From 4a238491f055ae4116bb0607d8ae31fa9e006974 Mon Sep 17 00:00:00 2001
From: David Manthey <david.manthey@kitware.com>
Date: Wed, 5 Oct 2022 13:29:09 -0400
Subject: [PATCH] Support etags on annotations to improve browser caching.

---
 CHANGELOG.md                                  |  1 +
 girder/girder_large_image/rest/tiles.py       |  8 +++++--
 .../rest/annotation.py                        | 22 ++++++++++---------
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 34ae69ca2..28ec13baa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - Show configured item lists even if there are no large images ([#972](../../pull/972))
 - Add metadata and annotation metadata search modes to Girder ([#974](../../pull/974))
 - Add the ability to show annotation metadata in item annotation lists ([#977](../../pull/977))
+- Support ETAG in annotation rest responses for better browser caching ([#978](../../pull/978))
 
 ## 1.17.0
 
diff --git a/girder/girder_large_image/rest/tiles.py b/girder/girder_large_image/rest/tiles.py
index a7a58ef86..800b30d14 100644
--- a/girder/girder_large_image/rest/tiles.py
+++ b/girder/girder_large_image/rest/tiles.py
@@ -83,9 +83,13 @@ def _handleETag(key, item, *args, **kwargs):
 
     :param key: key for making a distinc etag.
     :param item: item used for the item _id and updated timestamp.
+    :param max_age: the maximum cache duration.
     :param *args, **kwargs: additional arguments for generating an etag.
     """
-    etag = hashlib.md5(strhash(key, str(item['_id']), *args, **kwargs).encode()).hexdigest()
+    max_age = kwargs.get('max_age', 3600)
+    id = str(item['_id'])
+    date = item.get('updated', item.get('created'))
+    etag = hashlib.md5(strhash(key, id, date, *args, **kwargs).encode()).hexdigest()
     setResponseHeader('ETag', etag)
     conditions = [str(x) for x in cherrypy.request.headers.elements('If-Match') or []]
     if conditions and not (conditions == ['*'] or etag in conditions):
@@ -95,7 +99,7 @@ def _handleETag(key, item, *args, **kwargs):
     if conditions == ['*'] or etag in conditions:
         raise cherrypy.HTTPRedirect([], 304)
     # Explicitly set a max-age to recheck the cache after a while
-    setResponseHeader('Cache-control', 'max-age=3600')
+    setResponseHeader('Cache-control', f'max-age={max_age}')
 
 
 def _pickleParams(params):
diff --git a/girder_annotation/girder_large_image_annotation/rest/annotation.py b/girder_annotation/girder_large_image_annotation/rest/annotation.py
index 6efab9071..1c5aa8163 100644
--- a/girder_annotation/girder_large_image_annotation/rest/annotation.py
+++ b/girder_annotation/girder_large_image_annotation/rest/annotation.py
@@ -21,6 +21,7 @@
 import cherrypy
 import orjson
 from bson.objectid import ObjectId
+from girder_large_image.rest.tiles import _handleETag
 
 from girder import logger
 from girder.api import access
@@ -168,24 +169,23 @@ def getAnnotationSchema(self, params):
     @access.public(cookie=True)
     def getAnnotation(self, id, params):
         user = self.getCurrentUser()
-        return self._getAnnotation(user, id, params)
+        annotation = Annotation().load(
+            id, region=params, user=user, level=AccessType.READ, getElements=False)
+        _handleETag('getAnnotation', annotation, params, max_age=86400 * 30)
+        if annotation is None:
+            raise RestException('Annotation not found', 404)
+        return self._getAnnotation(annotation, params)
 
-    def _getAnnotation(self, user, id, params):
+    def _getAnnotation(self, annotation, params):
         """
         Get a generator function that will yield the json of an annotation.
 
-        :param user: the user that needs read access on the annotation and its
-            parent item.
-        :param id: the annotation id.
+        :param annotation: the annotation document without elements.
         :param params: paging and region parameters for the annotation.
         :returns: a function that will return a generator.
         """
         # Set the response time limit to a very long value
         setResponseTimeLimit(86400)
-        annotation = Annotation().load(
-            id, region=params, user=user, level=AccessType.READ, getElements=False)
-        if annotation is None:
-            raise RestException('Annotation not found', 404)
         # Ensure that we have read access to the parent item.  We could fail
         # faster when there are permissions issues if we didn't load the
         # annotation elements before checking the item access permissions.
@@ -509,7 +509,9 @@ def generateResult():
                 if not first:
                     yield b',\n'
                 try:
-                    annotationGenerator = self._getAnnotation(user, annotation['_id'], {})()
+                    annotation = Annotation().load(
+                        annotation['_id'], user=user, level=AccessType.READ, getElements=False)
+                    annotationGenerator = self._getAnnotation(annotation, {})()
                 except AccessException:
                     continue
                 yield from annotationGenerator