fix(library): optimize image scanning, fast raw preview extraction and lazy thumbnail loading

docker/frontend/src/engine/libraryBackup.ts

@@ -23,6 +23,7 @@
 import type { LibraryEdit, LibraryFolder } from './library';
 import {
   ensurePermission,
+  getPhotoThumb,
   listEdits,
   listFolders,
   listPhotos,
@@ -125,6 +126,7 @@ async function folderHandle(): Promise<FileSystemDirectoryHandle | null> {
 // without a click behind it is a prompt the browser may refuse outright, and the
 // buttons on the screen are where the click is.
 async function granted(handle: FileSystemHandle, write: boolean): Promise<boolean> {
+  if (!handle) return false;
   const askable = handle as FileSystemHandle & {
     queryPermission?: (o: { mode: string }) => Promise<PermissionState>;
   };
@@ -314,32 +316,22 @@ export async function backupNow(onProgress?: (p: BackupProgress) => void): Promi
   let done = 0;
   const rows: { id: string; size: number }[] = [];
   for (const photo of photos) {
-    // Progress counts frames and not tiles: a folder of frames read without one
-    // is still a reading, and a bar that does not move is a bar that reads as a
-    // screen that has stopped.
     if (++done % 64 === 0) onProgress?.({ done, total: photos.length });
-    if (!photo.thumb) continue;
-    if (had.get(photo.id) === photo.thumb.size) continue;
+    const blob = photo.thumb ?? (await getPhotoThumb(photo.id));
+    if (!blob) continue;
+    if (had.get(photo.id) === blob.size) continue;
     const parts = photo.id.split('/');
     parts.pop();
     const rel = [THUMBS, ...parts, photo.name].join('/');
     try {
-      await put(root, rel, photo.thumb);
+      await put(root, rel, blob);
     } catch (err) {
-      // A frame the browser will not write is not a library that is never
-      // written: the run goes on without it, and the name it stopped on goes to
-      // the console, since the line on the screen is one line over a strip of
-      // photographs. Whatever survives `spell` is a name longer than a folder
-      // will hold, and a name spelled back is a name the restore still finds.
       if (skipped < 5) console.warn('backup: could not write', rel, err);
       skipped++;
       continue;
     }
-    rows.push({ id: photo.id, size: photo.thumb.size });
+    rows.push({ id: photo.id, size: blob.size });
     written++;
-    // The list is kept in step with the writes: a run that is interrupted
-    // continues from the frame it stopped at instead of writing the folder
-    // again.
     if (rows.length >= 200) await keep(WRITTEN, rows.splice(0, rows.length));
   }
   await keep(WRITTEN, rows);