Implement caching

poetry.lock

@@ -353,6 +353,17 @@ python-versions = ">=3.7"
 [package.dependencies]
 Django = ">=3.2"
 
+[[package]]
+name = "django-solo"
+version = "2.0.0"
+description = "Django Solo helps working with singletons"
+category = "main"
+optional = false
+python-versions = ">=3.6"
+
+[package.dependencies]
+django = ">=2.2"
+
 [[package]]
 name = "factory-boy"
 version = "3.2.1"
@@ -1164,7 +1175,7 @@ h11 = ">=0.9.0,<1"
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.10"
-content-hash = "e0332f1446a90fc3a5dc2fa2ca5d1745eb0d90d8f033094d79b2df9376b79639"
+content-hash = "517db1c26bc459a29fdeae5f5ea18620c54121f95110d641b740ffdc322fb584"
 
 [metadata.files]
 ansicon = []
@@ -1288,6 +1299,7 @@ django-environ = [
 ]
 django-extensions = []
 django-htmx = []
+django-solo = []
 factory-boy = []
 faker = []
 filelock = []

pyproject.toml

@@ -22,6 +22,7 @@ crispy-bootstrap5 = "^0.6"
 matplotlib = "^3.5.1"
 freezegun = "^1.2.1"
 django-htmx = "^1.12.2"
+django-solo = "^2.0.0"
 
 [tool.poetry.dev-dependencies]
 pre-commit = "^2.7"

src/purchase/admin.py

@@ -1,8 +1,9 @@
 from django.contrib import admin
 from django.contrib.admin import register
 from django.utils.translation import gettext_lazy as _
+from solo.admin import SingletonModelAdmin
 
-from purchase.models import Basket, BasketItem, PaymentMethod, Product
+from purchase.models import Basket, BasketItem, CacheEtag, PaymentMethod, Product
 from purchase.templatetags.purchase import currency
 
 
@@ -70,3 +71,6 @@ class BasketAdmin(admin.ModelAdmin):
     @admin.display(description=_("price"))
     def price(self, instance) -> str:
         return currency(instance.price)
+
+
+admin.site.register(CacheEtag, SingletonModelAdmin)

src/purchase/apps.py

@@ -1,6 +1,17 @@
 from django.apps import AppConfig
+from django.db.models.signals import post_save
 
 
 class PurchaseConfig(AppConfig):
     default_auto_field = "django.db.models.BigAutoField"
     name = "purchase"
+
+    def ready(self):
+        from purchase.models import Basket, BasketItem, PaymentMethod, Product
+
+        from .signals import basket_item_on_save
+
+        post_save.connect(basket_item_on_save, sender=BasketItem)
+        post_save.connect(basket_item_on_save, sender=Basket)
+        post_save.connect(basket_item_on_save, sender=Product)
+        post_save.connect(basket_item_on_save, sender=PaymentMethod)

src/purchase/migrations/0009_basketitemetag.py

@@ -0,0 +1,33 @@
+# Generated by Django 4.1.1 on 2022-09-25 19:00
+
+import uuid
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("purchase", "0008_basketitem_unique_product_per_basket"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="BasketItemEtag",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("value", models.UUIDField(default=uuid.uuid4)),
+            ],
+            options={
+                "abstract": False,
+            },
+        ),
+    ]

src/purchase/migrations/0010_rename_basketitemetag_cacheetag.py

@@ -0,0 +1,17 @@
+# Generated by Django 4.1.1 on 2022-09-25 19:08
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("purchase", "0009_basketitemetag"),
+    ]
+
+    operations = [
+        migrations.RenameModel(
+            old_name="BasketItemEtag",
+            new_name="CacheEtag",
+        ),
+    ]

src/purchase/models.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import hashlib
+import uuid
 
 from django.db import models
 from django.db.models import Avg, Count, F, Sum, UniqueConstraint
@@ -9,6 +10,7 @@ from django.urls import reverse
 from django.utils.translation import gettext
 from django.utils.translation import gettext_lazy as _
 from PIL import Image, ImageOps
+from solo.models import SingletonModel
 
