import Cocoa
import SwiftUI
import Combine
import GhosttyKit

/// A base class for windows that can contain Ghostty windows. This base class implements
/// the bare minimum functionality that every terminal window in Ghostty should implement.
///
/// Usage: Specify this as the base class of your window controller for the window that contains
/// a terminal. The window controller must also be the window delegate OR the window delegate
/// functions on this base class must be called by your own custom delegate. For the terminal
/// view the TerminalView SwiftUI view must be used and this class is the view model and
/// delegate.
///
/// Special considerations to implement:
///
///   - Fullscreen: you must manually listen for the right notification and implement the
///   callback that calls toggleFullscreen on this base class.
///
/// Notably, things this class does NOT implement (not exhaustive):
///
///   - Tabbing, because there are many ways to get tabbed behavior in macOS and we
///   don't want to be opinionated about it.
///   - Window restoration or save state
///   - Window visual styles (such as titlebar colors)
///
/// The primary idea of all the behaviors we don't implement here are that subclasses may not
/// want these behaviors.
class BaseTerminalController: NSWindowController,
                              NSWindowDelegate,
                              TerminalViewDelegate,
                              TerminalViewModel,
                              ClipboardConfirmationViewDelegate,
                              FullscreenDelegate {
    /// The app instance that this terminal view will represent.
    let ghostty: Ghostty.App

    /// The currently focused surface.
    var focusedSurface: Ghostty.SurfaceView? {
        didSet { syncFocusToSurfaceTree() }
    }

    /// The tree of splits within this terminal window.
    @Published var surfaceTree: SplitTree<Ghostty.SurfaceView> = .init() {
        didSet { surfaceTreeDidChange(from: oldValue, to: surfaceTree) }
    }

    /// This can be set to show/hide the command palette.
    @Published var commandPaletteIsShowing: Bool = false

    /// Set if the terminal view should show the update overlay.
    @Published var updateOverlayIsVisible: Bool = false

    /// True when any surface in this controller currently has an active bell.
    @Published private(set) var bell: Bool = false

    /// Whether the terminal surface should focus when the mouse is over it.
    var focusFollowsMouse: Bool {
        self.derivedConfig.focusFollowsMouse
    }

    /// Non-nil when an alert is active so we don't overlap multiple.
    private var alert: NSAlert?

    /// The clipboard confirmation window, if shown.
    private var clipboardConfirmation: ClipboardConfirmationController?

    /// Fullscreen state management.
    private(set) var fullscreenStyle: FullscreenStyle?

    /// Event monitor (see individual events for why)
    private var eventMonitor: Any?

    /// The previous frame information from the window
    private var savedFrame: SavedFrame?

    /// Cache previously applied appearance to avoid unnecessary updates
    private var appliedColorScheme: ghostty_color_scheme_e?

    /// The configuration derived from the Ghostty config so we don't need to rely on references.
    private var derivedConfig: DerivedConfig

    /// Track whether background is forced opaque (true) or using config transparency (false)
    var isBackgroundOpaque: Bool = false

    /// The cancellables related to our focused surface.
    private var focusedSurfaceCancellables: Set<AnyCancellable> = []

    /// Cancellable for aggregating bell state across all surfaces in this controller.
    private var bellStateCancellable: AnyCancellable?

    /// An override title for the tab/window set by the user via prompt_tab_title.
    /// When set, this takes precedence over the computed title from the terminal.
    var titleOverride: String? {
        didSet { applyTitleToWindow() }
    }

    /// The last computed title from the focused surface (without the override).
    private var lastComputedTitle: String = "👻"

    /// The time that undo/redo operations that contain running ptys are valid for.
    var undoExpiration: Duration {
        ghostty.config.undoTimeout
    }

    /// The undo manager for this controller is the undo manager of the window,
    /// which we set via the delegate method.
    override var undoManager: ExpiringUndoManager? {
        // This should be set via the delegate method windowWillReturnUndoManager
        if let result = window?.undoManager as? ExpiringUndoManager {
            return result
        }

        // If the window one isn't set, we fallback to our global one.
        if let appDelegate = NSApplication.shared.delegate as? AppDelegate {
            return appDelegate.undoManager
        }

        return nil
    }

    struct SavedFrame {
        let window: NSRect
        let screen: NSRect
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) is not supported for this view")
    }

    init(_ ghostty: Ghostty.App,
         baseConfig base: Ghostty.SurfaceConfiguration? = nil,
         surfaceTree tree: SplitTree<Ghostty.SurfaceView>? = nil
    ) {
        self.ghostty = ghostty
        self.derivedConfig = DerivedConfig(ghostty.config)

        super.init(window: nil)

        // Initialize our initial surface.
        guard let ghostty_app = ghostty.app else { preconditionFailure("app must be loaded") }
        self.surfaceTree = tree ?? .init(view: Ghostty.SurfaceView(ghostty_app, baseConfig: base))

        // Setup our bell state for the window
        setupBellNotificationPublisher()

        // Setup our notifications for behaviors
        let center = NotificationCenter.default
        center.addObserver(
            self,
            selector: #selector(onConfirmClipboardRequest),
            name: Ghostty.Notification.confirmClipboard,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(didChangeScreenParametersNotification),
            name: NSApplication.didChangeScreenParametersNotification,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyConfigDidChangeBase(_:)),
            name: .ghosttyConfigDidChange,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyCommandPaletteDidToggle(_:)),
            name: .ghosttyCommandPaletteDidToggle,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyMaximizeDidToggle(_:)),
            name: .ghosttyMaximizeDidToggle,
            object: nil)

        // Splits
        center.addObserver(
            self,
            selector: #selector(ghosttyDidCloseSurface(_:)),
            name: Ghostty.Notification.ghosttyCloseSurface,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyDidNewSplit(_:)),
            name: Ghostty.Notification.ghosttyNewSplit,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyDidEqualizeSplits(_:)),
            name: Ghostty.Notification.didEqualizeSplits,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyDidFocusSplit(_:)),
            name: Ghostty.Notification.ghosttyFocusSplit,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyDidToggleSplitZoom(_:)),
            name: Ghostty.Notification.didToggleSplitZoom,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyDidResizeSplit(_:)),
            name: Ghostty.Notification.didResizeSplit,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttyDidPresentTerminal(_:)),
            name: Ghostty.Notification.ghosttyPresentTerminal,
            object: nil)
        center.addObserver(
            self,
            selector: #selector(ghosttySurfaceDragEndedNoTarget(_:)),
            name: .ghosttySurfaceDragEndedNoTarget,
            object: nil)

