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

import SnapKit
import UIKit

@MainActor
/// 主 Tab 容器，使用自定义底部栏展示四个一级入口和中间扫码按钮。
final class MainTabBarController: UIViewController {

    private let services: AppServices
    private let badgeViewModel = MainTabBadgeViewModel()
    private let contentContainer = UIView()
    private let customTabBar = CustomMainTabBarView()

    private var tabNavigationControllers: [AppTab: TabNavigationController] = [:]
    private var loadedTabs: Set<AppTab> = [.home]

    init(services: AppServices) {
        self.services = services
        super.init(nibName: nil, bundle: nil)
    }

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

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        configureLayout()
        bindRouter()
        bindBadgeViewModel()
        bindAccountContext()
        switchToTab(services.appRouter.selectedTab, animated: false)
        Task { await refreshOrderBadge() }
        #if DEBUG
        Task { await AppUITestRouteDriver.applyIfNeeded(services: services) }
        #endif
    }

    /// 控制自定义 TabBar 显隐，push 子页面时隐藏。
    func setCustomTabBarHidden(_ hidden: Bool, animated: Bool) {
        let updates = {
            self.customTabBar.alpha = hidden ? 0 : 1
            self.customTabBar.isUserInteractionEnabled = !hidden
        }

        guard animated else {
            updates()
            return
        }

        UIView.animate(withDuration: 0.2, delay: 0, options: [.curveEaseInOut], animations: updates)
    }

    private func configureLayout() {
        view.addSubview(contentContainer)
        view.addSubview(customTabBar)

        customTabBar.onTabSelected = { [weak self] tab in
            self?.services.appRouter.select(tab)
        }
        customTabBar.onScanTapped = { [weak self] in
            self?.presentScanner()
        }

        contentContainer.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview()
            make.bottom.equalTo(customTabBar.snp.top)
        }

        customTabBar.snp.makeConstraints { make in
            make.leading.trailing.equalToSuperview()
            make.bottom.equalTo(view.safeAreaLayoutGuide)
            make.height.equalTo(72)
        }
    }

    private func bindRouter() {
        services.appRouter.onChange = { [weak self] in
            self?.handleRouterChange()
        }
    }

    private func bindBadgeViewModel() {
        badgeViewModel.onChange = { [weak self] in
            self?.updateOrderBadge()
        }
    }

    private func bindAccountContext() {
        services.accountContext.onChange = { [weak self] in
            Task { await self?.refreshOrderBadge() }
        }
    }

    private func handleRouterChange() {
        switchToTab(services.appRouter.selectedTab, animated: false)
        if services.appRouter.selectedTab == .orders {
            Task { await refreshOrderBadge() }
        }
    }

    private func switchToTab(_ tab: AppTab, animated: Bool) {
        loadedTabs.insert(tab)
        customTabBar.selectedTab = tab

        let navigationController = navigationController(for: tab)
        for child in children where child !== navigationController {
            child.willMove(toParent: nil)
            child.view.removeFromSuperview()
            child.removeFromParent()
        }

        addChild(navigationController)
        contentContainer.addSubview(navigationController.view)
        navigationController.view.snp.makeConstraints { make in
            make.edges.equalToSuperview()
        }
        navigationController.didMove(toParent: self)

        let isRoot = navigationController.viewControllers.count <= 1
        setCustomTabBarHidden(!isRoot, animated: animated)
    }

    private func navigationController(for tab: AppTab) -> TabNavigationController {
        if let existing = tabNavigationControllers[tab] {
            return existing
        }

        let navigationController = TabNavigationController(tab: tab, services: services)
        navigationController.tabBarHost = self
        tabNavigationControllers[tab] = navigationController
        return navigationController
    }

    private func updateOrderBadge() {
        guard let count = badgeViewModel.pendingWriteOffCount, count > 0 else {
            customTabBar.orderBadgeText = nil
            return
        }
        customTabBar.orderBadgeText = "\(count)"
    }

    private func refreshOrderBadge() async {
        await badgeViewModel.refreshPendingWriteOffCount(
            api: services.ordersAPI,
            scenicId: services.accountContext.currentScenic?.id,
            storeId: services.accountContext.currentStore?.id
        )
    }

    private func presentScanner() {
        let scanner = OrderCodeScannerViewController()
        scanner.onScanResult = { [weak self] result in
            guard let self else { return }
            switch result {
            case .success(let rawCode):
                dismiss(animated: true) {
                    self.services.appRouter.routeToOrderVerification(scannedCode: rawCode)
                }
            case .failure(let error):
                showToast(error.localizedDescription)
            }
        }
        let navigation = UINavigationController(rootViewController: scanner)
        navigation.modalPresentationStyle = .fullScreen
        present(navigation, animated: true)
    }
}

/// 自定义主 TabBar，展示四个一级入口和中间扫码核销按钮。
private final class CustomMainTabBarView: UIView {

    var selectedTab: AppTab = .home {
        didSet { refreshSelection() }
    }

    var orderBadgeText: String? {
        didSet { ordersBadgeLabel.text = orderBadgeText; ordersBadgeLabel.isHidden = orderBadgeText == nil }
    }

    var onTabSelected: ((AppTab) -> Void)?
    var onScanTapped: (() -> Void)?

