From 5c6e78b9c14a41a3fff9c77b1d952ced962c1622 Mon Sep 17 00:00:00 2001
From: Vincent Bernat <vincent@bernat.im>
Date: Sun, 22 Apr 2018 12:17:31 +0200
Subject: [PATCH] api: ensure /feed is easily cacheable by issuing
 etag/last-modified headers

---
 isso/views/comments.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/isso/views/comments.py b/isso/views/comments.py
index ddc2b09..120fef3 100644
--- a/isso/views/comments.py
+++ b/isso/views/comments.py
@@ -950,7 +950,16 @@ class API(object):
         ET.ElementTree(feed).write(output,
                                    encoding='utf-8',
                                    xml_declaration=True)
-        return XML(output.getvalue(), 200)
+        response = XML(output.getvalue(), 200)
+
+        # Add an etag/last-modified value for caching purpose
+        if comment0 is None:
+            response.set_etag('empty')
+            response.last_modified = 0
+        else:
+            response.set_etag('{tid}-{id}'.format(**comment0))
+            response.last_modified = comment0['modified'] or comment0['created']
+        return response.make_conditional(request)
 
     def preview(self, environment, request):
         data = request.get_json()