NHL-Scoreboard/app/templates/sw.js.j2

const CACHE = 'nhl-scoreboard-{{ app_version }}';
const PRECACHE = {{ precache | tojson }};

self.addEventListener('install', event => {
    event.waitUntil(caches.open(CACHE).then(c => c.addAll(PRECACHE)));
    self.skipWaiting();
});

self.addEventListener('activate', event => {
    event.waitUntil(
        caches.keys().then(keys =>
            Promise.all(keys.filter(k => k !== CACHE).map(k => caches.delete(k)))
        )
    );
    self.clients.claim();
});

self.addEventListener('fetch', event => {
    if (event.request.method !== 'GET') return;
    const { pathname } = new URL(event.request.url);

    // Network-first for the live scoreboard API — stale data is useless
    if (pathname === '/scoreboard') {
        event.respondWith(
            fetch(event.request).catch(() => caches.match(event.request))
        );
        return;
    }

    // Network-first for HTML pages (root, bracket, series detail) so the
    // very next request after a deploy lands the new asset URLs
    if (pathname === '/' || pathname === '/bracket' || pathname.startsWith('/series/')) {
        event.respondWith(
            fetch(event.request).then(response => {
                if (response.ok) {
                    const clone = response.clone();
                    caches.open(CACHE).then(c => c.put(event.request, clone));
                }
                return response;
            }).catch(() => caches.match(event.request))
        );
        return;
    }

    // Stale-while-revalidate for everything else (versioned static assets,
    // manifest, icons): return cached bytes immediately, refresh in the
    // background so the next load is current
    event.respondWith(
        caches.match(event.request).then(cached => {
            const networkFetch = fetch(event.request).then(response => {
                if (response.ok) {
                    const clone = response.clone();
                    caches.open(CACHE).then(c => c.put(event.request, clone));
                }
                return response;
            }).catch(() => cached);
            return cached || networkFetch;
        })
    );
});