Add an outgoing Processor::Transformer

Respective handlers may transform the response
data into any other object.

This will be useful for handlers that perform
serialization, rendering, generating a rack
response etc ...

lib/substation.rb

@@ -42,6 +42,7 @@ module Substation
 require 'substation/processor'
 require 'substation/processor/evaluator'
 require 'substation/processor/wrapper'
+require 'substation/processor/transformer'
 require 'substation/environment'
 require 'substation/environment/dsl'
 require 'substation/dispatcher'

lib/substation/processor/transformer.rb

@@ -0,0 +1,23 @@
+module Substation
+  module Processor
+
+    # A processor that transforms output data into something else
+    class Transformer
+
+      include Processor::Outgoing
+
+      # Transform response data into something else
+      #
+      # @param [Response] response
+      #   the response to process
+      #
+      # @return [Response]
+      #
+      # @api private
+      def call(response)
+        respond_with(response, handler.call(response))
+      end
+
+    end # class Wrapper
+  end # module Processor
+end # module Substation

spec/spec_helper.rb

@@ -35,6 +35,12 @@ class Presenter
     include Concord.new(:data)
   end
 
+  class Transformer
+    def self.call(response)
+      :transformed
+    end
+  end
+
   module Handler
 
     class Evaluator

spec/unit/substation/processor/transformer/call_spec.rb

@@ -0,0 +1,21 @@
+# encoding: utf-8
+
+require 'spec_helper'
+
+describe Processor::Transformer, '#call' do
+  subject { object.call(response) }
+
+  let(:object)   { described_class.new(s_env, Spec::Transformer) }
+  let(:s_env)    { mock }
+  let(:response) { Response::Success.new(request, output) }
+  let(:request)  { Request.new(name, env, input) }
+  let(:name)     { mock }
+  let(:env)      { mock }
+  let(:input)    { mock }
+  let(:output)   { mock }
+
+  let(:transformed) { Response::Success.new(request, data) }
+  let(:data)        { Spec::Transformer.call(response) }
+
+  it { should eql(transformed) }
+end