#1866: Tumblr thumbnail rewriting

app/logical/downloads/strategies/base.rb

@@ -2,12 +2,26 @@ module Downloads
   module Strategies
     class Base
       def self.strategies
-        [Pixiv, Twitpic, DeviantArt]
+        [Pixiv, Twitpic, DeviantArt, Tumblr]
       end
 
       def rewrite(url, headers)
         return [url, headers]
       end
+
+    protected
+      def http_exists?(url, headers)
+        exists = false
+        uri = URI.parse(url)
+        Net::HTTP.start(uri.host, uri.port) do |http|
+          http.request_head(uri.request_uri, headers) do |res|
+            if res.is_a?(Net::HTTPSuccess)
+              exists = true
+            end
+          end
+        end
+        exists
+      end
     end
   end
 end