create_account(self.username, raw_password)