perf: implement IndexedDB connection pooling in dmDb.js

Refactor `js/storage/dmDb.js` to use a singleton connection pattern for IndexedDB.
Previously, the database was opened and closed for every single operation,
leading to significant overhead.

Changes:
- Introduced `dbInstance` and `dbPromise` to cache the database connection.
- Refactored `openDmDb` to reuse the existing connection or pending promise.
- Added `onversionchange` handler to safely close the connection if an upgrade is requested.
- Removed all manual `db.close()` calls from exported functions.
- Added a benchmark script in `tests/benchmark-dm-db.mjs` to verify the improvement.

Co-authored-by: PR0M3TH3AN <[email protected]>

js/storage/dmDb.js

@@ -100,8 +100,18 @@ function applyMigrations(db, oldVersion, newVersion, transaction) {
   }
 }
 
+let dbInstance = null;
+let dbPromise = null;
+
 function openDmDb() {
-  return new Promise((resolve, reject) => {
+  if (dbInstance) {
+    return Promise.resolve(dbInstance);
+  }
+  if (dbPromise) {
+    return dbPromise;
+  }
+
+  dbPromise = new Promise((resolve, reject) => {
     if (!isIndexedDbAvailable()) {
       resolve(null);
       return;
@@ -118,10 +128,25 @@ function openDmDb() {
       applyMigrations(db, oldVersion, newVersion, upgradeTransaction);
     };
 
-    request.onsuccess = () => resolve(request.result);
-    request.onerror = () =>
+    request.onsuccess = () => {
+      dbInstance = request.result;
+      dbPromise = null;
+
+      dbInstance.onversionchange = () => {
+        dbInstance.close();
+        dbInstance = null;
+      };
+
+      resolve(dbInstance);
+    };
+
+    request.onerror = () => {
+      dbPromise = null;
       reject(request.error || new Error("Failed to open DM database."));
+    };
   });
+
+  return dbPromise;
 }
 
 function sanitizeTimestamp(value) {
@@ -264,7 +289,6 @@ export async function writeConversationMetadata(conversation) {
     const tx = db.transaction(STORES.CONVERSATIONS, "readwrite");
     tx.objectStore(STORES.CONVERSATIONS).put(normalized);
     await finalizeTransaction(tx);
-    db.close();
     return normalized;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to write conversation metadata", error);
@@ -296,7 +320,6 @@ export async function writeMessages(messages) {
     }
 
     await finalizeTransaction(tx);
-    db.close();
     return normalized;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to persist messages", error);
@@ -319,7 +342,6 @@ export async function getConversation(conversationId) {
     const store = tx.objectStore(STORES.CONVERSATIONS);
     const result = await runRequest(store.get(conversationId.trim()));
     await finalizeTransaction(tx);
-    db.close();
     return result || null;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to read conversation metadata", error);
@@ -369,7 +391,7 @@ export async function listMessagesByConversation(conversationId, options = {}) {
         userLogger.warn("[dmDb] Failed to list messages", request.error);
         resolve(results);
       };
-    }).finally(() => db.close());
+    });
   } catch (error) {
     userLogger.warn("[dmDb] Failed to list messages", error);
     return [];
@@ -429,7 +451,6 @@ export async function updateConversationFromMessage(message, options = {}) {
 
     store.put(next);
     await finalizeTransaction(tx);
-    db.close();
     return next;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to update conversation metadata", error);
@@ -478,7 +499,6 @@ export async function updateConversationOpenState(
 
     store.put(next);
     await finalizeTransaction(tx);
-    db.close();
     return next;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to update conversation open state", error);
@@ -512,7 +532,7 @@ export async function listConversations() {
         userLogger.warn("[dmDb] Failed to list conversations", request.error);
         resolve(results);
       };
-    }).finally(() => db.close());
+    });
   } catch (error) {
     userLogger.warn("[dmDb] Failed to list conversations", error);
     return [];
@@ -542,7 +562,6 @@ export async function clearDmDb() {
     }
 
     await finalizeTransaction(tx);
-    db.close();
     return true;
   } catch (error) {
     devLogger.warn("[dmDb] Failed to clear DM database", error);

tests/benchmark-dm-db.mjs

@@ -0,0 +1,44 @@
+import { writeMessages } from "../js/storage/dmDb.js";
+import { indexedDB, IDBKeyRange } from "fake-indexeddb";
+
+if (!globalThis.indexedDB) {
+  globalThis.indexedDB = indexedDB;
+  globalThis.IDBKeyRange = IDBKeyRange;
+}
+
+const ITERATIONS = 500;
+
+async function benchmark() {
+  console.log(`Starting benchmark with ${ITERATIONS} iterations...`);
+
+  // Warm up
+  await writeMessages({
+    id: `warmup`,
+    conversationId: "bench-conv",
+    senderPubkey: "sender",
+    receiverPubkey: "receiver",
+    createdAt: Date.now(),
+    kind: 4,
+    content: "Warmup",
+  });
+
+  const start = performance.now();
+
+  for (let i = 0; i < ITERATIONS; i++) {
+    await writeMessages({
+      id: `msg-${i}`,
+      conversationId: "bench-conv",
+      senderPubkey: "sender",
+      receiverPubkey: "receiver",
+      createdAt: Date.now(),
+      kind: 4,
+      content: "Bench",
+    });
+  }
+
+  const end = performance.now();
+  console.log(`Total time for ${ITERATIONS} writes: ${(end - start).toFixed(2)}ms`);
+  console.log(`Average time per write: ${((end - start) / ITERATIONS).toFixed(2)}ms`);
+}
+
+benchmark().catch(console.error);