import copy

import datetime

from django.contrib.auth.models import User

from django.db import models

class RevisionableModel(models.Model):

    base = models.ForeignKey("self", models.SET_NULL, null=True)

    title = models.CharField(blank=True, max_length=255)

    when = models.DateTimeField(default=datetime.datetime.now)

    def save(self, *args, force_insert=None, force_update=None, **kwargs):

        super().save(

            *args, force_insert=force_insert, force_update=force_update, **kwargs

        )

        if not self.base:

            self.base = self

            super().save(*args, **kwargs)

    def new_revision(self):

        new_revision = copy.copy(self)

        new_revision.pk = None

        return new_revision

class Order(models.Model):

    created_by = models.ForeignKey(User, models.CASCADE)

    text = models.TextField()

class TestObject(models.Model):

    first = models.CharField(max_length=20)

    second = models.CharField(max_length=20)

    third = models.CharField(max_length=20)

    def __str__(self):

        return "TestObject: %s,%s,%s" % (self.first, self.second, self.third)