        // Listen for local events that we need to know of outside of
        // single surface handlers.
        self.eventMonitor = NSEvent.addLocalMonitorForEvents(
            matching: [.flagsChanged]
        ) { [weak self] event in self?.localEventHandler(event) }
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
        undoManager?.removeAllActions(withTarget: self)
        if let eventMonitor {
            NSEvent.removeMonitor(eventMonitor)
        }
    }

    // MARK: Methods

    /// Create a new split.
    @discardableResult
    func newSplit(
        at oldView: Ghostty.SurfaceView,
        direction: SplitTree<Ghostty.SurfaceView>.NewDirection,
        baseConfig config: Ghostty.SurfaceConfiguration? = nil
    ) -> Ghostty.SurfaceView? {
        // We can only create new splits for surfaces in our tree.
        guard surfaceTree.root?.node(view: oldView) != nil else { return nil }

        // Create a new surface view
        guard let ghostty_app = ghostty.app else { return nil }
        let newView = Ghostty.SurfaceView(ghostty_app, baseConfig: config)

        // Do the split
        let newTree: SplitTree<Ghostty.SurfaceView>
        do {
            newTree = try surfaceTree.inserting(
                view: newView,
                at: oldView,
                direction: direction)
        } catch {
            // If splitting fails for any reason (it should not), then we just log
            // and return. The new view we created will be deinitialized and its
            // no big deal.
            Ghostty.logger.warning("failed to insert split: \(error)")
            return nil
        }

        replaceSurfaceTree(
            newTree,
            moveFocusTo: newView,
            moveFocusFrom: oldView,
            undoAction: "New Split")

        return newView
    }

    /// Move focus to a surface view.
    func focusSurface(_ view: Ghostty.SurfaceView) {
        // Check if target surface is in our tree
        guard surfaceTree.contains(view) else { return }

        // Move focus to the target surface and activate the window/app
        DispatchQueue.main.async {
            Ghostty.moveFocus(to: view)
            view.window?.makeKeyAndOrderFront(nil)
            if !NSApp.isActive {
                NSApp.activate(ignoringOtherApps: true)
            }
        }
    }

    /// Called when the surfaceTree variable changed.
    ///
    /// Subclasses should call super first.
    func surfaceTreeDidChange(from: SplitTree<Ghostty.SurfaceView>, to: SplitTree<Ghostty.SurfaceView>) {
        // If our surface tree becomes empty then we have no focused surface.
        if to.isEmpty {
            focusedSurface = nil
        }
    }

    /// Update all surfaces with the focus state. This ensures that libghostty has an accurate view about
    /// what surface is focused. This must be called whenever a surface OR window changes focus.
    func syncFocusToSurfaceTree() {
        for surfaceView in surfaceTree {
            // Our focus state requires that this window is key and our currently
            // focused surface is the surface in this view.
            let focused: Bool = (window?.isKeyWindow ?? false) &&
                surfaceView == focusedSurface &&
                surfaceView.isFirstResponder
            surfaceView.focusDidChange(focused)
        }
    }

    // Call this whenever the frame changes
    private func windowFrameDidChange() {
        // We need to update our saved frame information in case of monitor
        // changes (see didChangeScreenParameters notification).
        savedFrame = nil
        guard let window, let screen = window.screen else { return }
        savedFrame = .init(window: window.frame, screen: screen.visibleFrame)
    }

    func confirmClose(
        messageText: String,
        informativeText: String,
        completion: @escaping () -> Void
    ) {
        // If we already have an alert, we need to wait for that one.
        guard alert == nil else { return }

        // If there is no window to attach the modal then we assume success
        // since we'll never be able to show the modal.
        guard let window else {
            completion()
            return
        }

        // If we need confirmation by any, show one confirmation for all windows
        // in the tab group.
        let alert = NSAlert()
        alert.messageText = messageText
        alert.informativeText = informativeText
        alert.addButton(withTitle: "Close")
        alert.addButton(withTitle: "Cancel")
        alert.alertStyle = .warning
        alert.beginSheetModal(for: window) { response in
            let alertWindow = alert.window
            self.alert = nil
            if response == .alertFirstButtonReturn {
                // This is important so that we avoid losing focus when Stage
                // Manager is used (#8336)
                alertWindow.orderOut(nil)
                completion()
            }
        }

        // Store our alert so we only ever show one.
        self.alert = alert
    }

    /// Prompt the user to change the tab/window title.
    func promptTabTitle() {
        guard let window else { return }

        let alert = NSAlert()
        alert.messageText = "Change Tab Title"
        alert.informativeText = "Leave blank to restore the default."
        alert.alertStyle = .informational

        let textField = NSTextField(frame: NSRect(x: 0, y: 0, width: 250, height: 24))
        textField.stringValue = titleOverride ?? window.title
        alert.accessoryView = textField

        alert.addButton(withTitle: "OK")
        alert.addButton(withTitle: "Cancel")

        alert.window.initialFirstResponder = textField

        alert.beginSheetModal(for: window) { [weak self] response in
            guard let self else { return }
            guard response == .alertFirstButtonReturn else { return }

            let newTitle = textField.stringValue
            if newTitle.isEmpty {
                self.titleOverride = nil
            } else {
                self.titleOverride = newTitle
            }
        }
    }

    /// Close a surface from a view.
    func closeSurface(
        _ view: Ghostty.SurfaceView,
        withConfirmation: Bool = true
    ) {
        guard let node = surfaceTree.root?.node(view: view) else { return }
        closeSurface(node, withConfirmation: withConfirmation)
    }

    /// Close a surface node (which may contain splits), requesting confirmation if necessary.
    ///
    /// This will also insert the proper undo stack information in.
    func closeSurface(
        _ node: SplitTree<Ghostty.SurfaceView>.Node,
        withConfirmation: Bool = true
    ) {
        // This node must be part of our tree
        guard surfaceTree.contains(node) else { return }

        // If the child process is not alive, then we exit immediately
        guard withConfirmation else {
            removeSurfaceNode(node)
            return
        }

