add disk-based metadata cache + refresh endpoint

server.js

@@ -4,8 +4,8 @@
  *
  * Strategy:
  * - SSH (server-side find+cat) for all NAS access — metadata and thumbnails
- * - Disk-based thumbnail cache at CACHE_DIR (survives container restarts)
+ * - Disk-based cache at CACHE_DIR for both metadata and thumbnails (survives container restarts)
- * - In-memory library metadata cache (reset on restart, cheap to rebuild)
+ * - In-memory library metadata cache (hot path after disk cache is warm)
  */
 
 const express = require('express');
@@ -95,13 +95,16 @@ function listLibraries() {
     .map(e => e.replace('.library', ''));
 }
 
-// --- In-memory library metadata cache ---
+// --- In-memory library metadata cache (populated from disk cache on hit) ---
 let libraryCache = {};
 
-// --- Thumbnail: disk cache path helper ---
+// --- Disk cache path helpers ---
 function thumbCachePath(library, imageId) {
   return path.join(CACHE_DIR, `${library}__${imageId}.png`);
 }
+function metaCachePath(libName) {
+  return path.join(CACHE_DIR, `meta__${libName}.json`);
+}
 
 // --- Routes ---
 
@@ -113,15 +116,56 @@ app.get('/api/libraries', (req, res) => {
   }
 });
 
-app.get('/api/library/:name', (req, res) => {
+app.get('/api/library/:name', async (req, res) => {
   try {
     const name = req.params.name + '.library';
-    console.log(`Loading library: ${name} …`);
+
+    // 1. In-memory cache (fastest — already loaded this session)
+    if (libraryCache[name]) {
+      const data = libraryCache[name];
+      return res.json({ folders: data.meta.folders, imageCount: data.images.length, images: data.images, cached: 'memory' });
+    }
+
+    // 2. Disk cache (fast — survives restarts)
+    const diskPath = metaCachePath(name);
+    try {
+      const raw = await fsp.readFile(diskPath, 'utf8');
+      const data = JSON.parse(raw);
+      libraryCache[name] = data; // also warm the in-memory cache
+      console.log(`Library ${name} loaded from disk cache (${data.images.length} images)`);
+      return res.json({ folders: data.meta.folders, imageCount: data.images.length, images: data.images, cached: 'disk' });
+    } catch { /* cache miss — fall through to SSH */ }
+
+    // 3. SSH fetch from NAS (slow — first time only)
+    console.log(`Loading library: ${name} from NAS via SSH…`);
     const t0 = Date.now();
     const data = loadLibrary(name);
     libraryCache[name] = data;
-    console.log(`Loaded ${data.images.length} images in ${Date.now() - t0}ms`);
+    console.log(`Loaded ${data.images.length} images in ${Date.now() - t0}ms — writing to disk cache`);
-    res.json({ folders: data.meta.folders, imageCount: data.images.length, images: data.images });
+
+    // Write to disk cache (fire-and-forget)
+    fsp.writeFile(diskPath, JSON.stringify(data)).catch(err =>
+      console.warn(`Failed to write metadata cache for ${name}:`, err.message)
+    );
+
+    res.json({ folders: data.meta.folders, imageCount: data.images.length, images: data.images, cached: 'miss' });
+  } catch (e) {
+    console.error(e);
+    res.status(500).json({ error: e.message });
+  }
+});
+
+// Force a fresh SSH fetch and update the disk cache (call this when library contents change)
+app.post('/api/library/:name/refresh', async (req, res) => {
+  try {
+    const name = req.params.name + '.library';
+    console.log(`Refreshing library: ${name} …`);
+    const t0 = Date.now();
+    const data = loadLibrary(name);
+    libraryCache[name] = data;
+    await fsp.writeFile(metaCachePath(name), JSON.stringify(data));
+    console.log(`Refreshed ${data.images.length} images in ${Date.now() - t0}ms`);
+    res.json({ ok: true, imageCount: data.images.length, ms: Date.now() - t0 });
   } catch (e) {
     console.error(e);
     res.status(500).json({ error: e.message });