#if os(macOS)
import SwiftUI

// 桌面根界面：NavigationSplitView 侧栏（传输 / 文件 / 消息 / 设备 / 设置）+ 详情 NavigationStack，
// 替代 iOS 的标签栏。离屏无头引擎 WebView 挂在背景保活（同 iOS RootView）。传输 / 文件 / 消息详情为
// 占位（随 Phase 3b 复用 iOS 视图）；设备 / 设置已接引擎真实态（presence / 账号 / 日志），作 3a 引擎
// 联通证明。分区标签暂硬编中文；接入 i18n（t()）待 Phase 3b 复用视图时统一。
struct MacRootView: View
{
    @Environment(EngineController.self) private var engine
    @Environment(AuthManager.self) private var auth
    @State private var selection: MacSection = .transfers

    var body: some View
    {
        NavigationSplitView
        {
            List(selection: $selection)
            {
                brandHeader
                    .listRowInsets(EdgeInsets(top: 10, leading: 8, bottom: 14, trailing: 8))
                    .listRowSeparator(.hidden)
                    .selectionDisabled()
                Section
                {
                    ForEach(MacSection.sidebar)
                    { section in
                        Label(section.title, systemImage: section.icon)
                            .badge(badge(for: section))
                            .tag(section)
                    }
                }
            }
            .navigationSplitViewColumnWidth(min: 200, ideal: 220, max: 280)
            .navigationTitle("Commilitia Drop")
        }
        detail:
        {
            NavigationStack
            {
                detail
            }
        }
        // 离屏无头引擎 WebView：零尺寸不可见，仅保持存活（登录后随本视图出现即 boot）。同 iOS RootView。
        .background
        {
            EngineWebView(controller: engine, auth: auth)
                .frame(width: 0, height: 0)
                .opacity(0)
                .allowsHitTesting(false)
        }
    }

    @ViewBuilder
    private var detail: some View
    {
        switch selection
        {
        case .transfers:
            MacPlaceholder(section: .transfers)
        case .files:
            MacPlaceholder(section: .files)
        case .messages:
            MacPlaceholder(section: .messages)
        case .devices:
            MacDevicesView()
        case .settings:
            MacSettingsView()
        }
    }

    private var brandHeader: some View
    {
        HStack(spacing: 10)
        {
            Image(systemName: "paperplane.fill")
                .font(.title2)
                .foregroundStyle(.tint)
            Text("Commilitia Drop")
                .font(.title3.weight(.semibold))
                .lineLimit(1)
        }
    }

    // 未读红点：消息 / 传输（对齐 iOS RootView 的 badge）。
    private func badge(for section: MacSection) -> Int
    {
        switch section
        {
        case .messages: return engine.unreadMessages
        case .transfers: return engine.unreadTransfers
        default: return 0
        }
    }
}

// 侧栏分区。与 iOS 标签一致：传输 / 文件 / 消息 / 设备 / 设置。
enum MacSection: Hashable, Identifiable, CaseIterable
{
    case transfers, files, messages, devices, settings

    var id: Self { self }

    var title: String
    {
        switch self
        {
        case .transfers: return "传输"
        case .files: return "文件"
        case .messages: return "消息"
        case .devices: return "设备"
        case .settings: return "设置"
        }
    }

    var icon: String
    {
        switch self
        {
        case .transfers: return "arrow.up.arrow.down"
        case .files: return "folder"
        case .messages: return "bubble.left.and.bubble.right"
        case .devices: return "laptopcomputer.and.iphone"
        case .settings: return "gearshape"
        }
    }

    static var sidebar: [MacSection] { MacSection.allCases }
}

// 阶段占位详情（传输 / 文件 / 消息，随 Phase 3b 替换为复用 iOS 视图）。
struct MacPlaceholder: View
{
    let section: MacSection

    var body: some View
    {
        ContentUnavailableView
        {
            Label(section.title, systemImage: section.icon)
        }
        description:
        {
            Text("即将接入（原生数据面复用 iOS 引擎，桌面功能适配中）。")
        }
        .navigationTitle(section.title)
    }
}

// 设备：引擎经桥推来的真实 presence（在线绿点 + 名称 + 类型），证明登录后引擎已联通信令 / SSE。
struct MacDevicesView: View
{
    @Environment(EngineController.self) private var engine

    var body: some View
    {
        Group
        {
            if engine.devices.isEmpty
            {
                ContentUnavailableView("暂无其他设备", systemImage: "laptopcomputer.and.iphone",
                                       description: Text("同账户的其他在线设备将显示在此。"))
            }
            else
            {
                List(engine.devices)
                { dev in
                    HStack(spacing: 10)
                    {
                        Circle()
                            .fill(dev.online ? Color.green : Color.secondary)
                            .frame(width: 9, height: 9)
                        Text(dev.name)
                        Spacer()
                        Text(dev.type)
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }
                }
            }
        }
        .navigationTitle("设备")
    }
}

// 设置：账号 + 本机设备名 + 登出 + 引擎日志（3a 联通与现场自检）。
struct MacSettingsView: View
{
    @Environment(EngineController.self) private var engine
    @Environment(AuthManager.self) private var auth

    var body: some View
    {
        Form
        {
            Section("账号")
            {
                LabeledContent("用户", value: auth.session?.user.name ?? "—")
                LabeledContent("本机设备", value: engine.deviceName)
                Button("登出", role: .destructive)
                {
                    engine.reset()
                    auth.logout()
                }
            }
            Section("引擎日志")
            {
                if engine.logs.isEmpty
                {
                    Text("暂无日志").foregroundStyle(.secondary)
                }
                else
                {
                    ForEach(engine.logs.prefix(30))
                    { entry in
                        Text(entry.message)
                            .font(.caption.monospaced())
                            .foregroundStyle(.secondary)
                            .lineLimit(2)
                            .textSelection(.enabled)
                    }
                }
            }
        }
        .formStyle(.grouped)
        .navigationTitle("设置")
    }
}
#endif