/*
Copyright 2020 Bruno Windels <bruno@windels.cloud>
Copyright 2020 The Matrix.org Foundation C.I.C.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

const GLOBAL_HASH = "%%GLOBAL_HASH%%";
const UNHASHED_PRECACHED_ASSETS = "%%UNHASHED_PRECACHED_ASSETS%%";
const HASHED_PRECACHED_ASSETS = "%%HASHED_PRECACHED_ASSETS%%";
const HASHED_CACHED_ON_REQUEST_ASSETS = "%%HASHED_CACHED_ON_REQUEST_ASSETS%%";
const unhashedCacheName = `hydrogen-assets-${GLOBAL_HASH}`;
const hashedCacheName = `hydrogen-assets`;

self.addEventListener('install', function(e) {
    e.waitUntil((async () => {
        const unhashedCache = await caches.open(unhashedCacheName);
        await unhashedCache.addAll(UNHASHED_PRECACHED_ASSETS);
        const hashedCache = await caches.open(hashedCacheName);
        await Promise.all(HASHED_PRECACHED_ASSETS.map(async asset => {
            if (!await hashedCache.match(asset)) {
                await hashedCache.add(asset);
            }
        }));
    })());
});

async function purgeOldCaches() {
    // remove any caches we don't know about
    const keyList = await caches.keys();
    for (const key of keyList) {
        if (key !== unhashedCacheName && key !== hashedCacheName) {
            await caches.delete(key);
        }
    }
    // remove the cache for any old hashed resource
    const hashedCache = await caches.open(hashedCacheName);
    const keys = await hashedCache.keys();
    const hashedAssetURLs =
        HASHED_PRECACHED_ASSETS
        .concat(HASHED_CACHED_ON_REQUEST_ASSETS)
        .map(a => new URL(a, self.registration.scope).href);

    for (const request of keys) {
        if (!hashedAssetURLs.some(url => url === request.url)) {
            hashedCache.delete(request);
        }
    }
}

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

self.addEventListener('fetch', (event) => {
    event.respondWith(handleRequest(event.request));
});

async function handleRequest(request) {
    const baseURL = self.registration.scope;
    if (request.url === baseURL) {
        request = new Request(new URL("index.html", baseURL));
    }
    let response = await readCache(request);
    if (!response) {
        response = await fetch(request);
        await updateCache(request, response);
    }
    return response;
}

async function updateCache(request, response) {
    const baseURL = self.registration.scope;
    if(!request.url.startsWith(baseURL)) {
        return;
    }
    let assetName = request.url.substr(baseURL.length);
    if (HASHED_CACHED_ON_REQUEST_ASSETS.includes(assetName)) {
        const cache = await caches.open(hashedCacheName);
        await cache.put(request, response.clone());
    }
}

async function readCache(request) {
    const unhashedCache = await caches.open(unhashedCacheName);
    let response = await unhashedCache.match(request);
    if (response) {
        return response;
    }
    const hashedCache = await caches.open(hashedCacheName);
    response = await hashedCache.match(request);
    return response;
}