import SwiftUI

struct CategoryHeaderOffsetPreferenceKey: PreferenceKey {
    static let defaultValue: [String: CGFloat] = [:]

    static func reduce(value: inout [String: CGFloat], nextValue: () -> [String: CGFloat]) {
        value.merge(nextValue(), uniquingKeysWith: { _, new in new })
    }
}

enum StoreDetailScrollCoordinateSpace {
    static let name = "store-detail-scroll"
}

struct ScrollOffsetPreferenceKey: PreferenceKey {
    static let defaultValue: CGFloat = 0

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

struct ScrollOffsetReader: View {
    @Binding var offsetY: CGFloat
    @State private var baseline: CGFloat? = nil

    var body: some View {
        Color.clear
            .frame(height: 0)
            .background(
                GeometryReader { geometry in
                    Color.clear.preference(
                        key: ScrollOffsetPreferenceKey.self,
                        value: geometry.frame(in: .named(StoreDetailScrollCoordinateSpace.name)).minY
                    )
                }
            )
            .onPreferenceChange(ScrollOffsetPreferenceKey.self) { minY in
                if baseline == nil { baseline = minY }
                let offset = (baseline ?? 0) - minY
                if abs(offsetY - offset) > 0.5 {
                    offsetY = offset
                }
            }
    }
}

struct AsyncStoreImage: View {
    let imageURL: String?
    var fallbackImageName: String = "placeholder-product"

    var body: some View {
        CachedRemoteImage(imageURL: imageURL) {
            fallback
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .background(AppColors.brandSoft)
        .clipped()
    }

    private var fallback: some View {
        Image(fallbackImageName)
            .resizable()
            .scaledToFill()
    }
}