How to build a public Looker integration: Building the Auth Flow

Hey there, fellow JavaScript enthusiast! Ready to dive into the world of Looker integrations? Let's roll up our sleeves and build a rock-solid auth flow that'll make your users feel like they're Fort Knox-level secure.

Introduction

Looker's a powerhouse for data visualization, but to tap into its full potential, we need to build a bulletproof integration. The cornerstone? A robust auth flow. It's not just about getting access; it's about doing it right and keeping your users' data locked down tight.

Prerequisites

Before we jump in, make sure you've got:

• Looker API credentials (if you don't have 'em, go grab 'em!)
• A Node.js environment with Express.js set up (I know you've got this covered)

OAuth 2.0 Flow Overview

We're using OAuth 2.0's Authorization Code Grant. It's like a secret handshake in three parts:

1. Get an authorization code
2. Swap it for access and refresh tokens
3. Use those tokens to access the API

Simple, right? Let's break it down.

Setting up the Authorization Request

First things first, we need to send users to Looker to approve our app. Here's how:

const authUrl = `https://your-looker-instance.com/auth?response_type=code&client_id=${CLIENT_ID}&redirect_uri=${REDIRECT_URI}&state=${STATE}`;

That STATE parameter? It's your CSRF shield. Generate it randomly for each request and store it in the session.

Exchanging the Authorization Code for Tokens

Once the user approves, Looker redirects them back with a code. Time to trade it in:

app.get('/callback', async (req, res) => {
  const { code, state } = req.query;
  
  // Verify state to prevent CSRF
  if (state !== req.session.state) {
    return res.status(400).send('Invalid state');
  }

  const tokenResponse = await axios.post('https://your-looker-instance.com/api/3.1/login', {
    client_id: CLIENT_ID,
    client_secret: CLIENT_SECRET,
    code,
    grant_type: 'authorization_code'
  });

  // Store these securely!
  const { access_token, refresh_token } = tokenResponse.data;
});

Implementing Token Refresh

Access tokens don't last forever. When they expire, use the refresh token to get a new one:

async function refreshAccessToken(refreshToken) {
  const response = await axios.post('https://your-looker-instance.com/api/3.1/login', {
    grant_type: 'refresh_token',
    client_id: CLIENT_ID,
    client_secret: CLIENT_SECRET,
    refresh_token: refreshToken
  });

  return response.data.access_token;
}

Making Authenticated Requests to Looker API

Now for the fun part - actually using the API:

async function getLookerData(accessToken) {
  const response = await axios.get('https://your-looker-instance.com/api/3.1/user', {
    headers: { Authorization: `Bearer ${accessToken}` }
  });

  return response.data;
}

Error Handling and Edge Cases

Always be prepared:

• Check for token expiration before each request
• Handle 401 errors by refreshing the token
• Implement exponential backoff for rate limiting

Security Considerations

Security isn't just a feature, it's a lifestyle:

• Always use HTTPS
• Store tokens in secure, encrypted storage
• Implement proper CSRF protection on all routes

Testing the Auth Flow

Don't just hope it works, know it works:

1. Test the happy path manually
2. Write integration tests for each step
3. Simulate error conditions (expired tokens, network issues)

Conclusion

And there you have it! You've just built a secure, robust auth flow for your Looker integration. Pat yourself on the back - you've taken a big step towards unleashing the full power of Looker in your app.

Remember, the auth flow is just the beginning. Now you can start building out those killer features that'll make your users wonder how they ever lived without your integration.

Keep coding, keep learning, and most importantly, keep being awesome!