import AppKit
import Combine
import SwiftUI

@MainActor
final class WindowToolbarController: NSObject, NSToolbarDelegate {
    private let commandItemIdentifier = NSToolbarItem.Identifier("cmux.focusedCommand")
    private let updateItemIdentifier = NSToolbarItem.Identifier("cmux.updatePill")

    private weak var tabManager: TabManager?
    private weak var updateViewModel: UpdateViewModel?

    private var commandLabels: [ObjectIdentifier: NSTextField] = [:]
    private var observers: [NSObjectProtocol] = []
    private var updateSizeCancellables: [ObjectIdentifier: AnyCancellable] = [:]
    private var updateViewConstraints: [ObjectIdentifier: (width: NSLayoutConstraint, height: NSLayoutConstraint)] = [:]

    init(updateViewModel: UpdateViewModel) {
        self.updateViewModel = updateViewModel
        super.init()
    }

    deinit {
        for observer in observers {
            NotificationCenter.default.removeObserver(observer)
        }
        for cancellable in updateSizeCancellables.values {
            cancellable.cancel()
        }
    }

    func start(tabManager: TabManager) {
        self.tabManager = tabManager
        attachToExistingWindows()
        installObservers()
        updateFocusedCommandText()
    }

    private func installObservers() {
        let center = NotificationCenter.default
        observers.append(center.addObserver(
            forName: .ghosttyDidSetTitle,
            object: nil,
            queue: .main
        ) { [weak self] _ in
            self?.updateFocusedCommandText()
        })

        observers.append(center.addObserver(
            forName: .ghosttyDidFocusTab,
            object: nil,
            queue: .main
        ) { [weak self] _ in
            self?.updateFocusedCommandText()
        })

        observers.append(center.addObserver(
            forName: NSWindow.didBecomeMainNotification,
            object: nil,
            queue: .main
        ) { [weak self] notification in
            guard let window = notification.object as? NSWindow else { return }
            Task { @MainActor in
                self?.attach(to: window)
            }
        })
    }

    private func attachToExistingWindows() {
        for window in NSApp.windows {
            attach(to: window)
        }
    }

    private func attach(to window: NSWindow) {
        guard window.toolbar == nil else { return }
        let toolbar = NSToolbar(identifier: NSToolbar.Identifier("cmux.toolbar"))
        toolbar.delegate = self
        toolbar.displayMode = .iconOnly
        toolbar.sizeMode = .small
        toolbar.allowsUserCustomization = false
        toolbar.autosavesConfiguration = false
        toolbar.showsBaselineSeparator = false
        window.toolbar = toolbar
        window.toolbarStyle = .unifiedCompact
        window.titleVisibility = .hidden
    }

    private func updateFocusedCommandText() {
        guard let tabManager else { return }
        let text: String
        if let selectedId = tabManager.selectedTabId,
           let tab = tabManager.tabs.first(where: { $0.id == selectedId }) {
            let title = tab.title.trimmingCharacters(in: .whitespacesAndNewlines)
            text = title.isEmpty ? "Cmd: —" : "Cmd: \(title)"
        } else {
            text = "Cmd: —"
        }

        for label in commandLabels.values {
            label.stringValue = text
        }
    }

    // MARK: - NSToolbarDelegate

    func toolbarAllowedItemIdentifiers(_ toolbar: NSToolbar) -> [NSToolbarItem.Identifier] {
        [commandItemIdentifier, .flexibleSpace, updateItemIdentifier]
    }

    func toolbarDefaultItemIdentifiers(_ toolbar: NSToolbar) -> [NSToolbarItem.Identifier] {
        [commandItemIdentifier, .flexibleSpace, updateItemIdentifier]
    }

    func toolbar(_ toolbar: NSToolbar, itemForItemIdentifier itemIdentifier: NSToolbarItem.Identifier, willBeInsertedIntoToolbar flag: Bool) -> NSToolbarItem? {
        if itemIdentifier == commandItemIdentifier {
            let item = NSToolbarItem(itemIdentifier: itemIdentifier)
            let label = NSTextField(labelWithString: "Cmd: —")
            label.font = NSFont.systemFont(ofSize: 12, weight: .medium)
            label.textColor = .secondaryLabelColor
            label.lineBreakMode = .byTruncatingMiddle
            label.setContentHuggingPriority(.defaultHigh, for: .horizontal)
            item.view = label
            commandLabels[ObjectIdentifier(toolbar)] = label
            updateFocusedCommandText()
            return item
        }

        #if DEBUG
        if itemIdentifier == updateItemIdentifier, let updateViewModel {
            let item = NSToolbarItem(itemIdentifier: itemIdentifier)
            let view = NonDraggableHostingView(rootView: UpdatePill(model: updateViewModel))
            let key = ObjectIdentifier(toolbar)
            item.view = view
            sizeToolbarItem(for: key, hostingView: view)
            updateSizeCancellables[key]?.cancel()
            updateSizeCancellables[key] = updateViewModel.$state
                .receive(on: DispatchQueue.main)
                .sink { [weak self, weak view] _ in
                    guard let self, let view else { return }
                    self.sizeToolbarItem(for: key, hostingView: view)
                }
            return item
        }
        #endif

        return nil
    }

    private func sizeToolbarItem(for key: ObjectIdentifier, hostingView: NSView) {
        hostingView.invalidateIntrinsicContentSize()
        hostingView.layoutSubtreeIfNeeded()
        let size = hostingView.fittingSize
        hostingView.setFrameSize(size)
        hostingView.setContentHuggingPriority(.required, for: .horizontal)
        hostingView.setContentHuggingPriority(.required, for: .vertical)
        hostingView.translatesAutoresizingMaskIntoConstraints = false
        if let constraints = updateViewConstraints[key] {
            constraints.width.constant = size.width
            constraints.height.constant = size.height
        } else {
            let width = hostingView.widthAnchor.constraint(equalToConstant: size.width)
            let height = hostingView.heightAnchor.constraint(equalToConstant: size.height)
            NSLayoutConstraint.activate([width, height])
            updateViewConstraints[key] = (width: width, height: height)
        }
    }
}