import uuid

from django.db import models

class Event(models.Model):

    # Oracle can have problems with a column named "date"

    date = models.DateField(db_column="event_date")

class Parent(models.Model):

    name = models.CharField(max_length=128)

class Child(models.Model):

    parent = models.ForeignKey(Parent, models.SET_NULL, editable=False, null=True)

    name = models.CharField(max_length=30, blank=True)

    age = models.IntegerField(null=True, blank=True)

class Genre(models.Model):

    name = models.CharField(max_length=20)

class Band(models.Model):

    name = models.CharField(max_length=20)

    nr_of_members = models.PositiveIntegerField()

    genres = models.ManyToManyField(Genre)

class Musician(models.Model):

    name = models.CharField(max_length=30)

    age = models.IntegerField(null=True, blank=True)

    def __str__(self):

        return self.name

class Group(models.Model):

    name = models.CharField(max_length=30)

    members = models.ManyToManyField(Musician, through="Membership")

    def __str__(self):

        return self.name

class Concert(models.Model):

    name = models.CharField(max_length=30)

    group = models.ForeignKey(Group, models.CASCADE)

class Membership(models.Model):

    music = models.ForeignKey(Musician, models.CASCADE)

    group = models.ForeignKey(Group, models.CASCADE)

    role = models.CharField(max_length=15)

class Quartet(Group):

    pass

class ChordsMusician(Musician):

    pass

class ChordsBand(models.Model):

    name = models.CharField(max_length=30)

    members = models.ManyToManyField(ChordsMusician, through="Invitation")

class Invitation(models.Model):

    player = models.ForeignKey(ChordsMusician, models.CASCADE)

    band = models.ForeignKey(ChordsBand, models.CASCADE)

    instrument = models.CharField(max_length=15)

class Swallow(models.Model):

    uuid = models.UUIDField(primary_key=True, default=uuid.uuid4)

    origin = models.CharField(max_length=255)

    load = models.FloatField()

    speed = models.FloatField()

    class Meta:

        ordering = ("speed", "load")

class SwallowOneToOne(models.Model):

    swallow = models.OneToOneField(Swallow, models.CASCADE)

class UnorderedObject(models.Model):

    """

    Model without any defined `Meta.ordering`.

    Refs #17198.

    """

    bool = models.BooleanField(default=True)

class OrderedObjectManager(models.Manager):

    def get_queryset(self):

        return super().get_queryset().order_by("number")

class OrderedObject(models.Model):

    """

    Model with Manager that defines a default order.

    Refs #17198.

    """

    name = models.CharField(max_length=255)

    bool = models.BooleanField(default=True)

    number = models.IntegerField(default=0, db_column="number_val")

    objects = OrderedObjectManager()

class CustomIdUser(models.Model):

    uuid = models.AutoField(primary_key=True)

class CharPK(models.Model):

    char_pk = models.CharField(max_length=100, primary_key=True)