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kiwix-js/service-worker.js
Jaifroid 3a56e9a7c9
Documentation updates (#1093)
2023-09-04 08:17:50 +01:00

457 lines
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JavaScript
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/**
* service-worker.js : Service Worker implementation,
* in order to capture the HTTP requests made by an article, and respond with the
* corresponding content, coming from the archive
*
* Copyright 2022 Mossroy, Jaifroid and contributors
* Licence GPL v3:
*
* This file is part of Kiwix.
*
* Kiwix is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public Licence as published by
* the Free Software Foundation, either version 3 of the Licence, or
* (at your option) any later version.
*
* Kiwix is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public Licence for more details.
*
* You should have received a copy of the GNU General Public Licence
* along with Kiwix (file LICENSE-GPLv3.txt). If not, see <http://www.gnu.org/licenses/>
*/
'use strict';
/* global chrome */
/**
* App version number - ENSURE IT MATCHES VALUE IN init.js
* DEV: Changing this will cause the browser to recognize that the Service Worker has changed, and it will
* download and install a new copy; we have to hard code this here because it is needed before any other file
* is cached in APP_CACHE
*/
const appVersion = '3.9.3';
/**
* The name of the Cache API cache in which assets defined in regexpCachedContentTypes will be stored
* The value is sometimes needed here before it can be passed from app.js, so we have to duplicate it
* @type {String}
*/
// DEV: Ensure this matches the name defined in app.js
const ASSETS_CACHE = 'kiwixjs-assetsCache';
/**
* The name of the application cache to use for caching online code so that it can be used offline
* The cache name is made up of the prefix below and the appVersion: this is necessary so that when
* the app is updated, a new cache is created. The new cache will start being used after the user
* restarts the app, when we will also delete the old cache.
* @type {String}
*/
const APP_CACHE = 'kiwixjs-appCache-' + appVersion;
/**
* A global Boolean that governs whether ASSETS_CACHE will be used
* Caching is on by default but can be turned off by the user in Configuration
* @type {Boolean}
*/
var useAssetsCache = true;
/**
* A global Boolean that governs whether the APP_CACHE will be used
* This is an expert setting in Configuration
* @type {Boolean}
*/
var useAppCache = true;
/**
* A regular expression that matches the Content-Types of assets that may be stored in ASSETS_CACHE
* Add any further Content-Types you wish to cache to the regexp, separated by '|'
* @type {RegExp}
*/
var regexpCachedContentTypes = /text\/css|text\/javascript|application\/javascript/i;
/**
* A regular expression that excludes listed schemata from caching attempts
* As of 08-2019 the chrome-extension: schema is incompatible with the Cache API
* 'example-extension' is included to show how to add another schema if necessary
* @type {RegExp}
*/
var regexpExcludedURLSchema = /^(?:file|chrome-extension|example-extension):/i;
/**
* Pattern for ZIM file namespace: see https://wiki.openzim.org/wiki/ZIM_file_format#Namespaces
* In our case, there is also the ZIM file name used as a prefix in the URL
* @type {RegExp}
*/
const regexpZIMUrlWithNamespace = /(?:^|\/)([^/]+\/)([-ABCIJMUVWX])\/(.+)/;
/**
* Pattern to parse the first offset of a "range" request header
* NB: this only reads the first offset of the first byte range, where the spec allows several ranges, and several units.
* See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Range
* But, in our case, we send a header to tell the browser we only accept the bytes unit.
* I did not see multiple ranges asked by a browser.
