importScripts('./js/nunjucks.min.js', './js/router.js', './js/render.js');

const NETWORK_TIMEOUT_MS = 3000;

const DOWNLOAD_TIMEOUT_MS = 30000;

const DOWNLOAD_AT_ONCE = 4;

const VERSION = 'dev';
const LIBRARY_VERSION = 'dev';
const LIBRARY = [];

const SHELL_CACHE = 'bible-shell-' + VERSION;
const LIBRARY_CACHE = 'bible-library-' + LIBRARY_VERSION;

const VERSIONS = { shell: VERSION, library: LIBRARY_VERSION };

const LIBRARY_URLS = new Set(LIBRARY.map((path) => new URL(path, location.href).href));

const PRECACHE = [
  './boot.html',
  './',
  './manifest.webmanifest',
  './css/app.css',
  './fonts/DayLeafInitials.woff2',
  './ornaments/group-l-49.svg',
  './js/htmx.min.js'
].concat(TEMPLATE_URLS);

function cacheFor(req) {
  return caches.open(LIBRARY_URLS.has(req.url) ? LIBRARY_CACHE : SHELL_CACHE);
}

self.addEventListener('install', (event) => {
  event.waitUntil((async () => {
    const cache = await caches.open(SHELL_CACHE);
    let failed = 0;
    await Promise.all(PRECACHE.map((url) =>
      cache.add(new Request(url, { cache: 'reload' })).catch(() => { failed++; })));
    if (failed) console.warn('precache: ' + failed + ' of ' + PRECACHE.length + ' failed');
    await self.skipWaiting();
  })());
});

self.addEventListener('activate', (event) => {
  event.waitUntil((async () => {
    const keys = await caches.keys();
    await Promise.all(keys
      .filter((k) => k.startsWith('bible-') && k !== SHELL_CACHE && k !== LIBRARY_CACHE)
      .map((k) => caches.delete(k)));
    await self.clients.claim();
  })());
});

function isFile(url) {
  return url.pathname.split('/').pop().indexOf('.') !== -1;
}

self.addEventListener('fetch', (event) => {
  const req = event.request;
  const url = new URL(req.url);
  if (url.origin !== location.origin) return;

  keepFilling(event);

  if (!isFile(url)) {
    const routed = router.handle(event, url);
    if (routed) {
      return event.respondWith(routed.then((res) => res || answer(req, event)));
    }
  }

  if (req.method !== 'GET') return;
  event.respondWith(answer(req, event));
});

async function fromNetwork(req, timeout) {
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), timeout || NETWORK_TIMEOUT_MS);
  try {
    return await fetch(req, { signal: controller.signal });
  } finally {
    clearTimeout(timer);
  }
}

function cached(req) {
  return caches.match(req, { ignoreSearch: true });
}

async function answer(input, event) {
  const req = typeof input === 'string' ? new Request(input) : input;

  const hit = await cached(req);
  if (hit) return hit;

  const res = await fromNetwork(req);
  if (res && res.ok && res.type === 'basic') {
    const copy = res.clone();
    const write = cacheFor(req).then((c) => c.put(req, copy));
    if (event) event.waitUntil(write);
    else write.catch(() => {});
  }
  return res;
}

function pageRequest(url) {
  return new Request(url, { cache: 'no-cache' });
}

async function readText(input, event) {
  const res = await answer(input, event);
  if (!res || !res.ok) throw new Error('cannot load ' + (input.url || input));
  return res.text();
}

async function readTemplate(path) {
  const hit = await cached(path);
  return hit ? hit.text() : readText(path);
}

const view = createRenderer(readTemplate);

const router = new Router(new URL('./', location.href).pathname);

const OFFLINE_NOTICE = ['Not available offline',
  'This page has not been opened on this device, so there is no copy stored ' +
  'here. Reconnect and try again, or open one you have read before.'];
const MISSING_NOTICE = ['Not found', 'There is no page at this address.'];

async function fragmentFor(path, event) {
  let res;
  try {
    res = await answer(pageRequest(path), event);
  } catch (err) {
    return view.notice(...OFFLINE_NOTICE);
  }
  return res.ok ? res.text() : view.notice(...MISSING_NOTICE);
}

async function servePage(path, code, call) {
  let fragment = await fragmentFor(path, call.event);
  if (!code) {
    fragment += '\n' + await view.render('version.njk', { version: VERSIONS });
  }
  if (!call.navigate && !call.restore) return fragment;
  try {
    return await view.compose(fragment);
  } catch (err) {
    console.error('compose failed: ' + err.message);
    return fragment;
  }
}

router.get('/', (call) => servePage('./', '', call));
router.get('/:page', (call) =>
  servePage('./' + call.params.page, call.params.page, call));

let filling = null;
let complete = false;

function keepFilling(event) {
  if (complete) return;
  if (!filling && self.navigator.onLine !== false) {
    filling = fillLibrary().catch(() => {}).finally(() => { filling = null; });
  }
  if (filling) event.waitUntil(filling);
}

async function fillLibrary() {
  const cache = await caches.open(LIBRARY_CACHE);
  const have = new Set((await cache.keys()).map((req) => req.url));
  const missing = [];
  LIBRARY_URLS.forEach((url) => { if (!have.has(url)) missing.push(url); });
  if (!missing.length) { complete = true; return; }

  let stopped = false;
  const runners = [];
  for (let i = 0; i < DOWNLOAD_AT_ONCE && i < missing.length; i++) runners.push(run());
  await Promise.all(runners);
  if (!stopped) complete = true;

  async function run() {
    while (missing.length && !stopped) {
      const url = missing.pop();
      try {
        const res = await fromNetwork(pageRequest(url), DOWNLOAD_TIMEOUT_MS);
        if (res.ok && res.type === 'basic') await cache.put(url, res);
      } catch (err) {
        stopped = true;
      }
    }
  }
}