//
//  OfflineCollectionDailyViewController.swift
//  suixinkan
//

import SnapKit
import UIKit

/// 日清列表的分区。
enum OfflineDailyListSection: Hashable {
    case records
    case batches
    case empty
}

/// 日清列表的条目数据。
enum OfflineDailyListItem: Hashable {
    case record(OfflineCollectionRecord)
    case batch(OfflineSettlementBatch)
    case empty(isToday: Bool)
}

/// 线下收款日清页，展示单营业日汇总、明细与独立补缴流水。
final class OfflineCollectionDailyViewController: BaseViewController {
    private let viewModel: OfflineCollectionDailyViewModel

    private let headerStack = UIStackView()
    private let dateControl = UIButton(type: .system)
    private let summaryCard = UIView()
    private let summaryStatusLabel = UILabel()
    private let totalMetric = OfflineDailyMetricView(title: "线下收款总额")
    private let countMetric = OfflineDailyMetricView(title: "登记笔数")
    private let settledMetric = OfflineDailyMetricView(title: "已补缴")
    private let pendingMetric = OfflineDailyMetricView(title: "待补缴")
    private let overdueBanner = UILabel()
    private let tableView = UITableView(frame: .zero, style: .plain)
    private var dataSource: UITableViewDiffableDataSource<OfflineDailyListSection, OfflineDailyListItem>!
    private var currentSections: [OfflineDailyListSection] = []
    private let bottomContainer = UIView()
    private let settlementButton = UIButton(type: .system)
    private var isFeedbackPresented = false

    /// 使用指定营业日、收款上下文与 Mock 服务创建日清页。
    init(
        businessDate: String,
        context: OfflineCollectionContext = .current(),
        service: OfflineCollectionMockService = .shared
    ) {
        viewModel = OfflineCollectionDailyViewModel(
            businessDate: businessDate,
            context: context,
            service: service
        )
        super.init(nibName: nil, bundle: nil)
    }

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

    override func setupNavigationBar() {
        title = "线下收款日清"
        #if DEBUG
        navigationItem.rightBarButtonItem = UIBarButtonItem(
            title: "模拟失败",
            style: .plain,
            target: self,
            action: #selector(simulateFailureTapped)
        )
        #endif
    }

    override func setupUI() {
        view.backgroundColor = AppColor.pageBackground
        headerStack.axis = .vertical
        headerStack.spacing = AppSpacing.sm

        dateControl.contentHorizontalAlignment = .leading
        dateControl.showsMenuAsPrimaryAction = true
        var dateConfiguration = UIButton.Configuration.plain()
        dateConfiguration.image = UIImage(systemName: "calendar")
        dateConfiguration.imagePadding = AppSpacing.sm
        dateConfiguration.baseForegroundColor = AppColor.textPrimary
        dateConfiguration.background.backgroundColor = .white
        dateConfiguration.background.cornerRadius = AppRadius.lg
        dateConfiguration.contentInsets = NSDirectionalEdgeInsets(
            top: 12,
            leading: AppSpacing.md,
            bottom: 12,
            trailing: AppSpacing.md
        )
        dateControl.configuration = dateConfiguration
        dateControl.accessibilityIdentifier = "offlineCollection.businessDate"

        summaryCard.backgroundColor = .white
        summaryCard.layer.cornerRadius = AppRadius.lg
        summaryStatusLabel.font = .systemFont(ofSize: 13, weight: .semibold)
        summaryStatusLabel.textAlignment = .center
        summaryStatusLabel.textColor = AppColor.success
        summaryStatusLabel.backgroundColor = UIColor(hex: 0xECFDF3)
        summaryStatusLabel.layer.cornerRadius = 12
        summaryStatusLabel.clipsToBounds = true