        // Confirm close. We use an NSAlert instead of a SwiftUI confirmationDialog
        // due to SwiftUI bugs (see Ghostty #560). To repeat from #560, the bug is that
        // confirmationDialog allows the user to Cmd-W close the alert, but when doing
        // so SwiftUI does not update any of the bindings to note that window is no longer
        // being shown, and provides no callback to detect this.
        confirmClose(
            messageText: "Close Terminal?",
            informativeText: "The terminal still has a running process. If you close the terminal the process will be killed."
        ) { [weak self] in
            if let self {
                self.removeSurfaceNode(node)
            }
        }
    }

    // MARK: Split Tree Management

    /// Find the next surface to focus when a node is being closed.
    /// Goes to previous split unless we're the leftmost leaf, then goes to next.
    private func findNextFocusTargetAfterClosing(node: SplitTree<Ghostty.SurfaceView>.Node) -> Ghostty.SurfaceView? {
        guard let root = surfaceTree.root else { return nil }

        // If we're the leftmost, then we move to the next surface after closing.
        // Otherwise, we move to the previous.
        if root.leftmostLeaf() == node.leftmostLeaf() {
            return surfaceTree.focusTarget(for: .next, from: node)
        } else {
            return surfaceTree.focusTarget(for: .previous, from: node)
        }
    }

    /// Remove a node from the surface tree and move focus appropriately.
    ///
    /// This also updates the undo manager to support restoring this node.
    ///
    /// This does no confirmation and assumes confirmation is already done.
    private func removeSurfaceNode(_ node: SplitTree<Ghostty.SurfaceView>.Node) {
        // Move focus if the closed surface was focused and we have a next target
        let nextFocus: Ghostty.SurfaceView? = if node.contains(
            where: { $0 == focusedSurface }
        ) {
            findNextFocusTargetAfterClosing(node: node)
        } else {
            nil
        }

        replaceSurfaceTree(
            surfaceTree.removing(node),
            moveFocusTo: nextFocus,
            moveFocusFrom: focusedSurface,
            undoAction: "Close Terminal"
        )
    }

    func replaceSurfaceTree(
        _ newTree: SplitTree<Ghostty.SurfaceView>,
        moveFocusTo newView: Ghostty.SurfaceView? = nil,
        moveFocusFrom oldView: Ghostty.SurfaceView? = nil,
        undoAction: String? = nil
    ) {
        // Setup our new split tree
        let oldTree = surfaceTree
        surfaceTree = newTree
        if let newView {
            DispatchQueue.main.async {
                Ghostty.moveFocus(to: newView, from: oldView)
            }
        }

        // Setup our undo
        guard let undoManager else { return }
        if let undoAction {
            undoManager.setActionName(undoAction)
        }

        undoManager.registerUndo(
            withTarget: self,
            expiresAfter: undoExpiration
        ) { target in
            target.surfaceTree = oldTree
            if let oldView {
                DispatchQueue.main.async {
                    Ghostty.moveFocus(to: oldView, from: target.focusedSurface)
                }
            }

            undoManager.registerUndo(
                withTarget: target,
                expiresAfter: target.undoExpiration
            ) { target in
                target.replaceSurfaceTree(
                    newTree,
                    moveFocusTo: newView,
                    moveFocusFrom: target.focusedSurface,
                    undoAction: undoAction)
            }
        }
    }

    // MARK: Notifications

    @objc private func didChangeScreenParametersNotification(_ notification: Notification) {
        // If we have a window that is visible and it is outside the bounds of the
        // screen then we clamp it back to within the screen.
        guard let window else { return }
        guard window.isVisible else { return }

        // We ignore fullscreen windows because macOS automatically resizes
        // those back to the fullscreen bounds.
        guard !window.styleMask.contains(.fullScreen) else { return }

        guard let screen = window.screen else { return }
        let visibleFrame = screen.visibleFrame
        var newFrame = window.frame

        // Clamp width/height
        if newFrame.size.width > visibleFrame.size.width {
            newFrame.size.width = visibleFrame.size.width
        }
        if newFrame.size.height > visibleFrame.size.height {
            newFrame.size.height = visibleFrame.size.height
        }

        // Ensure the window is on-screen. We only do this if the previous frame
        // was also on screen. If a user explicitly wanted their window off screen
        // then we let it stay that way.
        x: if newFrame.origin.x < visibleFrame.origin.x {
            if let savedFrame, savedFrame.window.origin.x < savedFrame.screen.origin.x {
                break x
            }

            newFrame.origin.x = visibleFrame.origin.x
        }
        y: if newFrame.origin.y < visibleFrame.origin.y {
            if let savedFrame, savedFrame.window.origin.y < savedFrame.screen.origin.y {
                break y
            }

            newFrame.origin.y = visibleFrame.origin.y
        }

        // Apply the new window frame
        window.setFrame(newFrame, display: true)
    }

    @objc private func ghosttyConfigDidChangeBase(_ notification: Notification) {
        // We only care if the configuration is a global configuration, not a
        // surface-specific one.
        guard notification.object == nil else { return }

        // Get our managed configuration object out
        guard let config = notification.userInfo?[
            Notification.Name.GhosttyConfigChangeKey
        ] as? Ghostty.Config else { return }

        // Update our derived config
        self.derivedConfig = DerivedConfig(config)
    }

    @objc private func ghosttyCommandPaletteDidToggle(_ notification: Notification) {
        guard let surfaceView = notification.object as? Ghostty.SurfaceView else { return }
        guard surfaceTree.contains(surfaceView) else { return }
        toggleCommandPalette(nil)
    }

    @objc private func ghosttyMaximizeDidToggle(_ notification: Notification) {
        guard let window else { return }
        guard let surfaceView = notification.object as? Ghostty.SurfaceView else { return }
        guard surfaceTree.contains(surfaceView) else { return }
        window.zoom(nil)
    }

    @objc private func ghosttyDidCloseSurface(_ notification: Notification) {
        guard let target = notification.object as? Ghostty.SurfaceView else { return }
        guard let node = surfaceTree.root?.node(view: target) else { return }
        closeSurface(
            node,
            withConfirmation: (notification.userInfo?["process_alive"] as? Bool) ?? false)
    }

