// Copyright © 2020 Metabolist. All rights reserved.

import Kingfisher
import SwiftUI
import ViewModels

struct TabNavigationView: View {
    @ObservedObject var viewModel: NavigationViewModel
    @EnvironmentObject var rootViewModel: RootViewModel
    @Environment(\.displayScale) var displayScale: CGFloat
    @State var selectedTab = NavigationViewModel.Tab.timelines

    @State private var contextMenuImages = [UUID: KFImage]()

    var body: some View {
        Group {
            if viewModel.identification.identity.pending {
                pendingView
            } else {
                TabView(selection: $selectedTab) {
                    ForEach(viewModel.tabs) { tab in
                        NavigationView {
                            view(tab: tab)
                        }
                        .navigationViewStyle(StackNavigationViewStyle())
                        .tabItem {
                            Label(tab.title, systemImage: tab.systemImageName)
                                .accessibility(label: Text(tab.title))
                        }
                        .tag(tab)
                        .overlay(newStatusButton, alignment: .bottomTrailing)
                    }
                }
            }
        }
        .environmentObject(viewModel.identification)
        .sheet(isPresented: $viewModel.presentingSecondaryNavigation) {
            SecondaryNavigationView(viewModel: viewModel)
                .environmentObject(viewModel)
                .environmentObject(rootViewModel)
        }
        .background(
            EmptyView()
                .fullScreenCover(isPresented: $viewModel.presentingNewStatus) {
                    NavigationView {
                        NewStatusView { rootViewModel.newStatusViewModel(identification: viewModel.identification) }
                        .navigationBarTitleDisplayMode(.inline)
                    }
                    .navigationViewStyle(StackNavigationViewStyle())
                    .environmentObject(viewModel)
                    .environmentObject(rootViewModel)
                })
        .alertItem($viewModel.alertItem)
        .onAppear(perform: viewModel.refreshIdentity)
        // Have to preload these, otherwise the context menu won't display them when first expanded
        .onReceive(viewModel.$recentIdentities) {
            contextMenuImages = Dictionary(uniqueKeysWithValues: $0.map {
                ($0.id, KFImage($0.image)
                    .downsampled(
                        dimension: .barButtonItemDimension,
                        scaleFactor: displayScale)
                    .renderingMode(.original))
            })
        }
        .onReceive(NotificationCenter.default
                    .publisher(for: UIScene.willEnterForegroundNotification)
                    .map { _ in () },
                   perform: viewModel.refreshIdentity)
    }
}

private extension TabNavigationView {
    @ViewBuilder
    var pendingView: some View {
        NavigationView {
            Text("pending.pending-confirmation")
                .navigationBarItems(leading: secondaryNavigationButton)
                .navigationTitle(viewModel.identification.identity.handle)
                .navigationBarTitleDisplayMode(.inline)
        }
        .navigationViewStyle(StackNavigationViewStyle())
    }

    @ViewBuilder
    // swiftlint:disable:next function_body_length
    func view(tab: NavigationViewModel.Tab) -> some View {
        switch tab {
        case .timelines:
            TableView { viewModel.timelineViewModel }
                .id(viewModel.timeline.id)
                .edgesIgnoringSafeArea(.all)
                .navigationTitle(viewModel.timeline.title)
                .navigationBarTitleDisplayMode(.inline)
                .toolbar {
                    ToolbarItem(placement: .principal) {
                        VStack {
                            Text(viewModel.timeline.title)
                                .font(.headline)
                            Text(viewModel.timelineSubtitle)
                                .font(.footnote)
                                .foregroundColor(.secondary)
                        }
                    }
                }
                .navigationBarItems(
                    leading: secondaryNavigationButton,
                    trailing: Menu {
                        ForEach(viewModel.timelinesAndLists) { timeline in
                            Button {
                                viewModel.timeline = timeline
                            } label: {
                                Label(timeline.title,
                                      systemImage: timeline.systemImageName)
                            }
                        }
                    } label: {
                        Image(systemName: viewModel.timeline.systemImageName)
                            .padding([.leading, .top, .bottom])
                    })
        case .notifications:
            if let notificationsViewModel = viewModel.notificationsViewModel {
                TableView { notificationsViewModel }
                    .id(tab)
                    .edgesIgnoringSafeArea(.all)
                    .navigationTitle("notifications")
                    .navigationBarTitleDisplayMode(.inline)
                    .navigationBarItems(leading: secondaryNavigationButton)
            }
        case .messages:
            if let conversationsViewModel = viewModel.conversationsViewModel {
                TableView { conversationsViewModel }
                    .id(tab)
                    .edgesIgnoringSafeArea(.all)
                    .navigationTitle("messages")
                    .navigationBarTitleDisplayMode(.inline)
                    .navigationBarItems(leading: secondaryNavigationButton)
            }
        default: Text(tab.title)
        }
    }