        let firstMetricRow = UIStackView(arrangedSubviews: [totalMetric, countMetric])
        firstMetricRow.axis = .horizontal
        firstMetricRow.distribution = .fillEqually
        let secondMetricRow = UIStackView(arrangedSubviews: [settledMetric, pendingMetric])
        secondMetricRow.axis = .horizontal
        secondMetricRow.distribution = .fillEqually
        let metricStack = UIStackView(arrangedSubviews: [firstMetricRow, secondMetricRow])
        metricStack.axis = .vertical
        metricStack.spacing = AppSpacing.md
        summaryCard.addSubview(metricStack)
        summaryCard.addSubview(summaryStatusLabel)
        metricStack.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview().inset(AppSpacing.md)
            make.bottom.equalToSuperview().inset(AppSpacing.md)
        }
        summaryStatusLabel.snp.makeConstraints { make in
            make.top.trailing.equalToSuperview().inset(AppSpacing.md)
            make.height.equalTo(24)
        }

        overdueBanner.text = "该营业日存在逾期未补缴，请尽快完成补缴"
        overdueBanner.font = .systemFont(ofSize: 13, weight: .medium)
        overdueBanner.textColor = AppColor.danger
        overdueBanner.backgroundColor = UIColor(hex: 0xFFF1F0)
        overdueBanner.layer.cornerRadius = AppRadius.md
        overdueBanner.clipsToBounds = true
        overdueBanner.textAlignment = .center
        overdueBanner.numberOfLines = 0

        tableView.backgroundColor = .clear
        tableView.separatorStyle = .none
        tableView.rowHeight = UITableView.automaticDimension
        tableView.estimatedRowHeight = 92
        tableView.delegate = self
        tableView.register(OfflineCollectionRecordCell.self, forCellReuseIdentifier: OfflineCollectionRecordCell.reuseIdentifier)
        tableView.register(OfflineSettlementBatchCell.self, forCellReuseIdentifier: OfflineSettlementBatchCell.reuseIdentifier)
        tableView.register(OfflineCollectionEmptyCell.self, forCellReuseIdentifier: OfflineCollectionEmptyCell.reuseIdentifier)
        dataSource = makeDataSource()

        bottomContainer.backgroundColor = .white
        bottomContainer.layer.shadowColor = UIColor.black.cgColor
        bottomContainer.layer.shadowOpacity = 0.06
        bottomContainer.layer.shadowRadius = 8
        bottomContainer.layer.shadowOffset = CGSize(width: 0, height: -2)

        var settlementConfiguration = UIButton.Configuration.filled()
        settlementConfiguration.title = "补缴今日全部"
        settlementConfiguration.baseBackgroundColor = AppColor.primary
        settlementConfiguration.baseForegroundColor = .white
        settlementConfiguration.cornerStyle = .medium
        settlementConfiguration.titleTextAttributesTransformer = UIConfigurationTextAttributesTransformer { incoming in
            var outgoing = incoming
            outgoing.font = .systemFont(ofSize: 17, weight: .semibold)
            return outgoing
        }
        settlementButton.configuration = settlementConfiguration
        settlementButton.accessibilityIdentifier = "offlineCollection.settle"

        view.addSubview(headerStack)
        [dateControl, summaryCard, overdueBanner].forEach(headerStack.addArrangedSubview)
        view.addSubview(tableView)
        view.addSubview(bottomContainer)
        bottomContainer.addSubview(settlementButton)
    }

    override func setupConstraints() {
        headerStack.snp.makeConstraints { make in
            make.top.equalTo(view.safeAreaLayoutGuide).offset(AppSpacing.sm)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.screenHorizontalInset)
        }
        dateControl.snp.makeConstraints { make in
            make.height.equalTo(50)
        }
        summaryCard.snp.makeConstraints { make in
            make.height.equalTo(172)
        }
        overdueBanner.snp.makeConstraints { make in
            make.height.greaterThanOrEqualTo(48)
        }
        bottomContainer.snp.makeConstraints { make in
            make.leading.trailing.bottom.equalToSuperview()
        }
        settlementButton.snp.makeConstraints { make in
            make.top.equalToSuperview().inset(AppSpacing.md)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.screenHorizontalInset)
            make.height.equalTo(50)
            make.bottom.equalTo(view.safeAreaLayoutGuide).inset(AppSpacing.md)
        }
        tableView.snp.makeConstraints { make in
            make.top.equalTo(headerStack.snp.bottom).offset(AppSpacing.sm)
            make.leading.trailing.equalToSuperview()
            make.bottom.equalTo(bottomContainer.snp.top)
        }
    }

    override func bindActions() {
        settlementButton.addTarget(self, action: #selector(settlementTapped), for: .touchUpInside)
        viewModel.onStateChange = { [weak self] in
            Task { @MainActor in self?.applyViewModel() }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        applyViewModel()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        viewModel.load()
    }

