web-scrobbler\core\background\main.js from https://github.com/inverse/web-scrobbler/tree/multi-scrobble

main.js

'use strict';

/**
 * Background script entry point
 *
 * - sets up injecting mechanism for supported sites
 * - creates controllers for each recognized tab
 * - sets up all chrome.* listeners, which are forwarded controllers if needed
 * - checks auth status on run (browser start or extension enabling) and prompts for login if needed
 */
require([
	'legacy/scrobbler',
	'services/background-ga',
	/* 'scrobblers/lastfm', */
	'scrobblers/librefm',
	'notifications',
	'inject',
	'objects/injectResult',
	'controller',
	'storage',
	'config',
	'chromeStorage',
	'services/scrobbleService'
], function(legacyScrobbler, GA, /* LastFM, */ LibreFM, Notifications, inject, injectResult, Controller, Storage, config, ChromeStorage, ScrobbleService) {

	/**
	 * Single controller instance for each tab with injected script
	 * This allows us to work with tabs independently
	 */
	var tabControllers = {};

	/**
	 * Flag for "page session" where at least single injection occurred
	 * Used for tracking number of actually active users
	 * @type {boolean}
	 */
	var isActiveSession = false;

	/**
	 * Callback for injecting script
	 *
	 * @param {InjectResult} result
	 */
	var injectCb = function(result) {
		var tabId = result.getTabId();

		// no match - do cleanup
		if (result.getResult() === injectResult.results.NO_MATCH) {
			// remove controller if any
			if (tabControllers[tabId] !== undefined) {
				delete tabControllers[tabId];
			}

			// hide action icon - there may be any
			try {
				chrome.pageAction.hide(tabId);
			} catch (e) {
				// ignore, the tab may no longer exist
			}
			return;
		}

		// matched, but the connector is disabled
		if (result.getResult() === injectResult.results.MATCHED_BUT_DISABLED) {
			legacyScrobbler.setActionIcon(config.ACTION_SITE_DISABLED, tabId);
			return;
		}

		// matched, create controller if needed
		if (result.getResult() === injectResult.results.MATCHED_AND_INJECTED) {
			// controllers are used for v2 connectors only
			if (result.getConnector().version === 2) {
				// intentionally overwrite previous controller, if any
				tabControllers[tabId] = new Controller(tabId, result.getConnector());
			}
			else {
				// show 'recognized' action icon until the track info is recognized and validated
				legacyScrobbler.setActionIcon(config.ACTION_SITE_RECOGNIZED, tabId);
			}

			GA.event('core', 'inject', result.getConnector().label);

			if (!isActiveSession) {
				isActiveSession = true;
				GA.send('pageview', '/background-injected?version=' + chrome.app.getDetails().version);
			}
		}
	};

	/**
	 * Returns controller for given tab. There should always be one
	 *
	 * @param {int} tabId
	 */
	function getControllerByTabId(tabId) {
		if (!tabControllers[tabId]) {
			console.warn('Missing controller for tab ' + tabId + ' (should only happen for legacy connector)');
		}

		return tabControllers[tabId];
	}



	// --- done once on background script load -------------------------------------------------------------------------

	// cleanup and other stuff to be done on specific version changes
	{
		var oldLfmStorage = Storage.getNamespace('LastFM');

		// update Core namespace to Chrome storage
		ChromeStorage.get(function(allData) {
			// init
			if (allData === null || Object.keys(allData).length === 0) {
				allData = {
					Core: {
						appVersion: chrome.app.getDetails().version
					},
					LastFM: { // attempt to migrate from localStorage so user doesn't have to re-auth
						token: oldLfmStorage.get('token') || null,
						sessionID: oldLfmStorage.get('sessionID') || null
					}
				};
			}
			// update
			else {
				allData.Core.appVersion = chrome.app.getDetails().version;
			}

			// save and proceed in starting up
			ChromeStorage.set(allData, startup);
		});
	}


	// setup listener for messages from connectors
	chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
		var ctrl;

		switch (request.type) {
			// Interface for new V2 functionality. Routes control flow to new structures, so we can
			// have two cores side by side. The old functionality will be later removed
			case 'v2.stateChanged':
				ctrl = getControllerByTabId(sender.tab.id);
				if (ctrl) {
					ctrl.onStateChanged(request.state);
				}
				break;

			// Returns current song object - used in page action popup.
			// Tab ID is stored inside request data
			case 'v2.getSong':
				ctrl = getControllerByTabId(request.tabId);
				if (ctrl) {
					sendResponse(ctrl.getCurrentSong()); // object or null
				} else {
					sendResponse(false); // no v2 controller, legacy mode
				}
				break;

			// Returns current song object - used in page action popup.
			// Tab ID is stored inside request data
			case 'v2.correctSong':
				ctrl = getControllerByTabId(request.tabId);
				if (ctrl) {
					ctrl.setUserSongData(request.data);
				}
				break;

			case 'v2.toggleLove':
				ctrl = getControllerByTabId(request.tabId);
				if (ctrl) {
					ctrl.toggleLove(request.data, sendResponse);
				}
				break;

			// Redirect all other messages to legacy listener
			default:
				legacyScrobbler.runtimeOnMessage(request, sender, sendResponse);
		}

		return true;
	});

	// setup listener for tab updates
	chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab) {
		// wait for navigation to complete (this does not mean page onLoad)
		if (changeInfo.status !== 'complete') {
			return;
		}

		inject.onTabsUpdated(tabId, changeInfo, tab, injectCb);
	});

	// setup listener for page action clicks
	chrome.pageAction.onClicked.addListener(function(tab) {
		// route events to controllers or assume legacy scrobbler if no controller is found
		var ctrl = getControllerByTabId(tab.id);
		if (ctrl) {
			ctrl.onPageActionClicked(tab);
		} else {
			legacyScrobbler.onPageActionClicked(tab);
		}
	});


	/**
	 * Called on the extension start, after maintenance storage reads/writes are done
	 */
	function startup() {
		// track background page loaded - happens once per browser session
		GA.send('pageview', '/background-loaded?version=' + chrome.app.getDetails().version);

		// debug log internal storage state for people who send logs (tokens are anonymized)
		ChromeStorage.debugLog();

		var scrobblerNotifications = ChromeStorage.getNamespace('ScrobblerNotifications');

		// check session ID status and show notification if authentication is needed
        /*
		LastFM.getSession(function(sessionID) {
			if (sessionID !== 'undefined') {
				Notifications.showAuthenticate(LastFM.getAuthUrl.bind(LastFM));
			} else {
				console.info(LastFM.getLabel() + ' Session ID ' + 'xxxxx' + sessionID.substr(5));
			}
		}.bind(LastFM));

		ScrobbleService.bindScrobbler(LastFM);
        */

		// check session ID status and show notification if authentication is needed
		LibreFM.getSession(function(sessionID) {
			if (sessionID !== 'undefined') {
				scrobblerNotifications.get(function(data) {
					if (typeof data.librefm === 'undefined') {
						Notifications.showAuthenticate(LibreFM.getAuthUrl.bind(LibreFM));
						data.librefm = true;
						scrobblerNotifications.set(data, null);
					}
				});
			} else {
				console.info(LibreFM.getLabel() + ' Session ID ' + 'xxxxx' + sessionID.substr(5));
			}
		}.bind(LibreFM));

		ScrobbleService.bindScrobbler(LibreFM);
	}

});