*
* @type {RegExp}
*/
const regexpByteRangeHeader = /^\s*bytes=(\d+)-/;
/**
* The list of files that the app needs in order to run entirely from offline code
*/
const precacheFiles = [
'.', // This caches the redirect to www/index.html, in case a user launches the app from its root directory
'manifest.json',
'service-worker.js',
'i18n/en.jsonp',
'i18n/es.jsonp',
'i18n/fr.jsonp',
'www/css/app.css',
'www/css/kiwixJS_invert.css',
'www/css/kiwixJS_mwInvert.css',
'www/css/transition.css',
'www/img/icons/kiwix-256.png',
'www/img/icons/kiwix-32.png',
'www/img/icons/kiwix-60.png',
'www/img/spinner.gif',
'www/img/Icon_External_Link.png',
'www/index.html',
'www/article.html',
'www/main.html',
'www/js/app.js',
'www/js/init.js',
'www/js/lib/abstractFilesystemAccess.js',
'www/js/lib/arrayFromPolyfill.js',
'www/js/lib/filecache.js',
'www/js/lib/promisePolyfill.js',
'www/js/lib/settingsStore.js',
'www/js/lib/translateUI.js',
'www/js/lib/uiUtil.js',
'www/js/lib/utf8.js',
'www/js/lib/util.js',
'www/js/lib/xzdec_wrapper.js',
'www/js/lib/zstddec_wrapper.js',
'www/js/lib/zimArchive.js',
'www/js/lib/zimArchiveLoader.js',
'www/js/lib/zimDirEntry.js',
'www/js/lib/zimfile.js',
'node_modules/bootstrap/dist/js/bootstrap.bundle.min.js',
'node_modules/bootstrap/dist/js/bootstrap.bundle.min.js.map',
'node_modules/bootstrap/dist/css/bootstrap.min.css',
'node_modules/bootstrap/dist/css/bootstrap.min.css.map',
'node_modules/jquery/dist/jquery.slim.min.js',
'node_modules/jquery/dist/jquery.slim.min.map'
];
if ('WebAssembly' in self) {
precacheFiles.push(
'www/js/lib/xzdec-wasm.js',
'www/js/lib/xzdec-wasm.wasm',
'www/js/lib/zstddec-wasm.js',
'www/js/lib/zstddec-wasm.wasm',
'www/js/lib/libzim-wasm.js',
'www/js/lib/libzim-wasm.wasm'
);
} else {
precacheFiles.push(
'www/js/lib/xzdec-asm.js',
'www/js/lib/zstddec-asm.js',
'www/js/lib/libzim-asm.js'
);
}
/**
* If we're in a Chromium extension, add a listener to launch the tab when the icon is clicked
*/
if (typeof chrome !== 'undefined' && chrome.action) {
chrome.action.onClicked.addListener(function () {
var newURL = chrome.runtime.getURL('www/index.html');
chrome.tabs.create({ url: newURL });
});
}
// Process install event
self.addEventListener('install', function (event) {
console.debug('[SW] Install Event processing');
// DEV: We can't skip waiting because too many params are loaded at an early stage from the old file before the new one can activate...
// self.skipWaiting();
// We try to circumvent the browser's cache by adding a header to the Request, and it ensures all files are explicitly versioned
var requests = precacheFiles.map(function (urlPath) {
return new Request(urlPath + '?v' + appVersion, { cache: 'no-cache' });
});
if (!regexpExcludedURLSchema.test(requests[0].url)) {
event.waitUntil(caches.open(APP_CACHE).then(function (cache) {
return Promise.all(
requests.map(function (request) {
return fetch(request).then(function (response) {
// Fail on 404, 500 etc
if (!response.ok) throw Error('Could not fetch ' + request.url);
return cache.put(request.url.replace(/\?v[^?/]+$/, ''), response);
}).catch(function (err) {
console.error('There was an error pre-caching files', err);
});
})
);
}));
}
});
// Allow sw to control current page
self.addEventListener('activate', function (event) {
// "Claiming" the ServiceWorker is necessary to make it work right away,
// without the need to reload the page.
// See https://developer.mozilla.org/en-US/docs/Web/API/Clients/claim
event.waitUntil(self.clients.claim());
console.debug('[SW] Claiming clients for current page');
// Check all the cache keys, and delete any old caches
event.waitUntil(
caches.keys().then(function (keyList) {
return Promise.all(keyList.map(function (key) {
console.debug('[SW] Current cache key is ' + key);
if (key !== APP_CACHE && key !== ASSETS_CACHE) {
console.debug('[SW] App updated to version ' + appVersion + ': deleting old cache');
return caches.delete(key);
}
}));
})
);
});
let outgoingMessagePort = null;
let fetchCaptureEnabled = false;
/**
* Intercept selected Fetch requests from the browser window
*/
self.addEventListener('fetch', function (event) {
// Only cache GET requests
if (event.request.method !== 'GET') return;
var rqUrl = event.request.url;
var urlObject = new URL(rqUrl);
// Test the URL with parameters removed
var strippedUrl = urlObject.pathname;
// Select cache depending on request format
var cache = /\.zim\//i.test(strippedUrl) ? ASSETS_CACHE : APP_CACHE;
if (cache === ASSETS_CACHE && !fetchCaptureEnabled) return;
// For APP_CACHE assets, we should ignore any querystring (whereas it should be conserved for ZIM assets,
// especially .js assets, where it may be significant). Anchor targets are irreleveant in this context.
