ghostty/macos/Sources/Features/Primary Window/PrimaryWindowManager.swift

import Cocoa
import Combine

// PrimaryWindowManager manages the windows and tabs in the primary window
// of the application. It keeps references to windows and cleans them up when
// they're cloned.
//
// If we ever have multiple tabbed window types we can make this generic but
// right now only our primary window is ever duplicated or tabbed so we're not
// doing that.
//
// It is based on the patterns presented in this blog post:
// https://christiantietze.de/posts/2019/07/nswindow-tabbing-multiple-nswindowcontroller/
class PrimaryWindowManager {
    struct ManagedWindow {
        let windowController: NSWindowController
        let window: NSWindow
        let closePublisher: AnyCancellable
    }

    private var ghostty: Ghostty.AppState
    private var managedWindows: [ManagedWindow] = []
    
    init(ghostty: Ghostty.AppState) {
        self.ghostty = ghostty
    }
    
    /// Add the initial window for the application. This should only be called once from the AppDelegate.
    func addInitialWindow() {
        guard let controller = createWindowController() else { return }
        controller.showWindow(self)
        let result = addManagedWindow(windowController: controller)
        if result == nil {
            preconditionFailure("Failed to create initial window")
        }
    }
    
    func addNewWindow() {
        guard let controller = createWindowController() else { return }
        guard let newWindow = addManagedWindow(windowController: controller)?.window else { return }
        newWindow.makeKeyAndOrderFront(nil)
    }
    
    func addNewTab() {
        guard let existingWindow = mainWindow() else { return }
        guard let controller = createWindowController() else { return }
        guard let newWindow = addManagedWindow(windowController: controller)?.window else { return  }
        existingWindow.addTabbedWindow(newWindow, ordered: .above)
        newWindow.makeKeyAndOrderFront(nil)
    }
    
    /// Returns the main window of the managed window stack.
    /// Falls back the first element if no window is main.
    private func mainWindow() -> NSWindow? {
        let mainManagedWindow = managedWindows.first { $0.window.isMainWindow }
        return (mainManagedWindow ?? managedWindows.first).map { $0.window }
    }

    private func createWindowController() -> PrimaryWindowController? {
        guard let appDelegate = NSApplication.shared.delegate as? AppDelegate else { return nil }
        return PrimaryWindowController.create(ghosttyApp: self.ghostty, appDelegate: appDelegate)
    }

    private func addManagedWindow(windowController: PrimaryWindowController) -> ManagedWindow? {
        guard let window = windowController.window else { return nil }

        let pubClose = NotificationCenter.default.publisher(for: NSWindow.willCloseNotification, object: window)
            .sink { notification in
                guard let window = notification.object as? NSWindow else { return }
                self.removeWindow(window: window)
            }
        
        let managed = ManagedWindow(windowController: windowController, window: window, closePublisher: pubClose)
        managedWindows.append(managed)

        return managed
    }
    
    private func removeWindow(window: NSWindow) {
        self.managedWindows.removeAll(where: { $0.window === window })
    }
}