import AppKit

/// Tiny NSView subclass whose only job is to surface mouse-enter /
/// mouse-exit transitions through a closure so the popover can
/// reveal hover-only chrome (the floating-piano expand button on
/// the visualizer bezel, etc.) without each call site having to
/// re-implement a tracking area.
final class HoverTrackingView: NSView {
    var onHoverChanged: ((Bool) -> Void)?
    private var trackingArea: NSTrackingArea?

    override func updateTrackingAreas() {
        super.updateTrackingAreas()
        if let trackingArea {
            removeTrackingArea(trackingArea)
        }
        let area = NSTrackingArea(
            rect: bounds,
            options: [.mouseEnteredAndExited, .activeAlways, .inVisibleRect],
            owner: self,
            userInfo: nil
        )
        addTrackingArea(area)
        self.trackingArea = area
    }

    override func mouseEntered(with event: NSEvent) {
        super.mouseEntered(with: event)
        onHoverChanged?(true)
    }

    override func mouseExited(with event: NSEvent) {
        super.mouseExited(with: event)
        onHoverChanged?(false)
    }
}