Firebase Cloud Functions with Google Spreadsheet

spreadsheet-authorize.js

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

// If modifying these scopes, delete token.json.
const SCOPES = ["https://www.googleapis.com/auth/spreadsheets"];
// 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 = "token.json";

/**
 * Get and store new token after prompting for user authorization, and then
 * execute the given callback with the authorized OAuth2 client.
 * @param {google.auth.OAuth2} oAuth2Client The OAuth2 client to get token for.
 * @param {getEventsCallback} callback The callback for the authorized client.
 */
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 while trying to retrieve access token",
                    err
                );
            oAuth2Client.setCredentials(token);
            // Store the token to disk for later program executions
            fs.writeFile(TOKEN_PATH, JSON.stringify(token), err => {
                if (err) return console.error(err);
                console.log("Token stored to", TOKEN_PATH);
            });
            callback(oAuth2Client);
        });
    });
};

/**
 * Create an OAuth2 client with the given credentials, and then execute the
 * given callback function.
 * @param {Object} credentials The authorization client credentials.
 * @param {function} callback The callback to call with the authorized client.
 */
authorization = (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);
    });
};

const authorize = callback => {
    // Load client secrets from a local file.
    fs.readFile("credentials.json", (err, content) => {
        if (err) return console.log("Error loading client secret file:", err);
        // Authorize a client with credentials, then call the Google Sheets API.
        authorization(JSON.parse(content), callback);
    });
};

module.exports = { authorize };