    @MainActor
    private func applyViewModel() {
        let datePrefix = viewModel.isToday ? "今日 · " : "营业日 · "
        dateControl.configuration?.title = datePrefix + viewModel.businessDate
        dateControl.menu = makeDateMenu()

        totalMetric.setValue(OfflineCollectionMoney.display(viewModel.summary.totalAmountFen))
        countMetric.setValue("\(viewModel.summary.totalCount) 笔")
        settledMetric.setValue(OfflineCollectionMoney.display(viewModel.summary.settledAmountFen))
        pendingMetric.setValue(OfflineCollectionMoney.display(viewModel.summary.pendingAmountFen), highlighted: viewModel.summary.pendingAmountFen > 0)

        let isSettled = viewModel.summary.totalCount > 0 && viewModel.summary.pendingAmountFen == 0
        summaryStatusLabel.text = "  本日已结清  "
        summaryStatusLabel.isHidden = !isSettled
        overdueBanner.isHidden = !viewModel.summary.hasOverdue

        let isProcessing = viewModel.settlementState == .processing
        settlementButton.isEnabled = viewModel.canSettle
        var configuration = settlementButton.configuration
        configuration?.showsActivityIndicator = isProcessing
        if isProcessing {
            configuration?.title = "补缴中"
        } else if isSettled {
            configuration?.title = "本日已全部补缴"
        } else if viewModel.summary.pendingAmountFen == 0 {
            configuration?.title = "当日暂无待补缴"
        } else {
            let prefix = viewModel.isToday ? "补缴今日全部" : "补缴本日全部"
            configuration?.title = "\(prefix) \(OfflineCollectionMoney.display(viewModel.summary.pendingAmountFen))"
        }
        settlementButton.configuration = configuration
        settlementButton.alpha = settlementButton.isEnabled || isProcessing ? 1 : 0.5

        applySnapshot()
        presentSettlementFeedbackIfNeeded()
    }

    @MainActor
    private func applySnapshot() {
        var snapshot = NSDiffableDataSourceSnapshot<OfflineDailyListSection, OfflineDailyListItem>()
        currentSections = []
        if viewModel.records.isEmpty {
            currentSections.append(.empty)
            snapshot.appendSections([.empty])
            snapshot.appendItems([.empty(isToday: viewModel.isToday)], toSection: .empty)
        } else {
            currentSections.append(.records)
            snapshot.appendSections([.records])
            snapshot.appendItems(viewModel.records.map(OfflineDailyListItem.record), toSection: .records)
        }
        if !viewModel.batches.isEmpty {
            currentSections.append(.batches)
            snapshot.appendSections([.batches])
            snapshot.appendItems(viewModel.batches.map(OfflineDailyListItem.batch), toSection: .batches)
        }
        dataSource.apply(snapshot, animatingDifferences: view.window != nil)
    }

    private func makeDataSource() -> UITableViewDiffableDataSource<OfflineDailyListSection, OfflineDailyListItem> {
        UITableViewDiffableDataSource(tableView: tableView) { [weak self] tableView, indexPath, item in
            switch item {
            case let .record(record):
                guard let cell = tableView.dequeueReusableCell(
                    withIdentifier: OfflineCollectionRecordCell.reuseIdentifier,
                    for: indexPath
                ) as? OfflineCollectionRecordCell else { return UITableViewCell() }
                cell.apply(record: record)
                return cell
            case let .batch(batch):
                guard let cell = tableView.dequeueReusableCell(
                    withIdentifier: OfflineSettlementBatchCell.reuseIdentifier,
                    for: indexPath
                ) as? OfflineSettlementBatchCell else { return UITableViewCell() }
                cell.apply(batch: batch)
                return cell
            case let .empty(isToday):
                guard let cell = tableView.dequeueReusableCell(
                    withIdentifier: OfflineCollectionEmptyCell.reuseIdentifier,
                    for: indexPath
                ) as? OfflineCollectionEmptyCell else { return UITableViewCell() }
                cell.apply(isToday: isToday)
                cell.onRegister = { [weak self] in self?.openRegistration() }
                return cell
            }
        }
    }

