import { build, files, version } from '$service-worker'

const ASSETS = `cache_${version}`

const to_cache = build.concat(files)
const staticAssets = new Set(to_cache)

self.addEventListener('install', event => {
	event.waitUntil(
		caches
			.open(ASSETS)
			.then(cache => cache.addAll(to_cache))
			.then(() => {
				self.skipWaiting()
			})
			.catch(console.error)
	)
})

self.addEventListener('activate', event => {
	event.waitUntil(
		caches
			.keys()
			.then(async keys => {
				for (const key of keys) {
					if (key !== ASSETS) await caches.delete(key)
				}

				self.clients.claim()
			})
			.catch(console.error)
	)
})

async function fetchAndCache(request) {
	const cache = await caches.open(`offline_${version}`)

	try {
		const response = await fetch(request)
		cache.put(request, response.clone())
		return response
	} catch (err) {
		const response = await cache.match(request)
		if (response) return response

		throw err
	}
}

self.addEventListener('fetch', event => {
	if (event.request.method !== 'GET' || event.request.headers.has('range')) return

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

	const isHttp = url.protocol.startsWith('http')
	const isDevServerRequest =
		url.hostname === self.location.hostname && url.port !== self.location.port
	const isSameOrigin = url.host === self.location.host
	const isStaticAsset = isSameOrigin && staticAssets.has(url.pathname)
	const skipBecauseUncached = event.request.cache === 'only-if-cached' && !isStaticAsset
	if (isHttp && isSameOrigin && !isDevServerRequest && !skipBecauseUncached) {
		event.respondWith(
			(async () => {
				const cachedAsset = isStaticAsset && (await caches.match(event.request))

				return cachedAsset || fetchAndCache(event.request)
			})()
		)
	}
})