Books: Fortschritt-Sync robuster — Pending-Flag statt Timestamp (SW v13)

Timestamp-Vergleich in _saveBookMeta entfernt: client-seitige
ISO-Strings (new Date().toISOString) lagen fast immer leicht vor dem
Serverwert und haben dadurch regelmässig korrekten Online-Fortschritt
überschrieben.

Neu: explizites Pending-Flag (localStorage diora_pending_progress) —
gesetzt wenn saveReaderProgress offline scheitert, gelöscht nach
erfolgreicher Synchronisierung.

- _saveBookMeta nutzt das Flag statt Zeitstempel: Server-Daten
  überschreiben lokalen Fortschritt nur wenn kein Pending-Flag gesetzt
- _syncPendingProgress: pusht ausstehenden Fortschritt beim
  online-Event bevor loadBookList läuft
- saveReaderProgress setzt das Flag nur wenn !navigator.onLine

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/js/app.js

@@ -2788,22 +2788,28 @@ async function _saveBookMeta(books) {
   try {
     const db = await _openBookCacheDb();
     const ids = new Set(books.map(b => String(b.id)));
-    // Read existing local entries to detect offline-modified progress
-    const existing = await new Promise(resolve => {
+    // Only load existing entries when there are books with pending offline progress
+    const pendingIds = new Set(
+      JSON.parse(localStorage.getItem(_PENDING_PROGRESS_KEY) || '[]').map(String)
+    );
+    const existing = pendingIds.size > 0 ? await new Promise(resolve => {
       const req = db.transaction(_BOOK_META_STORE).objectStore(_BOOK_META_STORE).getAll();
       req.onsuccess = e => resolve(Object.fromEntries((e.target.result || []).map(b => [b.id, b])));
       req.onerror   = ()  => resolve({});
-    });
+    }) : {};
     await new Promise(resolve => {
       const tx = db.transaction(_BOOK_META_STORE, 'readwrite');
       const store = tx.objectStore(_BOOK_META_STORE);
       for (const b of books) {
+        if (pendingIds.has(String(b.id))) {
           const loc = existing[b.id];
-        // Preserve local progress when it's newer than what the server returned
-        const localNewer = loc?.last_read && (!b.last_read || loc.last_read > b.last_read);
-        store.put(localNewer
-          ? {...b, scroll_fraction: loc.scroll_fraction, position_anchor: loc.position_anchor, last_read: loc.last_read}
-          : b);
+          if (loc) {
+            // Keep local progress until it has been pushed to the server
+            store.put({...b, scroll_fraction: loc.scroll_fraction, position_anchor: loc.position_anchor, last_read: loc.last_read});
+            continue;
+          }
+        }
+        store.put(b);
       }
       store.openCursor().onsuccess = e => {
         const cursor = e.target.result;
@@ -2874,6 +2880,7 @@ async function _loadAnnotationsCache(bookId, type) {
 }
 
 const _PENDING_SYNC_KEY     = 'diora_pending_sync';
+const _PENDING_PROGRESS_KEY = 'diora_pending_progress';
 
 function _markPendingSync(bookId, type) {
   try {
@@ -2910,6 +2917,36 @@ async function _syncPendingAnnotations() {
   } catch {}
 }
 
+function _markPendingProgress(bookId) {
+  try {
+    const pending = new Set(JSON.parse(localStorage.getItem(_PENDING_PROGRESS_KEY) || '[]').map(String));
+    pending.add(String(bookId));
+    localStorage.setItem(_PENDING_PROGRESS_KEY, JSON.stringify([...pending]));
+  } catch {}
+}
+
+async function _syncPendingProgress() {
+  try {
+    const pending = JSON.parse(localStorage.getItem(_PENDING_PROGRESS_KEY) || '[]');
+    if (!pending.length) return;
+    const localMeta = await _loadCachedBookMeta();
+    const localById = Object.fromEntries(localMeta.map(b => [b.id, b]));
+    const remaining = [];
+    for (const bookId of pending) {
+      const loc = localById[bookId];
+      if (!loc) continue;
+      try {
+        await fetch(`/books/${bookId}/progress/`, {
+          method: 'POST',
+          headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
+          body: JSON.stringify({scroll_fraction: loc.scroll_fraction, position_anchor: loc.position_anchor || ''}),
+        });
+      } catch { remaining.push(bookId); }
+    }
+    localStorage.setItem(_PENDING_PROGRESS_KEY, JSON.stringify(remaining));
+  } catch {}
+}
+
 // Reader settings
 let readerSettings = { fontSize: 16, lineHeight: 1.8, maxWidth: 65, theme: 'dark',
                         fontFamily: 'serif', noBold: false,
@@ -2995,22 +3032,22 @@ async function loadBookList() {
         decrypted.push({id: b.id, title: `Book #${b.id}`, author: '', type: 'epub', scroll_fraction: b.scroll_fraction, position_anchor: b.position_anchor || '', uploaded_at: b.uploaded_at, last_read: b.last_read || null, keyOk: false});
       }
     }
-    // Push any locally-cached progress that's newer than the server returned
+    // Use local progress for books that have unsaved offline changes
+    const _pendingIds = new Set(JSON.parse(localStorage.getItem(_PENDING_PROGRESS_KEY) || '[]').map(String));
+    if (_pendingIds.size > 0) {
       const _localMeta = await _loadCachedBookMeta();
       const _localById = Object.fromEntries(_localMeta.map(b => [b.id, b]));
       for (const b of decrypted) {
+        if (_pendingIds.has(String(b.id))) {
           const loc = _localById[b.id];
-      if (loc?.last_read && (!b.last_read || loc.last_read > b.last_read)) {
-        fetch(`/books/${b.id}/progress/`, {
-          method: 'POST',
-          headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
-          body: JSON.stringify({scroll_fraction: loc.scroll_fraction, position_anchor: loc.position_anchor || ''}),
-        }).catch(() => {});
+          if (loc) {
             b.scroll_fraction = loc.scroll_fraction;
             b.position_anchor = loc.position_anchor;
             b.last_read       = loc.last_read;
           }
         }
+      }
+    }
 
     decrypted.sort((a, b) => {
       if (a.last_read && b.last_read) return b.last_read.localeCompare(a.last_read);
@@ -3758,7 +3795,9 @@ async function saveReaderProgress() {
       headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
       body: _lastProgressBeacon.body,
     });
-  } catch (e) {}
+  } catch (e) {
+    if (!navigator.onLine) _markPendingProgress(currentBookId);
+  }
 }
 
 function closeReader() {
@@ -5162,8 +5201,9 @@ function openRadioSidebar() {
   });
   window.addEventListener('online', async () => {
     showOfflineBanner(false);
-    await _syncPendingAnnotations(); // push offline bookmark/highlight changes first
-    loadBookList(); // syncs progress and refreshes list
+    await _syncPendingAnnotations();
+    await _syncPendingProgress();
+    loadBookList();
   });
 
   // Show banner immediately if already offline at startup

static/js/sw.js

@@ -2,7 +2,7 @@
  * diora service worker — caches the app shell for offline use.
  */
 
-const CACHE = 'diora-v12';
+const CACHE = 'diora-v13';
 const PODCAST_CACHE = 'diora-podcast-v1';
 const SHELL = [
   '/static/css/app.css',