index.js

'use strict';
const Storage   = require('@google-cloud/storage');
const Translate = require('@google-cloud/translate');

// Instantiates a client
const storage = Storage();
const translate = Translate();

function getFileStream (file) {
  if (!file.bucket) {
    throw new Error('Bucket not provided. Make sure you have a "bucket" property in your request');
  }
  if (!file.name) {
    throw new Error('Filename not provided. Make sure you have a "name" property in your request');
  }

  return storage.bucket(file.bucket).file(file.name).createReadStream();
}

function getWriteFileStream (bucketname,filename) {
  return storage.bucket(bucketname).file(filename).createWriteStream();
}


exports.processFile = function(event, callback) {
  const file = event.data;
  console.log('Processing file: ' + file.name);

  if (file.resourceState === 'not_exists') {
    // This is a file deletion event, so skip it
    callback();
    return;
  }
  
  let remoteFile = getFileStream(file);
  let translatedFile = getWriteFileStream('cf-translation-bucket_es',file.name);
  
  let dataLength = 0;
  let dataContents = "";
  //Read the contents
  remoteFile
  .on('error', function(err) {})
  .on('response', function(response) {
    // Server connected and responded with the specified status and headers.
   })
  .on('data',function (chunk) {
    dataLength += chunk.length;
    dataContents += chunk;
  })
  .on('end', function() {
    console.log(dataContents);
    translate.translate(dataContents, 'es', function(err, translation) {
    if (!err) {
      console.log(translation);
      translatedFile.write(translation);
      translatedFile.end()
      callback('','Translation Done');
    }
    });
  })  
};