doorcontrol: Add change vs previous unit time to "Access per x" reports

doorcontrol/views.py

@@ -12,6 +12,9 @@ from django.utils.formats import date_format
 from django.utils.text import slugify
 from django.utils.timezone import localtime
 from django.views.generic.list import ListView
+from django.db.models import Window, F, FloatField
+from django.db.models.functions import Lead
+
 
 from .models import HIDEvent
 
@@ -149,16 +152,45 @@ class AccessPerUnitTime(BaseAccessReport):
             .values(unit_time=Trunc("timestamp", unit_time))
             .annotate(
                 members=Count("cardholder_id", distinct=True),
+                members_delta=(
+                    F("members")
+                    / Window(
+                        Lead("members"),
+                        order_by="-unit_time",
+                        output_field=FloatField(),
+                    )
+                    * 100
+                    - 100
+                ),
                 access_count=Count("cardholder_id"),
+                access_count_delta=(
+                    F("access_count")
+                    / Window(
+                        Lead("access_count"),
+                        order_by="-unit_time",
+                        output_field=FloatField(),
+                    )
+                    * 100
+                    - 100
+                ),
             )
             .order_by("-unit_time")
-            .values("unit_time", "members", "access_count")
         )
         return [
             {
                 unit_time: self._format_date(event["unit_time"]),
                 "members": event["members"],
+                "Δ members": (
+                    f'{event["members_delta"]:.2f}%'
+                    if event["members_delta"] is not None
+                    else ""
+                ),
                 "access count": event["access_count"],
+                "Δ access count": (
+                    f'{event["access_count_delta"]:.2f}%'
+                    if event["access_count_delta"] is not None
+                    else ""
+                ),
             }
             for event in events
         ]