Carpentry

carpentry.rb

require "carpentry/no_robots_middleware"

module Carpentry
  class Engine < ::Rails::Engine
    config.app_middleware.use NoRobotsMiddleware
  end
end

no_robots_middleware.rb

module Carpentry
  class NoRobotsMiddleware
    def initialize(app)
      @app = app
    end

    def call(env)
      status, headers, response = @app.call(env)

      if env["carpentry.prototype"] && status == 200
        no_robots_tag = %{<meta name="robots" content="noindex, nofollow"/>\n}
        response.body = response.body.sub("</head>", "#{no_robots_tag}</head>")
      end

      [status, headers, response]
    end
  end
end

prototypes_controller.rb

module Carpentry
  class PrototypesController < ApplicationController
    before_filter :before_carpentry,
      :if => proc { respond_to?(:before_carpentry, true) }

    def serve
      env["carpentry.prototype"] = true
      render "carpentry/prototypes/#{params[:file_path]}"
    end
  end
end

routes.rb

Rails.application.routes.draw do
  namespace "p", :module => :carpentry do
    root :to => "prototypes#serve", :file_path => "index"
    match "/*file_path" => "prototypes#serve"
  end
end