Enable transformation abilities

Author: waterlink

lib/rack_reverse_proxy/roundtrip.rb

@@ -208,7 +208,11 @@ def proxy
       setup_request
       setup_response_headers
 
-      rack_response
+      transform_response(rack_response)
+    end
+
+    def transform_response(response)
+      rule.transform(path, env, response, uri, headers, source_request)
     end
 
     def format_headers(headers)

lib/rack_reverse_proxy/rule.rb

@@ -25,6 +25,16 @@ def get_uri(path, env, *args)
       ).build_uri
     end
 
+    def transform(path, env, response, request_uri, *args)
+      Candidate.new(
+        self,
+        has_custom_url,
+        path,
+        env,
+        matches(path, *args)
+      ).transform(response, request_uri)
+    end
+
     def to_s
       %("#{spec}" => "#{url}")
     end
@@ -68,6 +78,10 @@ def build_uri
         raw_uri
       end
 
+      def transform(response, request_uri)
+        matches.transform(response, request_uri)
+      end
+
       private
 
       attr_reader :rule, :url, :has_custom_url, :path, :env, :matches
@@ -138,6 +152,16 @@ def substitute(url)
         end
       end
 
+      def transform(response, request_uri)
+        found.inject(response) do |response, match|
+          if match.respond_to?(:transform)
+            match.transform(response, request_uri)
+          else
+            response
+          end
+        end
+      end
+
       private
 
       attr_reader :spec, :url, :path, :headers, :rackreq, :spec_arity, :has_custom_url

spec/rack/reverse_proxy_spec.rb

@@ -1,4 +1,5 @@
 require "spec_helper"
+require "cgi"
 require "base64"
 
 RSpec.describe Rack::ReverseProxy do
@@ -582,6 +583,44 @@ def app
       end
     end
 
+    describe "with a matching and transforming class" do
+      #:nodoc:
+      class MatcherAndTransformer
+        def self.match(path)
+          MatcherAndTransformer.new
+        end
+
+        def url(path)
+          "http://example.org/redirecting"
+        end
+
+        def transform(response, request_uri)
+          status, headers, body = response
+          location = headers["Location"]
+          headers["Location"] = "?url=" + CGI.escape(location) + "&request_uri=" + CGI.escape(request_uri.to_s)
+          [status, headers, body]
+        end
+      end
+
+      def app
+        Rack::ReverseProxy.new(dummy_app) do
+          reverse_proxy MatcherAndTransformer
+        end
+      end
+
+      it "transforms the proxied response" do
+        stub_request(:get, "http://example.org/redirecting").to_return(
+          :headers => {
+            "Location" => "http://example.org/target"
+          }
+        )
+
+        get "/"
+        expect(last_response.headers["Location"])
+          .to eq("?url=http%3A%2F%2Fexample.org%2Ftarget&request_uri=http%3A%2F%2Fexample.org%2Fredirecting")
+      end
+    end
+
     describe "with a matching class" do
       #:nodoc:
       class RequestMatcher