    private func makeDateMenu() -> UIMenu {
        let actions = viewModel.availableBusinessDates.map { [weak self] date in
            let isCurrent = date == self?.viewModel.businessDate
            let title = date == self?.viewModel.service.todayBusinessDate ? "今日 \(date)" : date
            return UIAction(title: title, state: isCurrent ? .on : .off) { [weak self] _ in
                self?.viewModel.selectBusinessDate(date)
            }
        }
        return UIMenu(title: "选择营业日", children: actions)
    }

    @MainActor
    private func presentSettlementFeedbackIfNeeded() {
        guard !isFeedbackPresented else { return }
        switch viewModel.settlementState {
        case .idle, .processing:
            return
        case let .success(batch):
            isFeedbackPresented = true
            let message = """
            已补缴 \(OfflineCollectionMoney.display(batch.amountFen))
            共结清 \(batch.recordCount) 笔线下收款
            补缴流水号：\(batch.id)
            """
            let alert = UIAlertController(title: "补缴成功", message: message, preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "完成", style: .default) { [weak self] _ in
                self?.isFeedbackPresented = false
                self?.viewModel.clearSettlementFeedback()
            })
            present(alert, animated: true)
        case let .failed(message):
            isFeedbackPresented = true
            let alert = UIAlertController(title: "补缴失败", message: message, preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "暂不处理", style: .cancel) { [weak self] _ in
                self?.isFeedbackPresented = false
                self?.viewModel.cancelPreparedSettlement()
                self?.viewModel.clearSettlementFeedback()
            })
            alert.addAction(UIAlertAction(title: "重新补缴", style: .default) { [weak self] _ in
                guard let self else { return }
                self.isFeedbackPresented = false
                self.viewModel.clearSettlementFeedback()
                Task { await self.viewModel.confirmSettlement() }
            })
            present(alert, animated: true)
        }
    }

    private func openRegistration() {
        guard viewModel.isToday else { return }
        navigationController?.pushViewController(
            OfflineCollectionRegistrationViewController(
                context: viewModel.context,
                service: viewModel.service
            ),
            animated: true
        )
    }

    @objc private func settlementTapped() {
        do {
            let request = try viewModel.prepareSettlement()
            let message = """
            营业日：\(request.businessDate)
            待补缴记录：\(request.recordIds.count) 笔
            本次补缴金额：\(OfflineCollectionMoney.display(request.amountFen))

            补缴成功后，本批次记录将统一变为“已补缴”。
            """
            let alert = UIAlertController(title: "确认补缴", message: message, preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "取消", style: .cancel) { [weak self] _ in
                self?.viewModel.cancelPreparedSettlement()
            })
            alert.addAction(UIAlertAction(
                title: "确认补缴 \(OfflineCollectionMoney.display(request.amountFen))",
                style: .default
            ) { [weak self] _ in
                guard let self else { return }
                Task { await self.viewModel.confirmSettlement() }
            })
            present(alert, animated: true)
        } catch {
            showToast(error.localizedDescription)
            viewModel.load()
        }
    }

    @objc private func simulateFailureTapped() {
        viewModel.simulateNextSettlementFailure()
        showToast("下一次补缴将模拟失败，可验收失败后重试")
    }
}

extension OfflineCollectionDailyViewController: UITableViewDelegate {
    func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
        currentSections[safe: section] == .empty ? 0 : 40
    }

    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        guard let listSection = currentSections[safe: section], listSection != .empty else { return nil }
        let container = UIView()
        container.backgroundColor = AppColor.pageBackground
        let label = UILabel()
        label.text = listSection == .records ? "线下收款明细" : "线下收款补缴流水"
        label.font = .systemFont(ofSize: 15, weight: .semibold)
        label.textColor = AppColor.textPrimary
        container.addSubview(label)
        label.snp.makeConstraints { make in
            make.leading.trailing.equalToSuperview().inset(AppSpacing.screenHorizontalInset)
            make.bottom.equalToSuperview().inset(AppSpacing.xs)
        }
        return container
    }
}

