def call(env)
      case [env['REQUEST_METHOD'], env['PATH_INFO']]
        when ['GET', login_path(env)];                provide_login_html(env)
        when ['GET', login_path(env) + '/login.css']; provide_login_css
        else                                          @app.call(env)
      end
    end
def call(env)
      case [env['REQUEST_METHOD'], env['PATH_INFO']]
        when ['GET', login_path(env)];                provide_login_html(env)
        when ['GET', login_path(env) + '/login.css']; provide_login_css
        else                                          @app.call(env)
      end
    end
Instantiates the middleware.

 @param app [Rack app] The Rack application on which this middleware
   should be layered.
 @param login_path [String] the login path

 Rack entry point.

 `call` returns one of three responses, depending on the path and
 method.

 * If the method is GET and the path is `login_path`, `call` returns
   an HTML form for submitting a username and password.
 * If the method is GET and the path is `login_path + "/login.css"`,
   `call` returns the CSS for the aforementioned form.
 * Otherwise, `call` passes the request down through the Rack stack.

 @return a finished Rack response