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Introduction

This tutorial demonstrates using Google Cloud Functions to record incoming voice calls using Twilio. The recordings are then transcribed by the Google Cloud Speech API and analyzed by the Google Cloud Natural Language API. The final results are stored in a Google Cloud Storage bucket. The Cloud Function is implemented in Node.js.

The sample Cloud Function is triggered by a webhook request from Twilio when a voice call is made to your Twilio phone number. The webhook validates that the request came from Twilio, prompts the user to leave a recording, then records the call. When the recording becomes available, the recording is transcribed and analyzed for sentiment, entities, and syntax. The final results are stored in a Cloud Storage bucket.

Objectives

Obtain a phone number from Twilio.
Deploy a Cloud Function that can receive and record voice calls.
Deploy a Cloud Function that can download voice recordings from Twilio and save them to Cloud Storage.
Deploy a Cloud Function that can transcribe the voice recordings, analyze them, and save the results to Cloud Storage.

Costs

Twilio has a free trial, but you need to upgrade to disable the default message that is played for anyone who calls your Twilio phone number.

This tutorial uses billable components of Google Cloud Platform, including:

Google Cloud Functions
Google Cloud Natural Language API
Google Cloud Speech API
Google Cloud Storage

Use the Pricing Calculator to generate a cost estimate based on your projected usage.

Prerequisites

Create a project in the Google Cloud Platform Console.
Enable billing for your project.
Enable the Google Cloud Functions API.
Enable the Google Cloud Speech API.
Enable the Google Cloud Natural Language API.
Create a Cloud Storage bucket in which to store voice recordings and the results of your analysis:
```
gsutil mb -p [YOUR_PROJECT_ID] gs://[RESULTS_BUCKET]
```
- Replace [YOUR_PROJECT_ID] with your Google Cloud Platform project ID.
- Replace [RESULTS_BUCKET] with the name you want for your new bucket. You'll need the name of this bucket later in this tutorial.
You can also create a bucket in the Google Cloud Console.
Install and initialize the Google Cloud SDK.
1. After initializing the SDK, install the Beta components:
```
gcloud components install beta
```

Getting started with Twilio

Create a Twilio account. It is recommended that you upgrade your Twilio account to a paid account to avoid the trial restrictions, namely a message played to anyone who calls your Twilio phone number.
In your Twilio console, create a phone number.
Once you have a phone number, click Manage Numbers and then click on your phone number.
Under Voice:
1. Set Configure with to Webhooks/TwiML.
2. Set A Call Comes In to Webhook and enter the following URL:
```
https://us-central1-[YOUR_PROJECT_ID].cloudfunctions.net/handleCall
```
  Replace [YOUR_PROJECT_ID] with your Google Cloud Platform project ID.
3. Click Save.
Return to your Twilio Account Settings and take note of the Auth Token for your Live Credentials. You will need it later in this tutorial.

Preparing the function

Create a package.json file by running the following:
```
npm init
```
or
```
yarn init
```

Install the dependencies used by the Cloud Function:

npm install --save twilio got @google-cloud/speech @google-cloud/language @google-cloud/storage

yarn add twilio got @google-cloud/speech @google-cloud/language @google-cloud/storage

Create a file named config.json with the following contents:
```
{
  "RESULTS_BUCKET": "[RESULTS_BUCKET]",
  "TWILIO_AUTH_TOKEN": "[YOUR_TWILIO_AUTH_TOKEN]"
}
```
- Replace [RESULTS_BUCKET] with the name of the bucket you created in step 7 of the Prerequisites section.
- Replace [YOUR_TWILIO_AUTH_TOKEN] with your Twilio Auth Token from step 5 of the Getting Started with Twilio section.

Writing the function code

Receiving a phone call

First, you'll write a function that will:

Trigger when someone calls your Twilio phone number.
Prompt the caller to leave a message.
Record the caller's message.
- Maximum message length specified as 60 seconds.
- The recording status callback URL set to a second function you'll implement later in this tutorial.
Finally, hang up.

