eventPage.js

// jshint jquery: true, undef: true,curly: true, bitwise: true, eqeqeq: true, immed: true, strict: false, unused: vars, devel: true, browser: true, newcap: false, multistr: true
/* global chrome, firebase */
'use strict';

chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
    console.log(request);
    if (request.updated) {
        let user = firebase.auth().currentUser;
        if (user) {
            firebase.database().ref('users/' + user.uid + '/' + request.updated).set(request.val);
        }
    } else if (request.authCheck) {
        if (firebase.auth().currentUser) {
            sendResponse({ authStatus: true });
        } else {
            sendResponse({ authStatus: false });
            startAuth(true);
        }
    } else if (request.relayGET) {
        $.ajax({
            url: request.url,
            success: (data) => {
                sendResponse({success: true, data});
            },
            error: () => {
                sendResponse({error: true});
            },
          });
        //indicates that sendResponse will be called asynchronously.
        return true;
    }
});

let config = {
    apiKey: 'AIzaSyCisxFC0G30N0Yh8meI3eSCl6BZOD5CF-I',
    authDomain: 'better-fanfiction.firebaseapp.com',
    databaseURL: 'https://better-fanfiction.firebaseio.com',
    projectId: 'better-fanfiction',
    storageBucket: 'better-fanfiction.appspot.com',
    messagingSenderId: '658655686523',
};
firebase.initializeApp(config);
startAuth(false);

firebase.auth().onAuthStateChanged(function (user) {
    if (user) {
        // User is signed in.
        firebase.database.enableLogging(function(message) {
            console.log("[FIREBASE]", message);
          });
        setUpDBListeners(user.uid);
    } else {
    }
});

function setUpDBListeners(uid) {
    let dbRef = firebase.database().ref('users/' + uid);
    dbRef.on('child_added', onDBUpdate);
    dbRef.on('child_changed', onDBUpdate);
    dbRef.on('child_removed', snap => {
        let key = snap.key;
        let msgObj = {};
        if (key.startsWith('Read:')) {
            msgObj.updated = 'Read';
            msgObj.id = key.substr(5);
        } else if (key.startsWith('shelf:')) {
            msgObj.updated = 'Shelf';
            msgObj.id = parseInt(key.substr(6), 10);
        } else {
            msgObj = undefined;
        }
        chrome.storage.local.remove(key, () => tabUpdate(msgObj));
    });
}

function onDBUpdate(snap) {
    let key = snap.key;
    chrome.storage.local.get(key, x => {
        if (!jsonEqual(x[key], snap.val())) {
            let storeObj = { [key]: snap.val() };
            let msgObj = {};
            if (key.startsWith('Read:')) {
                msgObj.updated = 'Read';
                msgObj.id = key.substr(5);
            } else if (key.startsWith('shelf:')) {
                msgObj.updated = 'Shelf';
                msgObj.id = parseInt(key.substr(6), 10);
            } else if (key === 'ReadLater') {
                msgObj.updated = 'ReadLater';
            } else if (key === 'Liked') {
                msgObj.updated = 'Liked';
            } else if (key === 'FavoritesLastModified') {
                msgObj.updated = 'Favorites';
            } else if (key === 'AlertsLastModified') {
                msgObj.updated = 'Alerts';
            } else if (key === 'SubscriptionsLastModified') {
                msgObj.updated = 'Subscriptions'
            } else if (key === 'Bookshelves') {
                let oldData = x[key] || {};
                storeObj[key] = Array.from(snap.val()).filter(el => el != null);
                storeObj[key].forEach((shelf, i) => {
                    if (!jsonEqual(shelf, oldData[i])) {
                        if (shelf === undefined || shelf === null) {
                            shelf = oldData[i];
                        } else if (oldData[i] === undefined || oldData[i] === null) {
                            msgObj.added = true;
                        }
                        msgObj.updated = 'Bookshelves';
                        msgObj.fandom = shelf.fandom;
                        msgObj.id = shelf.id;
                        msgObj.name = shelf.name;
                        //break
                        return false;
                    }
                });
            } else {
                msgObj = undefined;
            }
            chrome.storage.local.set(storeObj, () => tabUpdate(msgObj));
        }
    });
}

function tabUpdate(data) {
    if (data !== undefined) {
        chrome.tabs.query({ url: ['https://www.fanfiction.net/*', 'https://archiveofourown.org/*'] }, function (tabs) {
            tabs.forEach(t => {
                console.log("Sending message to tab: ", t.title, data);
                chrome.tabs.sendMessage(t.id, data)
            });
        });
    }
}

//from Google Firebase Auth Example: https://github.com/firebase/quickstart-js/blob/master/auth/chromextension/credentials.js
/**
 * Start the auth flow and authorizes to Firebase.
 * @param{boolean} interactive True if the OAuth flow should request with an interactive mode.
 */
function startAuth(interactive) {
    // Request an OAuth token from the Chrome Identity API.
    chrome.identity.getAuthToken({ interactive: !!interactive }, function (token) {
        if (chrome.runtime.lastError && !interactive) {
            console.log('It was not possible to get a token programmatically.');
        } else if (chrome.runtime.lastError) {
            console.error(chrome.runtime.lastError);
        } else if (token) {
            // Authorize Firebase with the OAuth Access Token.
            var credential = firebase.auth.GoogleAuthProvider.credential(null, token);
            firebase.auth().signInWithCredential(credential).catch(function (error) {
                // The OAuth token might have been invalidated. Lets' remove it from cache.
                if (error.code === 'auth/invalid-credential') {
                    chrome.identity.removeCachedAuthToken({ token: token }, function () {
                        startAuth(interactive);
                    });
                }
            });
        } else {
            console.error('The OAuth Token was null');
        }
    });
}

function jsonEqual(a, b) {
    return JSON.stringify(a) === JSON.stringify(b);
}