/// 日清汇总卡片中的单项指标视图。
final class OfflineDailyMetricView: UIView {
    private let titleLabel = UILabel()
    private let valueLabel = UILabel()

    /// 使用指标名称创建汇总视图。
    init(title: String) {
        super.init(frame: .zero)
        titleLabel.text = title
        setupUI()
    }

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

    /// 更新指标值及是否使用警示色强调。
    func setValue(_ value: String, highlighted: Bool = false) {
        valueLabel.text = value
        valueLabel.textColor = highlighted ? UIColor(hex: 0xD97706) : AppColor.textPrimary
    }

    private func setupUI() {
        titleLabel.font = .systemFont(ofSize: 12)
        titleLabel.textColor = AppColor.textTertiary
        valueLabel.font = .systemFont(ofSize: 19, weight: .bold)
        valueLabel.textColor = AppColor.textPrimary
        valueLabel.adjustsFontSizeToFitWidth = true
        valueLabel.minimumScaleFactor = 0.75
        let stack = UIStackView(arrangedSubviews: [titleLabel, valueLabel])
        stack.axis = .vertical
        stack.spacing = 4
        addSubview(stack)
        stack.snp.makeConstraints { make in
            make.edges.equalToSuperview().inset(UIEdgeInsets(top: 2, left: 4, bottom: 2, right: 4))
        }
    }
}

/// 线下收款明细单元格。
final class OfflineCollectionRecordCell: UITableViewCell {
    static let reuseIdentifier = "OfflineCollectionRecordCell"

    private let cardView = UIView()
    private let timeLabel = UILabel()
    private let methodLabel = UILabel()
    private let identifierLabel = UILabel()
    private let amountLabel = UILabel()
    private let statusLabel = UILabel()

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        setupUI()
    }

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

    /// 用线下收款记录刷新单元格。
    func apply(record: OfflineCollectionRecord) {
        timeLabel.text = OfflineCollectionDate.timeText(record.registeredAt)
        methodLabel.text = record.paymentMethod.displayName
        identifierLabel.text = record.id
        amountLabel.text = OfflineCollectionMoney.display(record.amountFen)
        statusLabel.text = "  \(record.status.displayName)  "

        let color: UIColor
        let background: UIColor
        switch record.status {
        case .pending:
            color = UIColor(hex: 0xD97706)
            background = UIColor(hex: 0xFFF7E6)
        case .settled:
            color = AppColor.success
            background = UIColor(hex: 0xECFDF3)
        case .overdue:
            color = AppColor.danger
            background = UIColor(hex: 0xFFF1F0)
        }
        statusLabel.textColor = color
        statusLabel.backgroundColor = background
    }

    private func setupUI() {
        selectionStyle = .none
        backgroundColor = .clear
        contentView.backgroundColor = .clear
        cardView.backgroundColor = .white
        cardView.layer.cornerRadius = AppRadius.lg

        timeLabel.font = .systemFont(ofSize: 15, weight: .semibold)
        timeLabel.textColor = AppColor.textPrimary
        methodLabel.font = .systemFont(ofSize: 14)
        methodLabel.textColor = AppColor.textSecondary
        identifierLabel.font = .systemFont(ofSize: 11)
        identifierLabel.textColor = AppColor.textTertiary
        amountLabel.font = .systemFont(ofSize: 19, weight: .bold)
        amountLabel.textColor = AppColor.textPrimary
        amountLabel.textAlignment = .right
        statusLabel.font = .systemFont(ofSize: 12, weight: .semibold)
        statusLabel.textAlignment = .center
        statusLabel.layer.cornerRadius = 11
        statusLabel.clipsToBounds = true