Create a file named index.js with the following contents:

'use strict';

const config = require('./config.json');
const twilio = require('twilio');

const VoiceResponse = twilio.twiml.VoiceResponse;

const projectId = process.env.GCLOUD_PROJECT;
const region = 'us-central1';

exports.handleCall = (req, res) => {
  if (!isValidRequest(req, res, 'handleCall')) {
    return;
  }

  const recordingStatusCallbackUrl = `https://${region}-${projectId}.cloudfunctions.net/getRecording`;

  // Prepare a response to the voice call
  const response = new VoiceResponse();

  // Prompt the user to leave a message
  response.say('Hello from Cloud Functions. Please leave a message after the beep.');

  console.log('Recording message.');

  // Record the user's message
  response.record({
    // Limit the recording to 60 seconds
    maxLength: 60,
    // Give Twilio the deployed url of the other function for when the recorded
    // audio is available
    recordingStatusCallback: recordingStatusCallbackUrl
  });

  // End the call
  response.hangup();

  // Send the response
  res
    .status(200)
    .type('text/xml')
    .send(response.toString())
    .end();
};

Validating the request

Next, you need to add the helper function that validates requests. Add the following to your index.js file:

function isValidRequest (req, res, pathname) {
  let isValid = true;

  // Only validate that requests came from Twilio when the function has been
  // deployed to production.
  if (process.env.NODE_ENV === 'production') {
    isValid = twilio.validateExpressRequest(req, config.TWILIO_AUTH_TOKEN, {
      url: `https://${region}-${projectId}.cloudfunctions.net/${pathname}`
    });
  }

  // Halt early if the request was not sent from Twilio
  if (!isValid) {
    res
      .type('text/plain')
      .status(403)
      .send('Twilio Request Validation Failed.')
      .end();
  }

  return isValid;
}

Retrieving the recording

Next, you need to retrieve the voice recording from Twilio. You'll add a second function that will:

Trigger when the audio recording is available for retrieval. Twilio will send a webhook request to this function.
Download the audio file from Twilio and save it to Cloud Storage.

Add the following to your index.js file:

exports.getRecording = (req, res) => {
  if (!isValidRequest(req, res, 'getRecording')) {
    return;
  }

  const got = require('got');
  const path = require('path');
  const storage = require('@google-cloud/storage')();

  const filename = `recordings/${path.parse(req.body.RecordingUrl).name}/audio.wav`;
  const file = storage
    .bucket(config.RESULTS_BUCKET)
    .file(filename);

  console.log(`Saving recording to: ${filename}`);

  got.stream(req.body.RecordingUrl)
    .pipe(file.createWriteStream({
      metadata: {
        contentType: 'audio/x-wav'
      }
    }))
    .on('error', (err) => {
      console.error(err);
      res
        .status(500)
        .send(err)
        .end();
    })
    .on('finish', () => {
      res
        .status(200)
        .end();
    });
};

Analyzing the recording

Finally, you need to transcribe and analyze the voice recording. Now you'll add a third function that will:

Trigger when the audio recording is saved to Cloud Storage.
Transcribe the audio using the Cloud Speech API.
Analyze the transcription using the Cloud Natural Language API.
Save the analysis to Cloud Storage.

