@trusthab/composable-resources/src/resources/kpi/devices_offline.js

migrating https://github.com/knetikmedia/hab-api/tree/integration/app/resources/composable

const composer = require('../../mixin_loader');

module.exports = (App) => {
  const { underscore } = require('inflected');
  const PROPERTY_VALUE = 'offline';

  class DevicesOfflineResource {
    static mixins() {
      return ['Kpi'];
    }

    getMetricId() {
      return `devices_${PROPERTY_VALUE}`;
    }

    getMetricType() {
      return 'gauge';
    }

    getValue() {
      if (this.get('obj').device_type === 'gateway') { return 0; }
      
      const { value, oldValue } = this.get('diff');
      if (oldValue !== PROPERTY_VALUE && value === PROPERTY_VALUE) {
        return 1;
      }

      return 0;
    }
  }

  return composer(DevicesOfflineResource, App);
};