from django.contrib.auth.models import User

from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

from django.contrib.contenttypes.models import ContentType

from django.db import models

class Review(models.Model):

    source = models.CharField(max_length=100)

    content_type = models.ForeignKey(ContentType, models.CASCADE)

    object_id = models.PositiveIntegerField()

    content_object = GenericForeignKey()

    class Meta:

        ordering = ("source",)

    def __str__(self):

        return self.source

class PersonManager(models.Manager):

    def get_by_natural_key(self, name):

        return self.get(name=name)

class Person(models.Model):

    name = models.CharField(max_length=100, unique=True)

    objects = PersonManager()

    class Meta:

        ordering = ("name",)

    def __str__(self):

        return self.name

# This book manager doesn't do anything interesting; it just

# exists to strip out the 'extra_arg' argument to certain

# calls. This argument is used to establish that the BookManager

# is actually getting used when it should be.

class BookManager(models.Manager):

    def create(self, *args, extra_arg=None, **kwargs):

        return super().create(*args, **kwargs)

    def get_or_create(self, *args, extra_arg=None, **kwargs):

        return super().get_or_create(*args, **kwargs)

class Book(models.Model):

    title = models.CharField(max_length=100)

    published = models.DateField()

    authors = models.ManyToManyField(Person)

    editor = models.ForeignKey(

        Person, models.SET_NULL, null=True, related_name="edited"

    )

    reviews = GenericRelation(Review)

    pages = models.IntegerField(default=100)

    objects = BookManager()

    class Meta:

        ordering = ("title",)

    def __str__(self):

        return self.title

class Pet(models.Model):

    name = models.CharField(max_length=100)

    owner = models.ForeignKey(Person, models.CASCADE)

    class Meta:

        ordering = ("name",)

class UserProfile(models.Model):

    user = models.OneToOneField(User, models.SET_NULL, null=True)

    flavor = models.CharField(max_length=100)

    class Meta:

        ordering = ("flavor",)