Class MiddlewareSequence

packages/rest/src/sequence.ts:189–293

 */
@injectable({scope: BindingScope.SINGLETON})
export class MiddlewareSequence implements SequenceHandler {
  private middlewareView: MiddlewareView;

  static defaultOptions: InvokeMiddlewareOptions = {
    chain: RestTags.REST_MIDDLEWARE_CHAIN,
    orderedGroups: [
      // Please note that middleware is cascading. The `sendResponse` is
      // added first to invoke downstream middleware to get the result or
      // catch errors so that it can produce the http response.
      RestMiddlewareGroups.SEND_RESPONSE,

      RestMiddlewareGroups.CORS,
      RestMiddlewareGroups.API_SPEC,
      RestMiddlewareGroups.MIDDLEWARE,

      RestMiddlewareGroups.FIND_ROUTE,

      // authentication depends on the route
      RestMiddlewareGroups.AUTHENTICATION,

      RestMiddlewareGroups.PARSE_PARAMS,

      RestMiddlewareGroups.INVOKE_METHOD,
    ],

    /**
     * Reports an error if there are middleware groups are unreachable as they
     * are ordered after the `invokeMethod` group.
     */
    validate: groups => {
      const index = groups.indexOf(RestMiddlewareGroups.INVOKE_METHOD);
      if (index !== -1) {
        const unreachableGroups = groups.slice(index + 1);
        if (unreachableGroups.length > 0) {
          throw new Error(
            `Middleware groups "${unreachableGroups.join(
              ',',
            )}" are not invoked as they are ordered after "${
              RestMiddlewareGroups.INVOKE_METHOD
            }"`,
          );
        }
      }
    },
  };

  /**
   * Constructor: Injects `InvokeMiddleware` and `InvokeMiddlewareOptions`
   *
   * @param invokeMiddleware - invoker for registered middleware in a chain.
   * To be injected via RestBindings.INVOKE_MIDDLEWARE_SERVICE.
   */
  constructor(
    @inject.context()
    context: Context,

    @inject(RestBindings.INVOKE_MIDDLEWARE_SERVICE)
    readonly invokeMiddleware: InvokeMiddleware,