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const CACHE_NAME = "static-shared-assets";
const FALLBACK_PATHS = {
img: "/fallback-image-FIXME.svg",
data: {
static: "/fallback-data-FIXME.json",
},
};
const leafValues = tree =>
Object.values(tree).map(x =>
typeof x !== "object"
? x
: leafValues(x)
);
const collectLeaves = tree =>
leafValues(tree).flat(Infinity);
const DEFAULT_INSTALL_PATHS = [
"/",
"index.html",
"style.css",
"img/favicon.svg",
"papo.js",
].concat(collectLeaves(FALLBACK_PATHS));
const mkInstallHandler = ({ self, caches }) => event => {
self.skipWaiting();
event.waitUntil(
caches.open(CACHE_NAME).then(
cache => cache.addAll(DEFAULT_INSTALL_PATHS),
),
);
};
const store = async (caches, request, response) => {
const cache = await caches.open(CACHE_NAME);
await cache.put(request, response);
};
const getPrefixIn = (paths, segments) => {
if (paths === undefined) {
return null;
}
if (segments.length === 0) {
return null;
}
if (typeof paths === "string") {
return paths;
}
return getPrefixIn(paths[segments[0]], segments.slice(1));
};
const maybeFallback = async (caches, request, paths = FALLBACK_PATHS) => {
const url = new URL(request.url)
const segments = url.pathname.split("/").filter(s => !!s)
const fallbackPath = getPrefixIn(paths, segments);
if (fallbackPath) {
return await caches.match(fallbackPath);
}
return null;
}
const fromCache = async (caches, fetch, { request, preloadResponse }) => {
const cachedResponse = await caches.match(request);
if (cachedResponse) {
fetch(request).then(async freshResponse =>
store(caches, request, freshResponse));
return cachedResponse;
}
const preloadedResponse = await preloadResponse;
if (preloadedResponse) {
store(caches, request, preloadeResponse.clone());
return preloadedResponse;
}
try {
// FIXME: do integration test with real lack of internet.
const fetchedResponse = await fetch(request);
store(caches, request, fetchedResponse.clone());
return fetchedResponse;
} catch (e) {
const fallbackResponse = await maybeFallback(caches, request);
if (fallbackResponse) {
return fallbackResponse;
}
throw e;
}
};
const mkFetchHandler = ({ caches }) => (event, mkfetch = () => fetch) => {
if (event.request.method !== "GET") {
return;
}
event.respondWith(fromCache(caches, mkfetch(), event));
};
const mkActivateHandler = ({ self, clients }) => event =>
event.waitUntil(Promise.all([
clients.claim(),
self.registration.navigationPreload?.enable(),
]));
const registerListeners = env => {
env.self.addEventListener("install", mkInstallHandler(env));
env.self.addEventListener("activate", mkActivateHandler(env));
env.self.addEventListener("fetch", mkFetchHandler(env));
};
const main = ({
self,
caches,
clients,
out = console.log,
err = console.warn,
} = {}) =>
registerListeners({
self,
caches,
clients,
out,
err,
});
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