chartHeatmap.mjs

"use strict";

import { chartExportOptions } from "./chartExport.mjs";

/**
 * Format the response from SensorThings API to make it suitable for use in a heatmap
 * @param {Array} obsArray Array of observations (timestamp + value) that is response from SensorThings API
 * @returns {Array} Array of formatted observations suitable for use in a heatmap
 */
const formatSensorThingsApiResponseForHeatMap = function (obsArray) {
  if (!obsArray) return;

  return obsArray.map((obs) => {
    // Get the date/time string; first element in input array; remove trailing "Z"
    const obsDateTimeInput = obs[0].slice(0, -1);
    // Get the "date" part of an observation
    const obsDateInput = obs[0].slice(0, 10);
    // Create Date objects
    const obsDateTime = new Date(obsDateTimeInput);
    const obsDate = new Date(obsDateInput);
    // x-axis -> timestamp; will be the same for observations from the same date
    const timestamp = Date.parse(obsDate);
    // y-axis -> hourOfDay
    const hourOfDay = obsDateTime.getHours();
    // value -> the observation's value; second element in input array
    const value = obs[1];
    return [timestamp, hourOfDay, value];
  });
};

/**
 * Calculate the minimum and maximum values for a heatmap's color axis
 * @param {Array} formattedObsArrHeatmap Response from SensorThings API formatted for use in a heatmap
 * @returns {Object} An object containing the minimum and maximum values
 */
const calculateMinMaxValuesForHeatmapColorAxis = function (
  formattedObsArrHeatmap
) {
  // The observation value is the third element in array
  const obsValueArr = formattedObsArrHeatmap.map((obs) => obs[2]);

  // Extract integer part
  const minValue = Math.trunc(Math.min(...obsValueArr));
  const maxValue = Math.trunc(Math.max(...obsValueArr));

  // Calculate the closest multiple of 5
  const minObsValue = minValue - (minValue % 5);
  const maxObsValue = maxValue + (5 - (maxValue % 5));

  return { minObsValue, maxObsValue };
};

/**
 * Draw a heatmap using Highcharts library
 * @param {Array} formattedObsArrayForHeatmap Response from SensorThings API formatted for use in a heatmap
 * @param {Object} extractedFormattedDatastreamProperties An object that contains arrays of formatted Datastream properties
 * @returns {undefined} undefined
 */
const drawHeatMapHighcharts = function (
  formattedObsArrayForHeatmap,
  extractedFormattedDatastreamProperties
) {
  // Arrays of datastream properties
  const {
    datastreamDescriptionsArr,
    datastreamNamesArr,
    phenomenonNamesArr,
    unitOfMeasurementSymbolsArr,
  } = extractedFormattedDatastreamProperties;