from django.db import models

class Tag(models.Model):

    name = models.CharField(max_length=10)

    parent = models.ForeignKey(

        "self",

        models.SET_NULL,

        blank=True,

        null=True,

        related_name="children",

    )

    class Meta:

        ordering = ["name"]

    def __str__(self):

        return self.name

class Celebrity(models.Model):

    name = models.CharField("Name", max_length=20)

    greatest_fan = models.ForeignKey(

        "Fan",

        models.SET_NULL,

        null=True,

        unique=True,

    )

    def __str__(self):

        return self.name

class Fan(models.Model):

    fan_of = models.ForeignKey(Celebrity, models.CASCADE)

class Staff(models.Model):

    id = models.IntegerField(primary_key=True)

    name = models.CharField(max_length=50)

    organisation = models.CharField(max_length=100)

    tags = models.ManyToManyField(Tag, through="StaffTag")

    coworkers = models.ManyToManyField("self")

    def __str__(self):

        return self.name

class StaffTag(models.Model):

    staff = models.ForeignKey(Staff, models.CASCADE)

    tag = models.ForeignKey(Tag, models.CASCADE)

    def __str__(self):

        return "%s -> %s" % (self.tag, self.staff)