From 88e2098d6523770d2749e340517151c308c86fa8 Mon Sep 17 00:00:00 2001
From: Denny Abraham Cheriyan <dennyac@gmail.com>
Date: Sun, 12 Feb 2017 15:55:32 -0800
Subject: [PATCH] Handle protocol relative urls

---
 lib/fastimage.rb | 8 +++++++-
 test/test.rb     | 6 ++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lib/fastimage.rb b/lib/fastimage.rb
index 5d0b1e4..c85b283 100644
--- a/lib/fastimage.rb
+++ b/lib/fastimage.rb
@@ -239,7 +239,9 @@ class FastImage
         begin
           newly_parsed_uri = Addressable::URI.parse(res['Location'])
           # The new location may be relative - check for that
-          if newly_parsed_uri.scheme != "http" && newly_parsed_uri.scheme != "https"
+          if protocol_relative_url?(res['Location'])
+            @parsed_uri = newly_parsed_uri.tap { |obj| obj.scheme = @parsed_uri.scheme }
+          elsif newly_parsed_uri.scheme != "http" && newly_parsed_uri.scheme != "https"
             @parsed_uri.path = res['Location']
           else
             @parsed_uri = newly_parsed_uri
@@ -282,6 +284,10 @@ class FastImage
     end
   end
 
+  def protocol_relative_url?(url)
+    url.start_with?("//")
+  end
+
   def proxy_uri
     begin
       if @options[:proxy]
diff --git a/test/test.rb b/test/test.rb
index 2da6c98..e578d4a 100644
--- a/test/test.rb
+++ b/test/test.rb
@@ -232,6 +232,12 @@ class FastImageTest < Test::Unit::TestCase
     assert_equal GoodFixtures[GoodFixtures.keys.first][1], FastImage.size(url, :raise_on_failure=>true)
   end
 
+  def test_should_handle_permanent_redirect_with_protocol_relative_url
+    url = "http://example.nowhere/foo.jpeg"
+    register_redirect(url, "//example.nowhere/" + GoodFixtures.keys.first)
+    assert_equal GoodFixtures[GoodFixtures.keys.first][1], FastImage.size(url, :raise_on_failure=>true)
+  end
+
   def register_redirect(from, to)
     resp = Net::HTTPMovedPermanently.new(1.0, 302, "Moved")
     resp['Location'] = to