support for twitter downloads

app/logical/downloads/rewrite_strategies/base.rb

@@ -6,7 +6,7 @@ module Downloads
       end
 
       def self.strategies
-        [Pixiv, NicoSeiga, Twitpic, DeviantArt, Tumblr, Moebooru]
+        [Pixiv, NicoSeiga, Twitpic, DeviantArt, Tumblr, Moebooru, Twitter]
       end
 
       def rewrite(url, headers, data = {})

app/logical/downloads/rewrite_strategies/twitter.rb

@@ -0,0 +1,27 @@
+module Downloads
+  module RewriteStrategies
+    class Twitter < Base
+      def rewrite(url, headers, data = {})
+        if url =~ %r!^https?://(?:mobile\.)?twitter\.com!
+          url, headers = rewrite_image_url(url, headers)
+        end
+
+        return [url, headers, data]
+      end
+
+    protected
+      def rewrite_image_url(url, headers)
+        # example: http://twitter.com/status
+        url = url.sub(%r!^https?://twitter\.com!, "http://mobile.twitter.com")
+
+        if url =~ %r!^https?://mobile\.twitter\.com/\w+/status/\d+!
+          source = ::Sources::Strategies::Twitter.new(url)
+          source.get
+          url = source.image_url
+        end
+
+        return [url, headers]
+      end
+    end
+  end
+end