openmct/example/generator/WorkerInterface.js

/*****************************************************************************
 * Open MCT, Copyright (c) 2014-2023, United States Government
 * as represented by the Administrator of the National Aeronautics and Space
 * Administration. All rights reserved.
 *
 * Open MCT is licensed under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0.
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * Open MCT includes source code licensed under additional open source
 * licenses. See the Open Source Licenses file (LICENSES.md) included with
 * this source code distribution or the Licensing information page available
 * at runtime from the About dialog for additional information.
 *****************************************************************************/

import { v4 as uuid } from 'uuid';

export default function WorkerInterface(openmct, StalenessProvider) {
  // eslint-disable-next-line no-undef
  const workerUrl = `${openmct.getAssetPath()}${__OPENMCT_ROOT_RELATIVE__}generatorWorker.js`;
  this.StalenessProvider = StalenessProvider;
  this.worker = new Worker(workerUrl);
  this.worker.onmessage = this.onMessage.bind(this);
  this.callbacks = {};
  this.staleTelemetryIds = {};

  this.watchStaleness();
}

WorkerInterface.prototype.watchStaleness = function () {
  this.StalenessProvider.on('stalenessEvent', ({ id, isStale }) => {
    this.staleTelemetryIds[id] = isStale;
  });
};

WorkerInterface.prototype.onMessage = function (message) {
  message = message.data;
  var callback = this.callbacks[message.id];
  if (callback) {
    callback(message);
  }
};

WorkerInterface.prototype.dispatch = function (request, data, callback) {
  var message = {
    request: request,
    data: data,
    id: uuid()
  };

  if (callback) {
    this.callbacks[message.id] = callback;
  }

  this.worker.postMessage(message);

  return message.id;
};

WorkerInterface.prototype.request = function (request) {
  var deferred = {};
  var promise = new Promise(function (resolve, reject) {
    deferred.resolve = resolve;
    deferred.reject = reject;
  });
  var messageId;

  let self = this;
  function callback(message) {
    if (message.error) {
      deferred.reject(message.error);
    } else {
      deferred.resolve(message.data);
    }

    delete self.callbacks[messageId];
  }

  messageId = this.dispatch('request', request, callback.bind(this));

  return promise;
};

WorkerInterface.prototype.subscribe = function (request, cb) {
  const { id, loadDelay } = request;
  const messageId = this.dispatch('subscribe', request, (message) => {
    if (!this.staleTelemetryIds[id]) {
      setTimeout(() => cb(message.data), Math.max(loadDelay, 0));
    }
  });

  return function () {
    this.dispatch('unsubscribe', {
      id: messageId
    });
    delete this.callbacks[messageId];
  }.bind(this);
};