Implement Cross-Origin Resource Sharing:

* Add Api::ApplicationController
* Route OPTION requests (CORS preflight) to API application controller
* Filter all API requests through #cor_filter in API application
  controller

app/controllers/api/application_controller.rb

@@ -0,0 +1,14 @@
+class Api::ApplicationController < ApplicationController
+  before_filter :cor_filter
+
+  def cor_filter
+    headers['Access-Control-Allow-Origin'] = request.headers['Origin']
+  end
+
+  def cor_preflight
+    headers['Access-Control-Allow-Methods'] = 'GET, POST, PUT, DELETE'
+    headers['Access-Control-Allow-Headers'] = 'Content-Type, X-Requested-With'
+
+    head :ok
+  end
+end

app/controllers/api/v0/playlists_controller.rb

@@ -1,4 +1,4 @@
-class Api::V0::PlaylistsController < ApplicationController
+class Api::V0::PlaylistsController < Api::ApplicationController
   respond_to :json
 
   def index

config/routes.rb

@@ -3,6 +3,8 @@ Scube::Application.routes.draw do
     namespace :v0 do
       resources :playlists, :only => [:index]
     end
+
+    match '*all' => 'application#cor_preflight', :via => :options
   end
 
   resources :sounds, :only => [:show]

spec/controllers/api/application_controller_spec.rb

@@ -0,0 +1,49 @@
+require 'spec_helper'
+
+describe Api::ApplicationController do
+  before do
+    controller.current_user = Factory.create(:user)
+  end
+
+  context 'CORS: Cross-Origin Ressource Sharing' do
+    before do
+      request.env['Origin'] = 'http://origin.example/'
+    end
+
+    context 'preflight' do
+      controller(Api::ApplicationController) do
+        alias_method :index, :cor_preflight
+      end
+
+      def options(action)
+        process action, nil, nil, nil, 'OPTIONS'
+      end
+
+      it 'sets Access-Control-Allow-Methods header' do
+        options :index
+        response.headers['Access-Control-Allow-Methods'].should ==
+          'GET, POST, PUT, DELETE'
+      end
+
+      it 'sets Access-Control-Allow-Methods header' do
+        options :index
+        response.headers['Access-Control-Allow-Headers'].should ==
+          'Content-Type, X-Requested-With'
+      end
+    end
+
+    describe 'before filter' do
+      controller(Api::ApplicationController) do
+        def index
+          head :ok
+        end
+      end
+
+      it 'sets Access-Control-Allow-Origin header' do
+        get :index
+        response.headers['Access-Control-Allow-Origin'].should ==
+          request.env['Origin']
+      end
+    end
+  end
+end

spec/integration/api/cross_origin_request_spec.rb

@@ -0,0 +1,41 @@
+require 'spec_helper'
+
+feature 'API cross origin request' do
+  include UserIntegrationHelpers
+
+  let(:user)    { Factory.create(:user) }
+  let(:origin)  { 'http://origin.example/' }
+
+  background do
+    post sessions_path, :session => {
+      :email    => user.email,
+      :password => user.password
+    }
+  end
+
+  scenario 'preflight request' do
+    # FIXME: replace with a more stable/generic action
+    # FIXME: request without redirect
+    request_via_redirect(
+      :options,
+      api_v0_playlists_path(:format => :json),
+      nil,
+      { 'Origin' => origin }
+    )
+
+    response.headers['Access-Control-Allow-Origin'].should == origin
+    response.headers['Access-Control-Allow-Methods'].should ==
+      'GET, POST, PUT, DELETE'
+    response.headers['Access-Control-Allow-Headers'].should ==
+      'Content-Type, X-Requested-With'
+  end
+
+  scenario 'basic request' do
+    # FIXME: replace with a more stable/generic action
+    get api_v0_playlists_path(:format => :json), nil, {
+      'Origin' => origin
+    }
+
+    response.headers['Access-Control-Allow-Origin'].should == origin
+  end
+end

spec/routing/options_requests_spec.rb

@@ -0,0 +1,11 @@
+require 'spec_helper'
+
+describe '/api OPTIONS requests routing' do
+  it 'routes to Api::ApplicationController#cor_preflight' do
+    { :options => '/api/v0' }.should route_to(
+      :controller => 'api/application',
+      :action => 'cor_preflight',
+      :all => 'v0'
+    )
+  end
+end