How to build a public Big Cartel integration: Building the Auth Flow

Hey there, fellow JavaScript enthusiast! Ready to dive into the world of Big Cartel integrations? Today, we're going to walk through building a rock-solid authorization flow for your next big project. Let's get started!

Introduction

Big Cartel's API is a powerful tool for creating custom integrations, and nailing the authorization flow is crucial. We'll be focusing on building a secure, user-friendly auth process that'll make your integration shine.

Prerequisites

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

• Node.js and npm installed
• A basic understanding of OAuth 2.0 (don't worry, we'll cover the essentials)
• A Big Cartel developer account (if you don't have one, go grab it!)

Setting up the project

Let's kick things off by setting up our project:

mkdir big-cartel-integration
cd big-cartel-integration
npm init -y
npm install express axios dotenv

Configuring environment variables

Create a .env file in your project root and add these variables:

CLIENT_ID=your_client_id
CLIENT_SECRET=your_client_secret
REDIRECT_URI=http://localhost:3000/callback

Remember, keep these secret! Don't commit your .env file to version control.

Creating the authorization request

Now, let's create our app.js file and set up the initial route:

require('dotenv').config();
const express = require('express');
const app = express();

app.get('/auth', (req, res) => {
  const authUrl = `https://my.bigcartel.com/oauth/authorize?client_id=${process.env.CLIENT_ID}&redirect_uri=${encodeURIComponent(process.env.REDIRECT_URI)}&response_type=code`;
  res.redirect(authUrl);
});

app.listen(3000, () => console.log('Server running on port 3000'));

This route will redirect users to Big Cartel's authorization page. Pretty neat, huh?

Handling the callback

Let's add a route to handle the callback:

app.get('/callback', async (req, res) => {
  const { code } = req.query;
  // We'll use this code in the next step
  res.send('Authorization successful! Check the console for the access token.');
});

Exchanging the code for an access token

Now for the exciting part - getting that access token! Add this to your callback route:

const axios = require('axios');

// Inside the callback route
try {
  const response = await axios.post('https://api.bigcartel.com/oauth/token', {
    client_id: process.env.CLIENT_ID,
    client_secret: process.env.CLIENT_SECRET,
    code,
    grant_type: 'authorization_code',
    redirect_uri: process.env.REDIRECT_URI
  });
  
  const { access_token, refresh_token, expires_in } = response.data;
  console.log('Access Token:', access_token);
  // Store these tokens securely!
} catch (error) {
  console.error('Error getting access token:', error.response.data);
  res.status(500).send('Error getting access token');
}

Storing and managing tokens

For this example, we'll keep it simple and store tokens in memory. In a real-world app, you'd want to use a database:

let tokens = {};

// After getting the tokens
tokens = {
  access_token,
  refresh_token,
  expires_at: Date.now() + expires_in * 1000
};

Refreshing the access token

Let's add a function to refresh the token when it expires:

async function refreshAccessToken() {
  try {
    const response = await axios.post('https://api.bigcartel.com/oauth/token', {
      client_id: process.env.CLIENT_ID,
      client_secret: process.env.CLIENT_SECRET,
      refresh_token: tokens.refresh_token,
      grant_type: 'refresh_token'
    });
    
    const { access_token, refresh_token, expires_in } = response.data;
    tokens = {
      access_token,
      refresh_token,
      expires_at: Date.now() + expires_in * 1000
    };
  } catch (error) {
    console.error('Error refreshing token:', error.response.data);
  }
}

Making authenticated requests

Now that we have our token, let's use it to make a request:

app.get('/shop-info', async (req, res) => {
  if (Date.now() >= tokens.expires_at) {
    await refreshAccessToken();
  }
  
  try {
    const response = await axios.get('https://api.bigcartel.com/v1/accounts', {
      headers: { Authorization: `Bearer ${tokens.access_token}` }
    });
    res.json(response.data);
  } catch (error) {
    res.status(500).json({ error: 'Failed to fetch shop info' });
  }
});

Error handling and edge cases

Always be prepared for things to go wrong. Add proper error handling to each step of the process, and don't forget to handle cases like expired tokens or revoked access.

Security considerations

Remember these key points:

• Always use HTTPS in production
• Never expose your client secret
• Store tokens securely (preferably encrypted in a database)
• Use the principle of least privilege when requesting scopes

Conclusion

And there you have it! You've just built a solid authorization flow for your Big Cartel integration. From here, you can expand your app's functionality, add more API calls, and create an awesome integration.

Remember, the key to a great integration is a smooth user experience and rock-solid security. Keep iterating, testing, and most importantly, have fun building!

Happy coding, and may your integration be ever awesome! 🚀