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const CACHE_NAME = 'markdown-viewer-cache-v3.10.4';

// PERF-011: Split precache into critical (local files) and lazy (CDN libraries)

// Critical assets are precached during SW install for instant offline startup

const CRITICAL_ASSETS = [

'./',

'./index.html',

'./workspace-storage.js',

'./visual-settings-adapters.js',

'./visual-settings-store.js',

'./script.js',

'./preview-worker.js',

'./styles.css',

'./assets/seo-metadata.mjs',

'./seo/locales.mjs',

'./seo/welcome-content.mjs',

'./assets/lucide-icons.css',

'./assets/document-toc.js',

'./RELEASE_NOTES',

'./sample.md',

'./assets/icon.jpg',

'./manifest.json'

];

// CDN assets are cached lazily on first use via runtime cache-first strategy

// This prevents the SW install from downloading ~5.4 MB of CDN resources upfront

const CDN_ORIGINS = [

'cdnjs.cloudflare.com',

'cdn.jsdelivr.net'

];

const NETWORK_FIRST_LOCAL_PATHS = new Set([

'/',

'/index.html',

'/workspace-storage.js',

'/visual-settings-adapters.js',

'/visual-settings-store.js',

'/script.js',

'/preview-worker.js',

'/styles.css',

'/assets/seo-metadata.mjs',

'/seo/locales.mjs',

'/seo/welcome-content.mjs',

'/assets/lucide-icons.css',

'/assets/document-toc.js',

'/sw.js'

]);

self.addEventListener('install', event => {

event.waitUntil(

caches.open(CACHE_NAME)

.then(cache => cache.addAll(CRITICAL_ASSETS))

.then(() => self.skipWaiting())

);

});

self.addEventListener('activate', event => {

event.waitUntil(

caches.keys().then(keys => Promise.all(

keys.map(key => {

if (key !== CACHE_NAME) {

return caches.delete(key);

}

})

)).then(() => self.clients.claim())

);

});

self.addEventListener('fetch', event => {

const url = new URL(event.request.url);

const isLocal = url.origin === self.location.origin;

const isCDN = CDN_ORIGINS.some(origin => url.hostname.includes(origin));

if (isLocal) {

const localPath = url.pathname.endsWith('/') ? '/' : url.pathname;

const shouldUseNetworkFirst =

event.request.mode === 'navigate' ||

NETWORK_FIRST_LOCAL_PATHS.has(localPath) ||

localPath.startsWith('/assets/i18n/');

if (shouldUseNetworkFirst) {

event.respondWith(

caches.open(CACHE_NAME).then(cache => {

return fetch(event.request).then(networkResponse => {

if (networkResponse && networkResponse.status === 200) {

cache.put(event.request, networkResponse.clone());

}

return networkResponse;

}).catch(() => cache.match(event.request));

})

);

return;

}

// Stale-While-Revalidate strategy for non-code local assets

event.respondWith(

caches.open(CACHE_NAME).then(cache => {

return cache.match(event.request).then(cachedResponse => {

const fetchPromise = fetch(event.request).then(networkResponse => {

if (networkResponse && networkResponse.status === 200) {

cache.put(event.request, networkResponse.clone());

}

return networkResponse;

}).catch(err => {

console.warn('Background fetch failed for:', event.request.url, err);

});

return cachedResponse || fetchPromise;

});

})

);

} else if (isCDN) {

// Cache-First strategy for stable third-party CDN libraries

// PERF-011: CDN resources are cached on first use (lazy) rather than precached

event.respondWith(

caches.match(event.request)

.then(cachedResponse => {

if (cachedResponse) {

return cachedResponse;

}

return fetch(event.request).then(response => {

if (response && response.status === 200) {

const responseToCache = response.clone();

caches.open(CACHE_NAME).then(cache => {

cache.put(event.request, responseToCache);

});

}

return response;

});

})

);

} else {

// Let arbitrary external resources use the browser's normal request path.

// Wrapping user-supplied images in service-worker fetch() makes them subject

// to connect-src instead of img-src, which blocks otherwise valid images.

return;

}

});