//
// 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 JellyfinAPI
import SwiftUI
import UIKit

// TODO: Generalize this view such that it can be used in other contexts like for a library

struct HomeCinematicViewItem: Hashable {

    enum TopRowType {
        case resume
        case nextUp
        case plain
    }

    let item: BaseItemDto
    let type: TopRowType

    func hash(into hasher: inout Hasher) {
        hasher.combine(item)
        hasher.combine(type)
    }
}

struct HomeCinematicView: View {

    @FocusState
    var selectedItem: BaseItemDto?
    @ObservedObject
    var viewModel: HomeViewModel
    @State
    private var updatedSelectedItem: BaseItemDto?
    @State
    private var initiallyAppeared = false
    private let forcedItemSubtitle: String?
    private let items: [HomeCinematicViewItem]
    private let backgroundViewModel = DynamicCinematicBackgroundViewModel()

    init(viewModel: HomeViewModel, items: [HomeCinematicViewItem], forcedItemSubtitle: String? = nil) {
        self.viewModel = viewModel
        self.items = items
        self.forcedItemSubtitle = forcedItemSubtitle
    }

    var body: some View {

        ZStack(alignment: .bottom) {

            CinematicBackgroundView(viewModel: backgroundViewModel)
                .frame(height: UIScreen.main.bounds.height - 50)

            LinearGradient(
                stops: [
                    .init(color: .clear, location: 0.5),
                    .init(color: .black.opacity(0.6), location: 0.7),
                    .init(color: .black, location: 1),
                ],
                startPoint: .top,
                endPoint: .bottom
            )
            .ignoresSafeArea()

            VStack(alignment: .leading, spacing: 0) {

                VStack(alignment: .leading, spacing: 0) {

                    if let forcedItemSubtitle = forcedItemSubtitle {
                        Text(forcedItemSubtitle)
                            .font(.callout)
                            .fontWeight(.medium)
                            .foregroundColor(Color.secondary)
                    } else {
                        if updatedSelectedItem?.type == .episode {
                            Text(updatedSelectedItem?.episodeLocator ?? "")
                                .font(.callout)
                                .fontWeight(.medium)
                                .foregroundColor(Color.secondary)
                        } else {
                            Text("")
                        }
                    }

                    Text("\(updatedSelectedItem?.seriesName ?? updatedSelectedItem?.name ?? "")")
                        .font(.title)
                        .fontWeight(.semibold)
                        .foregroundColor(.primary)
                        .lineLimit(1)
                        .fixedSize(horizontal: false, vertical: true)
                }
                .padding(.horizontal, 50)

                ScrollView(.horizontal, showsIndicators: false) {
                    HStack {
                        ForEach(items, id: \.self) { item in
                            switch item.type {
                            case .nextUp:
                                CinematicNextUpCardView(item: item.item, showOverlay: true)
                                    .focused($selectedItem, equals: item.item)
                            case .resume:
                                CinematicResumeCardView(viewModel: viewModel, item: item.item)
                                    .focused($selectedItem, equals: item.item)
                            case .plain:
                                CinematicNextUpCardView(item: item.item, showOverlay: false)
                                    .focused($selectedItem, equals: item.item)
                            }
                        }
                    }
                    .padding(.horizontal, 50)
                    .padding(.bottom)
                }
                .focusSection()
            }
        }
        .onChange(of: selectedItem) { newValue in
            if let newItem = newValue {
                backgroundViewModel.select(item: newItem)
                updatedSelectedItem = newItem
            }
        }
        .onAppear {
            guard !initiallyAppeared else { return }
            selectedItem = items.first?.item
            updatedSelectedItem = items.first?.item
            initiallyAppeared = true
        }
    }
}