Saves a file to Firebase storage with token authentication as if created from the console.

firebaseSaveFile.js

const storage = require('@google-cloud/storage')
const createUuid = require("uuid-v4")

const credentials = require('./test-firebase-credentials.json')
const firebaseProjectName = 'test'
const bucketName = `${firebaseProjectName}.appspot.com`

const bucket = storage({ credentials }).bucket(bucketName)

module.exports = firebaseSaveFile

function firebaseSaveFile(fileName, contentType, data) {
  const file = bucket.file(fileName)
  return file.getMetadata().catch(e => [])
    .then(([m]) => ((m || {}).metadata || {}).firebaseStorageDownloadTokens)
    .then((token = createUuid()) => file.save(data, { validation: 'md5', resumable: false, metadata: { contentType, metadata: { firebaseStorageDownloadTokens: token } } }).then(_ => token))
    .then(token => getDownloadUrl(fileName, token))
}

function getDownloadUrl(fileName, token) { return `https://firebasestorage.googleapis.com/v0/b/${bucketName}/o/${fileName}?alt=media&token=${token}` }