rack power

class App
  def initialize
    router.get '/sparta' do
      [200, { 'Content-Type' => 'text/plain' }, ["This is Rack!"]]
    end

    router.get '/knock' do
      [200, { 'Content-Type' => 'text/plain' }, ["Who's there?"]]
    end
  end

  def call(env)
    router.call(env)
  end  
private
  def router
    @router ||= Router.new
  end
end

class Router
  def get(path, &block)
    register("GET #{path}", &block)
  end

  def call(env)
    method_and_path = "#{env['REQUEST_METHOD']} #{env['PATH_INFO']}"
    if routes[method_and_path].nil?
      [404, { 'Content-Type' => 'text/plain' }, []]
    else
      routes[method_and_path].call(env)
    end
  end
private
  def register(method_and_path, &block)
    routes[method_and_path] = block
  end  

  def routes
    @routes ||= {}
  end
end