import SwiftUI

enum AppTab: String, Identifiable {
    case home
    case movie
    case series
    case variety
    case anime
    case search
    case settings

    var id: String { rawValue }

    var title: String {
        switch self {
        case .home: return "首页"
        case .movie: return "电影"
        case .series: return "电视剧"
        case .variety: return "综艺"
        case .anime: return "动漫"
        case .search: return "搜索"
        case .settings: return "设置"
        }
    }

    var icon: String {
        switch self {
        case .home: return "house"
        case .movie: return "film"
        case .series: return "tv"
        case .variety: return "theatermasks"
        case .anime: return "sparkles"
        case .search: return "magnifyingglass"
        case .settings: return "gearshape"
        }
    }

    var category: ContentCategory? {
        switch self {
        case .movie: return .movie
        case .series: return .series
        case .variety: return .variety
        case .anime: return .anime
        default: return nil
        }
    }

    static var visibleTabs: [AppTab] {
        #if os(tvOS)
        return [.home, .movie, .series, .variety, .anime, .search, .settings]
        #else
        return [.home, .movie, .series, .variety, .anime, .settings]
        #endif
    }
}

struct AppNavigation: View {
    @State private var selectedTab: AppTab = .home
    // 持有各 tab 的 ViewModel，切换 tab 不丢失状态
    @State private var homeVM = HomeViewModel()
    @State private var movieVM = BrowseViewModel()
    @State private var seriesVM = BrowseViewModel()
    @State private var varietyVM = BrowseViewModel()
    @State private var animeVM = BrowseViewModel()

    var body: some View {
        #if os(macOS)
        sidebarLayout
        #elseif os(tvOS)
        tabLayout
        #elseif os(visionOS)
        sidebarLayout
        #else
        if UIDevice.current.userInterfaceIdiom == .pad {
            sidebarLayout
        } else {
            tabLayout
        }
        #endif
    }

    private var tabLayout: some View {
        TabView(selection: $selectedTab) {
            ForEach(AppTab.visibleTabs) { tab in
                NavigationStack {
                    tabContent(for: tab)
                }
                .tabItem {
                    Label(tab.title, systemImage: tab.icon)
                }
                .tag(tab)
            }
        }
    }

    private var sidebarLayout: some View {
        NavigationSplitView {
            List(AppTab.visibleTabs, selection: $selectedTab) { tab in
                Label(tab.title, systemImage: tab.icon)
                    .tag(tab)
            }
            .navigationTitle("低端影视")
        } detail: {
            NavigationStack {
                tabContent(for: selectedTab)
            }
        }
    }

    @ViewBuilder
    private func tabContent(for tab: AppTab) -> some View {
        switch tab {
        case .home:
            HomeView(viewModel: homeVM)
        case .movie:
            BrowseView(category: .movie, viewModel: movieVM)
        case .series:
            BrowseView(category: .series, viewModel: seriesVM)
        case .variety:
            BrowseView(category: .variety, viewModel: varietyVM)
        case .anime:
            BrowseView(category: .anime, viewModel: animeVM)
        case .search:
            #if os(tvOS)
            TVSearchView()
            #else
            EmptyView()
            #endif
        case .settings:
            SettingsView()
        }
    }
}