openmct/example/eventGenerator/EventTelemetryProvider.js

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 * as represented by the Administrator of the National Aeronautics and Space
 * Administration. All rights reserved.
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 * Open MCT is licensed under the Apache License, Version 2.0 (the
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 * License for the specific language governing permissions and limitations
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/**
 * Module defining EventTelemetryProvider. Created by chacskaylo on 06/18/2015.
 */

import messages from './transcript.json';

class EventTelemetryProvider {
  constructor() {
    this.defaultSize = 25;
  }

  generateData(firstObservedTime, count, startTime, duration, name) {
    const millisecondsSinceStart = startTime - firstObservedTime;
    const utc = startTime + count * duration;
    const ind = count % messages.length;
    const message = messages[ind] + ' - [' + millisecondsSinceStart + ']';

    return {
      name,
      utc,
      message
    };
  }

  supportsRequest(domainObject) {
    return domainObject.type === 'eventGenerator';
  }

  supportsSubscribe(domainObject) {
    return domainObject.type === 'eventGenerator';
  }

  subscribe(domainObject, callback) {
    const duration = domainObject.telemetry.duration * 1000;
    const firstObservedTime = Date.now();
    let count = 0;

    const interval = setInterval(() => {
      const startTime = Date.now();
      const datum = this.generateData(
        firstObservedTime,
        count,
        startTime,
        duration,
        domainObject.name
      );
      count += 1;
      callback(datum);
    }, duration);

    return function () {
      clearInterval(interval);
    };
  }

  request(domainObject, options) {
    let start = options.start;
    const end = Math.min(Date.now(), options.end); // no future values
    const duration = domainObject.telemetry.duration * 1000;
    const size = options.size ? options.size : this.defaultSize;
    const data = [];
    const firstObservedTime = options.start;
    let count = 0;

    if (options.strategy === 'latest' || options.size === 1) {
      start = end;
    }

    while (start <= end && data.length < size) {
      const startTime = options.start + count;
      data.push(
        this.generateData(firstObservedTime, count, startTime, duration, domainObject.name)
      );
      start += duration;
      count += 1;
    }

    return Promise.resolve(data);
  }
}

export default EventTelemetryProvider;