postinstall.js

const http = require('http')
const fs = require('fs')
const constants = require('./constants')

const dependencies = {
  [constants.VENDOR_PDF_BOX_JAR]: 'http://archive.apache.org/dist/pdfbox/2.0.16/pdfbox-app-2.0.16.jar',
  [constants.VENDOR_TIKA_JAR]: 'http://archive.apache.org/dist/tika/tika-app-1.22.jar'
}

const download = (filename) => {
  const filePath = constants.DIRECTORY.VENDOR + filename
  fs.access(filePath, fs.constants.F_OK, (err) => {
    if (err) {
      console.log(`Started downloading dependency ${filename}.`)
      const request = http.get(dependencies[filename], (response) => {
        if (response.statusCode === 200) {
          const fileStream = fs.createWriteStream(filePath)
          response.pipe(fileStream)
          fileStream.addListener('finish', () => {
            console.log(`Finished downloading dependency ${filename}.`)
          })
        } else {
          throw new Error(`Failed downloading dependency ${filename}.`)
        }
      })
      request.on('error', () => {
        throw new Error(`Failed downloading dependency ${filename}.`)
      })
    }
  })
}

const filenames = Object.keys(dependencies)
filenames.forEach((filename) => {
  download(filename)
})