    @ViewBuilder
    var secondaryNavigationButton: some View {
        Button {
            viewModel.presentingSecondaryNavigation.toggle()
        } label: {
            KFImage(viewModel.identification.identity.image)
                .downsampled(
                    dimension: .barButtonItemDimension,
                    scaleFactor: displayScale)
                .placeholder { Image(systemName: "gear") }
                .renderingMode(.original)
                .contextMenu(ContextMenu {
                    ForEach(viewModel.recentIdentities) { recentIdentity in
                        Button {
                            rootViewModel.identitySelected(id: recentIdentity.id)
                        } label: {
                            Label(
                                title: { Text(recentIdentity.handle) },
                                icon: { contextMenuImages[recentIdentity.id] })
                        }
                    }
                })
                .padding([.trailing, .top, .bottom])
        }
    }

    @ViewBuilder
    var newStatusButton: some View {
        if viewModel.identification.identity.authenticated
            && !viewModel.identification.identity.pending {
            Button {
                viewModel.presentingNewStatus = true
            } label: {
                VisualEffectBlur(vibrancyStyle: .label) {
                    Image(systemName: "pencil")
                        .resizable()
                        .frame(width: .newStatusButtonDimension / 2,
                               height: .newStatusButtonDimension / 2)
                }
                .clipShape(Circle())
                .frame(width: .newStatusButtonDimension,
                       height: .newStatusButtonDimension)
                .shadow(radius: .defaultShadowRadius)
                .padding()
            }
        }
    }
}

// TODO: move
extension Timeline {
    var title: String {
        switch self {
        case .home:
            return NSLocalizedString("timelines.home", comment: "")
        case .local:
            return NSLocalizedString("timelines.local", comment: "")
        case .federated:
            return NSLocalizedString("timelines.federated", comment: "")
        case let .list(list):
            return list.title
        case let .tag(tag):
            return "#".appending(tag)
        case .profile:
            return ""
        case .favorites:
            return NSLocalizedString("favorites", comment: "")
        case .bookmarks:
            return NSLocalizedString("bookmarks", comment: "")
        }
    }

    func subtitle(identification: Identification) -> String? {
        switch self {
        case .home:
            return identification.identity.handle
        default:
            return identification.identity.instance?.uri
        }
    }

    func description(instanceName: String?) -> String? {
        switch self {
        case .home:
            return NSLocalizedString("timelines.home.description", comment: "")
        case .local:
            guard let instanceName = instanceName else { return nil }

            return String.localizedStringWithFormat(
                NSLocalizedString("timelines.local.description-%@", comment: ""),
                instanceName)
        case .federated:
            guard let instanceName = instanceName else { return nil }

            return String.localizedStringWithFormat(
                NSLocalizedString("timelines.federated.description-%@", comment: ""),
                instanceName)
        default:
            return nil
        }
    }

    var systemImageName: String {
        switch self {
        case .home: return "house"
        case .local: return "building.2.crop.circle"
        case .federated: return "network"
        case .list: return "scroll"
        case .tag: return "number"
        case .profile: return "person"
        case .favorites: return "star"
        case .bookmarks: return "bookmark"
        }
    }
}

#if DEBUG
import PreviewViewModels

struct TabNavigation_Previews: PreviewProvider {
    static var previews: some View {
        TabNavigationView(viewModel: NavigationViewModel(identification: .preview))
            .environmentObject(Identification.preview)
            .environmentObject(RootViewModel.preview)
    }
}
#endif