Add the following to your index.js file:

exports.analyzeRecording = (event) => {
  const object = event.data;

  if (object.resourceState === 'not_exists') {
    // Ignore file deletions
    return true;
  } else if (!/^recordings\/\S+\/audio\.wav$/.test(object.name)) {
    // Ignore changes to non-audio files
    return true;
  }

  console.log(`Analyzing gs://${object.bucket}/${object.name}`);

  // Import the Google Cloud client libraries
  const language = require('@google-cloud/language').v1beta2;
  const speech = require('@google-cloud/speech');
  const storage = require('@google-cloud/storage')();

  const nlclient = new language.LanguageServiceClient();
  const spclient = new speech.SpeechClient();
  const bucket = storage.bucket(object.bucket);
  const dir = require('path').parse(object.name).dir;

  // Configure audio settings for Twilio voice recordings
  const audioConfig = {
    sampleRateHertz: 8000,
    encoding: 'LINEAR16',
    languageCode: 'en-US'
  };

  const audioPath = {
    uri: `gs://${object.bucket}/${object.name}`
  };

  const audioRequest = {
    audio: audioPath,
    config: audioConfig,
  };

  // Transcribe the audio file
  return spclient.recognize(audioRequest)
    // Perform Sentiment, Entity, and Syntax analysis on the transcription
    .then(data => {
      const sresponse = data[0];
      const transcription = sresponse.results
        .map(result => result.alternatives[0].transcript)
        .join('\n');
      return nlclient.analyzeSentiment({document: {content: `${transcription}`, type: 'PLAIN_TEXT'}});
    })
    // Finally, save the analysis
    .then(responses => {
      const filename = `${dir}/analysis.json`;
      console.log(`Saving gs://${object.bucket}/${dir}/${filename}`);
      return bucket
        .file(filename)
        .save(JSON.stringify(responses[0].documentSentiment, null, 1));
      });
};

Deploying and testing the function

Read about deploying Cloud Functions.
Run the following to deploy the handleCall function:
```
gcloud beta functions deploy handleCall --trigger-http --stage-bucket=[YOUR_STAGE_BUCKET]
```
Replace [YOUR_STAGE_BUCKET] with your Cloud Functions staging bucket.
Run the following to deploy the getRecording function:
```
gcloud beta functions deploy getRecording --trigger-http --stage-bucket=[YOUR_STAGE_BUCKET]
```
Replace [YOUR_STAGE_BUCKET] with your Cloud Functions staging bucket.
Run the following to deploy the analyzeRecording function:
```
gcloud beta functions deploy analyzeRecording --trigger-bucket=[RESULTS_BUCKET] --stage-bucket=[YOUR_STAGE_BUCKET] --timeout=240
```
- Replace [YOUR_STAGE_BUCKET] with your Cloud Functions staging bucket.
- Replace [RESULTS_BUCKET] with the name of the bucket you created in step 7 of the Prerequisites section.
- Replace [YOUR_STAGE_BUCKET] with your Cloud Functions staging bucket.
Note that you used --timeout=240 to deploy the analyzeRecording function. This is because analyzeRecording does a lot and may take a while, and you don't want the function stopped prematurely.
Call your Twilio phone number and leave a recording.
Open your results bucket in the Google Cloud Console to view the saved analyses.

To view the logs for the Cloud Functions, run the following:

gcloud beta functions logs view handleCall
gcloud beta functions logs view getRecording
gcloud beta functions logs view analyzeRecording

Cleaning up

Congratulations, you've now deployed several functions to Google Cloud Functions, and can receive and analyze phone calls.

You can follow these steps to clean up resources and save on costs.

Delete the functions:

gcloud beta functions delete -q handleCall
gcloud beta functions delete -q getRecording
gcloud beta functions delete -q analyzeRecording

Release your Twilio phone number.
Remove all files in your results bucket:
```
gsutil rm -r gs://[RESULTS_BUCKET]/
```
- Replace [RESULTS_BUCKET] with the name of the bucket you created in step 6 of the Prerequisites section.

Of course, you can also delete the entire project, but you would have to disable billing and lose any setup you have done. Additionally, deleting a project will only happen after the current billing cycle ends.

Next steps

Learn more about Twilio and Programmable Voice.
View other Cloud Functions community tutorials.
View other Twilio community tutorials.
View other Cloud Speech API community tutorials.
View other Cloud Natural Language API community tutorials.
View other Node.js community tutorials.

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