add helper functions to models

stories/writingtogether/models.py

@@ -15,6 +15,10 @@ class StoryRound(models.Model):
     def get_absolute_url(self):
         return reverse('writing:detail', kwargs={'pk': self.pk})
 
+    def get_next_story_part(self, user: User) -> 'StoryPart':
+        # TODO: implement, for each story get unfinished part and check user
+        pass
+
 
 class Participant(models.Model):
     user = models.ForeignKey(User, on_delete=CASCADE)
@@ -27,10 +31,27 @@ class Story(models.Model):
     created = models.DateTimeField(auto_now_add=True)
     part_of_round = models.ForeignKey(StoryRound, on_delete=CASCADE)
     started_by = models.ForeignKey(User, on_delete=CASCADE)
+    finished = models.BooleanField(default=False)
+
+    def get_first_unfinished_part(self):
+        if self.finished:
+            return None
+
+        first_part = StoryPart.objects.get(part_of_id=self.pk, previous_part__isnull=True)
+
+        last_unfinished_part = first_part
+        while last_unfinished_part.finished:
+            last_unfinished_part = StoryPart.objects.get(previous_part=last_unfinished_part)
+
+        return last_unfinished_part
 
 
 class StoryPart(models.Model):
     user = models.ForeignKey(User, on_delete=CASCADE)
     previous_part = models.ForeignKey('StoryPart', on_delete=CASCADE, null=True, blank=True)
-    text = models.TextField()
+    text = models.TextField(null=True, blank=True)
     part_of = models.ForeignKey('Story', on_delete=CASCADE)
+
+    @property
+    def finished(self):
+        return self.text