oauth.js

const fs = require("fs");
const readline = require("readline");
const { google } = require("googleapis");

// If modifying these scopes, delete token.json.
const SCOPES = [
    "https://mail.google.com/",
    "https://www.googleapis.com/auth/gmail.send",
];
const TOKEN_PATH = "token.json";

// Load client secrets from a local file.
fs.readFile("client.json", (err, content) => {
    if (err) return console.log("Error loading client secret file:", err);
    authorize(JSON.parse(content), saveToken);
});

function authorize(credentials, callback) {
    const { client_secret, client_id, redirect_uris } = credentials.installed;
    const oAuth2Client = new google.auth.OAuth2(
        client_id,
        client_secret,
        redirect_uris[0]
    );

    // Check if we have previously stored a token.
    fs.readFile(TOKEN_PATH, (err, token) => {
        if (err) return getNewToken(oAuth2Client, callback);
        oAuth2Client.setCredentials(JSON.parse(token));
        callback(oAuth2Client);
    });
}

function getNewToken(oAuth2Client, callback) {
    const authUrl = oAuth2Client.generateAuthUrl({
        access_type: "offline",
        scope: SCOPES,
    });
    console.log("Authorize this app by visiting this url:", authUrl);
    const rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout,
    });
    rl.question("Enter the code from that page here: ", (code) => {
        rl.close();
        oAuth2Client.getToken(code, (err, token) => {
            if (err) return console.error("Error retrieving access token", err);
            oAuth2Client.setCredentials(token);
            callback(oAuth2Client);
        });
    });
}

function saveToken(oAuth2Client) {
    fs.writeFile(
        TOKEN_PATH,
        JSON.stringify(oAuth2Client.credentials),
        (err) => {
            if (err) return console.error(err);
            console.log("Token stored to", TOKEN_PATH);
        }
    );
}
module.exports = { authorize,saveToken};