 
 class Model(models.Model):
@@ -220,3 +222,14 @@ class BasketItem(Model):
         constraints = [
             UniqueConstraint("product", "basket", name="unique_product_per_basket")
         ]
+
+
+class CacheEtag(SingletonModel):
+    value = models.UUIDField(default=uuid.uuid4)
+
+    def __str__(self) -> str:
+        return str(self.value)
+
+    def refresh(self):
+        self.value = uuid.uuid4()
+        self.save()

src/purchase/signals.py

@@ -0,0 +1,4 @@
+def basket_item_on_save(sender, **kwargs):
+    from purchase.models import CacheEtag
+
+    CacheEtag.get_solo().refresh()

src/purchase/views/basket.py

@@ -5,14 +5,16 @@ from django.shortcuts import get_object_or_404, redirect
 from django.template.response import TemplateResponse
 from django.urls import reverse
 from django.utils.translation import gettext_lazy as _
-from django.views.decorators.http import require_http_methods
+from django.views.decorators.http import condition, require_http_methods
 
 from purchase.forms import BasketForm
 from purchase.models import Basket
+from purchase.views.reports import reports_etag
 
 
 @require_http_methods(["GET", "POST"])
 @permission_required("purchase.add_basket")
+@condition(etag_func=reports_etag)
 def new_basket(request: HttpRequest) -> HttpResponse:
     if request.method == "POST":
         form = BasketForm(request.POST)
@@ -32,6 +34,7 @@ def new_basket(request: HttpRequest) -> HttpResponse:
 
 @require_http_methods(["GET", "POST"])
 @permission_required("purchase.change_basket")
+@condition(etag_func=reports_etag)
 def update_basket(request: HttpRequest, pk: int) -> HttpResponse:
     basket = get_object_or_404(Basket.objects.priced(), pk=pk)
     if request.method == "POST":
@@ -49,6 +52,7 @@ def update_basket(request: HttpRequest, pk: int) -> HttpResponse:
 
 
 @permission_required("purchase.view_basket")
+@condition(etag_func=reports_etag)
 def list_baskets(request: HttpRequest) -> HttpResponse:
     context = {"baskets": Basket.objects.priced().order_by("-id")}
     return TemplateResponse(request, "purchase/basket_list.html", context)

src/purchase/views/reports.py

@@ -10,6 +10,7 @@ from django.contrib.auth.decorators import permission_required
 from django.shortcuts import render
 from django.template.response import TemplateResponse
 from django.utils.translation import gettext as _
+from django.views.decorators.http import condition
 from matplotlib import pyplot as plt
 from matplotlib import ticker
 from matplotlib.axes import Axes
@@ -17,12 +18,17 @@ from matplotlib.container import BarContainer
 from matplotlib.dates import AutoDateLocator, ConciseDateFormatter, HourLocator
 from matplotlib.figure import Figure
 
-from purchase.models import Basket, PaymentMethod, Product, ProductQuerySet
+from purchase.models import Basket, CacheEtag, PaymentMethod, Product, ProductQuerySet
 
 matplotlib.use("SVG")
 
 
+def reports_etag(request):
+    return str(CacheEtag.get_solo().value)
+
+
 @permission_required("purchase.view_basket")
+@condition(etag_func=reports_etag)
 def products_plots_view(request):
     products = Product.objects.with_turnover().with_sold()
     (
@@ -37,6 +43,7 @@ def products_plots_view(request):
 
 
 @permission_required("purchase.view_basket")
+@condition(etag_func=reports_etag)
 def by_hour_plot_view(request):
     baskets = list(Basket.objects.priced().order_by("created_at"))
     context = {
@@ -46,6 +53,7 @@ def by_hour_plot_view(request):
 
 
 @permission_required("purchase.view_basket")
+@condition(etag_func=reports_etag)
 def reports(request):
     template_name = "purchase/reports.html"
     baskets = list(Basket.objects.priced().order_by("created_at"))