    @objc private func ghosttyDidNewSplit(_ notification: Notification) {
        // The target must be within our tree
        guard let oldView = notification.object as? Ghostty.SurfaceView else { return }
        guard surfaceTree.root?.node(view: oldView) != nil else { return }

        // Notification must contain our base config
        let configAny = notification.userInfo?[Ghostty.Notification.NewSurfaceConfigKey]
        let config = configAny as? Ghostty.SurfaceConfiguration

        // Determine our desired direction
        guard let directionAny = notification.userInfo?["direction"] else { return }
        guard let direction = directionAny as? ghostty_action_split_direction_e else { return }
        let splitDirection: SplitTree<Ghostty.SurfaceView>.NewDirection
        switch direction {
        case GHOSTTY_SPLIT_DIRECTION_RIGHT: splitDirection = .right
        case GHOSTTY_SPLIT_DIRECTION_LEFT: splitDirection = .left
        case GHOSTTY_SPLIT_DIRECTION_DOWN: splitDirection = .down
        case GHOSTTY_SPLIT_DIRECTION_UP: splitDirection = .up
        default: return
        }

        newSplit(at: oldView, direction: splitDirection, baseConfig: config)
    }

    @objc private func ghosttyDidEqualizeSplits(_ notification: Notification) {
        guard let target = notification.object as? Ghostty.SurfaceView else { return }

        // Check if target surface is in current controller's tree
        guard surfaceTree.contains(target) else { return }

        // Equalize the splits
        surfaceTree = surfaceTree.equalized()
    }

    @objc private func ghosttyDidFocusSplit(_ notification: Notification) {
        // The target must be within our tree
        guard let target = notification.object as? Ghostty.SurfaceView else { return }
        guard surfaceTree.root?.node(view: target) != nil else { return }

        // Get the direction from the notification
        guard let directionAny = notification.userInfo?[Ghostty.Notification.SplitDirectionKey] else { return }
        guard let direction = directionAny as? Ghostty.SplitFocusDirection else { return }

        // Find the node for the target surface
        guard let targetNode = surfaceTree.root?.node(view: target) else { return }

        // Find the next surface to focus
        guard let nextSurface = surfaceTree.focusTarget(for: direction.toSplitTreeFocusDirection(), from: targetNode) else {
            return
        }

        if surfaceTree.zoomed != nil {
            if derivedConfig.splitPreserveZoom.contains(.navigation) {
                surfaceTree = SplitTree(
                    root: surfaceTree.root,
                    zoomed: surfaceTree.root?.node(view: nextSurface))
            } else {
                surfaceTree = SplitTree(root: surfaceTree.root, zoomed: nil)
            }
        }

        // Move focus to the next surface
        DispatchQueue.main.async {
            Ghostty.moveFocus(to: nextSurface, from: target)
        }
    }

    @objc private func ghosttyDidToggleSplitZoom(_ notification: Notification) {
        // The target must be within our tree
        guard let target = notification.object as? Ghostty.SurfaceView else { return }
        guard let targetNode = surfaceTree.root?.node(view: target) else { return }

        // Toggle the zoomed state
        if surfaceTree.zoomed == targetNode {
            // Already zoomed, unzoom it
            surfaceTree = SplitTree(root: surfaceTree.root, zoomed: nil)
        } else {
            // We require that the split tree have splits
            guard surfaceTree.isSplit else { return }

            // Not zoomed or different node zoomed, zoom this node
            surfaceTree = SplitTree(root: surfaceTree.root, zoomed: targetNode)
        }

        // Move focus to our window. Importantly this ensures that if we click the
        // reset zoom button in a tab bar of an unfocused tab that we become focused.
        window?.makeKeyAndOrderFront(nil)

        // Ensure focus stays on the target surface. We lose focus when we do
        // this so we need to grab it again.
        DispatchQueue.main.async {
            Ghostty.moveFocus(to: target)
        }
    }

    @objc private func ghosttyDidResizeSplit(_ notification: Notification) {
        // The target must be within our tree
        guard let target = notification.object as? Ghostty.SurfaceView else { return }
        guard let targetNode = surfaceTree.root?.node(view: target) else { return }

        // Extract direction and amount from notification
        guard let directionAny = notification.userInfo?[Ghostty.Notification.ResizeSplitDirectionKey] else { return }
        guard let direction = directionAny as? Ghostty.SplitResizeDirection else { return }

        guard let amountAny = notification.userInfo?[Ghostty.Notification.ResizeSplitAmountKey] else { return }
        guard let amount = amountAny as? UInt16 else { return }

        // Convert Ghostty.SplitResizeDirection to SplitTree.Spatial.Direction
        let spatialDirection: SplitTree<Ghostty.SurfaceView>.Spatial.Direction
        switch direction {
        case .up: spatialDirection = .up
        case .down: spatialDirection = .down
        case .left: spatialDirection = .left
        case .right: spatialDirection = .right
        }

        // Use viewBounds for the spatial calculation bounds
        let bounds = CGRect(origin: .zero, size: surfaceTree.viewBounds())

        // Perform the resize using the new SplitTree resize method
        do {
            surfaceTree = try surfaceTree.resizing(node: targetNode, by: amount, in: spatialDirection, with: bounds)
        } catch {
            Ghostty.logger.warning("failed to resize split: \(error)")
        }
    }

    @objc private func ghosttyDidPresentTerminal(_ notification: Notification) {
        guard let target = notification.object as? Ghostty.SurfaceView else { return }
        guard surfaceTree.contains(target) else { return }

        // Bring the window to front and focus the surface.
        window?.makeKeyAndOrderFront(nil)

        // We use a small delay to ensure this runs after any UI cleanup
        // (e.g., command palette restoring focus to its original surface).
        Ghostty.moveFocus(to: target)
        Ghostty.moveFocus(to: target, delay: 0.1)

        // Show a brief highlight to help the user locate the presented terminal.
        target.highlight()
    }

    @objc private func ghosttySurfaceDragEndedNoTarget(_ notification: Notification) {
        guard let target = notification.object as? Ghostty.SurfaceView else { return }
        guard let targetNode = surfaceTree.root?.node(view: target) else { return }

        // If our tree isn't split, then we never create a new window, because
        // it is already a single split.
        guard surfaceTree.isSplit else { return }

