from django.db import models

class User(models.Model):

    username = models.CharField(max_length=100)

    email = models.EmailField()

class UserProfile(models.Model):

    user = models.OneToOneField(User, models.CASCADE)

    city = models.CharField(max_length=100)

    state = models.CharField(max_length=2)

class UserStatResult(models.Model):

    results = models.CharField(max_length=50)

class UserStat(models.Model):

    user = models.OneToOneField(User, models.CASCADE, primary_key=True)

    posts = models.IntegerField()

    results = models.ForeignKey(UserStatResult, models.CASCADE)

class StatDetails(models.Model):

    base_stats = models.OneToOneField(UserStat, models.CASCADE)

    comments = models.IntegerField()

class AdvancedUserStat(UserStat):

    karma = models.IntegerField()

class Image(models.Model):

    name = models.CharField(max_length=100)

class Product(models.Model):

    name = models.CharField(max_length=100)

    image = models.OneToOneField(Image, models.SET_NULL, null=True)

class Parent1(models.Model):

    name1 = models.CharField(max_length=50)

class Parent2(models.Model):

    # Avoid having two "id" fields in the Child1 subclass

    id2 = models.AutoField(primary_key=True)

    name2 = models.CharField(max_length=50)

class Child1(Parent1, Parent2):

    value = models.IntegerField()

class Child2(Parent1):

    parent2 = models.OneToOneField(Parent2, models.CASCADE)

    value = models.IntegerField()

class Child3(Child2):

    value3 = models.IntegerField()

class Child4(Child1):

    value4 = models.IntegerField()

class LinkedList(models.Model):

    name = models.CharField(max_length=50)

    previous_item = models.OneToOneField(

        "self",

        models.CASCADE,

        related_name="next_item",

        blank=True,

        null=True,

    )