From d2766860c5d940326fb7e17691642a3dddb3be4b Mon Sep 17 00:00:00 2001
From: Michael Manfre <mike@manfre.net>
Date: Sun, 25 Dec 2022 16:26:15 -0500
Subject: [PATCH] Views that return fixed content only generate the content
 once (#271)

---
 core/views.py              | 48 ++++++++++++++++++++++++++++++++++----
 users/views/activitypub.py | 27 ++++++++++++---------
 2 files changed, 60 insertions(+), 15 deletions(-)

diff --git a/core/views.py b/core/views.py
index 9f90857..d8fddd4 100644
--- a/core/views.py
+++ b/core/views.py
@@ -1,9 +1,13 @@
+import json
+from typing import ClassVar
+
 import markdown_it
-from django.http import JsonResponse
+from django.http import HttpResponse
 from django.shortcuts import redirect
 from django.templatetags.static import static
 from django.utils.decorators import method_decorator
 from django.utils.safestring import mark_safe
+from django.views.decorators.cache import cache_control
 from django.views.generic import TemplateView, View
 from django.views.static import serve
 
@@ -36,14 +40,50 @@ class About(TemplateView):
         }
 
 
-class AppManifest(View):
+class StaticContentView(View):
+    """
+    A view that returns a bit of static content.
+    """
+
+    # Content type of the static payload
+    content_type: str
+
+    # The static content that will be returned by the view
+    static_content: ClassVar[str | bytes]
+
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+        if getattr(StaticContentView, "static_content", None) is None:
+            StaticContentView.static_content = self.get_static_content()
+
+    def get(self, request, *args, **kwargs):
+        return HttpResponse(
+            StaticContentView.static_content,
+            content_type=self.content_type,
+        )
+
+    def get_static_content(self) -> str | bytes:
+        """
+        Override to generate the view's static content.
+        """
+        raise NotImplementedError()
+
+
+@method_decorator(cache_control(max_age=60 * 15), name="dispatch")
+class AppManifest(StaticContentView):
     """
     Serves a PWA manifest file. This is a view as we want to drive some
     items from settings.
+
+    NOTE: If this view changes to need runtime Config, it should change from
+          StaticContentView to View, otherwise the settings will only get
+          picked up during boot time.
     """
 
-    def get(self, request):
-        return JsonResponse(
+    content_type = "application/json"
+
+    def get_static_content(self) -> str | bytes:
+        return json.dumps(
             {
                 "$schema": "https://json.schemastore.org/web-manifest-combined.json",
                 "name": "Takahē",
diff --git a/users/views/activitypub.py b/users/views/activitypub.py
index c28fed3..c6d671f 100644
--- a/users/views/activitypub.py
+++ b/users/views/activitypub.py
@@ -4,6 +4,7 @@ from asgiref.sync import async_to_sync
 from django.conf import settings
 from django.http import Http404, HttpResponse, HttpResponseBadRequest, JsonResponse
 from django.utils.decorators import method_decorator
+from django.views.decorators.cache import cache_control
 from django.views.decorators.csrf import csrf_exempt
 from django.views.generic import View
 
@@ -18,6 +19,7 @@ from core.signatures import (
     VerificationError,
     VerificationFormatError,
 )
+from core.views import StaticContentView
 from takahe import __version__
 from users.models import Identity, InboxMessage, SystemActor
 from users.shortcuts import by_handle_or_404
@@ -216,35 +218,38 @@ class Outbox(View):
         )
 
 
-class EmptyOutbox(View):
+@method_decorator(cache_control(max_age=60 * 15), name="dispatch")
+class EmptyOutbox(StaticContentView):
     """
     A fixed-empty outbox for the system actor
     """
 
-    def get(self, request, *args, **kwargs):
-        return JsonResponse(
+    content_type: str = "application/activity+json"
+
+    def get_static_content(self) -> str | bytes:
+        return json.dumps(
             canonicalise(
                 {
                     "type": "OrderedCollection",
                     "totalItems": 0,
                     "orderedItems": [],
                 }
-            ),
-            content_type="application/activity+json",
+            )
         )
 
 
-@method_decorator(cache_page(), name="dispatch")
-class SystemActorView(View):
+@method_decorator(cache_control(max_age=60 * 15), name="dispatch")
+class SystemActorView(StaticContentView):
     """
     Special endpoint for the overall system actor
     """
 
-    def get(self, request):
-        return JsonResponse(
+    content_type: str = "application/activity+json"
+
+    def get_static_content(self) -> str | bytes:
+        return json.dumps(
             canonicalise(
                 SystemActor().to_ap(),
                 include_security=True,
-            ),
-            content_type="application/activity+json",
+            )
         )