    private struct TabItem {
        let tab: AppTab
        let title: String
        let selectedImage: String
        let unselectedImage: String
    }

    private let items: [TabItem] = [
        .init(tab: .home, title: "首页", selectedImage: "TabHomeSelected", unselectedImage: "TabHomeUnselected"),
        .init(tab: .orders, title: "订单", selectedImage: "TabOrderSelected", unselectedImage: "TabOrderUnselected"),
        .init(tab: .statistics, title: "数据", selectedImage: "TabDataSelected", unselectedImage: "TabDataUnselected"),
        .init(tab: .profile, title: "我的", selectedImage: "TabProfileSelected", unselectedImage: "TabProfileUnselected")
    ]

    private var tabButtons: [AppTab: UIButton] = [:]
    private var tabTitleLabels: [AppTab: UILabel] = [:]
    private let ordersBadgeLabel = UILabel()
    private let topDivider = UIView()

    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .white
        configureViews()
        refreshSelection()
    }

    required init?(coder: NSCoder) {
        nil
    }

    private func configureViews() {
        topDivider.backgroundColor = UIColor.black.withAlphaComponent(0.04)
        addSubview(topDivider)
        topDivider.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview()
            make.height.equalTo(0.5)
        }

        let leftStack = UIStackView()
        leftStack.axis = .horizontal
        leftStack.distribution = .fillEqually
        leftStack.spacing = 0

        let rightStack = UIStackView()
        rightStack.axis = .horizontal
        rightStack.distribution = .fillEqually
        rightStack.spacing = 0

        for (index, item) in items.enumerated() {
            let buttonContainer = makeTabButton(for: item)
            if index < 2 {
                leftStack.addArrangedSubview(buttonContainer)
            } else {
                rightStack.addArrangedSubview(buttonContainer)
            }
        }

        let scanButton = UIButton(type: .system)
        scanButton.backgroundColor = AppDesign.primary
        scanButton.layer.cornerRadius = 29
        scanButton.tintColor = .white
        scanButton.setImage(
            UIImage(systemName: "qrcode.viewfinder")?.withConfiguration(
                UIImage.SymbolConfiguration(pointSize: 30, weight: .bold)
            ),
            for: .normal
        )
        scanButton.accessibilityLabel = "扫码核销"
        scanButton.accessibilityIdentifier = "main.scan"
        scanButton.addTarget(self, action: #selector(scanTapped), for: .touchUpInside)

        let row = UIStackView(arrangedSubviews: [leftStack, scanButton, rightStack])
        row.axis = .horizontal
        row.alignment = .center
        row.spacing = 0
        addSubview(row)

        scanButton.snp.makeConstraints { make in
            make.width.equalTo(74)
            make.height.equalTo(64)
        }

        row.snp.makeConstraints { make in
            make.leading.trailing.equalToSuperview().inset(22)
            make.top.bottom.equalToSuperview()
        }

        leftStack.snp.makeConstraints { make in
            make.width.equalTo(rightStack)
        }
    }

    private func makeTabButton(for item: TabItem) -> UIView {
        let container = UIView()

        let button = UIButton(type: .custom)
        button.accessibilityLabel = item.title
        button.accessibilityIdentifier = "main.tab.\(item.tab.rawValue)"
        button.tag = items.firstIndex(where: { $0.tab == item.tab }) ?? 0
        button.addTarget(self, action: #selector(tabTapped(_:)), for: .touchUpInside)
        tabButtons[item.tab] = button

        let titleLabel = UILabel()
        titleLabel.text = item.title
        titleLabel.font = .systemFont(ofSize: 12)
        titleLabel.textAlignment = .center
        tabTitleLabels[item.tab] = titleLabel

        container.addSubview(button)
        container.addSubview(titleLabel)

        button.snp.makeConstraints { make in
            make.top.equalToSuperview().offset(8)
            make.centerX.equalToSuperview()
            make.width.height.equalTo(24)
        }

        titleLabel.snp.makeConstraints { make in
            make.top.equalTo(button.snp.bottom).offset(3)
            make.centerX.equalToSuperview()
            make.bottom.lessThanOrEqualToSuperview()
        }

        if item.tab == .orders {
            ordersBadgeLabel.font = .systemFont(ofSize: 9, weight: .bold)
            ordersBadgeLabel.textColor = .white
            ordersBadgeLabel.backgroundColor = UIColor(hex: 0xEF4444)
            ordersBadgeLabel.textAlignment = .center
            ordersBadgeLabel.layer.cornerRadius = 7.5
            ordersBadgeLabel.clipsToBounds = true
            ordersBadgeLabel.isHidden = true
            container.addSubview(ordersBadgeLabel)
            ordersBadgeLabel.snp.makeConstraints { make in
                make.top.equalTo(button).offset(-4)
                make.leading.equalTo(button.snp.trailing).offset(-6)
                make.height.equalTo(15)
                make.width.greaterThanOrEqualTo(15)
            }
        }

        return container
    }

    private func refreshSelection() {
        for item in items {
            let isSelected = item.tab == selectedTab
            let imageName = isSelected ? item.selectedImage : item.unselectedImage
            tabButtons[item.tab]?.setImage(UIImage(named: imageName), for: .normal)
            tabTitleLabels[item.tab]?.textColor = isSelected ? AppDesign.primary : UIColor(hex: 0x7D8DA3)
            tabTitleLabels[item.tab]?.font = .systemFont(ofSize: 12, weight: isSelected ? .medium : .regular)
        }
    }

    @objc private func tabTapped(_ sender: UIButton) {
        guard sender.tag >= 0, sender.tag < items.count else { return }
        onTabSelected?(items[sender.tag].tab)
    }

    @objc private func scanTapped() {
        onScanTapped?()
    }
}