From fa85c8ba80a92e2d0a9210865dcb9b5655ae9b5a Mon Sep 17 00:00:00 2001
From: Jake Howard <git@theorangeone.net>
Date: Tue, 4 Oct 2022 20:14:26 +0100
Subject: [PATCH] Cache fragments for longer, and clear when editing page

---
 .../templates/common/content-details.html     |  2 +-
 .../common/templates/common/listing-item.html |  2 +-
 website/common/wagtail_hooks.py               | 23 +++++++++++++++++++
 website/utils/context_processors.py           |  9 +++++++-
 4 files changed, 33 insertions(+), 3 deletions(-)
 create mode 100644 website/common/wagtail_hooks.py

diff --git a/website/common/templates/common/content-details.html b/website/common/templates/common/content-details.html
index 114c25c..b326719 100644
--- a/website/common/templates/common/content-details.html
+++ b/website/common/templates/common/content-details.html
@@ -1,6 +1,6 @@
 {% load wagtailcore_tags humanize_tags cache util_tags %}
 
-{% cache 600|jitter:60 "content-details" page.id request.is_preview %}
+{% cache FRAGMENT_CACHE_TTL|jitter:FRAGMENT_CACHE_TTL_JITTER "content-details" page.id request.is_preview %}
   <div class="content-details field is-grouped">
     {% if page.date %}
       <span class="icon-text">
diff --git a/website/common/templates/common/listing-item.html b/website/common/templates/common/listing-item.html
index c986dff..df0c2fa 100644
--- a/website/common/templates/common/listing-item.html
+++ b/website/common/templates/common/listing-item.html
@@ -13,7 +13,7 @@
       <div>
         <h2 class="title is-3"><a href="{% pageurl page %}">{{ page.title }}</a></h2>
         {% include "common/content-details.html" %}
-        {% cache 900|jitter:60 "summary" page.id request.is_preview %}
+        {% cache FRAGMENT_CACHE_TTL|jitter:FRAGMENT_CACHE_TTL_JITTER "summary" page.id request.is_preview %}
           <p>{{ page.summary }}</p>
         {% endcache %}
       </div>
diff --git a/website/common/wagtail_hooks.py b/website/common/wagtail_hooks.py
new file mode 100644
index 0000000..30df29e
--- /dev/null
+++ b/website/common/wagtail_hooks.py
@@ -0,0 +1,23 @@
+from django.core.cache import cache
+from django.core.cache.utils import make_template_fragment_key
+from django.http.request import HttpRequest
+from wagtail import hooks
+from wagtail.models import Page
+
+from website.common.models import BasePage
+
+FRAGMENT_CACHES = {"summary", "content-details"}
+
+
+@hooks.register("after_edit_page")
+def clear_fragment_cache(request: HttpRequest, page: Page) -> None:
+    if not isinstance(page, BasePage):
+        return
+
+    cache.delete_many(
+        [
+            # Empty string is for the empty value of `request.is_preview`
+            make_template_fragment_key(cache_name, [page.id, False])
+            for cache_name in FRAGMENT_CACHES
+        ]
+    )
diff --git a/website/utils/context_processors.py b/website/utils/context_processors.py
index fc7fa77..6f6099e 100644
--- a/website/utils/context_processors.py
+++ b/website/utils/context_processors.py
@@ -3,4 +3,11 @@ from django.http.request import HttpRequest
 
 
 def global_vars(request: HttpRequest) -> dict:
-    return {"SEO_INDEX": settings.SEO_INDEX, "DEBUG": settings.DEBUG}
+    # noop caching in preview
+    fragment_cache_ttl = 0 if getattr(request, "is_preview", False) else 3600
+    return {
+        "SEO_INDEX": settings.SEO_INDEX,
+        "DEBUG": settings.DEBUG,
+        "FRAGMENT_CACHE_TTL": fragment_cache_ttl,
+        "FRAGMENT_CACHE_TTL_JITTER": fragment_cache_ttl * 0.1,
+    }