// Authentication tasks
// --------------------
const fs        = require('fs');
const {google}  = require('googleapis');

// If modifying these scopes, delete token.json.
const SCOPES = ['https://www.googleapis.com/auth/photoslibrary.readonly.appcreateddata'];

// 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';

function run(req, res, 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 Drive API.
        authorize(JSON.parse(content), req, res, callback);
    });
}

// Authentication related
function auth_redirect(req, res) {
    // 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
        const credentials = JSON.parse(content);
        const {client_secret, client_id, redirect_uris} = credentials.web;
        const oAuth2Client = new google.auth.OAuth2(client_id, client_secret, redirect_uris[0]);
        // oAuth2Client.getToken(ur.searchParams.get("code"), (err, token) => {
        oAuth2Client.getToken(req.param("code"), (err, token) => {
            if (err) {
                return console.error('Error retrieving 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);
            });

            res.redirect(301, '/tiny');
        });
    });
}

/**
 * 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.
 */
function authorize(credentials, req, res, callback) {
    const {client_secret, client_id, redirect_uris} = credentials.web;
    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 getAccessToken(oAuth2Client, req, res, callback);
        oAuth2Client.setCredentials(JSON.parse(token));
        var apis = google.getSupportedAPIs();
        console.log(apis);
        // TODO: Need to wait until googleapis supports Google Photos.
        //       Will revisit this at that point
        var api = google;
        callback(req, res, api);
    });
}

/**
 * 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.
 */
function getAccessToken(oAuth2Client, req, res, callback) {
    const authUrl = oAuth2Client.generateAuthUrl({
        access_type: 'online',
        scope: SCOPES,
    });
    res.redirect(301, authUrl);
}

// Exported functions
module.exports = {
    run: run,
    redirect: auth_redirect
}

// vim: ai ts=4 sts=4 et sw=4 ft=javascript