        // If we are removing our focused surface then we move it. We need to
        // keep track of our old one so undo sends focus back to the right place.
        let oldFocusedSurface = focusedSurface
        if focusedSurface == target {
            focusedSurface = findNextFocusTargetAfterClosing(node: targetNode)
        }

        // Remove the surface from our tree
        let removedTree = surfaceTree.removing(targetNode)

        // Create a new tree with the dragged surface and open a new window
        let newTree = SplitTree<Ghostty.SurfaceView>(view: target)

        // Treat our undo below as a full group.
        undoManager?.beginUndoGrouping()
        undoManager?.setActionName("Move Split")
        defer {
            undoManager?.endUndoGrouping()
        }

        replaceSurfaceTree(removedTree, moveFocusFrom: oldFocusedSurface)
        _ = TerminalController.newWindow(
            ghostty,
            tree: newTree,
            position: notification.userInfo?[Notification.Name.ghosttySurfaceDragEndedNoTargetPointKey] as? NSPoint,
            confirmUndo: false)
    }

    // MARK: Local Events

    private func localEventHandler(_ event: NSEvent) -> NSEvent? {
        return switch event.type {
        case .flagsChanged:
            localEventFlagsChanged(event)

        default:
            event
        }
    }

    private func localEventFlagsChanged(_ event: NSEvent) -> NSEvent? {
        var surfaces: [Ghostty.SurfaceView] = surfaceTree.map { $0 }

        // If we're the main window receiving key input, then we want to avoid
        // calling this on our focused surface because that'll trigger a double
        // flagsChanged call.
        if NSApp.mainWindow == window {
            surfaces = surfaces.filter { $0 != focusedSurface }
        }

        for surface in surfaces {
            surface.flagsChanged(with: event)
        }

        return event
    }

    // MARK: TerminalViewDelegate

    func focusedSurfaceDidChange(to: Ghostty.SurfaceView?) {
        let lastFocusedSurface = focusedSurface
        focusedSurface = to

        // Important to cancel any prior subscriptions
        focusedSurfaceCancellables = []

        // Setup our title listener. If we have a focused surface we always use that.
        // Otherwise, we try to use our last focused surface. In either case, we only
        // want to care if the surface is in the tree so we don't listen to titles of
        // closed surfaces.
        if let titleSurface = focusedSurface ?? lastFocusedSurface,
           surfaceTree.contains(titleSurface) {
            // If we have a surface, we want to listen for title changes.
            titleSurface.$title
                .combineLatest(titleSurface.$bell)
                .map { [weak self] in self?.computeTitle(title: $0, bell: $1) ?? "" }
                .sink { [weak self] in self?.titleDidChange(to: $0) }
                .store(in: &focusedSurfaceCancellables)
        } else {
            // There is no surface to listen to titles for.
            titleDidChange(to: "👻")
        }
    }

    private func computeTitle(title: String, bell: Bool) -> String {
        var result = title
        if bell && ghostty.config.bellFeatures.contains(.title) {
            result = "🔔 \(result)"
        }

        return result
    }

    private func titleDidChange(to: String) {
        lastComputedTitle = to
        applyTitleToWindow()
    }

    private func applyTitleToWindow() {
        guard let window else { return }

        if let titleOverride {
            window.title = computeTitle(
                title: titleOverride,
                bell: focusedSurface?.bell ?? false)
            return
        }

        window.title = lastComputedTitle
    }

    func pwdDidChange(to: URL?) {
        guard let window else { return }

        if derivedConfig.macosTitlebarProxyIcon == .visible {
            // Use the 'to' URL directly
            window.representedURL = to
        } else {
            window.representedURL = nil
        }
    }

    func cellSizeDidChange(to: NSSize) {
        guard derivedConfig.windowStepResize else { return }
        // Stage manager can sometimes present windows in such a way that the
        // cell size is temporarily zero due to the window being tiny. We can't
        // set content resize increments to this value, so avoid an assertion failure.
        guard to.width > 0 && to.height > 0 else { return }
        self.window?.contentResizeIncrements = to
    }

    func performSplitAction(_ action: TerminalSplitOperation) {
        switch action {
        case .resize(let resize):
            splitDidResize(node: resize.node, to: resize.ratio)
        case .drop(let drop):
            splitDidDrop(source: drop.payload, destination: drop.destination, zone: drop.zone)
        }
    }

    private func splitDidResize(node: SplitTree<Ghostty.SurfaceView>.Node, to newRatio: Double) {
        let resizedNode = node.resizing(to: newRatio)
        do {
            surfaceTree = try surfaceTree.replacing(node: node, with: resizedNode)
        } catch {
            Ghostty.logger.warning("failed to replace node during split resize: \(error)")
        }
    }

    private func splitDidDrop(
        source: Ghostty.SurfaceView,
        destination: Ghostty.SurfaceView,
        zone: TerminalSplitDropZone
    ) {
        // Map drop zone to split direction
        let direction: SplitTree<Ghostty.SurfaceView>.NewDirection = switch zone {
        case .top: .up
        case .bottom: .down
        case .left: .left
        case .right: .right
        }

        // Check if source is in our tree
        if let sourceNode = surfaceTree.root?.node(view: source) {
            // Source is in our tree - same window move
            let treeWithoutSource = surfaceTree.removing(sourceNode)
            let newTree: SplitTree<Ghostty.SurfaceView>
            do {
                newTree = try treeWithoutSource.inserting(view: source, at: destination, direction: direction)
            } catch {
                Ghostty.logger.warning("failed to insert surface during drop: \(error)")
                return
            }

            replaceSurfaceTree(
                newTree,
                moveFocusTo: source,
                moveFocusFrom: focusedSurface,
                undoAction: "Move Split")
            return
        }

        // Source is not in our tree - search other windows
        var sourceController: BaseTerminalController?
        var sourceNode: SplitTree<Ghostty.SurfaceView>.Node?
        for window in NSApp.windows {
            guard let controller = window.windowController as? BaseTerminalController else { continue }
            guard controller !== self else { continue }
            if let node = controller.surfaceTree.root?.node(view: source) {
                sourceController = controller
                sourceNode = node
                break
            }
        }

        guard let sourceController, let sourceNode else {
            Ghostty.logger.warning("source surface not found in any window during drop")
            return
        }

