Merit API getpurchorders request example with saving to CSV

merit-api-nodejs-get-purchases.js

// Merit API spec:
// https://www.merit.ee/juhend/muud/Merit_Aktiva_API_specification.pdf

// Install required packages:
//   npm install crypto-js moment request request-debug

const CryptoJS = require('crypto-js');
const moment = require('moment');
const axios = require('axios')
const json2csv = require('json2csv').parse;

const API_KEY = '...';
const API_ID = '...';
const URL = 'https://aktiva.merit.ee/api/v1/getpurchorders'
const VENDOR_REGEXES = [
  /aktsiaselts Tartu Veevärk/,
  /Eesti Energia Aktsiaselts|Elektrum Eesti OÜ/,
  /AS Tartu Keskkatlamaja/,
  /Osaühing EKOVIR/,
  /SECURITAS EESTI AKTSIASELTS/
]

function calculateSignature(timestamp) {
  const dataString = API_ID + timestamp
  const hash = CryptoJS.HmacSHA256(dataString, API_KEY)
  const signature = CryptoJS.enc.Base64.stringify(hash)
  return signature
}

async function makeApiRequest(queryParams, requestBody) {
  const options = {
    url: URL,
    params: queryParams,
    headers: { 'content-type': 'application/json' },
    data: requestBody
  }
  const response = await axios(options)
  return JSON.parse(response.data)
}

function makeRequestBody(month) {
  const end = month < 11 ? { y: 2017, M: month + 1, d: 1} : { y: 2017, M: 11, d: 31}
  return {
    periodStart: moment({ y: 2017, M: month, d: 1}).format('YYYYMMDD'),
    periodEnd: moment(end).format('YYYYMMDD')
  }
}

function filterAndCleanupPurchases(purchases, vendorNameRegex) {
  const electricityPurchases = purchases.filter(p => p.VendorName.match(vendorNameRegex))
  return electricityPurchases.map(p => {
    const date = p.TransactionDate.replace(/\/Date\((\d+)\)\//, '$1')
    return {
      vendor: p.VendorName,
      billNumber: p.BillNo,
      date: moment(Number(date)).format('YYYY-MM-DD'),
      amount: p.TotalAmount,
      tax: p.TaxAmount
    }
  })
}

async function processPurchases() {
  const timestamp = moment().format('YYYYMMDDHHmmss')
  const signature = calculateSignature(timestamp)
  const queryParams = {
    ApiId: API_ID,
    timestamp: timestamp,
    signature: signature
  }

  result = {}
  VENDOR_REGEXES.forEach(vendorRegex => result[String(vendorRegex)] = [])

  for (let month of Array(12).keys()) {
    const requestBody = makeRequestBody(month)
    try {
      const purchases = await makeApiRequest(queryParams, requestBody)
      for (let vendorRegex of VENDOR_REGEXES) {
        const filteredPurchases = filterAndCleanupPurchases(purchases, vendorRegex)
        result[String(vendorRegex)].push(...filteredPurchases)
      }
      console.log('Month ' + (month + 1) + ' done')
    } catch (e) {
      console.log('Request error: ', e)
    }
  }
  const csvFile = fs.openSync('purchases.csv', 'w')
  Object.entries(result).forEach((entry) => { // entry = [key, value]
    const csv = json2csv(entry[1])
    fs.writeSync(csvFile, csv)
    fs.writeSync(csvFile, "\r\n\r\n")
  })
}

processPurchases()