Snapshot table

nummi/main/models.py

@@ -81,6 +81,9 @@ class Snapshot(models.Model):
     previous = models.OneToOneField(
         "self", on_delete=models.SET_NULL, blank=True, null=True, editable=False
     )
+    diff = models.DecimalField(
+        max_digits=12, decimal_places=2, default=0, editable=False
+    )
 
     def __str__(self):
         if self.previous is None:
@@ -94,9 +97,10 @@ class Snapshot(models.Model):
                 .filter(date__lt=self.date)
                 .first()
             )
+            print(_prev)
 
             try:
-                _next = self.__class__.objects.get(previous=_prev)
+                _next = self.__class__.objects.exclude(id=self.id).get(previous=_prev)
             except self.__class__.DoesNotExist:
                 pass
             else:
@@ -104,6 +108,11 @@ class Snapshot(models.Model):
                 _next.save(only_super=True)
 
             self.previous = _prev
+
+        if self.previous is None:
+            self.diff = 0
+        else:
+            self.diff = self.value - self.previous.value
         super().save(*args, **kwargs)
 
     def delete(self, *args, only_super=False, **kwargs):
@@ -119,5 +128,14 @@ class Snapshot(models.Model):
         else:
             super().delete(*args, **kwargs)
 
+    @property
+    def sum(self):
+        if self.previous is None:
+            return None
+        trans = Transaction.objects.filter(
+            date__lt=self.date, date__gte=self.previous.date
+        ).aggregate(sum=models.Sum("value"))
+        return trans["sum"] or 0
+
     class Meta:
         ordering = ["-date"]