refactor(dm-db): use singleton IndexedDB connection to avoid N+1 overhead

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

js/storage/dmDb.js

@@ -84,6 +84,9 @@ const MIGRATIONS = [
   },
 ];
 
+let dbInstance = null;
+let dbPromise = null;
+
 function isIndexedDbAvailable() {
   try {
     return typeof indexedDB !== "undefined";
@@ -101,7 +104,15 @@ function applyMigrations(db, oldVersion, newVersion, transaction) {
 }
 
 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 +129,39 @@ function openDmDb() {
       applyMigrations(db, oldVersion, newVersion, upgradeTransaction);
     };
 
-    request.onsuccess = () => resolve(request.result);
-    request.onerror = () =>
+    request.onsuccess = () => {
+      const db = request.result;
+      dbInstance = db;
+
+      db.onversionchange = () => {
+        db.close();
+        dbInstance = null;
+        dbPromise = null;
+      };
+
+      db.onclose = () => {
+        dbInstance = null;
+        dbPromise = null;
+      };
+
+      resolve(db);
+    };
+
+    request.onerror = () => {
+      dbPromise = null;
       reject(request.error || new Error("Failed to open DM database."));
+    };
   });
+
+  return dbPromise;
+}
+
+export async function closeDmDb() {
+  if (dbInstance) {
+    dbInstance.close();
+    dbInstance = null;
+  }
+  dbPromise = null;
 }
 
 function sanitizeTimestamp(value) {
@@ -264,7 +304,7 @@ export async function writeConversationMetadata(conversation) {
     const tx = db.transaction(STORES.CONVERSATIONS, "readwrite");
     tx.objectStore(STORES.CONVERSATIONS).put(normalized);
     await finalizeTransaction(tx);
-    db.close();
+    // db.close(); // Keep connection open
     return normalized;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to write conversation metadata", error);
@@ -296,7 +336,7 @@ export async function writeMessages(messages) {
     }
 
     await finalizeTransaction(tx);
-    db.close();
+    // db.close(); // Keep connection open
     return normalized;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to persist messages", error);
@@ -319,7 +359,7 @@ export async function getConversation(conversationId) {
     const store = tx.objectStore(STORES.CONVERSATIONS);
     const result = await runRequest(store.get(conversationId.trim()));
     await finalizeTransaction(tx);
-    db.close();
+    // db.close(); // Keep connection open
     return result || null;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to read conversation metadata", error);
@@ -369,7 +409,7 @@ export async function listMessagesByConversation(conversationId, options = {}) {
         userLogger.warn("[dmDb] Failed to list messages", request.error);
         resolve(results);
       };
-    }).finally(() => db.close());
+    }); // removed finally db.close()
   } catch (error) {
     userLogger.warn("[dmDb] Failed to list messages", error);
     return [];
@@ -429,7 +469,7 @@ export async function updateConversationFromMessage(message, options = {}) {
 
     store.put(next);
     await finalizeTransaction(tx);
-    db.close();
+    // db.close(); // Keep connection open
     return next;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to update conversation metadata", error);
@@ -478,7 +518,7 @@ export async function updateConversationOpenState(
 
     store.put(next);
     await finalizeTransaction(tx);
-    db.close();
+    // db.close(); // Keep connection open
     return next;
   } catch (error) {
     userLogger.warn("[dmDb] Failed to update conversation open state", error);
@@ -512,7 +552,7 @@ export async function listConversations() {
         userLogger.warn("[dmDb] Failed to list conversations", request.error);
         resolve(results);
       };
-    }).finally(() => db.close());
+    }); // removed finally db.close()
   } catch (error) {
     userLogger.warn("[dmDb] Failed to list conversations", error);
     return [];
@@ -542,7 +582,7 @@ export async function clearDmDb() {
     }
 
     await finalizeTransaction(tx);
-    db.close();
+    // db.close(); // Keep connection open
     return true;
   } catch (error) {
     devLogger.warn("[dmDb] Failed to clear DM database", error);