/* ===========================================================

* sw.js
* ===========================================================
* Copyright 2016 @huxpro
* Licensed under Apache 2.0 
* Register service worker.
* ========================================================== */

const PRECACHE = 'precache-v1'; const RUNTIME = 'runtime'; const HOSTNAME_WHITELIST = [

self.location.hostname,
"aiokr.github.io",

]

// The Util Function to hack URLs of intercepted requests const getFixedUrl = (req) => {

var now = Date.now();
url = new URL(req.url)
// 1. fixed http URL
// Just keep syncing with location.protocol 
// fetch(httpURL) belongs to active mixed content. 
// And fetch(httpRequest) is not supported yet.
url.protocol = self.location.protocol
// 2. add query for caching-busting.
// Github Pages served with Cache-Control: max-age=600
// max-age on mutable content is error-prone, with SW life of bugs can even extend.
// Until cache mode of Fetch API landed, we have to workaround cache-busting with query string.
// Cache-Control-Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=453190
url.search += (url.search ? '&' : '?') + 'cache-bust=' + now;
return url.href

}

// The Util Function to detect and polyfill req.mode=“navigate” // request.mode of 'navigate' is unfortunately not supported in Chrome // versions older than 49, so we need to include a less precise fallback, // which checks for a GET request with an Accept: text/html header. const isNavigationReq = (req) => (req.mode === 'navigate' || (req.method === 'GET' && req.headers.get('accept').includes('text/html')))

// The Util Function to detect if a req is end with extension // Accordin to Fetch API spec <fetch.spec.whatwg.org/#concept-request-destination> // Any HTML's navigation has consistently mode=“navigate” type=“” and destination=“document” // including requesting an img (or any static resources) from URL Bar directly. // So It ends up with that regExp is still the king of URL routing ;) // P.S. An url.pathname has no '.' can not indicate it ends with extension (e.g. /api/version/1.2/) const endWithExtension = (req) => Boolean(new URL(req.url).pathname.match(/.w+$/))

// Redirect in SW manually fixed github pages arbitray 404s on things?blah // what we want: // repo?blah -> !(gh 404) -> sw 302 -> repo/?blah // .ext?blah -> !(sw 302 -> .ext/?blah -> gh 404) -> .ext?blah // If It's a navigation req and it's url.pathname isn't end with '/' or '.ext' // it should be a dir/repo request and need to be fixed (a.k.a be redirected) // Tracking twitter.com/Huxpro/status/798816417097224193 const shouldRedirect = (req) => (isNavigationReq(req) && new URL(req.url).pathname.substr(-1) !== “/” && !endWithExtension(req))

// The Util Function to get redirect URL // `${url}/` would mis-add “/” in the end of query, so we use URL object. // P.P.S. Always trust url.pathname instead of the whole url string. const getRedirectUrl = (req) => {

url = new URL(req.url)
url.pathname += "/"
return url.href

}

/**

*  @Lifecycle Install
*  Precache anything static to this version of your app.
*  e.g. App Shell, 404, JS/CSS dependencies...
*
*  waitUntil() : installing ====> installed
*  skipWaiting() : waiting(installed) ====> activating
*/

self.addEventListener('install', e => {

e.waitUntil(
  caches.open(PRECACHE).then(cache => {
    return cache.add('offline.html')
    .then(self.skipWaiting())
    .catch(err => console.log(err))
  })
)

});

/**

*  @Lifecycle Activate
*  New one activated when old isnt being used.
*
*  waitUntil(): activating ====> activated
*/

self.addEventListener('activate', event => {

console.log('service worker activated.')
event.waitUntil(self.clients.claim());

});

/**

*  @Functional Fetch
*  All network requests are being intercepted here.
* 
*  void respondWith(Promise<Response> r);
*/

self.addEventListener('fetch', event => {

// logs for debugging
console.log(`fetch ${event.request.url}`)
//console.log(` - type: ${event.request.type}; destination: ${event.request.destination}`)
//console.log(` - mode: ${event.request.mode}, accept: ${event.request.headers.get('accept')}`)
// Skip some of cross-origin requests, like those for Google Analytics.
if (HOSTNAME_WHITELIST.indexOf(new URL(event.request.url).hostname) > -1) {
  // Redirect in SW manually fixed github pages 404s on repo?blah 
  if(shouldRedirect(event.request)){
    event.respondWith(Response.redirect(getRedirectUrl(event.request)))
    return;
  }
  // Stale-while-revalidate 
  // similar to HTTP's stale-while-revalidate: https://www.mnot.net/blog/2007/12/12/stale
  // Upgrade from Jake's to Surma's: https://gist.github.com/surma/eb441223daaedf880801ad80006389f1
  const cached = caches.match(event.request);
  const fixedUrl = getFixedUrl(event.request);
  const fetched = fetch(fixedUrl, {cache: "no-store"});
  const fetchedCopy = fetched.then(resp => resp.clone());
  // Call respondWith() with whatever we get first.
  // If the fetch fails (e.g disconnected), wait for the cache.
  // If there’s nothing in cache, wait for the fetch. 
  // If neither yields a response, return offline pages.
  event.respondWith(
    Promise.race([fetched.catch(_ => cached), cached])
      .then(resp => resp || fetched)
      .catch(_ => caches.match('offline.html'))
  );
  // Update the cache with the version we fetched (only for ok status)
  event.waitUntil(
    Promise.all([fetchedCopy, caches.open(RUNTIME)])
      .then(([response, cache]) => response.ok && cache.put(event.request, response))
      .catch(_ => {/* eat any errors */})
  );
}

});