feat(offline): make the web UI usable without a reachable backend

Three tiers of offline support, all scoped to the active backend's localStorage namespace (mirroring the auth slice): Tier 1 — persist client state. queue + player slices are saved (queue entries/index/source; player track/position/volume/repeat/shuffle) and rehydrated on load, so a reload with no backend restores where the user left off. Playback never auto-resumes (browsers block autoplay). Retires the DEMO_QUEUE and isQueueOpen:true stubs. Tier 2 — persist the RTK Query cache. Last-seen library/albums/artists are snapshotted (fulfilled queries only) and replayed via RTKQ's extractRehydrationInfo at startup, so the library renders read-only when the backend is down. ConnectionStatus tooltip flags cached data offline. No server data is copied into a slice — the cache feeds itself back. Tier 3 — service worker audio + cover cache (PWA). Audio streams are cached keyed by content id (token stripped), range-aware (synthetic 206 slicing), with a 500MB LRU cap, so already-played tracks play fully offline. Cover art uses stale-while-revalidate in its own bounded cache. Module worker (ESM); pure helpers split into sw-core.js and unit-tested. Web app manifest enables "Install app". Player source badge now reflects real cached state. tsc clean, lint clean, 19 new tests pass, production build verified. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-07 19:59:31 +03:00
parent 61dbb1abd2
commit ceee9b9d12
21 changed files with 1054 additions and 53 deletions
@@ -0,0 +1,19 @@
+{
+  "name": "MCMA — Music",
+  "short_name": "MCMA",
+  "description": "Self-hosted music — control center and offline-capable player.",
+  "start_url": "/",
+  "scope": "/",
+  "display": "standalone",
+  "orientation": "any",
+  "background_color": "#0b0b0b",
+  "theme_color": "#0b0b0b",
+  "icons": [
+    {
+      "src": "/favicon.png",
+      "sizes": "128x128",
+      "type": "image/png",
+      "purpose": "any"
+    }
+  ]
+}
@@ -0,0 +1,98 @@
+/*
+ * Service-worker core: pure helpers with NO side effects (no `self`, no
+ * `caches`, no `fetch`). Split out from `sw.js` so the tricky bits — HTTP Range
+ * parsing, LRU eviction, cache-key normalization — can be unit-tested in Node.
+ *
+ * This is an ES module: `sw.js` imports it (the SW is registered with
+ * { type: 'module' }) and tests import it natively — one source, no drift.
+ */
+
+// Bump the version to invalidate every cached blob on a breaking change.
+export const AUDIO_CACHE = 'mcma-audio-v1';
+// Synthetic same-origin key holding the LRU index ({ key: {size, lastAccess} }).
+export const INDEX_URL = '/__mcma_audio_index__';
+// Soft cap on total cached audio. LRU eviction keeps us under this.
+export const MAX_BYTES = 500 * 1024 * 1024; // 500 MB
+
+// Cover art (album/artist/playlist images) gets its own cache with a simple
+// count cap — covers are small and stable, so no per-byte LRU is needed.
+export const COVER_CACHE = 'mcma-covers-v1';
+export const MAX_COVERS = 600;
+
+// Backend stream route: /api/v1/streaming/tracks/<trackId>?token=...
+const STREAM_RE = /\/streaming\/tracks\/([^/?#]+)/;
+
+/** The track (content) id from a stream URL, or null if it isn't one. */
+export function trackIdFromUrl(url) {
+  const m = STREAM_RE.exec(url);
+  return m ? m[1] : null;
+}
+
+/**
+ * Canonical cache key for a stream URL: origin + path, query dropped. The auth
+ * token rides in the query and rotates on refresh, so keying by content path
+ * (origin keeps two backends from colliding) makes the cache token-stable —
+ * the same track is one entry regardless of which token fetched it.
+ */
+export function cacheKeyFor(url) {
+  try {
+    const u = new URL(url);
+    return u.origin + u.pathname;
+  } catch {
+    return String(url).split('?')[0];
+  }
+}
+
+/**
+ * Parse an HTTP `Range` header against a known resource size. Returns inclusive
+ * { start, end } byte offsets, or null for "no range / serve the whole thing".
+ * Handles `bytes=a-b`, `bytes=a-` (open-ended) and `bytes=-n` (last n bytes).
+ */
+export function parseRangeHeader(rangeHeader, size) {
+  if (!rangeHeader) return null;
+  const m = /^bytes=(\d*)-(\d*)$/.exec(String(rangeHeader).trim());
+  if (!m) return null;
+  let start = m[1] === '' ? null : parseInt(m[1], 10);
+  let end = m[2] === '' ? null : parseInt(m[2], 10);
+  if (start === null && end === null) return null;
+  if (start === null) {
+    // suffix range: the final `end` bytes
+    start = Math.max(0, size - end);
+    end = size - 1;
+  } else if (end === null) {
+    end = size - 1;
+  }
+  if (Number.isNaN(start) || Number.isNaN(end)) return null;
+  if (end >= size) end = size - 1;
+  if (start < 0 || start > end) return null;
+  return { start, end };
+}
+
+/**
+ * Choose which cached entries to evict (least-recently-used first) so that the
+ * existing total plus an incoming blob fits under `maxBytes`. Returns the list
+ * of keys to delete; empty when there's already room.