if (cache === APP_CACHE) rqUrl = strippedUrl;
event.respondWith(
// First see if the content is in the cache
fromCache(cache, rqUrl).then(function (response) {
// The response was found in the cache so we respond with it
return response;
}, function () {
// The response was not found in the cache so we look for it in the ZIM
// and add it to the cache if it is an asset type (css or js)
if (cache === ASSETS_CACHE && regexpZIMUrlWithNamespace.test(strippedUrl)) {
const range = event.request.headers.get('range');
return fetchUrlFromZIM(urlObject, range).then(function (response) {
// Add css or js assets to ASSETS_CACHE (or update their cache entries) unless the URL schema is not supported
if (regexpCachedContentTypes.test(response.headers.get('Content-Type')) &&
!regexpExcludedURLSchema.test(event.request.url)) {
event.waitUntil(updateCache(ASSETS_CACHE, rqUrl, response.clone()));
}
return response;
}).catch(function (msgPortData) {
console.error('Invalid message received from app.js for ' + strippedUrl, msgPortData);
return msgPortData;
});
} else {
// It's not an asset, or it doesn't match a ZIM URL pattern, so we should fetch it with Fetch API
return fetch(event.request).then(function (response) {
// If request was successful, add or update it in the cache, but be careful not to cache the ZIM archive itself!
if (!regexpExcludedURLSchema.test(event.request.url) && !/\.zim\w{0,2}$/i.test(strippedUrl)) {
event.waitUntil(updateCache(APP_CACHE, rqUrl, response.clone()));
}
return response;
}).catch(function (error) {
console.debug('[SW] Network request failed and no cache.', error);
});
}
})
);
});
/**
* Handle custom commands sent from app.js
*/
self.addEventListener('message', function (event) {
if (event.data.action) {
if (event.data.action === 'init') {
// On 'init' message, we initialize the outgoingMessagePort and enable the fetchEventListener
outgoingMessagePort = event.ports[0];
fetchCaptureEnabled = true;
} else if (event.data.action === 'disable') {
// On 'disable' message, we delete the outgoingMessagePort and disable the fetchEventListener
outgoingMessagePort = null;
fetchCaptureEnabled = false;
}
var oldValue;
if (event.data.action.assetsCache) {
// Turns caching on or off (a string value of 'enable' turns it on, any other string turns it off)
oldValue = useAssetsCache;
useAssetsCache = event.data.action.assetsCache === 'enable';
if (useAssetsCache !== oldValue) console.debug('[SW] Use of assetsCache was switched to: ' + useAssetsCache);
}
if (event.data.action.appCache) {
// Enables or disables use of appCache
oldValue = useAppCache;
useAppCache = event.data.action.appCache === 'enable';
if (useAppCache !== oldValue) console.debug('[SW] Use of appCache was switched to: ' + useAppCache);
}
if (event.data.action === 'getCacheNames') {
event.ports[0].postMessage({ app: APP_CACHE, assets: ASSETS_CACHE });
}
if (event.data.action.checkCache) {
// Checks and returns the caching strategy: checkCache key should contain a sample URL string to test
testCacheAndCountAssets(event.data.action.checkCache).then(function (cacheArr) {
event.ports[0].postMessage({ type: cacheArr[0], name: cacheArr[1], description: cacheArr[2], count: cacheArr[3] });
});
}
}
});
/**
* Handles URLs that need to be extracted from the ZIM archive
*
* @param {URL} urlObject The URL object to be processed for extraction from the ZIM
* @param {String} range Optional byte range string
* @returns {Promise<Response>} A Promise for the Response, or rejects with the invalid message port data
*/
function fetchUrlFromZIM (urlObject, range) {
return new Promise(function (resolve, reject) {
// Note that titles may contain bare question marks or hashes, so we must use only the pathname without any URL parameters.
// Be sure that you haven't encoded any querystring along with the URL.
var barePathname = decodeURIComponent(urlObject.pathname);
var partsOfZIMUrl = regexpZIMUrlWithNamespace.exec(barePathname);
var prefix = partsOfZIMUrl[1];
var nameSpace = partsOfZIMUrl[2];
var title = partsOfZIMUrl[3];
var titleWithNameSpace = nameSpace + '/' + title;
// Let's instantiate a new messageChannel, to allow app.js to give us the content
var messageChannel = new MessageChannel();
messageChannel.port1.onmessage = function (msgPortEvent) {
if (msgPortEvent.data.action === 'giveContent') {
// Content received from app.js
var contentLength = msgPortEvent.data.content ? (msgPortEvent.data.content.byteLength || msgPortEvent.data.content.length) : null;
var contentType = msgPortEvent.data.mimetype;
var headers = new Headers();
if (contentLength) headers.set('Content-Length', contentLength);
// Set Content-Security-Policy to sandbox the content (prevent XSS attacks from malicious ZIMs)
headers.set('Content-Security-Policy', "default-src 'self' data: blob: about: chrome-extension: moz-extension: https://browser-extension.kiwix.org https://kiwix.github.io 'unsafe-inline' 'unsafe-eval'; sandbox allow-scripts allow-same-origin allow-modals allow-popups allow-forms allow-downloads;");
headers.set('Referrer-Policy', 'no-referrer');
if (contentType) headers.set('Content-Type', contentType);
// Test if the content is a video or audio file. In this case, Chrome & Edge need us to support ranges.
