import AppKit
import SwiftUI

@MainActor
class MenuController: NSObject {
    static private(set) weak var shared: MenuController?

    let statusItem: NSStatusItem
    let popover = NSPopover()
    var eventMonitor: EventMonitor?

    init(statusItem: NSStatusItem) {
        self.statusItem = statusItem
        super.init()

        if let button = statusItem.button {
            button.action = #selector(togglePopover(_:))
            button.target = self
        }

        // Explicitly set content size to match MainView's frame
        popover.contentSize = NSSize(width: 450, height: 640)
        popover.behavior = .transient
        popover.contentViewController = NSHostingController(rootView: MainView())

        eventMonitor = EventMonitor(mask: [.leftMouseDown, .rightMouseDown]) { [weak self] event in
            if let self = self, self.popover.isShown {
                self.closePopover(sender: event)
            }
        }

        MenuController.shared = self
    }

    /// Keep the popover open while a modal window (e.g. an NSOpenPanel) is up.
    /// A transient popover otherwise dismisses itself the moment another window
    /// takes focus, which closed the folder picker before it could be used.
    func beginModalPresentation() {
        eventMonitor?.stop()
        popover.behavior = .applicationDefined
    }

    func endModalPresentation() {
        popover.behavior = .transient
        if popover.isShown {
            eventMonitor?.start()
        }
    }
    
    @objc func togglePopover(_ sender: AnyObject?) {
        if popover.isShown {
            closePopover(sender: sender)
        } else {
            showPopover(sender: sender)
        }
    }
    
    func showPopover(sender: AnyObject?) {
        if let button = statusItem.button {
            popover.show(relativeTo: button.bounds, of: button, preferredEdge: .minY)
            eventMonitor?.start()
        }
    }
    
    func closePopover(sender: AnyObject?) {
        popover.performClose(sender)
        eventMonitor?.stop()
    }
}

class EventMonitor {
    private var monitor: Any?
    private let mask: NSEvent.EventTypeMask
    private let handler: (NSEvent?) -> Void
    
    init(mask: NSEvent.EventTypeMask, handler: @escaping (NSEvent?) -> Void) {
        self.mask = mask
        self.handler = handler
    }
    
    deinit {
        stop()
    }
    
    func start() {
        monitor = NSEvent.addGlobalMonitorForEvents(matching: mask, handler: handler)
    }
    
    func stop() {
        if let monitor = monitor {
            NSEvent.removeMonitor(monitor)
            self.monitor = nil
        }
    }
}