+ *
+ * `index` is { [key]: { size, lastAccess } }.
+ */
+export function selectEvictions(index, incomingSize, maxBytes) {
+  let total = incomingSize;
+  for (const k in index) total += index[k].size || 0;
+  if (total <= maxBytes) return [];
+
+  const entries = Object.keys(index)
+    .map((k) => ({
+      key: k,
+      lastAccess: index[k].lastAccess || 0,
+      size: index[k].size || 0,
+    }))
+    .sort((a, b) => a.lastAccess - b.lastAccess); // oldest first
+
+  const evict = [];
+  for (const e of entries) {
+    if (total <= maxBytes) break;
+    evict.push(e.key);
+    total -= e.size;
+  }
+  return evict;
+}
@@ -0,0 +1,256 @@
+/*
+ * MCMA service worker — Tier 3 offline support: audio blob cache.
+ *
+ * It sits between the app and the network for audio-stream requests only
+ * (`/streaming/tracks/<id>`). The first time a track is streamed it's copied
+ * into the Cache API (keyed by content id, token stripped); afterwards — or
+ * whenever the backend is unreachable — playback is served straight from the
+ * cache, so already-heard tracks play with no network at all.
+ *
+ * Pure helpers (range parsing, LRU, key normalization) live in sw-core.js so
+ * they can be unit-tested; this file owns the side-effectful cache/network I/O.
+ * Registered as a module worker ({ type: 'module' }), so it uses ES imports.
+ */
+import {
+  AUDIO_CACHE,
+  INDEX_URL,
+  MAX_BYTES,
+  COVER_CACHE,
+  MAX_COVERS,
+  trackIdFromUrl,
+  cacheKeyFor,
+  parseRangeHeader,
+  selectEvictions,
+} from './sw-core.js';
+
+self.addEventListener('install', () => {
+  // Activate immediately on first install / update — no stale SW lingering.
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(self.clients.claim());
+});
+
+self.addEventListener('fetch', (event) => {
+  const req = event.request;
+  if (req.method !== 'GET') return;
+  if (trackIdFromUrl(req.url)) {
+    event.respondWith(handleAudio(event)); // audio stream → range-aware cache
+    return;
+  }
+  if (req.destination === 'image') {
+    event.respondWith(handleImage(event)); // cover art → stale-while-revalidate
+  }
+});
+
+async function handleAudio(event) {
+  const req = event.request;
+  const key = cacheKeyFor(req.url);
+  const range = req.headers.get('range');
+  const cache = await caches.open(AUDIO_CACHE);
+
+  // 1) Serve from cache when we have it (works fully offline).
+  const cached = await cache.match(key);
+  if (cached) {
+    event.waitUntil(touch(key));
+    return range ? buildRangeResponse(cached, range) : cached.clone();
+  }
+
+  // 2) Cache miss → fetch the WHOLE file (strip Range) so we can store a
+  //    complete copy, then satisfy the original request (range-sliced if asked).
+  try {
+    const fullReq = new Request(req.url, { headers: withoutRange(req.headers) });
+    const resp = await fetch(fullReq);
+    if (isCacheable(resp)) {
+      event.waitUntil(storeInCache(key, resp.clone()));
+    }
+    return range ? buildRangeResponse(resp, range) : resp;
+  } catch {
+    // Offline and never cached — nothing we can do for this one.
+    return new Response('Offline and not cached', {
+      status: 504,
+      statusText: 'Offline',
+    });
+  }
+}
+
+/**
+ * Cover art: stale-while-revalidate. Serve the cached image instantly (so the
+ * library renders offline), refresh it in the background, and cache fresh hits.
+ * Cover URLs are token-free and stable, and `<img>` is happy with opaque
+ * cross-origin responses — so unlike audio, these cache even cross-origin.
