Connecting to Gmail with OAuth2

To securely connect to Gmail using OAuth2, follow these steps:

1. Create Gmail API Credentials:

• Go to the Google Cloud Console.

• Create a new project.

• Enable the Gmail API for your project.

• Under Credentials, create an OAuth Client ID.

• Select "Web Application" and set the redirect URL to https://developers.google.com/oauthplayground.

2. Obtain Client ID and Client Secret:

Grab the Client ID and Client Secret generated in the previous step.

3. Install googleapis Library:

Install the googleapis library for integration with Google’s APIs:

bash

npm install googleapis

4. Configure OAuth2 Playground:

In OAuth Playground:

• Click the settings gear -> OAuth2 configuration.

• Check "Use your own OAuth credentials."

• Enter your Client ID and Client Secret.

• Close settings.

5. Obtain Refresh Token:

• Select "Gmail API v1" from the list of APIs.

• Click "Authorize APIs" and grant access to your account.

• Click "Exchange authorization code for tokens."

• Grab the refresh_token value provided; this is crucial for generating access tokens.

6. Store Credentials in .env File:

Update your .env file with the obtained credentials:

env

EMAIL_USER=yourgmailusername

EMAIL_PASS=yourgmailpassword

OAUTH_CLIENT_ID=xxxxxxxxxxx

OAUTH_CLIENT_SECRET=xxxxxxxxxx

OAUTH_REFRESH_TOKEN=xxxxxxxxxx

Replace the values for OAUTH_CLIENT_ID, OAUTH_CLIENT_SECRET, and OAUTH_REFRESH_TOKEN with your credentials. Never commit this file to source control for security.

Building the Email API Routes

Create routes for general emails, confirmation emails, and password reset emails:

1. General Email Route (routes/email.js):

javascript

const router = require('express').Router();

const nodemailer = require('nodemailer');

router.post('/', async (req, res) => {

try {

const { to, from, subject, html } = req.body;

const mailOptions = { from, to, subject, html };

const info = await transporter.sendMail(mailOptions);

return res.json({ message: 'Email sent successfully' });

} catch (error) {

return res.status(500).json({ error: error.message });

}

});

module.exports = router;

2. Confirmation Email Route (routes/confirm.js):

javascript

const router = require('express').Router();

const emailTemplate = require('../templates/email-confirmation');

router.post('/', async (req, res) => {

try {

const { email, name, items, total } = req.body;

const template = emailTemplate.replace('{{name}}', name).replace('{{items}}', items).replace('{{total}}', total);

const mailOptions = { from: '"Company Name" <company@email.com>', to: email, subject: 'Your order confirmation', html: template };

await transporter.sendMail(mailOptions);

return res.json({ message: 'Order confirmation sent!' });

} catch (error) {

return res.status(500).json({ error: error.message });

}

});

module.exports = router;

3. Password Reset Route (routes/reset.js):

javascript

const router = require('express').Router();

const emailTemplate = require('../templates/password-reset');

router.post('/', async (req, res) => {

try {

const { email, name, resetUrl } = req.body;

const template = emailTemplate.replace('{{name}}', name).replace('{{resetUrl}}', resetUrl);

const mailOptions = { from: '"Company" <company@email.com>', to: email, subject: 'Password reset request', html: template };

await transporter.sendMail(mailOptions);

return res.json({ message: 'Password reset email sent!' });

} catch (error) {

return res.status(500).json({ error: error.message });

}

});

module.exports = router;

Creating the React Form

Build a simple React form for capturing user data to send emails. Replace App.js in your React project with:

javascript

import { useState } from 'react';

function App() {

const [email, setEmail] = useState('');

const handleSubmit = async (e) => {

e.preventDefault();

// Send email API request

};

return (

<div className="app">

<h1>Send Email</h1>

<form onSubmit={handleSubmit}>

<input

placeholder="Email address"

value={email}

onChange={(e) => setEmail(e.target.value)}

/>

<button type="submit">Send Test Email</button>

</form>

</div>

);

}

export default App;

Connecting to a Database

To connect to a database, install Mongoose:

bash

npm install mongoose

Then, connect to MongoDB in index.js:

javascript

const mongoose = require('mongoose');

mongoose.connect(connectionURI, {

useNewUrlParser: true,

useUnifiedTopology: true

});

const db = mongoose.connection;

db.on('error', err => {

// error handling

});

db.once('open', () => {

// connected

});

Adding Email Scheduling

Incorporate the Agenda library to schedule and queue emails. Install Agenda:

bash

npm install agenda

Configure and use Agenda in index.js:

javascript

const Agenda = require('agenda');

const agenda = new Agenda({ db: { address: connectionURI } });

agenda.define('send email', async job => {

// send email here

});

(async function () {

// Start scheduler

await agenda.start();

// Schedule email for future

await agenda.schedule('in 20 minutes', 'send email', {

to: 'test@example.com',

subject: 'Scheduled Email',

body: 'This email was scheduled!'

});

})();

Now, you can queue emails and schedule them for future delivery using Agenda.

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