import Defaults
import SwiftUI

struct VideosCellsVertical: View {
    #if os(iOS)
        @Environment(\.verticalSizeClass) private var verticalSizeClass
    #endif

    var videos = [Video]()

    var body: some View {
        EmptyView().id("cellsTop")

        ScrollViewReader { scrollView in
            ScrollView(.vertical, showsIndicators: scrollViewShowsIndicators) {
                LazyVGrid(columns: items, alignment: .center) {
                    ForEach(videos) { video in
                        VideoView(video: video)
                        #if os(tvOS)
                            .padding(.horizontal)
                        #endif
                    }
                }
                .padding()
            }
            .onChange(of: videos) { [videos] newVideos in
                guard !videos.isEmpty else {
                    return
                }

                scrollView.scrollTo("cellsTop", anchor: .top)
            }
            #if os(tvOS)
                .padding(.horizontal, 10)
            #endif
        }
        .edgesIgnoringSafeArea(.horizontal)
        #if os(macOS)
            .background()
            .frame(minWidth: 360)
        #endif
    }

    var items: [GridItem] {
        #if os(tvOS)
            videos.count < 3 ? Array(repeating: GridItem(.fixed(540)), count: [videos.count, 1].max()!) : adaptiveItem
        #else
            adaptiveItem
        #endif
    }

    var adaptiveItem: [GridItem] {
        [GridItem(.adaptive(minimum: adaptiveGridItemMinimumSize))]
    }

    var adaptiveGridItemMinimumSize: Double {
        #if os(iOS)
            return verticalSizeClass == .regular ? 320 : 800
        #elseif os(tvOS)
            return 540
        #else
            return 320
        #endif
    }

    var scrollViewShowsIndicators: Bool {
        #if !os(tvOS)
            true
        #else
            false
        #endif
    }
}

struct VideoCellsVertical_Previews: PreviewProvider {
    static var previews: some View {
        VideosCellsVertical(videos: Video.allFixtures)
            .injectFixtureEnvironmentObjects()
    }
}