display files with cache image

mobile/services/thumbnailCache.ts

@@ -0,0 +1,65 @@
+import { createMMKV } from 'react-native-mmkv';
+
+const storage = createMMKV({ id: 'vaultdrop-thumbnails' });
+
+const BLOB_KEY = 'thumbnail_urls';
+const STALE_MS = 50 * 60 * 1000;
+
+interface ThumbnailCacheEntry {
+  url: string;
+  expiresAt: number;
+}
+
+let memoryCache: Record<string, ThumbnailCacheEntry> | null = null;
+
+function loadCache(): Record<string, ThumbnailCacheEntry> {
+  if (memoryCache) return memoryCache;
+  const raw = storage.getString(BLOB_KEY);
+  memoryCache = raw ? JSON.parse(raw) : {};
+  return memoryCache!;
+}
+
+function saveCache(cache: Record<string, ThumbnailCacheEntry>) {
+  memoryCache = cache;
+  storage.set(BLOB_KEY, JSON.stringify(cache));
+}
+
+export const thumbnailCache = {
+  get(fileId: string): string | null {
+    const cache = loadCache();
+    const entry = cache[fileId];
+    if (!entry) return null;
+    if (Date.now() > entry.expiresAt) {
+      delete cache[fileId];
+      saveCache(cache);
+      return null;
+    }
+    return entry.url;
+  },
+
+  set(fileId: string, url: string, expiresAt: number) {
+    const cache = loadCache();
+    cache[fileId] = { url, expiresAt };
+    saveCache(cache);
+  },
+
+  setBatch(entries: Array<{ fileId: string; url: string; expiresAt: number }>) {
+    if (entries.length === 0) return;
+    const cache = loadCache();
+    for (const e of entries) {
+      cache[e.fileId] = { url: e.url, expiresAt: e.expiresAt };
+    }
+    saveCache(cache);
+  },
+
+  remove(fileId: string) {
+    const cache = loadCache();
+    delete cache[fileId];
+    saveCache(cache);
+  },
+
+  clear() {
+    memoryCache = {};
+    storage.remove(BLOB_KEY);
+  },
+};