AWS Polly use example using nodejs async / await

polly.js

/**
 * Use as proxy between front and AWS Polly API
 * Everything come in querystring
 * voiceId : see Polly API for the list http://docs.aws.amazon.com/fr_fr/polly/latest/dg/API_Voice.html#API_Voice_Contents
 * type :
 *   - file (default) : generate mp3 file on public bucket
 *   - stream : stream response
 */
export const textToSpeech = async (req, res) => {

  const { voiceId = 'Kimberly', text = '', filename = 'speech.mp3', type = 'file' } = req.query

  try {
    const audio = await generatePollyAudio(text, voiceId)

    if(type === 'file') {
      const data = await writeAudioStreamToS3(audio.AudioStream, filename)
      res.send(data)
    }
    else if (type === 'stream') {
      res.send(audio.AudioStream)
    }
    else throw { errorCode: 400, error: 'Wrong type for output provided.' }
  }
  catch (e) {
    if(e.errorCode && e.error) res.status(e.errorCode).send(e.error)
    else res.status(500).send(e)
  }
}

// Generate audio from Polly and check if output is a Buffer
const generatePollyAudio = (text, voiceId) => {
  const params = {
    Text: text,
    OutputFormat: 'mp3',
    VoiceId: voiceId
  }

  return polly.synthesizeSpeech(params).promise().then( audio => {
    if (audio.AudioStream instanceof Buffer) return audio
    else throw 'AudioStream is not a Buffer.'
  })

}

const writeAudioStreamToS3 = ( audioStream, filename ) =>
  putObject(aws_publicBucket, filename, audioStream,'audio/mp3').then( res => {
    if(!res.ETag) throw res
    else return {
      msg: 'File successfully generated.',
      ETag: res.ETag,
      url: `https://s3-eu-west-1.amazonaws.com/${aws_publicBucket}/${filename}`
    }
  })

const putObject = (bucket, key, body, ContentType) =>
  s3.putObject({
    Bucket: bucket,
    Key: key,
    Body: body,
    ContentType
  }).promise()