class Page(models.Model):
    name = models.CharField('Имя страницы', max_length=50)
    slug = models.SlugField()

    class Meta:
        verbose_name = 'Page'
        verbose_name_plural = 'Pages'

    def __str__(self):
        return self.name


class Article(models.Model):
    name = models.CharField('Имя статьи', max_length=50)
    slug = models.SlugField()

    class Meta:
        verbose_name = 'Article'
        verbose_name_plural = 'Articles'

    def __str__(self):
        return self.name


class Menu(models.Model):
    name = models.CharField('Имя меню', max_length=50)

    class Meta:
        verbose_name = 'Menu'
        verbose_name_plural = 'Menus'

    def __str__(self):
        return self.name


class MenuItem(models.Model):
    name = models.CharField('Имя пункта меню', max_length=50)
    url = models.URLField('Ссылка пункта меню', max_length=200)
    menu = models.ForeignKey(Menu, on_delete=models.CASCADE)


    content_type = models.ForeignKey(
        ContentType, limit_choices_to={
        'model__in': (
            'page',
            'article',)
    }, on_delete=models.CASCADE)

    object_id = models.PositiveIntegerField()
    obj = GenericForeignKey('content_type', 'object_id')

    class Meta:
        verbose_name = 'MenuItem'
        verbose_name_plural = 'MenuItems'

    def __str__(self):
        return self.name

class MenuItemObjectAdminInLine(admin.StackedInline):
  model = MenuItem
  ct_field = "content_type"
  ct_fk_field = "object_id"
  extra = 0

class MenuAdmin(admin.ModelAdmin):
  inlines = [MenuItemObjectAdminInLine]

admin.site.register(Menu, MenuAdmin)