import SwiftUI

/// A ScrollView that is as tall as its content, up to a cap.
///
/// Exists because a plain `ScrollView` inside a `VStack` has a tiny ideal
/// height: given only `.frame(maxHeight:)` it collapses to nearly nothing. That
/// bug shipped twice — once emptying the share list, once emptying the whole
/// settings window — so the fix lives in one place now.
/// File scope, not nested: a generic type cannot hold the static storage a
/// PreferenceKey needs.
private struct HeightKey: PreferenceKey {
    static let defaultValue: CGFloat = 0
    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
        value = max(value, nextValue())
    }
}

struct MeasuredScrollView<Content: View>: View {
    var minHeight: CGFloat = 0
    var maxHeight: CGFloat
    @ViewBuilder var content: Content

    @State private var measured: CGFloat = 0

    var body: some View {
        ScrollView {
            content
                .background(
                    GeometryReader { geometry in
                        Color.clear.preference(
                            key: HeightKey.self, value: geometry.size.height)
                    }
                )
        }
        .frame(height: min(max(measured, minHeight), maxHeight))
        .onPreferenceChange(HeightKey.self) { measured = $0 }
    }
}