Simplify codebase with NotificationObserver helper and convenience methods

Add NotificationObserver helper class to eliminate repetitive notification observer management patterns across MenuController and ModelManager. This consolidates observer lifecycle handling (registration, removal, cleanup) into a single reusable component.

Add convenience methods to ModelManager (isInstalled, isDownloading, downloadProgress) to reduce pattern matching boilerplate in view layer. These methods provide cleaner, more readable alternatives to repeatedly checking ModelStatus enums.

Remove duplicate isModelDownloaded method in favor of the new isInstalled method for consistency.

Changes:
- Add Common/NotificationObserver.swift with automatic cleanup in deinit
- Refactor MenuController to use NotificationObserver (removed deinit, simplified addObservers)
- Refactor ModelManager to use NotificationObserver and add convenience methods
- Update InstalledModelItemView to use convenience methods instead of status pattern matching
- Update Sections.swift to use convenience methods in filter logic

Net result: -27 lines, improved readability, reduced duplication.

Author: erusev

LlamaBarn/Common/NotificationObserver.swift

@@ -0,0 +1,30 @@
+import Foundation
+
+/// Manages notification observers with automatic cleanup.
+/// Eliminates boilerplate for adding/removing NotificationCenter observers.
+final class NotificationObserver {
+  private var tokens: [NSObjectProtocol] = []
+
+  /// Adds an observer for the specified notification name.
+  func observe(
+    _ name: Notification.Name, object: Any? = nil, using block: @escaping (Notification) -> Void
+  ) {
+    let token = NotificationCenter.default.addObserver(
+      forName: name,
+      object: object,
+      queue: .main,
+      using: block
+    )
+    tokens.append(token)
+  }
+
+  /// Removes all registered observers.
+  func removeAll() {
+    tokens.forEach { NotificationCenter.default.removeObserver($0) }
+    tokens.removeAll()
+  }
+
+  deinit {
+    tokens.forEach { NotificationCenter.default.removeObserver($0) }
+  }
+}

LlamaBarn/Menu/InstalledModelItemView.swift

@@ -153,29 +153,24 @@ final class InstalledModelItemView: ItemView, NSGestureRecognizerDelegate {
   }
 
   private func toggle() {
-    let status = modelManager.status(for: model)
-    switch status {
-    case .installed:
+    if modelManager.isInstalled(model) {
       if server.isActive(model: model) { server.stop() } else { server.start(model: model) }
-    case .downloading:
+    } else if modelManager.isDownloading(model) {
       modelManager.cancelModelDownload(model)
       membershipChanged(model)
-    case .available:
-      break
     }
     refresh()
   }
 
   func refresh() {
-    let status = modelManager.status(for: model)
     let isActive = server.isActive(model: model)
     let isLoading = isActive && server.isLoading
 
     modelNameLabel.stringValue = model.fullName
     metadataLabel.attributedStringValue = ModelMetadataFormatters.makeMetadataTextOnly(for: model)
 
     // Progress and cancel button only for downloading
-    if case .downloading(let progress) = status {
+    if let progress = modelManager.downloadProgress(for: model) {
       modelNameLabel.textColor = Typography.secondaryColor
       progressLabel.stringValue = ProgressFormatters.percentText(progress)
       cancelImageView.isHidden = false
@@ -188,7 +183,7 @@ final class InstalledModelItemView: ItemView, NSGestureRecognizerDelegate {
     }
 
     // Delete button only for installed models on hover
-    deleteLabel.isHidden = status != .installed || !isHighlighted
+    deleteLabel.isHidden = !modelManager.isInstalled(model) || !isHighlighted
 
     // Update icon state
     iconView.setLoading(isLoading)
@@ -198,8 +193,7 @@ final class InstalledModelItemView: ItemView, NSGestureRecognizerDelegate {
   }
 
   override func highlightDidChange(_ highlighted: Bool) {
-    let status = modelManager.status(for: model)
-    deleteLabel.isHidden = status != .installed || !highlighted
+    deleteLabel.isHidden = !modelManager.isInstalled(model) || !highlighted
   }
 
   override func viewDidChangeEffectiveAppearance() {
@@ -212,8 +206,7 @@ final class InstalledModelItemView: ItemView, NSGestureRecognizerDelegate {
   }
 
   @objc private func performDelete() {
-    let status = modelManager.status(for: model)
-    guard case .installed = status else { return }
+    guard modelManager.isInstalled(model) else { return }
     modelManager.deleteDownloadedModel(model)
     membershipChanged(model)
   }

