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',
  './css/bootstrap.min.css',
  './js/htmx.min.js',
  './js/bootstrap.bundle.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 VERSES_URL = './verses.json';

let verses = null;

function readVerses() {
  if (!verses) {
    verses = readText(pageRequest(VERSES_URL))
      .then(JSON.parse)
      .catch((err) => { verses = null; throw err; });
  }
  return verses;
}

function parseAnchor(id) {
  const chapter = /^ch(\d+)$/.exec(id || '');
  if (chapter) return { chapter: +chapter[1], verse: null };
  const verse = /^v(\d+)_[0-9-]+$/.exec(id || '');
  if (verse) return { chapter: +verse[1], verse: id };
  return null;
}

function verseLabels(chapters, number) {
  const entry = chapters[number - 1];
  if (typeof entry !== 'number') return entry || [];
  const out = [];
  for (let i = 1; i <= entry; i++) out.push(String(i));
  return out;
}

function referenceFor(map, code, anchor) {
  const chapters = map && Object.prototype.hasOwnProperty.call(map, code)
    ? map[code] : null;
  if (!chapters || !chapters.length) return null;

  if (!chapters.some((entry) => (typeof entry === 'number' ? entry : entry.length))) {
    return null;
  }

  const at = parseAnchor(anchor) || { chapter: 1, verse: null };
  const number = at.chapter >= 1 && at.chapter <= chapters.length ? at.chapter : 1;
  const verse = at.chapter === number ? at.verse : null;

  return {
    book: code,
    chapter: 'ch' + number,
    chapters: chapters.map((_, i) => ({ id: 'ch' + (i + 1), label: String(i + 1) })),
    verse: verse,
    verses: verseLabels(chapters, number)
      .map((label) => ({ id: 'v' + number + '_' + label, label: label }))
  };
}

function bookOf(url) {
  return url ? router.relative(url).slice(1) : '';
}

async function referenceOf(code, anchor) {
  if (!code) return null;
  try {
    return referenceFor(await readVerses(), code, anchor);
  } catch (err) {
    return null;
  }
}

async function verseOf(page, at) {
  const code = bookOf(page);
  const anchor = parseAnchor(at);
  if (!page || !code || !anchor || !anchor.verse) return null;

  const reference = await referenceOf(code, at);
  if (!reference) return null;
  const option = reference.verses.find((verse) => verse.id === at);
  if (!option) return null;

  return {
    ref: code + ' ' + anchor.chapter + ':' + option.label,
    href: code + '#' + at,
    url: page.origin + page.pathname + '#' + at
  };
}

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 });
  }
  const reference = await referenceOf(code, null);
  if (!call.navigate && !call.restore) {
    return fragment + '\n'
      + await view.render('reference.njk', { reference: reference, oob: true });
  }
  try {
    return await view.compose(fragment, { mark: await getBookmark(),
                                          reference: reference });
  } 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));

router.get('/api/reference', async (call) => {
  const params = call.url.searchParams;
  const page = call.currentUrl();
  const moved = params.has('at') ? params.get('at') : null;

  const reference = await referenceOf(
    bookOf(page), moved === null ? (page && page.hash.slice(1)) : moved);

  if (moved === null) {
    return view.render('reference.njk', { reference: reference, settled: true });
  }
  if (!reference) return new Response('', { status: 204 });

  const target = reference.verse || reference.chapter;
  return new Response(await view.render('verses.njk', { reference: reference }), {
    headers: {
      'Content-Type': 'text/html; charset=utf-8',
      'Cache-Control': 'no-store',
      'HX-Reswap': 'innerHTML settle:0 show:#' + target + ':top',
      'HX-Replace-Url': page.pathname + page.search + '#' + target
    }
  });
});

router.get('/api/verse', async (call) => {
  const verse = await verseOf(call.currentUrl(), call.url.searchParams.get('at'));
  if (!verse) return new Response('', { status: 204 });
  return view.render('verse.njk', { verse: verse });
});

router.post('/api/bookmark', async (call) => {
  try {
    const form = await call.form();
    const ref = String(form.get('ref') || '').trim();
    const href = String(form.get('href') || '').trim();
    if (!ref || !href) return new Response('', { status: 400 });
    await withStore('readwrite',
      (s) => s.put({ ref: ref, href: href, savedAt: Date.now() }, BOOKMARK_KEY));
    return new Response(await bookmarkFragment('bookmarked'), {
      headers: {
        'Content-Type': 'text/html; charset=utf-8',
        'Cache-Control': 'no-store',
        'HX-Trigger-After-Settle': 'verse-done'
      }
    });
  } catch (err) {
    return bookmarkFragment('bookmark-refused');
  }
});

const TOASTS = {
  'copied': { text: 'Link copied.' },
  'copy-refused': { text: 'Copy the link above: this browser would not '
                          + 'take it.', bad: true },
  'bookmarked': { text: 'Bookmark set.' },
  'bookmark-refused': { text: 'Could not save the bookmark: storage '
                              + 'unavailable.', bad: true }
};

function toastFragment(say, oob) {
  const toast = TOASTS[say];
  return view.render('toast.njk', { text: toast.text, bad: toast.bad, oob: oob });
}

router.get('/api/toast', (call) => {
  const say = call.url.searchParams.get('say');
  if (!TOASTS[say]) return new Response('', { status: 204 });
  return toastFragment(say, false);
});

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;
      }
    }
  }
}

const DB_NAME = 'bible';
const DB_STORE = 'kv';
const BOOKMARK_KEY = 'bookmark';

const DEFAULT_BOOKMARK = { ref: 'GEN 1:1', href: 'GEN#v1_1' };

function openDb() {
  return new Promise((resolve, reject) => {
    const req = indexedDB.open(DB_NAME, 1);
    req.onupgradeneeded = () => req.result.createObjectStore(DB_STORE);
    req.onsuccess = () => resolve(req.result);
    req.onerror = () => reject(req.error);
  });
}

async function withStore(mode, fn) {
  const db = await openDb();
  try {
    return await new Promise((resolve, reject) => {
      const tx = db.transaction(DB_STORE, mode);
      const req = fn(tx.objectStore(DB_STORE));
      tx.oncomplete = () => resolve(req ? req.result : undefined);
      tx.onabort = tx.onerror = () => reject(tx.error);
    });
  } finally {
    db.close();
  }
}

function getBookmark() {
  return withStore('readonly', (s) => s.get(BOOKMARK_KEY))
    .catch(() => null)
    .then((mark) => mark || DEFAULT_BOOKMARK);
}

async function bookmarkFragment(say) {
  return await view.render('bookmark.njk', { mark: await getBookmark() })
       + '\n' + await toastFragment(say, true);
}