population.js

import unzipper from 'unzipper'
import { parse } from 'csv-parse/sync'
import { countryToCode } from './utils.js'

const readRemoteZippedCSV = async (url) => {
  const response = await fetch(url)
  const buffer = await response.arrayBuffer()
  const directory = await unzipper.Open.buffer(Buffer.from(buffer))
  const mainFile = await directory.files[0].buffer()
  return parse(mainFile,
    { columns: true, skipEmptyLines: true, encoding: 'utf8' })
}

const fixBrokenUtf8 = (s) => Buffer.from(s, 'ascii').toString('utf8')

const getPopulationDataFromItem = (item) => {
  const countryName = fixBrokenUtf8(item['Country or Area'])
  const population = Math.round(parseFloat(fixBrokenUtf8(item.Value)) * 1000)
  const countryCode = countryToCode(countryName)
  return { countryCode, population }
}

const getPopulationZip = async () => {
  const populationUrl = 'http://data.un.org/Handlers/DownloadHandler.ashx?DataFilter=variableID:12;varID:2&DataMartId=PopDiv&Format=csv&c=2,4,7&s=_crEngNameOrderBy:asc,_timeEngNameOrderBy:desc,_varEngNameOrderBy:asc'
  return await readRemoteZippedCSV(populationUrl)
}

export const populationInfo = async () => {
  const itemsRaw = await getPopulationZip()
  const thisYear = new Date().getFullYear().toString()
  const items = itemsRaw.filter(i => i['Year(s)'] === thisYear)
  const result = {}
  for (const item of items) {
    try {
      const { countryCode, population } = getPopulationDataFromItem(item)
      result[countryCode] = population
    } catch (e) {
      console.log(e.message)
    }
  }
  return result
}