Method sendMessageInternal_

src/service/viewer-impl.js:786–840

* Sends the message to the viewer. * * @param {string} eventType * @param {?JsonObject|string|undefined} data * @param {boolean} cancelUnsent * @param {boolean} awaitResponse * @return {!Promise<(?JsonObject|string|undefined)>} the response promise

(eventType, data, cancelUnsent, awaitResponse)

   * @return {!Promise<(?JsonObject|string|undefined)>} the response promise
   */
  sendMessageInternal_(eventType, data, cancelUnsent, awaitResponse) {
    if (this.messageDeliverer_) {
      // Certain message deliverers return fake "Promise" instances called
      // "Thenables". Convert from these values into trusted Promise instances,
      // assimilating with the resolved (or rejected) internal value.
      return /** @type {!Promise<?JsonObject|string|undefined>} */ (
        tryResolve(() =>
          this.messageDeliverer_(
            eventType,
            /** @type {?JsonObject|string|undefined} */ (data),
            awaitResponse
          )
        )
      );
    }

    if (!this.messagingReadyPromise_) {
      if (awaitResponse) {
        return Promise.reject(getChannelError());
      } else {
        return Promise.resolve();
      }
    }

    if (!cancelUnsent) {
      return this.messagingReadyPromise_.then(() => {
        return this.messageDeliverer_(eventType, data, awaitResponse);
      });
    }

    const found = findIndex(
      this.messageQueue_,
      (m) => m.eventType == eventType
    );

    let message;
    if (found != -1) {
      message = this.messageQueue_.splice(found, 1)[0];
      message.data = data;
      message.awaitResponse = message.awaitResponse || awaitResponse;
    } else {
      const deferred = new Deferred();
      const {promise: responsePromise, resolve: responseResolver} = deferred;

      message = {
        eventType,
        data,
        awaitResponse,
        responsePromise,
        responseResolver,
      };
    }
    this.messageQueue_.push(message);
    return message.responsePromise;
  }

  /** @override */
  broadcast(message) {