import binascii
import os

from django.conf import settings
from django.db import models
from django.utils.encoding import python_2_unicode_compatible

# Prior to Django 1.5, the AUTH_USER_MODEL setting does not exist.
# Note that we don't perform this code in the compat module due to
# bug report #1297
# See: https://github.com/tomchristie/django-rest-framework/issues/1297
AUTH_USER_MODEL = getattr(settings, 'AUTH_USER_MODEL', 'auth.User')


@python_2_unicode_compatible
class Token(models.Model):
    """
    The default authorization token model.
    """
    key = models.CharField(max_length=40, primary_key=True)
    user = models.OneToOneField(AUTH_USER_MODEL, related_name='auth_token',
                                on_delete=models.CASCADE)
    created = models.DateTimeField(auto_now_add=True)

    class Meta:
        # Work around for a bug in Django:
        # https://code.djangoproject.com/ticket/19422
        #
        # Also see corresponding ticket:
        # https://github.com/tomchristie/django-rest-framework/issues/705
        abstract = 'rest_framework.authtoken' not in settings.INSTALLED_APPS

    def save(self, *args, **kwargs):
        if not self.key:
            self.key = self.generate_key()
        return super(Token, self).save(*args, **kwargs)

    def generate_key(self):
        return binascii.hexlify(os.urandom(20)).decode()

    def __str__(self):
        return self.key