+ */
+async function handleImage(event) {
+  const req = event.request;
+  const cache = await caches.open(COVER_CACHE);
+  const cached = await cache.match(req);
+
+  const fromNetwork = fetch(req)
+    .then((resp) => {
+      if (resp && (resp.status === 200 || resp.type === 'opaque')) {
+        return cache
+          .put(req, resp.clone())
+          .then(() => trimCovers(cache))
+          .then(() => resp);
+      }
+      return resp;
+    })
+    .catch(() => null);
+
+  if (cached) {
+    event.waitUntil(fromNetwork); // revalidate without blocking the response
+    return cached;
+  }
+  const resp = await fromNetwork;
+  return resp || new Response('', { status: 504, statusText: 'Offline' });
+}
+
+/** Keep the cover cache bounded — drop the oldest entries past the cap. */
+async function trimCovers(cache) {
+  const keys = await cache.keys();
+  const excess = keys.length - MAX_COVERS;
+  for (let i = 0; i < excess; i++) await cache.delete(keys[i]);
+}
+
+/** Only cache readable, complete 200 responses — opaque/partial are useless. */
+function isCacheable(resp) {
+  return (
+    resp.status === 200 &&
+    resp.type !== 'opaque' &&
+    resp.type !== 'opaqueredirect'
+  );
+}
+
+function withoutRange(headers) {
+  const out = new Headers();
+  for (const [k, v] of headers.entries()) {
+    if (k.toLowerCase() !== 'range') out.set(k, v);
+  }
+  return out;
+}
+
+/** Build a 206 Partial Content response by slicing a full cached/fetched body. */
+async function buildRangeResponse(response, rangeHeader) {
+  const buf = await response.clone().arrayBuffer();
+  const size = buf.byteLength;
+  const r = parseRangeHeader(rangeHeader, size);
+  const type = response.headers.get('content-type') || 'application/octet-stream';
+
+  if (!r) {
+    return new Response(buf, {
+      status: 200,
+      headers: {
+        'content-type': type,
+        'content-length': String(size),
+        'accept-ranges': 'bytes',
+      },
+    });
+  }
+
+  const sliced = buf.slice(r.start, r.end + 1);
+  return new Response(sliced, {
+    status: 206,
+    statusText: 'Partial Content',
+    headers: {
+      'content-type': type,
+      'content-range': `bytes ${r.start}-${r.end}/${size}`,
+      'content-length': String(sliced.byteLength),
+      'accept-ranges': 'bytes',
+    },
+  });
+}
+
+async function responseSize(resp) {
+  const len = resp.headers.get('content-length');
+  if (len) return Number(len);
+  const blob = await resp.blob();
+  return blob.size;
+}
+
+// --- LRU index -------------------------------------------------------------
+// The index lives as a JSON entry in the same cache. All mutations go through a
+// single serialized chain so concurrent fetch handlers can't clobber it.
+let indexChain = Promise.resolve();
+
+async function readIndex(cache) {
+  try {
+    const res = await cache.match(INDEX_URL);
+    if (!res) return {};
+    return (await res.json()) || {};
+  } catch {
+    return {};
+  }
+}
+
+function writeIndex(mutator) {
+  indexChain = indexChain
+    .then(async () => {
+      const cache = await caches.open(AUDIO_CACHE);
+      const index = await readIndex(cache);
+      await mutator(cache, index);
+      await cache.put(
+        INDEX_URL,
+        new Response(JSON.stringify(index), {
+          headers: { 'content-type': 'application/json' },
+        }),
+      );
+    })
+    .catch(() => {
+      /* keep the chain alive even if one write fails */
+    });
+  return indexChain;
+}
+
+async function storeInCache(key, resp) {
+  const size = await responseSize(resp.clone());
+  await writeIndex(async (cache, index) => {
+    for (const ek of selectEvictions(index, size, MAX_BYTES)) {
+      await cache.delete(ek);
+      delete index[ek];
+    }
+    await cache.put(key, resp);
+    index[key] = { size, lastAccess: Date.now() };
+  });
+}
+
+function touch(key) {
+  return writeIndex((_cache, index) => {
+    if (index[key]) index[key].lastAccess = Date.now();
+  });
+}
+
+// --- client messaging ------------------------------------------------------
+// The app talks to the SW over a MessageChannel: it sends a port, we reply on
+// it. Used for the offline-cache stats/controls in the UI.
+self.addEventListener('message', (event) => {
+  const data = event.data || {};
+  const reply = (result) => {
+    if (event.ports && event.ports[0]) event.ports[0].postMessage(result);
+  };
+  event.waitUntil(
+    (async () => {
+      try {
+        const cache = await caches.open(AUDIO_CACHE);
+        const index = await readIndex(cache);
+        if (data.type === 'STATS') {
+          const keys = Object.keys(index);
+          const bytes = keys.reduce((s, k) => s + (index[k].size || 0), 0);
+          reply({ count: keys.length, bytes, maxBytes: MAX_BYTES });
+        } else if (data.type === 'HAS') {
+          reply({ cached: !!index[cacheKeyFor(data.url)] });
+        } else if (data.type === 'CLEAR') {
+          await Promise.all([
+            caches.delete(AUDIO_CACHE),
+            caches.delete(COVER_CACHE),
+          ]);
+          reply({ ok: true });
+        } else {
+          reply({ error: 'unknown-message' });
+        }
+      } catch (e) {
+        reply({ error: String(e) });
+      }
+    })(),
+  );
+});