const currentVersion = '28402';

const addResourcesToCache = async (resources) => {
    const cache = await caches.open(currentVersion);
    await cache.addAll(resources);
};

const putInCache = async (request, response) => {
    const cache = await caches.open(currentVersion);
    await cache.put(request, response);
};

const cacheFirst = async ({ request, preloadResponsePromise }) => {
    // First try to get the resource from the cache
    const responseFromCache = await caches.match(request);
    if (responseFromCache) {
        return responseFromCache;
    }

    // Next try to use the preloaded response, if it's there
    const preloadResponse = await preloadResponsePromise;
    if (preloadResponse) {
        console.info('using preload response', preloadResponse);
        putInCache(request, preloadResponse.clone());
        return preloadResponse;
    }

    // Next try to get the resource from the network
    try {
        const responseFromNetwork = await fetch(request);
        // response may be used only once
        // we need to save clone to put one copy in cache
        // and serve second one
        putInCache(request, responseFromNetwork.clone());
        return responseFromNetwork;
    } catch (error) {
        return new Response('Network error happened', {
            status: 408,
            headers: { 'Content-Type': 'text/plain' },
        });
    }
};

const deleteCache = async key => {
    await caches.delete(key)
}

const deleteOldCaches = async () => {
    const cacheKeepList = [currentVersion];
    const keyList = await caches.keys()
    const cachesToDelete = keyList.filter(key => !cacheKeepList.includes(key))
    await Promise.all(cachesToDelete.map(deleteCache));
}

self.addEventListener('activate', (event) => {
    event.waitUntil(deleteOldCaches());
});

const enableNavigationPreload = async () => {
    if (self.registration.navigationPreload) {
        // Enable navigation preloads!
        await self.registration.navigationPreload.enable();
    }
};

self.addEventListener('activate', (event) => {
    event.waitUntil(enableNavigationPreload());
});

self.addEventListener('install', (event) => {
    event.waitUntil(
        addResourcesToCache([
            './heonian-resources/wordlist.json',
            './heonian-ime/ime.js',
            './font.otf',
            './index.html',
            './main.css',
            './main.js',
            './manifest.json'
        ])
    );
});

self.addEventListener('fetch', (event) => {
    event.respondWith(
        cacheFirst({
            request: event.request,
            preloadResponsePromise: event.preloadResponse
        })
    );
});