        // Remove from source controller's tree and add it to our tree.
        // We do this first because if there is an error then we can
        // abort.
        let newTree: SplitTree<Ghostty.SurfaceView>
        do {
            newTree = try surfaceTree.inserting(view: source, at: destination, direction: direction)
        } catch {
            Ghostty.logger.warning("failed to insert surface during cross-window drop: \(error)")
            return
        }

        // Treat our undo below as a full group.
        undoManager?.beginUndoGrouping()
        undoManager?.setActionName("Move Split")
        defer {
            undoManager?.endUndoGrouping()
        }

        // Remove the node from the source.
        sourceController.removeSurfaceNode(sourceNode)

        // Add in the surface to our tree
        replaceSurfaceTree(
            newTree,
            moveFocusTo: source,
            moveFocusFrom: focusedSurface)
    }

    func performAction(_ action: String, on surfaceView: Ghostty.SurfaceView) {
        guard let surface = surfaceView.surface else { return }
        let len = action.utf8CString.count
        if len == 0 { return }
        _ = action.withCString { cString in
            ghostty_surface_binding_action(surface, cString, UInt(len - 1))
        }
    }

    // MARK: Appearance

    /// Toggle the background opacity between transparent and opaque states.
    /// Do nothing if the configured background-opacity is >= 1 (already opaque).
    /// Subclasses should override this to add platform-specific checks and sync appearance.
    func toggleBackgroundOpacity() {
        // Do nothing if config is already fully opaque
        guard ghostty.config.backgroundOpacity < 1 else { return }

        // Do nothing if in fullscreen (transparency doesn't apply in fullscreen)
        guard let window, !window.styleMask.contains(.fullScreen) else { return }

        // Toggle between transparent and opaque
        isBackgroundOpaque.toggle()

        // Update our appearance
        syncAppearance()
    }

    /// Override this to resync any appearance related properties. This will be called automatically
    /// when certain window properties change that affect appearance. The list below should be updated
    /// as we add new things:
    ///
    ///  - ``toggleBackgroundOpacity``
    func syncAppearance() {
        // Purposely a no-op. This lets subclasses override this and we can call
        // it virtually from here.
    }

    // MARK: Fullscreen

    /// Toggle fullscreen for the given mode.
    func toggleFullscreen(mode: FullscreenMode) {
        // We need a window to fullscreen
        guard let window = self.window else { return }

        // If we have a previous fullscreen style initialized, we want to check if
        // our mode changed. If it changed and we're in fullscreen, we exit so we can
        // toggle it next time. If it changed and we're not in fullscreen we can just
        // switch the handler.
        var newStyle = mode.style(for: window)
        newStyle?.delegate = self
        old: if let oldStyle = self.fullscreenStyle {
            // If we're not fullscreen, we can nil it out so we get the new style
            if !oldStyle.isFullscreen {
                self.fullscreenStyle = newStyle
                break old
            }

            assert(oldStyle.isFullscreen)

            // We consider our mode changed if the types change (obvious) but
            // also if its nil (not obvious) because nil means that the style has
            // likely changed but we don't support it.
            if newStyle == nil || type(of: newStyle!) != type(of: oldStyle) {
                // Our mode changed. Exit fullscreen (since we're toggling anyways)
                // and then set the new style for future use
                oldStyle.exit()
                self.fullscreenStyle = newStyle

                // We're done
                return
            }

            // Style is the same.
        } else {
            // We have no previous style
            self.fullscreenStyle = newStyle
        }
        guard let fullscreenStyle else { return }

        if fullscreenStyle.isFullscreen {
            fullscreenStyle.exit()
        } else {
            fullscreenStyle.enter()
        }
    }

    func fullscreenDidChange() {
        guard let fullscreenStyle else { return }

        // When we enter fullscreen, we want to show the update overlay so that it
        // is easily visible. For native fullscreen this is visible by showing the
        // menubar but we don't want to rely on that.
        if fullscreenStyle.isFullscreen {
            updateOverlayIsVisible = true
        } else {
            updateOverlayIsVisible = defaultUpdateOverlayVisibility()
        }

        // Always resync our appearance
        syncAppearance()
    }

    // MARK: Clipboard Confirmation

    @objc private func onConfirmClipboardRequest(notification: SwiftUI.Notification) {
        guard let target = notification.object as? Ghostty.SurfaceView else { return }
        guard target == self.focusedSurface else { return }
        guard let surface = target.surface else { return }

        // We need a window
        guard let window = self.window else { return }

        // Check whether we use non-native fullscreen
        guard let str = notification.userInfo?[Ghostty.Notification.ConfirmClipboardStrKey] as? String else { return }
        guard let state = notification.userInfo?[Ghostty.Notification.ConfirmClipboardStateKey] as? UnsafeMutableRawPointer? else { return }
        guard let request = notification.userInfo?[Ghostty.Notification.ConfirmClipboardRequestKey] as? Ghostty.ClipboardRequest else { return }

        // If we already have a clipboard confirmation view up, we ignore this request.
        // This shouldn't be possible...
        guard self.clipboardConfirmation == nil else {
            Ghostty.App.completeClipboardRequest(surface, data: "", state: state, confirmed: true)
            return
        }

        // Show our paste confirmation
        self.clipboardConfirmation = ClipboardConfirmationController(
            surface: surface,
            contents: str,
            request: request,
            state: state,
            delegate: self
        )
        window.beginSheet(self.clipboardConfirmation!.window!)
    }

    func clipboardConfirmationComplete(_ action: ClipboardConfirmationView.Action, _ request: Ghostty.ClipboardRequest) {
        // End our clipboard confirmation no matter what
        guard let cc = self.clipboardConfirmation else { return }
        self.clipboardConfirmation = nil

        // Close the sheet
        if let ccWindow = cc.window {
            window?.endSheet(ccWindow)
        }

        switch request {
        case let .osc_52_write(pasteboard):
            guard case .confirm = action else { break }
            let pb = pasteboard ?? NSPasteboard.general
            pb.declareTypes([.string], owner: nil)
            pb.setString(cc.contents, forType: .string)
        case .osc_52_read, .paste:
            let str: String
            switch action {
            case .cancel:
                str = ""

            case .confirm:
                str = cc.contents
            }

            Ghostty.App.completeClipboardRequest(cc.surface, data: str, state: cc.state, confirmed: true)
        }
    }

    // MARK: NSWindowController

    override func windowDidLoad() {
        super.windowDidLoad()

        // Setup our undo manager.

