//
//  MainTabBarController.swift
//  suixinkan
//

import UIKit

@MainActor
/// 主 Tab 容器，使用系统 `UITabBarController` 展示四个一级入口。
final class MainTabBarController: UITabBarController, UITabBarControllerDelegate {

    private let services: AppServices
    private let badgeViewModel = MainTabBadgeViewModel()
    private var tabNavigationControllers: [AppTab: TabNavigationController] = [:]
    private var isSyncingTabSelection = false

    /// 初始化实例。
    init(services: AppServices) {
        self.services = services
        super.init(nibName: nil, bundle: nil)
        delegate = self
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    /// 视图加载完成后的 UI 初始化与数据绑定。
    override func viewDidLoad() {
        super.viewDidLoad()
        configureTabBarAppearance()
        configureTabs()
        bindRouter()
        bindBadgeViewModel()
        bindAccountContext()
        syncSelectedTabFromRouter(animated: false)
        Task { await refreshOrderBadge() }
        #if DEBUG
        Task { await AppUITestRouteDriver.applyIfNeeded(services: services) }
        #endif
    }

    /// 配置系统 TabBar 外观。
    private func configureTabBarAppearance() {
        tabBar.tintColor = AppDesign.primary
        tabBar.backgroundColor = .white
    }

    /// 为每个 Tab 创建独立导航栈并绑定 TabBarItem。
    private func configureTabs() {
        viewControllers = AppTab.allCases.map { tab in
            let navigationController = TabNavigationController(tab: tab, services: services)
            navigationController.tabBarItem = tab.makeTabBarItem()
            tabNavigationControllers[tab] = navigationController
            return navigationController
        }
    }

    /// 绑定 Router 回调，同步程序化 Tab 切换。
    private func bindRouter() {
        services.appRouter.onChange = { [weak self] in
            self?.handleRouterChange()
        }
    }

    /// 绑定角标 ViewModel 回调。
    private func bindBadgeViewModel() {
        badgeViewModel.onChange = { [weak self] in
            self?.updateOrderBadge()
        }
    }

    /// 绑定账号上下文，景区或门店变化时刷新角标。
    private func bindAccountContext() {
        services.accountContext.onChange = { [weak self] in
            Task { await self?.refreshOrderBadge() }
        }
    }

    /// 处理 Router 变更，保持选中 Tab 与 `AppRouter` 一致。
    private func handleRouterChange() {
        syncSelectedTabFromRouter(animated: false)
        if services.appRouter.selectedTab == .orders {
            Task { await refreshOrderBadge() }
        }
    }

    /// 将 `AppRouter.selectedTab` 同步到系统 TabBar 选中项。
    private func syncSelectedTabFromRouter(animated: Bool) {
        guard let index = AppTab.allCases.firstIndex(of: services.appRouter.selectedTab) else { return }
        guard selectedIndex != index else { return }

        isSyncingTabSelection = true
        selectedIndex = index
        isSyncingTabSelection = false
    }

    /// 更新订单 Tab 待核销角标。
    private func updateOrderBadge() {
        let badgeValue: String?
        if let count = badgeViewModel.pendingWriteOffCount, count > 0 {
            badgeValue = "\(count)"
        } else {
            badgeValue = nil
        }
        tabNavigationControllers[.orders]?.tabBarItem.badgeValue = badgeValue
    }

    /// 刷新订单 Tab 待核销角标数据。
    private func refreshOrderBadge() async {
        await badgeViewModel.refreshPendingWriteOffCount(
            api: services.ordersAPI,
            scenicId: services.accountContext.currentScenic?.id,
            storeId: services.accountContext.currentStore?.id
        )
    }

    /// 用户点击 TabBar 时同步选中状态到 `AppRouter`。
    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
        guard !isSyncingTabSelection,
              let navigationController = viewController as? TabNavigationController else { return }

        services.appRouter.select(navigationController.appTab)
        if navigationController.appTab == .orders {
            Task { await refreshOrderBadge() }
        }
    }
}