[AltServer] Refactors common NSMenu logic into MenuController

AltServer/MenuController.swift

@@ -0,0 +1,115 @@
+//
+//  MenuController.swift
+//  AltServer
+//
+//  Created by Riley Testut on 3/3/21.
+//  Copyright © 2021 Riley Testut. All rights reserved.
+//
+
+import Foundation
+import AppKit
+
+protocol MenuDisplayable
+{
+    var name: String { get }
+}
+
+class MenuController<T: MenuDisplayable & Hashable>: NSObject, NSMenuDelegate
+{
+    let menu: NSMenu
+    
+    var items: [T] {
+        didSet {
+            self.submenus.removeAll()
+            self.updateMenu()
+        }
+    }
+    
+    var placeholder: String? {
+        didSet {
+            self.updateMenu()
+        }
+    }
+    
+    var action: ((T) -> Void)?
+    
+    var submenuHandler: ((T) -> NSMenu)?
+    private var submenus = [T: NSMenu]()
+    
+    init(menu: NSMenu, items: [T])
+    {
+        self.menu = menu
+        self.items = items
+        
+        super.init()
+        
+        self.menu.delegate = self
+    }
+    
+    @objc
+    private func performAction(_ menuItem: NSMenuItem)
+    {
+        guard case let index = self.menu.index(of: menuItem), index != -1 else { return }
+        
+        let item = self.items[index]
+        self.action?(item)
+    }
+    
+    @objc
+    func numberOfItems(in menu: NSMenu) -> Int
+    {
+        let numberOfItems = (self.items.isEmpty && self.placeholder != nil) ? 1 : self.items.count
+        return numberOfItems
+    }
+    
+    @objc
+    func menu(_ menu: NSMenu, update menuItem: NSMenuItem, at index: Int, shouldCancel: Bool) -> Bool
+    {
+        if let text = self.placeholder, self.items.isEmpty
+        {
+            menuItem.title = text
+            menuItem.isEnabled = false
+            menuItem.target = nil
+            menuItem.action = nil
+        }
+        else
+        {
+            let item = self.items[index]
+            
+            menuItem.title = item.name
+            menuItem.isEnabled = true
+            menuItem.target = self
+            menuItem.action = #selector(MenuController.performAction(_:))
+            menuItem.tag = index
+            
+            if let submenu = self.submenus[item] ?? self.submenuHandler?(item)
+            {
+                menuItem.submenu = submenu
+                
+                // Cache submenu to prevent duplicate calls to submenuHandler.
+                self.submenus[item] = submenu
+            }
+        }
+        
+        return true
+    }
+}
+
+private extension MenuController
+{
+    func updateMenu()
+    {        
+        self.menu.removeAllItems()
+        
+        let numberOfItems = self.numberOfItems(in: self.menu)
+        for index in 0 ..< numberOfItems
+        {
+            let menuItem = NSMenuItem(title: "", action: nil, keyEquivalent: "")
+            guard self.menu(self.menu, update: menuItem, at: index, shouldCancel: false) else { break }
+            
+            self.menu.addItem(menuItem)
+        }
+        
+        self.menu.update()
+    }
+}