        // Everything beyond here is setting up the window
        guard let window else { return }

        // We always initialize our fullscreen style to native if we can because
        // initialization sets up some state (i.e. observers). If its set already
        // somehow we don't do this.
        if fullscreenStyle == nil {
            fullscreenStyle = NativeFullscreen(window)
            fullscreenStyle?.delegate = self
        }

        // Set our update overlay state
        updateOverlayIsVisible = defaultUpdateOverlayVisibility()
    }

    func defaultUpdateOverlayVisibility() -> Bool {
        guard let window else { return true }

        // No titlebar we always show the update overlay because it can't support
        // updates in the titlebar
        guard window.styleMask.contains(.titled) else {
            return true
        }

        // If it's a non terminal window we can't trust it has an update accessory,
        // so we always want to show the overlay.
        guard let window = window as? TerminalWindow else {
            return true
        }

        // Show the overlay if the window isn't.
        return !window.supportsUpdateAccessory
    }

    // MARK: NSWindowDelegate

    // This is called when performClose is called on a window (NOT when close()
    // is called directly). performClose is called primarily when UI elements such
    // as the "red X" are pressed.
    func windowShouldClose(_ sender: NSWindow) -> Bool {
        // We must have a window. Is it even possible not to?
        guard let window = self.window else { return true }

        // If we have no surfaces, close.
        if surfaceTree.isEmpty { return true }

        // If we already have an alert, continue with it
        guard alert == nil else { return false }

        // If our surfaces don't require confirmation, close.
        if !surfaceTree.contains(where: { $0.needsConfirmQuit }) { return true }

        // We require confirmation, so show an alert as long as we aren't already.
        confirmClose(
            messageText: "Close Terminal?",
            informativeText: "The terminal still has a running process. If you close the terminal the process will be killed."
        ) {
            window.close()
        }

        return false
    }

    func windowWillClose(_ notification: Notification) {
        guard let window else { return }

        // Emit a final bell-state transition so any observers can clear state
        // without separately tracking NSWindow lifecycle events.
        if bell {
            bell = false
            NotificationCenter.default.post(
                name: .terminalWindowBellDidChangeNotification,
                object: self,
                userInfo: [Notification.Name.terminalWindowHasBellKey: false]
            )
        }

        // I don't know if this is required anymore. We previously had a ref cycle between
        // the view and the window so we had to nil this out to break it but I think this
        // may now be resolved. We should verify that no memory leaks and we can remove this.
        window.contentView = nil

        // Make sure we clean up all our undos
        window.undoManager?.removeAllActions(withTarget: self)
    }

    func windowDidBecomeKey(_ notification: Notification) {
        // If when we become key our first responder is the window itself, then we
        // want to move focus to our focused terminal surface. This works around
        // various weirdness with moving surfaces around.
        if let window, window.firstResponder == window, let focusedSurface {
            DispatchQueue.main.async {
                Ghostty.moveFocus(to: focusedSurface)
            }
        }

        // Becoming key can race with responder updates when activating a window.
        // Sync on the next runloop so split focus has settled first.
        DispatchQueue.main.async {
            self.syncFocusToSurfaceTree()
        }
    }

    func windowDidResignKey(_ notification: Notification) {
        // Becoming/losing key means we have to notify our surface(s) that we have focus
        // so things like cursors blink, pty events are sent, etc.
        self.syncFocusToSurfaceTree()
    }

    func windowDidChangeOcclusionState(_ notification: Notification) {
        let visible = self.window?.occlusionState.contains(.visible) ?? false
        for view in surfaceTree {
            if let surface = view.surface {
                ghostty_surface_set_occlusion(surface, visible)
            }
        }
    }

    func windowDidResize(_ notification: Notification) {
        windowFrameDidChange()
    }

    func windowDidMove(_ notification: Notification) {
        windowFrameDidChange()
    }

    func windowWillReturnUndoManager(_ window: NSWindow) -> UndoManager? {
        guard let appDelegate = NSApplication.shared.delegate as? AppDelegate else { return nil }
        return appDelegate.undoManager
    }

    // MARK: First Responder

    @IBAction func close(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.requestClose(surface: surface)
    }

    @IBAction func closeWindow(_ sender: Any) {
        guard let window = window else { return }
        window.performClose(sender)
    }

    @IBAction func changeTabTitle(_ sender: Any) {
        if let targetWindow = window {
            let inlineHostWindow =
                targetWindow.tabbedWindows?
                    .first(where: { $0.tabBarView != nil }) as? TerminalWindow
                ?? (targetWindow as? TerminalWindow)

            if let inlineHostWindow, inlineHostWindow.beginInlineTabTitleEdit(for: targetWindow) {
                return
            }
        }

        promptTabTitle()
    }

    @IBAction func splitRight(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.split(surface: surface, direction: GHOSTTY_SPLIT_DIRECTION_RIGHT)
    }

    @IBAction func splitLeft(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.split(surface: surface, direction: GHOSTTY_SPLIT_DIRECTION_LEFT)
    }

    @IBAction func splitDown(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.split(surface: surface, direction: GHOSTTY_SPLIT_DIRECTION_DOWN)
    }

    @IBAction func splitUp(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.split(surface: surface, direction: GHOSTTY_SPLIT_DIRECTION_UP)
    }

    @IBAction func splitZoom(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.splitToggleZoom(surface: surface)
    }

    @IBAction func splitMoveFocusPrevious(_ sender: Any) {
        splitMoveFocus(direction: .previous)
    }

    @IBAction func splitMoveFocusNext(_ sender: Any) {
        splitMoveFocus(direction: .next)
    }

    @IBAction func splitMoveFocusAbove(_ sender: Any) {
        splitMoveFocus(direction: .up)
    }

    @IBAction func splitMoveFocusBelow(_ sender: Any) {
        splitMoveFocus(direction: .down)
    }

    @IBAction func splitMoveFocusLeft(_ sender: Any) {
        splitMoveFocus(direction: .left)
    }

    @IBAction func splitMoveFocusRight(_ sender: Any) {
        splitMoveFocus(direction: .right)
    }

    @IBAction func equalizeSplits(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.splitEqualize(surface: surface)
    }

