app_for_reddit/Reddit App/App/AppDelegate.swift

import AppKit

@MainActor
final class AppDelegate: NSObject, NSApplicationDelegate, NSWindowDelegate {
    private var windowObservers: [NSObjectProtocol] = []

    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
        false
    }

    func applicationShouldHandleReopen(_ sender: NSApplication, hasVisibleWindows flag: Bool) -> Bool {
        if !flag {
            showMainWindow()
        }
        return true
    }

    func applicationDidFinishLaunching(_ notification: Notification) {
        installWindowObservers()
        configureMainWindows()
    }

    func applicationDidBecomeActive(_ notification: Notification) {
        configureMainWindows()
        showMainWindowIfNeeded()
    }

    func windowShouldClose(_ sender: NSWindow) -> Bool {
        sender.orderOut(nil)
        return false
    }

    func configureMainWindows() {
        for window in NSApp.windows where isMainAppWindow(window) {
            window.isReleasedWhenClosed = false
            if window.delegate !== self {
                window.delegate = self
            }
        }
    }

    private func installWindowObservers() {
        let center = NotificationCenter.default

        windowObservers = [
            center.addObserver(
                forName: NSWindow.didBecomeKeyNotification,
                object: nil,
                queue: .main
            ) { [weak self] _ in
                Task { @MainActor in
                    self?.configureMainWindows()
                }
            },
            center.addObserver(
                forName: NSApplication.didUpdateNotification,
                object: nil,
                queue: .main
            ) { [weak self] _ in
                Task { @MainActor in
                    self?.configureMainWindows()
                }
            },
        ]
    }

    private func showMainWindowIfNeeded() {
        guard !NSApp.windows.contains(where: { isMainAppWindow($0) && $0.isVisible }) else { return }
        showMainWindow()
    }

    private func showMainWindow() {
        guard let window = NSApp.windows.first(where: isMainAppWindow) else { return }
        window.makeKeyAndOrderFront(nil)
        NSApp.activate(ignoringOtherApps: true)
    }

    private func isMainAppWindow(_ window: NSWindow) -> Bool {
        guard window.canBecomeMain, !(window is NSPanel) else { return false }
        if window.title == "Sign in to Reddit" { return false }
        return window.level == .normal
    }
}