module Rack
  class PrefetchKiller
    
    def initialize(app, options = {})
      @app = app
    end
    
    def call(env)
      google_prefetch?(env) ? head_forbidden : @app.call(env)
    end
    
    
    private
    
    
    def google_prefetch?(environment)
      environment["HTTP_X_MOZ"] == "prefetch"
    end
    
    def head_forbidden
      [403, {'Content-Type' => 'text/html; charset=utf-8'}, [' ']]
    end
    
  end
end