authorize.js

import fs from 'fs/promises';
import path from 'path';
import process from 'process';
import { authenticate } from '@google-cloud/local-auth';
import { google } from 'googleapis';

// If modifying these scopes, delete token.json.
const SCOPES = [
    'https://www.googleapis.com/auth/gmail.send',
];
// The file token.json stores the user's access and refresh tokens, and is
// created automatically when the authorization flow completes for the first
// time.
const TOKEN_PATH = path.join(process.cwd(), 'token.json');
const CREDENTIALS_PATH = path.join(process.cwd(), 'credentials.json');

/**
 * Reads previously authorized credentials from the save file.
 *
 * @return {Promise<OAuth2Client|null>}
 */
async function loadSavedCredentialsIfExist() {
    try {
        const content = await fs.readFile(TOKEN_PATH);
        const credentials = JSON.parse(content);
        return google.auth.fromJSON(credentials);
    } catch (err) {
        return null;
    }
}

/**
 * Serializes credentials to a file compatible with GoogleAUth.fromJSON.
 *
 * @param {OAuth2Client} client
 * @return {Promise<void>}
 */
async function saveCredentials(client) {
    const content = await fs.readFile(CREDENTIALS_PATH);
    const keys = JSON.parse(content);
    const key = keys.installed || keys.web;
    const payload = JSON.stringify({
        type: 'authorized_user',
        client_id: key.client_id,
        client_secret: key.client_secret,
        refresh_token: client.credentials.refresh_token,
    });
    await fs.writeFile(TOKEN_PATH, payload);
}

/**
 * Load or request or authorization to call APIs.
 *
 */
async function authorize() {
    let client = await loadSavedCredentialsIfExist();
    if (client) {
        return client;
    }
    client = await authenticate({
        scopes: SCOPES,
        keyfilePath: CREDENTIALS_PATH,
    });
    if (client.credentials) {
        await saveCredentials(client);
    }
    return client;
}

/**
 * Lists the labels in the user's account.
 *
 * @param {google.auth.OAuth2} auth An authorized OAuth2 client.
 */


async function sendMail(auth, email, subject, context) {
    const gmail = google.gmail({ version: 'v1', auth });
    const res = await gmail.users.messages.send({
        userId: 'me',
        requestBody: {
            raw: btoa(
                "From: " + email + "\r\n" +
                "To: " + email + "\r\n" +
                "Subject: " + subject + "\r\n\r\n" +
                context

                // "The message text goes here"
            ).replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '')
        }
    });
}

// authorize().then((auth) => sendMail(auth, 'icerkure@gmail.com', 'test', 'fake\n')).catch(console.error);
export default authorize;