// See kiwix-js #519 and openzim/zimwriterfs #113 for why we test for invalid types like "mp4" or "webm" (without "video/")
// The full list of types produced by zimwriterfs is in https://github.com/openzim/zimwriterfs/blob/master/src/tools.cpp
if (contentLength >= 1 && /^(video|audio)|(^|\/)(mp4|webm|og[gmv]|mpeg)$/i.test(contentType)) {
headers.set('Accept-Ranges', 'bytes');
}
var slicedData = msgPortEvent.data.content;
if (range) {
// The browser asks for a range of bytes (usually for a video or audio stream)
// In this case, we partially honor the request: if it asks for offsets x to y,
// we send partial contents starting at x offset, till the end of the data (ignoring y offset)
// Our backend can currently only read the whole content from the ZIM file.
// So it's probably better to send all we have: hopefully it will avoid some subsequent requests of
// the browser to get the following chunks (which would trigger some other complete reads in the ZIM file)
// This might be improved in the future with the libzim wasm backend, that should be able to handle ranges.
const partsOfRangeHeader = regexpByteRangeHeader.exec(range);
const begin = partsOfRangeHeader[1];
const end = contentLength - 1;
slicedData = slicedData.slice(begin);
headers.set('Content-Range', 'bytes ' + begin + '-' + end + '/' + contentLength);
headers.set('Content-Length', end - begin + 1);
}
var responseInit = {
// HTTP status is usually 200, but has to bee 206 when partial content (range) is sent
status: range ? 206 : 200,
statusText: 'OK',
headers
};
var httpResponse = new Response(slicedData, responseInit);
// Let's send the content back from the ServiceWorker
resolve(httpResponse);
} else if (msgPortEvent.data.action === 'sendRedirect') {
resolve(Response.redirect(prefix + msgPortEvent.data.redirectUrl));
} else {
reject(msgPortEvent.data, titleWithNameSpace);
}
};
outgoingMessagePort.postMessage({
action: 'askForContent',
title: titleWithNameSpace
}, [messageChannel.port2]);
});
}
/**
* Looks up a Request in a cache and returns a Promise for the matched Response
* @param {String} cache The name of the cache to look in
* @param {String} requestUrl The Request URL to fulfill from cache
* @returns {Promise<Response>} A Promise for the cached Response, or rejects with strings 'disabled' or 'no-match'
*/
function fromCache (cache, requestUrl) {
// Prevents use of Cache API if user has disabled it
if (!(useAppCache && cache === APP_CACHE || useAssetsCache && cache === ASSETS_CACHE)) {
return Promise.reject(new Error('disabled'));
}
return caches.open(cache).then(function (cacheObj) {
return cacheObj.match(requestUrl).then(function (matching) {
if (!matching || matching.status === 404) {
return Promise.reject(new Error('no-match'));
}
console.debug('[SW] Supplying ' + requestUrl + ' from ' + cache + '...');
return matching;
});
});
}
/**
* Stores or updates in a cache the given Request/Response pair
* @param {String} cache The name of the cache to open
* @param {Request|String} request The original Request object or the URL string requested
* @param {Response} response The Response received from the server/ZIM
* @returns {Promise} A Promise for the update action
*/
function updateCache (cache, request, response) {
// Prevents use of Cache API if user has disabled it
if (!response.ok || !(useAppCache && cache === APP_CACHE || useAssetsCache && cache === ASSETS_CACHE)) {
return Promise.resolve();
}
return caches.open(cache).then(function (cacheObj) {
console.debug('[SW] Adding ' + (request.url || request) + ' to ' + cache + '...');
return cacheObj.put(request, response);
});
}
/**
* Tests the caching strategy available to this app and if it is Cache API, count the
* number of assets in ASSETS_CACHE
* @param {String} url A URL to test against excludedURLSchema
* @returns {Promise<Array>} A Promise for an array of format [cacheType, cacheDescription, assetCount]
*/
function testCacheAndCountAssets (url) {
if (regexpExcludedURLSchema.test(url)) return Promise.resolve(['custom', 'custom', 'Custom', '-']);
if (!useAssetsCache) return Promise.resolve(['none', 'none', 'None', 0]);
return caches.open(ASSETS_CACHE).then(function (cache) {
return cache.keys().then(function (keys) {
return ['cacheAPI', ASSETS_CACHE, 'Cache API', keys.length];
}).catch(function (err) {
return err;
});
}).catch(function (err) {
return err;
});
}
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