tabular-data.js

{
  "ambient": {  // Ambient sensor.
    "ambient": [{x: timestamp, y: temperature}, /* more... */]
  },
  "1-1": {  // Silo 1, cable 1.
    "1": [{x: timestamp, y: temperature}, /* more... */],  // Node 1.
    "2": [{x: timestamp, y: temperature}, /* more... */]   // Node 2.
  }
}

xlsx.js

import {DateTime} from 'luxon'
import xlsx from 'xlsx'

import i18n from '@/i18n'

function formatSheetName(key) {
	// TODO: Silo alias.
	return key === 'ambient' ? i18n.t('ambientLabel') : key
}

function formatNodeName(key) {
	return key === 'ambient' ? i18n.t('ambientLabel') : key
}

const baseDate = new Date(1899, 11, 30, 0, 0, 0)

function timestampToExcelDate(timestamp, timezone) {
	const v = DateTime
		.fromMillis(timestamp, {zone: 'utc'})
		.setZone(timezone)
		.toJSDate()
	const dnthresh = baseDate.getTime() +
		(v.getTimezoneOffset() - baseDate.getTimezoneOffset()) * 60000
	return (v.getTime() - dnthresh) / (24 * 60 * 60 * 1000)
}

export function exportTemperatures(tabularData, timezone, filename) {
	const book = xlsx.utils.book_new()

	for (const [key, entry] of Object.entries(tabularData)) {
		const aoa = [['', ...entry.nodes.map(formatNodeName)]]
		for (const [ts, data] of Object.entries(entry.data)) {
			const timestamp = Number(ts)
			if (Number.isNaN(timestamp)) {
				continue
			}
			const date = timestampToExcelDate(timestamp)
			const dateCell = {v: date, t: 'n', z: 'yyyy-mm-dd" "hh:MM:ss'}
			const temperatures = entry.nodes.map((nid) => {
				const value = data[nid]
				const temperature = Number(value)
				return Number.isNaN(temperature) ? (value || '') : temperature
			})
			aoa.push([dateCell, ...temperatures])
		}
		const sheet = xlsx.utils.aoa_to_sheet(aoa)
		sheet['!cols'] = [{wch: 16}, {wch: 8}]
		xlsx.utils.book_append_sheet(book, sheet, formatSheetName(key))
	}

	xlsx.writeFile(book, filename)
}