LlamaBarn/Menu/MenuController.swift

@@ -26,7 +26,7 @@ final class MenuController: NSObject, NSMenuDelegate {
 
   private var isSettingsVisible = false
   private var menuWidth: CGFloat = 260
-  private var observers: [NSObjectProtocol] = []
+  private let observer = NotificationObserver()
   private weak var currentlyHighlightedView: ItemView?
 
   init(modelManager: ModelManager? = nil, server: LlamaServer? = nil) {
@@ -37,10 +37,6 @@ final class MenuController: NSObject, NSMenuDelegate {
     configureStatusItem()
   }
 
-  deinit {
-    observers.forEach { NotificationCenter.default.removeObserver($0) }
-  }
-
   private func configureStatusItem() {
     if let button = statusItem.button {
       button.image =
@@ -72,7 +68,7 @@ final class MenuController: NSObject, NSMenuDelegate {
     guard menu === statusItem.menu else { return }
     currentlyHighlightedView?.setHighlight(false)
     currentlyHighlightedView = nil
-    removeObservers()
+    observer.removeAll()
     isSettingsVisible = false
   }
 
@@ -125,80 +121,62 @@ final class MenuController: NSObject, NSMenuDelegate {
 
   // Observe server and download changes while the menu is open.
   private func addObservers() {
-    removeObservers()
-    let center = NotificationCenter.default
+    observer.removeAll()
 
     // Server started/stopped - update icon and views
-    observers.append(
-      center.addObserver(forName: .LBServerStateDidChange, object: nil, queue: .main) {
-        [weak self] _ in
-        MainActor.assumeIsolated {
-          self?.refresh()
-        }
-      })
+    observer.observe(.LBServerStateDidChange) { [weak self] _ in
+      MainActor.assumeIsolated {
+        self?.refresh()
+      }
+    }
 
     // Server memory usage changed - update running model stats
-    observers.append(
-      center.addObserver(forName: .LBServerMemoryDidChange, object: nil, queue: .main) {
-        [weak self] _ in
-        MainActor.assumeIsolated {
-          self?.refresh()
-        }
-      })
+    observer.observe(.LBServerMemoryDidChange) { [weak self] _ in
+      MainActor.assumeIsolated {
+        self?.refresh()
+      }
+    }
 
     // Download progress updated - refresh progress indicators
-    observers.append(
-      center.addObserver(forName: .LBModelDownloadsDidChange, object: nil, queue: .main) {
-        [weak self] _ in
-        MainActor.assumeIsolated {
-          self?.refresh()
-        }
-      })
+    observer.observe(.LBModelDownloadsDidChange) { [weak self] _ in
+      MainActor.assumeIsolated {
+        self?.refresh()
+      }
+    }
 
     // Model downloaded or deleted - rebuild both installed and catalog sections
-    observers.append(
-      center.addObserver(forName: .LBModelDownloadedListDidChange, object: nil, queue: .main) {
-        [weak self] _ in
-        MainActor.assumeIsolated {
-          if let menu = self?.statusItem.menu {
-            self?.installedSection.rebuild(in: menu)
-            self?.catalogSection.rebuild(in: menu)
-          }
-          self?.refresh()
+    observer.observe(.LBModelDownloadedListDidChange) { [weak self] _ in
+      MainActor.assumeIsolated {
+        if let menu = self?.statusItem.menu {
+          self?.installedSection.rebuild(in: menu)
+          self?.catalogSection.rebuild(in: menu)
         }
-      })
+        self?.refresh()
+      }
+    }
 
     // Settings visibility toggled - rebuild menu
-    observers.append(
-      center.addObserver(forName: .LBToggleSettingsVisibility, object: nil, queue: .main) {
-        [weak self] _ in
-        MainActor.assumeIsolated {
-          self?.isSettingsVisible.toggle()
-          if let menu = self?.statusItem.menu {
-            self?.rebuildMenu(menu)
-          }
+    observer.observe(.LBToggleSettingsVisibility) { [weak self] _ in
+      MainActor.assumeIsolated {
+        self?.isSettingsVisible.toggle()
+        if let menu = self?.statusItem.menu {
+          self?.rebuildMenu(menu)
         }
-      })
+      }
+    }
 
