gistfile1.rb

class MyAppMiddleware

  PATH_MATCHER = %r{^/app}


  def initialize app
    @app = app
  end


  def call env
    if env['PATH_INFO'] =~ PATH_MATCHER
      do_thing
    else
      @app.call(env)
    end
  end


  def build_response status, body
    body = [body] unless body.respond_to?(:each)
    [status, {'Content-Length' => '', 'Content-Type' => ''}, body]
  end


  def do_thing

    build_response()
  rescue => e
    build_response(500, "Something bad happened")
  end
end