Rack middleware for enabling CORS

enable_cors.rb

class EnableCors
  def initialize(app)
    @app = app
  end

  def call(env)
    requesting_host = env["HTTP_ORIGIN"]
    cors_headers = {}
    cors_headers['Access-Control-Allow-Origin'] = "#{requesting_host}"
    cors_headers['Access-Control-Request-Method'] = "GET, PUT, DELETE, POST, OPTIONS"
    cors_headers['Access-Control-Allow-Headers'] = 'Origin, X-Requested-With, Content-Type, Accept'
    cors_headers['Access-Control-Max-Age'] = '1728000'
    if env["REQUEST_METHOD"] == "OPTIONS"
      cors_headers["Content-Type"] = "text/plain"
      [200, cors_headers, []]
    else
      status, headers, body = @app.call(env)
      [status, headers.merge(cors_headers), body]
    end
  end
end

enable_cors_spec.rb

require 'spec_helper'

describe "EnableCors" do
  
  before(:each) do
    class DummyApp
      def call(env)
        return [{}, {}, {}]
      end
    end
  end
  
  it "should parrot the origin from request" do
    middleware = EnableCors.new(DummyApp.new)
    status, headers, body = middleware.call({'HTTP_ORIGIN' => "http://google.com"})
    headers['Access-Control-Allow-Origin'].should eq('http://google.com')
  end
  
  it "should allow ORIGIN HTTP method" do
    middleware = EnableCors.new(DummyApp.new)
    status, headers, body = middleware.call({})
    headers['Access-Control-Request-Method'].should match(/OPTIONS/)
  end
  
  it "should respond to ORIGIN method wtih zero length response and 200 code" do
    middleware = EnableCors.new(DummyApp.new)
    status, headers, body = middleware.call({'REQUEST_METHOD' => "OPTIONS"})
    status.should == 200
    body.length.should == 0
    headers["Content-Type"].should == "text/plain"
  end
end