import HostRegistry
import SwiftUI

/// T-iOS-15 / T-iPad-2 · App 根入口。历史上这里是单一 `NavigationStack` +
/// 隐私遮罩 + sheets/scenePhase/deepLink 的全部布线；iPad 自适应（T-iPad-2）
/// 把它拆成两层：
/// - `RootView`（本 struct）保持 `@main` 的唯一实例化点不变（WebTermApp 仍
///   `RootView(coordinator:)`），内部只委托给 `AdaptiveRootView`。
/// - `AdaptiveRootView` 按 `horizontalSizeClass` 选 `StackRootView`（compact，
///   现有路径，字节级不变）或 `SplitRootView`（regular，iPad 分栏），并把
///   隐私遮罩 / scenePhase / deepLink / sheets 这些**设备无关的横切布线**
///   上提到唯一一处，两分支共享（遮罩因此仍是两分支共同的 ZStack 顶层）。
///
/// `StackRootView` 是原 `RootView` 的 body **原样搬迁** —— compact 分支复用它
/// 不改一行，故 iPhone 逐屏渲染与适配前一致（零回归硬性要求）。
struct RootView: View {
    @Bindable var coordinator: AppCoordinator

    var body: some View {
        AdaptiveRootView(coordinator: coordinator)
    }
}

/// T-iPad-2 · compact 宽度（iPhone / iPad Slide Over）的根视图 —— 原
/// `RootView` 的 `NavigationStack` 主体原样搬迁，行为字节级不变。横切布线
/// （遮罩/scenePhase/deepLink/sheets）不在这里，已上提到 `AdaptiveRootView`。
struct StackRootView: View {
    @Bindable var coordinator: AppCoordinator

    var body: some View {
        NavigationStack {
            rootContent
                .navigationDestination(isPresented: terminalBinding) {
                    terminalDestination
                }
        }
    }

    // MARK: - Route switch

    @ViewBuilder private var rootContent: some View {
        switch coordinator.route {
        case .loading:
            ProgressView()
        case .pairing:
            firstRunPairing
        case .sessions:
            sessionList
        }
    }

    @ViewBuilder private var firstRunPairing: some View {
        if let viewModel = coordinator.rootPairingViewModel {
            PairingScreen(viewModel: viewModel) { host in
                coordinator.completeFirstPairing(host)
            }
        } else {
            ProgressView()
        }
    }

    private var sessionList: some View {
        SessionListScreen(
            viewModel: coordinator.sessionList,
            onOpen: { coordinator.open($0) },
            onAddHost: { coordinator.presentAddHost() }
        )
        .safeAreaInset(edge: .bottom) { continueLastBanner }
        // T-iOS-26 · Projects 入口挂在 RootView 层（SessionListScreen 是
        // T-iOS-23 的 W7 独占文件 —— 列表侧入口整合移交给它）。leading 位，
        // 避开列表自己的 topBarTrailing hostMenu。
        .toolbar { projectsToolbarItem }
    }

    @ToolbarContentBuilder private var projectsToolbarItem: some ToolbarContent {
        ToolbarItem(placement: .topBarLeading) {
            Button {
                coordinator.presentProjects()
            } label: {
                Label(RootCopy.projects, systemImage: "folder")
            }
            .disabled(coordinator.sessionList.activeHost == nil)
            .accessibilityIdentifier("sessions.projectsButton")
        }
    }

    // MARK: - "继续上次" highlight (cold start step 5)

    @ViewBuilder private var continueLastBanner: some View {
        if coordinator.continueLastSessionId != nil {
            Button {
                coordinator.openContinueLast()
            } label: {
                Label(RootCopy.continueLast, systemImage: "arrow.uturn.forward.circle.fill")
                    .frame(maxWidth: .infinity)
            }
            .buttonStyle(.borderedProminent)
            .padding(.horizontal, RootMetrics.bannerHorizontalPadding)
            .padding(.vertical, RootMetrics.bannerVerticalPadding)
            .background(.thinMaterial)
        }
    }

    // MARK: - Terminal push

    private var terminalBinding: Binding<Bool> {
        Binding(
            get: { coordinator.terminalController != nil },
            set: { presented in
                guard !presented else { return }
                coordinator.closeTerminal() // back → engine.close() (detach)
            }
        )
    }

    @ViewBuilder private var terminalDestination: some View {
        if let controller = coordinator.terminalController {
            TerminalContainerView(
                controller: controller,
                onNewSessionInCwd: { coordinator.openNewSessionInCurrentCwd() },
                onKillSession: { coordinator.killCurrentSession() } // T-iPad-3
            )
            // T-iOS-29 · identity PER CONTROLLER: an in-place session switch
            // (new-in-cwd, deep link) swaps the controller while the
            // destination stays presented — without a new identity SwiftUI
            // keeps the old SwiftTerm UIView and the new ViewModel's output
            // sink never attaches (makeUIView never re-runs). Also resets the
            // container's per-session @State (plan-gate dismissal, timeline).
            .id(controller.id)
        }
    }
}

enum RootMetrics {
    static let bannerHorizontalPadding: CGFloat = 16
    static let bannerVerticalPadding: CGFloat = 8
}

/// 根层用户可见文案（internal —— `SplitRootView` 复用同一「项目」标签，DRY）。
enum RootCopy {
    static let continueLast = "继续上次会话"
    static let projects = "项目"
}