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

Hey there, fellow JavaScript enthusiast! Ready to dive into the world of Strava integrations? Let's roll up our sleeves and build an auth flow that'll make your users' fitness data dreams come true.

The Strava API: Your New Best Friend

Before we jump in, let's chat about the Strava API. It's a powerful tool that lets you tap into a treasure trove of fitness data, but it comes with a catch – you need to play nice with their authentication rules. Don't worry, though; we'll tackle this together!

Setting the Stage

First things first, you'll need to set up your Strava API application. Head over to the Strava developers site, create your app, and grab your Client ID and Client Secret. These are your golden tickets, so keep them safe!

The OAuth 2.0 Dance

Strava uses OAuth 2.0 for authentication. It might sound fancy, but it's just a secure way for users to grant your app access to their data without sharing their passwords. Here's how it goes:

1. Your app asks Strava for permission
2. User logs in and agrees
3. Strava gives you a special code
4. You trade that code for access tokens

Simple, right? Let's make it happen!

Kicking Off the Auth Flow

Time to get our hands dirty with some code. First, we need to send users to Strava's authorization page:

const authUrl = `https://www.strava.com/oauth/authorize?client_id=${YOUR_CLIENT_ID}&redirect_uri=${YOUR_REDIRECT_URI}&response_type=code&scope=read,activity:read_all`;

// Redirect the user to authUrl

Pro tip: Use encodeURIComponent() for your redirect URI to avoid any nasty surprises!

Handling the Callback

Once the user says "yes," Strava will send them back to your redirect URI with a shiny new authorization code. Catch it like this:

const code = new URLSearchParams(window.location.search).get('code');

Token Time!

Now, let's trade that code for some tokens:

async function getTokens(code) {
  const response = await fetch('https://www.strava.com/oauth/token', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      client_id: YOUR_CLIENT_ID,
      client_secret: YOUR_CLIENT_SECRET,
      code,
      grant_type: 'authorization_code'
    })
  });
  return response.json();
}

This will give you access and refresh tokens. Store them securely – they're the keys to the kingdom!

Keeping Things Fresh

Access tokens expire, but don't sweat it. Use your refresh token to get a new one:

async function refreshAccessToken(refreshToken) {
  // Similar to getTokens, but use 'refresh_token' as grant_type
}

Making API Requests

With your access token in hand, you're ready to fetch some data:

async function getAthleteActivities(accessToken) {
  const response = await fetch('https://www.strava.com/api/v3/athlete/activities', {
    headers: { 'Authorization': `Bearer ${accessToken}` }
  });
  return response.json();
}

Remember to play nice with Strava's rate limits. Nobody likes a data hog!

When Things Go Wrong

Error handling is key. Watch out for expired tokens, user denials, and network hiccups. A little defensive programming goes a long way:

try {
  // Your API call here
} catch (error) {
  if (error.response && error.response.status === 401) {
    // Time to refresh that token!
  } else {
    // Handle other errors
  }
}

Keeping It Secure

Always use HTTPS, never expose your client secret on the frontend, and consider using environment variables for sensitive info. Security first, folks!

Testing, Testing, 1-2-3

Tools like Postman are great for testing your OAuth flow. And remember, the Strava API has a sandbox mode – use it to avoid cluttering up your actual Strava feed during development.

You've Got This!

And there you have it – a shiny new Strava integration with a rock-solid auth flow. You're now ready to build some amazing fitness apps. The sky's the limit!

Remember, the Strava API docs are your friend. When in doubt, give them a shout (or, you know, a read).

Now go forth and code! Your users' KOMs and PRs await. Happy integrating!