refactor: improve code quality and add debug logging

- Extract saveAllTabStates() helper method in AppDelegate
- Add DEBUG-only error logging in TabStateStorage
- Remove trailing whitespace and improve formatting
- Clean up code structure for better readability

Author: datlechin

OpenTable/AppDelegate.swift

@@ -58,42 +58,33 @@ class AppDelegate: NSObject, NSApplicationDelegate {
 
         // Clean up window tracking
         configuredWindows.remove(ObjectIdentifier(window))
-        
+
         // Check if main window is being closed
         if isMainWindow(window) {
             // CRITICAL: Save tab state SYNCHRONOUSLY before any async operations
             // Otherwise sessions might be cleared before we save
-            let sessions = DatabaseManager.shared.activeSessions
-            
-            for (connectionId, session) in sessions {
-                // Only save if there are tabs; otherwise clear saved state
-                if session.tabs.isEmpty {
-                    TabStateStorage.shared.clearTabState(connectionId: connectionId)
-                } else {
-                    TabStateStorage.shared.saveTabState(
-                        connectionId: connectionId,
-                        tabs: session.tabs,
-                        selectedTabId: session.selectedTabId
-                    )
-                }
-            }
-            
+            saveAllTabStates()
+
             // NOW disconnect sessions asynchronously (after save is complete)
             Task { @MainActor in
                 await DatabaseManager.shared.disconnectAll()
             }
-            
+
             // Reopen welcome window after a brief delay
             DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
                 self.openWelcomeWindow()
             }
         }
     }
-    
+
     func applicationWillTerminate(_ notification: Notification) {
         // Save tab state synchronously before app terminates (backup mechanism)
-        let sessions = DatabaseManager.shared.activeSessions
-        for (connectionId, session) in sessions {
+        saveAllTabStates()
+    }
+
+    /// Save tab state for all active sessions
+    private func saveAllTabStates() {
+        for (connectionId, session) in DatabaseManager.shared.activeSessions {
             if session.tabs.isEmpty {
                 TabStateStorage.shared.clearTabState(connectionId: connectionId)
             } else {

OpenTable/Core/Storage/TabStateStorage.swift

@@ -13,7 +13,6 @@ struct TabState: Codable {
     let selectedTabId: UUID?
 }
 
-
 /// Service for persisting tab state per connection
 final class TabStateStorage {
     static let shared = TabStateStorage()
@@ -36,7 +35,9 @@ final class TabStateStorage {
             let key = tabStateKey(for: connectionId)
             defaults.set(data, forKey: key)
         } catch {
-            // Silent failure - tab state is not critical
+            #if DEBUG
+            print("[TabStateStorage] Failed to encode tab state: \(error.localizedDescription)")
+            #endif
         }
     }
 
@@ -52,6 +53,9 @@ final class TabStateStorage {
             let decoder = JSONDecoder()
             return try decoder.decode(TabState.self, from: data)
         } catch {
+            #if DEBUG
+            print("[TabStateStorage] Failed to decode tab state: \(error.localizedDescription)")
+            #endif
             return nil
         }
     }

OpenTable/Models/QueryTab.swift

@@ -24,7 +24,6 @@ struct PersistedTab: Codable {
     let tableName: String?
 }
 
-
 /// Stores pending changes for a tab (used to preserve state when switching tabs)
 struct TabPendingChanges: Equatable {
     var changes: [RowChange]
@@ -214,7 +213,6 @@ struct QueryTab: Identifiable, Equatable {
     }
 }
 
-
 /// Manager for query tabs
 final class QueryTabManager: ObservableObject {
     @Published var tabs: [QueryTab] = []

OpenTable/Views/MainContentView.swift

@@ -313,10 +313,11 @@ struct MainContentView: View {
                    let session = DatabaseManager.shared.activeSessions[sessionId],
                    !session.tabs.isEmpty {
                     // Set flag to prevent onChange(tabManager.tabs) from syncing back
+                    // Use defer to ensure flag is always reset even if an error occurs
                     isRestoringTabs = true
+                    defer { isRestoringTabs = false }
                     tabManager.tabs = session.tabs
                     tabManager.selectedTabId = session.selectedTabId
-                    isRestoringTabs = false
                 }
             }
             .onChange(of: selectedTables) { oldTables, newTables in