from django.db import models
from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin, BaseUserManager
from django.utils import timezone
from django.utils.translation import gettext_lazy as _


class CustomUserManager(BaseUserManager):
    """
    Custom user manager where email is the unique identifier
    for authentication instead of username.
    """
    
    def create_user(self, email, password=None, **extra_fields):
        """
        Create and save a regular user with the given email and password.
        """
        if not email:
            raise ValueError(_('The Email field must be set'))
        
        email = self.normalize_email(email)
        user = self.model(email=email, **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user
    
    def create_superuser(self, email, password=None, **extra_fields):
        """
        Create and save a SuperUser with the given email and password.
        """
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)
        extra_fields.setdefault('is_active', 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 CustomUser(AbstractBaseUser, PermissionsMixin):
    """
    Custom user model where email is used instead of username.
    
    Fields:
    - email: unique email address (used for login)
    - first_name: user's first name
    - last_name: user's last name
    - is_staff: designates whether user can log into admin site
    - is_active: designates whether user account is active
    - date_joined: when the user account was created
    """
    
    email = models.EmailField(
        _('email address'),
        unique=True,
        error_messages={
            'unique': _("A user with that email already exists."),
        }
    )
    first_name = models.CharField(_('first name'), max_length=150, blank=True)
    last_name = models.CharField(_('last name'), max_length=150, blank=True)
    is_staff = models.BooleanField(
        _('staff status'),
        default=False,
        help_text=_('Designates whether the user can log into this admin site.'),
    )
    is_active = models.BooleanField(
        _('active'),
        default=True,
        help_text=_(
            'Designates whether this user should be treated as active. '
            'Unselect this instead of deleting accounts.'
        ),
    )
    active_until = models.DateTimeField(
        _('active until'),
        null=True,
        blank=True,
        help_text=_('If set, the account is automatically deactivated after this date.'),
    )
    date_joined = models.DateTimeField(_('date joined'), default=timezone.now)
    
    # Specify that we use email as the username field
    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = []  # Email is already required by USERNAME_FIELD
    
    objects = CustomUserManager()
    
    class Meta:
        verbose_name = _('user')
        verbose_name_plural = _('users')
    
    def __str__(self):
        return self.email
    
    def get_full_name(self):
        """
        Return the first_name plus the last_name, with a space in between.
        """
        full_name = f'{self.first_name} {self.last_name}'
        return full_name.strip()
    
    def get_short_name(self):
        """
        Return the short name for the user.
        """
        return self.first_name

    def is_expired(self):
        """Return True when account usage period has ended."""
        return bool(self.active_until and timezone.now() >= self.active_until)

    def deactivate_if_expired(self, save=True):
        """Deactivate account if active_until has passed."""
        if self.is_active and self.is_expired():
            self.is_active = False
            if save:
                self.save(update_fields=['is_active'])
            return True
        return False

    def set_active_for_days(self, days, save=True):
        """Enable user for a fixed number of days from now."""
        self.active_until = timezone.now() + timezone.timedelta(days=days)
        self.is_active = True
        if save:
            self.save(update_fields=['active_until', 'is_active'])