//
// Swiftfin is subject to the terms of the Mozilla Public
// License, v2.0. If a copy of the MPL was not distributed with this
// file, you can obtain one at https://mozilla.org/MPL/2.0/.
//
// Copyright (c) 2022 Jellyfin & Jellyfin Contributors
//

import SwiftUI

struct BackgroundParallaxHeaderModifier<Header: View>: ViewModifier {

    @Binding
    var scrollViewOffset: CGFloat

    let height: CGFloat
    let multiplier: CGFloat
    let header: () -> Header

    init(
        _ scrollViewOffset: Binding<CGFloat>,
        height: CGFloat,
        multiplier: CGFloat = 1,
        @ViewBuilder header: @escaping () -> Header
    ) {
        self._scrollViewOffset = scrollViewOffset
        self.height = height
        self.multiplier = multiplier
        self.header = header
    }

    func body(content: Content) -> some View {
        content.background(alignment: .top) {
            header()
                .offset(y: scrollViewOffset > 0 ? -scrollViewOffset * multiplier : 0)
                .scaleEffect(scrollViewOffset < 0 ? (height - scrollViewOffset) / height : 1, anchor: .top)
                .ignoresSafeArea()
        }
    }
}