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const CACHE_NAME = 'offline-cache-v1'
const ASSETS = [
'/',
'/index.html',
'/styles.css',
'/styles3.css',
'/tempo.md',
'/bell.png',
'/bell.svg',
'/by-sa.png',
'/cc-by-sa-legalcode.txt',
'/symbols.txt'
]
self.addEventListener('install', e => {
console.log('installing sw')
e.waitUntil(caches.open(CACHE_NAME).then(cache => cache.addAll(ASSETS)))
self.skipWaiting()
})
self.addEventListener('activate', e => {
console.log('sw activated')
e.waitUntil(self.clients.claim())
})
const checkChange = (r1, r2) => {
const h1 = r1.headers
const h2 = r2.headers
if (h1.get('etag') && h2.get('etag')) return h1.get('etag') !== h2.get('etag')
if (h1.get('last-modified') && h2.get('last-modified')) return h1.get('last-modified') !== h2.get('last-modified')
return h1.get('content-length') !== h2.get('content-length')
}
self.addEventListener('fetch', e => {
const url = new URL(e.request.url)
const isTarget = ASSETS.includes(url.pathname) || url.pathname.startsWith('/fonts/')
if (!isTarget) return
e.respondWith((async () => {
const cache = await caches.open(CACHE_NAME)
const cachedResponse = await cache.match(e.request)
const networkFetch = fetch(e.request, { cache: 'no-cache' }).then(async networkResponse => {
if (!networkResponse.ok) return networkResponse
const freshCopy = networkResponse.clone()
let changed = false
if (cachedResponse) {
changed = checkChange(cachedResponse, networkResponse)
} else {
console.log(`fetch ${url.pathname}`)
}
await cache.put(e.request, freshCopy)
if (changed) {
console.log(`content changed, signaling refresh: ${url.pathname}`)
const clients = await self.clients.matchAll()
clients.forEach(client => {
client.postMessage({
type: 'REFRESH',
url: url.pathname
})
})
}
return networkResponse
}).catch(err => {
console.error(`failed ${url.pathname}:`, err)
})
if (cachedResponse) {
console.log(`cache ${url.pathname}`)
e.waitUntil(networkFetch)
return cachedResponse
}
return networkFetch
})())
})
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