     // User settings changed (e.g., show quantized models) - rebuild menu
-    observers.append(
-      center.addObserver(forName: .LBUserSettingsDidChange, object: nil, queue: .main) {
-        [weak self] _ in
-        MainActor.assumeIsolated {
-          if let menu = self?.statusItem.menu {
-            self?.rebuildMenu(menu)
-          }
+    observer.observe(.LBUserSettingsDidChange) { [weak self] _ in
+      MainActor.assumeIsolated {
+        if let menu = self?.statusItem.menu {
+          self?.rebuildMenu(menu)
         }
-      })
+      }
+    }
 
     refresh()
   }
 
-  private func removeObservers() {
-    observers.forEach { NotificationCenter.default.removeObserver($0) }
-    observers.removeAll()
-  }
-
   private func refresh() {
     if let button = statusItem.button {
       let running = server.isRunning

LlamaBarn/Menu/Sections.swift

@@ -136,10 +136,7 @@ final class InstalledSection {
   }
 
   private func installedModels() -> [CatalogEntry] {
-    let downloading = Catalog.allEntries().filter {
-      if case .downloading = modelManager.status(for: $0) { return true }
-      return false
-    }
+    let downloading = Catalog.allEntries().filter { modelManager.isDownloading($0) }
     return (modelManager.downloadedModels + downloading)
       .sorted(by: CatalogEntry.displayOrder(_:_:))
   }
@@ -261,8 +258,7 @@ final class CatalogSection {
   private func filterAvailableModels() -> [CatalogEntry] {
     let showQuantized = UserSettings.showQuantizedModels
     return Catalog.allEntries().filter { model in
-      let status = modelManager.status(for: model)
-      let isAvailable = status == .available
+      let isAvailable = !modelManager.isInstalled(model) && !modelManager.isDownloading(model)
       let isCompatible = Catalog.isModelCompatible(model)
       return isAvailable && isCompatible && (showQuantized || model.isFullPrecision)
     }

LlamaBarn/Models/ModelManager.swift

@@ -35,18 +35,14 @@ class ModelManager: NSObject {
 
   private let downloader = ModelDownloader.shared
   private let logger = Logger(subsystem: Logging.subsystem, category: "ModelManager")
-  private var observers: [NSObjectProtocol] = []
+  private let observer = NotificationObserver()
 
   override init() {
     super.init()
     refreshDownloadedModels()
     addObservers()
   }
 
-  deinit {
-    observers.forEach { NotificationCenter.default.removeObserver($0) }
-  }
-
   /// Downloads a model by delegating to the downloader.
   func downloadModel(_ model: CatalogEntry) throws {
     try downloader.downloadModel(model)
@@ -64,11 +60,6 @@ class ModelManager: NSObject {
     return .available
   }
 
-  /// Checks if a model has been completely downloaded.
-  func isModelDownloaded(_ model: CatalogEntry) -> Bool {
-    downloadedModelIds.contains(model.id)
-  }
-
   /// Safely deletes a downloaded model and its associated files.
   func deleteDownloadedModel(_ model: CatalogEntry) {
     let llamaServer = LlamaServer.shared
@@ -128,17 +119,32 @@ class ModelManager: NSObject {
     downloader.cancelModelDownload(model)
   }
 
+  // MARK: - Convenience Methods
+
+  /// Returns true if the model is installed (fully downloaded).
+  func isInstalled(_ model: CatalogEntry) -> Bool {
+    status(for: model) == .installed
+  }
+
+  /// Returns true if the model is currently downloading.
+  func isDownloading(_ model: CatalogEntry) -> Bool {
+    if case .downloading = status(for: model) { return true }
+    return false
+  }
+
+  /// Returns the download progress if the model is currently downloading, nil otherwise.
+  func downloadProgress(for model: CatalogEntry) -> Progress? {
+    if case .downloading(let progress) = status(for: model) { return progress }
+    return nil
+  }
+
   private func addObservers() {
-    let center = NotificationCenter.default
     // When the downloader finishes a set of files for a model, it posts this notification.
     // We observe it to refresh our list of fully downloaded models.
-    observers.append(
-      center.addObserver(forName: .LBModelDownloadFinished, object: downloader, queue: .main) {
-        [weak self] _ in
-        MainActor.assumeIsolated {
-          self?.refreshDownloadedModels()
-        }
+    observer.observe(.LBModelDownloadFinished, object: downloader) { [weak self] _ in
+      MainActor.assumeIsolated {
+        self?.refreshDownloadedModels()
       }
-    )
+    }
   }
 }