import SwiftUI

enum HomeScrollCoordinateSpace {
    static let name = "home-scroll"
}

#if os(iOS)
struct HomeScrollOffsetPreferenceKey: PreferenceKey {
    static let defaultValue: CGFloat = 0

    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
        value = nextValue()
    }
}

struct ScrollOffsetObserver: View {
    let onOffsetChange: (CGFloat) -> Void

    var body: some View {
        Color.clear
            .frame(height: 0)
            .background(
                GeometryReader { geometry in
                    Color.clear.preference(
                        key: HomeScrollOffsetPreferenceKey.self,
                        value: geometry.frame(in: .named(HomeScrollCoordinateSpace.name)).minY
                    )
                }
            )
            .onPreferenceChange(HomeScrollOffsetPreferenceKey.self) { minY in
                onOffsetChange(-minY)
            }
    }
}
#endif