From d64b0f81c998f925ff70dacd2bbbcd4361d6a152 Mon Sep 17 00:00:00 2001
From: Will Norris <will@willnorris.com>
Date: Wed, 14 Jun 2017 20:04:41 -0400
Subject: [PATCH] return 304 from TransformingTransport

If the caching headers in the request are valid, return a 304 response
instead of doing the transformation.

Ref #92
---
 imageproxy.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/imageproxy.go b/imageproxy.go
index a4ca19e..850fd32 100644
--- a/imageproxy.go
+++ b/imageproxy.go
@@ -294,6 +294,11 @@ func (t *TransformingTransport) RoundTrip(req *http.Request) (*http.Response, er
 		return nil, err
 	}
 
+	if should304(req, resp) {
+		// bare 304 response, full response will be used from cache
+		return &http.Response{StatusCode: http.StatusNotModified}, nil
+	}
+
 	defer resp.Body.Close()
 	b, err := ioutil.ReadAll(resp.Body)
 	if err != nil {