//
// 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 BlurHashKit
import SwiftUI

extension ItemView {

    struct CompactLogoScrollView<Content: View>: View {

        @EnvironmentObject
        private var itemRouter: ItemCoordinator.Router
        @State
        private var scrollViewOffset: CGFloat = 0
        @State
        private var blurHashBottomEdgeColor: Color = .secondarySystemFill
        @ObservedObject
        var viewModel: ItemViewModel

        let content: () -> Content

        private var topOpacity: CGFloat {
            let start = UIScreen.main.bounds.height * 0.25
            let end = UIScreen.main.bounds.height * 0.44
            let diff = end - start
            let opacity = min(max((scrollViewOffset - start) / diff, 0), 1)
            return opacity
        }

        @ViewBuilder
        private var headerView: some View {
            ImageView(viewModel.item.imageSource(.backdrop, maxWidth: UIScreen.main.bounds.width))
                .frame(height: UIScreen.main.bounds.height * 0.35)
                .bottomEdgeGradient(bottomColor: blurHashBottomEdgeColor)
                .onAppear {
                    if let backdropBlurHash = viewModel.item.blurHash(.backdrop) {
                        let bottomRGB = BlurHash(string: backdropBlurHash)!.averageLinearRGB
                        blurHashBottomEdgeColor = Color(
                            red: Double(bottomRGB.0),
                            green: Double(bottomRGB.1),
                            blue: Double(bottomRGB.2)
                        )
                    }
                }
        }

        var body: some View {
            ScrollView(showsIndicators: false) {
                VStack(spacing: 0) {

                    Color.clear
                        .frame(height: UIScreen.main.bounds.height * 0.25)

                    OverlayView(scrollViewOffset: $scrollViewOffset, viewModel: viewModel)
                        .padding(.horizontal)
                        .padding(.bottom)
                        .background {
                            BlurView(style: .systemThinMaterialDark)
                                .mask {
                                    LinearGradient(
                                        stops: [
                                            .init(color: .clear, location: 0),
                                            .init(color: .white, location: 0.15),
                                        ],
                                        startPoint: .top,
                                        endPoint: .bottom
                                    )
                                }
                        }
                        .overlay {
                            Color.systemBackground
                                .opacity(topOpacity)
                        }

                    VStack(alignment: .leading, spacing: 10) {
                        if let firstTagline = viewModel.item.taglines?.first {
                            Text(firstTagline)
                                .font(.body)
                                .fontWeight(.semibold)
                                .multilineTextAlignment(.leading)
                                .lineLimit(2)
                                .fixedSize(horizontal: false, vertical: true)
                        }

                        if let itemOverview = viewModel.item.overview {
                            TruncatedTextView(text: itemOverview) {
                                itemRouter.route(to: \.itemOverview, viewModel.item)
                            }
                            .font(.footnote)
                            .lineLimit(4)
                            .fixedSize(horizontal: false, vertical: true)
                        }
                    }
                    .padding(.horizontal)
                    .padding(.top)
                    .frame(maxWidth: .infinity)
                    .background(Color.systemBackground)

                    content()
                        .padding(.vertical)
                        .background(Color.systemBackground)
                }
            }
            .edgesIgnoringSafeArea(.top)
            .scrollViewOffset($scrollViewOffset)
            .navBarOffset(
                $scrollViewOffset,
                start: UIScreen.main.bounds.height * 0.43,
                end: UIScreen.main.bounds.height * 0.43 + 50
            )
            .backgroundParallaxHeader(
                $scrollViewOffset,
                height: UIScreen.main.bounds.height * 0.35,
                multiplier: 0.3
            ) {
                headerView
            }
        }
    }
}

extension ItemView.CompactLogoScrollView {

    struct OverlayView: View {

        @EnvironmentObject
        private var itemRouter: ItemCoordinator.Router
        @Binding
        var scrollViewOffset: CGFloat
        @ObservedObject
        var viewModel: ItemViewModel

        private var topOpacity: CGFloat {
            let start = UIScreen.main.bounds.height * 0.25
            let end = UIScreen.main.bounds.height * 0.44
            let diff = end - start
            let opacity = min(max((scrollViewOffset - start) / diff, 0), 1)
            return 1 - opacity
        }

        var body: some View {
            VStack(alignment: .center, spacing: 10) {
                ImageView(viewModel.item.imageURL(.logo, maxWidth: UIScreen.main.bounds.width, maxHeight: 100))
                    .resizingMode(.aspectFit)
                    .failure {
                        Text(viewModel.item.displayName)
                            .font(.largeTitle)
                            .fontWeight(.semibold)
                            .multilineTextAlignment(.center)
                            .foregroundColor(.white)
                    }
                    .frame(maxWidth: .infinity)
                    .frame(height: 100)

                DotHStack {
                    if let firstGenre = viewModel.item.genres?.first {
                        Text(firstGenre)
                    }

                    if let premiereYear = viewModel.item.premiereDateYear {
                        Text(premiereYear)
                    }

                    if let playButtonitem = viewModel.playButtonItem, let runtime = playButtonitem.getItemRuntime() {
                        Text(runtime)
                    }
                }
                .font(.caption)
                .foregroundColor(Color(UIColor.lightGray))
                .padding(.horizontal)

                ItemView.AttributesHStack(viewModel: viewModel)

                ItemView.PlayButton(viewModel: viewModel)
                    .frame(maxWidth: 300)
                    .frame(height: 50)

                ItemView.ActionButtonHStack(viewModel: viewModel)
                    .font(.title)
                    .frame(maxWidth: 300)
            }
        }
    }
}