    @IBAction func moveSplitDividerUp(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.splitResize(surface: surface, direction: .up, amount: 10)
    }

    @IBAction func moveSplitDividerDown(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.splitResize(surface: surface, direction: .down, amount: 10)
    }

    @IBAction func moveSplitDividerLeft(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.splitResize(surface: surface, direction: .left, amount: 10)
    }

    @IBAction func moveSplitDividerRight(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.splitResize(surface: surface, direction: .right, amount: 10)
    }

    private func splitMoveFocus(direction: Ghostty.SplitFocusDirection) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.splitMoveFocus(surface: surface, direction: direction)
    }

    @IBAction func increaseFontSize(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.changeFontSize(surface: surface, .increase(1))
    }

    @IBAction func decreaseFontSize(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.changeFontSize(surface: surface, .decrease(1))
    }

    @IBAction func resetFontSize(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.changeFontSize(surface: surface, .reset)
    }

    @IBAction func toggleCommandPalette(_ sender: Any?) {
        commandPaletteIsShowing.toggle()
    }

    @IBAction func find(_ sender: Any) {
        focusedSurface?.find(sender)
    }

    @IBAction func selectionForFind(_ sender: Any) {
        focusedSurface?.selectionForFind(sender)
    }

    @IBAction func scrollToSelection(_ sender: Any) {
        focusedSurface?.scrollToSelection(sender)
    }

    @IBAction func findNext(_ sender: Any) {
        focusedSurface?.findNext(sender)
    }

    @IBAction func findPrevious(_ sender: Any) {
        focusedSurface?.findNext(sender)
    }

    @IBAction func findHide(_ sender: Any) {
        focusedSurface?.findHide(sender)
    }

    @objc func resetTerminal(_ sender: Any) {
        guard let surface = focusedSurface?.surface else { return }
        ghostty.resetTerminal(surface: surface)
    }

    private struct DerivedConfig {
        let macosTitlebarProxyIcon: Ghostty.MacOSTitlebarProxyIcon
        let windowStepResize: Bool
        let focusFollowsMouse: Bool
        let splitPreserveZoom: Ghostty.Config.SplitPreserveZoom

        init() {
            self.macosTitlebarProxyIcon = .visible
            self.windowStepResize = false
            self.focusFollowsMouse = false
            self.splitPreserveZoom = .init()
        }

        init(_ config: Ghostty.Config) {
            self.macosTitlebarProxyIcon = config.macosTitlebarProxyIcon
            self.windowStepResize = config.windowStepResize
            self.focusFollowsMouse = config.focusFollowsMouse
            self.splitPreserveZoom = config.splitPreserveZoom
        }
    }
}

extension BaseTerminalController: NSMenuItemValidation {
    func validateMenuItem(_ item: NSMenuItem) -> Bool {
        switch item.action {
        case #selector(findHide):
            return focusedSurface?.searchState != nil

        default:
            return true
        }
    }

    // MARK: - Surface Color Scheme

    /// Update the surface tree's color scheme only when it actually changes.
    ///
    /// Calling ``ghostty_surface_set_color_scheme`` triggers
    /// ``syncAppearance(_:)`` via notification,
    /// so we avoid redundant calls.
    func updateColorSchemeForSurfaceTree() {
        /// Derive the target scheme from `window-theme` or system appearance.
        /// We set the scheme on surfaces so they pick the correct theme
        /// and let ``syncAppearance(_:)`` update the window accordingly.
        ///
        /// Using App's effectiveAppearance here to prevent incorrect updates.
        let themeAppearance = NSApplication.shared.effectiveAppearance
        let scheme: ghostty_color_scheme_e
        if themeAppearance.isDark {
            scheme = GHOSTTY_COLOR_SCHEME_DARK
        } else {
            scheme = GHOSTTY_COLOR_SCHEME_LIGHT
        }
        guard scheme != appliedColorScheme else {
            return
        }
        for surfaceView in surfaceTree {
            if let surface = surfaceView.surface {
                ghostty_surface_set_color_scheme(surface, scheme)
            }
        }
        appliedColorScheme = scheme
    }
}

// MARK: Combine Methods

extension BaseTerminalController {
    /// Publishes an app-wide notification whenever this terminal window's aggregate
    /// bell state changes.
    private func setupBellNotificationPublisher() {
        bellStateCancellable = surfaceValuesPublisher(valueKeyPath: \.bell, publisherKeyPath: \.$bell)
            .map { $0.values.contains(true) }
            .removeDuplicates()
            .receive(on: DispatchQueue.main)
            .sink { [weak self] hasBell in
                guard let self else { return }
                bell = hasBell
                NotificationCenter.default.post(
                    name: .terminalWindowBellDidChangeNotification,
                    object: self,
                    userInfo: [Notification.Name.terminalWindowHasBellKey: hasBell]
                )
            }
    }

    /// Creates a publisher for values on all surfaces in this controller's tree.
    ///
    /// The publisher emits a dictionary of surface IDs to values whenever the tree changes
    /// or any surface publishes a new value for the key path.
    func surfaceValuesPublisher<Value>(
        valueKeyPath: KeyPath<Ghostty.SurfaceView, Value>,
        publisherKeyPath: KeyPath<Ghostty.SurfaceView, Published<Value>.Publisher>
    ) -> AnyPublisher<[Ghostty.SurfaceView.ID: Value], Never> {
        // `surfaceTree` can be replaced entirely when splits are added/removed/closed.
        // For each tree snapshot we build a fresh publisher that watches all surfaces
        // in that snapshot.
        $surfaceTree
            .map { tree in
                tree.valuesPublisher(
                    valueKeyPath: valueKeyPath,
                    publisherKeyPath: publisherKeyPath
                )
            }
            // Keep only the latest tree publisher active. This automatically cancels
            // subscriptions for old/removed surfaces when the tree changes.
            .switchToLatest()
            .eraseToAnyPublisher()
    }
}

// MARK: Notifications

extension Notification.Name {
    /// Terminal window aggregate bell state changed.
    static let terminalWindowBellDidChangeNotification = Notification.Name("com.mitchellh.ghostty.terminalWindowBellDidChange")
    static let terminalWindowHasBellKey = terminalWindowBellDidChangeNotification.rawValue + ".hasBell"
}