        let leftStack = UIStackView(arrangedSubviews: [timeLabel, methodLabel, identifierLabel])
        leftStack.axis = .vertical
        leftStack.spacing = 4
        let rightStack = UIStackView(arrangedSubviews: [amountLabel, statusLabel])
        rightStack.axis = .vertical
        rightStack.alignment = .trailing
        rightStack.spacing = 8
        cardView.addSubview(leftStack)
        cardView.addSubview(rightStack)
        contentView.addSubview(cardView)
        cardView.snp.makeConstraints { make in
            make.top.bottom.equalToSuperview().inset(5)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.screenHorizontalInset)
        }
        leftStack.snp.makeConstraints { make in
            make.leading.top.bottom.equalToSuperview().inset(AppSpacing.md)
            make.trailing.lessThanOrEqualTo(rightStack.snp.leading).offset(-AppSpacing.sm)
        }
        rightStack.snp.makeConstraints { make in
            make.trailing.equalToSuperview().inset(AppSpacing.md)
            make.centerY.equalToSuperview()
        }
        statusLabel.snp.makeConstraints { make in
            make.height.equalTo(22)
        }
    }
}

/// 线下收款补缴流水单元格。
final class OfflineSettlementBatchCell: UITableViewCell {
    static let reuseIdentifier = "OfflineSettlementBatchCell"

    private let cardView = UIView()
    private let identifierLabel = UILabel()
    private let amountLabel = UILabel()
    private let detailLabel = UILabel()

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        setupUI()
    }

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

    /// 用成功补缴流水刷新单元格。
    func apply(batch: OfflineSettlementBatch) {
        identifierLabel.text = batch.id
        amountLabel.text = OfflineCollectionMoney.display(batch.amountFen)
        detailLabel.text = "\(OfflineCollectionDate.dateTimeText(batch.paidAt)) · \(batch.payerName) · 关联 \(batch.recordCount) 笔"
    }

    private func setupUI() {
        selectionStyle = .none
        backgroundColor = .clear
        contentView.backgroundColor = .clear
        cardView.backgroundColor = UIColor(hex: 0xF4FBF7)
        cardView.layer.cornerRadius = AppRadius.lg
        cardView.layer.borderColor = UIColor(hex: 0xCDEED8).cgColor
        cardView.layer.borderWidth = 1

        identifierLabel.font = .systemFont(ofSize: 13, weight: .semibold)
        identifierLabel.textColor = AppColor.success
        amountLabel.font = .systemFont(ofSize: 18, weight: .bold)
        amountLabel.textColor = AppColor.textPrimary
        amountLabel.textAlignment = .right
        detailLabel.font = .systemFont(ofSize: 12)
        detailLabel.textColor = AppColor.textSecondary
        detailLabel.numberOfLines = 0

        let topRow = UIStackView(arrangedSubviews: [identifierLabel, amountLabel])
        topRow.axis = .horizontal
        topRow.distribution = .fillEqually
        let stack = UIStackView(arrangedSubviews: [topRow, detailLabel])
        stack.axis = .vertical
        stack.spacing = AppSpacing.sm
        cardView.addSubview(stack)
        contentView.addSubview(cardView)
        cardView.snp.makeConstraints { make in
            make.top.bottom.equalToSuperview().inset(5)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.screenHorizontalInset)
        }
        stack.snp.makeConstraints { make in
            make.edges.equalToSuperview().inset(AppSpacing.md)
        }
    }
}

/// 日清页在指定营业日无记录时展示的空状态单元格。
final class OfflineCollectionEmptyCell: UITableViewCell {
    static let reuseIdentifier = "OfflineCollectionEmptyCell"
    var onRegister: (() -> Void)?

    private let titleLabel = UILabel()
    private let detailLabel = UILabel()
    private let registerButton = UIButton(type: .system)

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        setupUI()
    }

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

    /// 更新空状态，仅今日允许前往登记。
    func apply(isToday: Bool) {
        registerButton.isHidden = !isToday
    }

    override func prepareForReuse() {
        super.prepareForReuse()
        onRegister = nil
    }

    private func setupUI() {
        selectionStyle = .none
        backgroundColor = .clear
        contentView.backgroundColor = .clear
        titleLabel.text = "当日暂无线下收款记录"
        titleLabel.font = .systemFont(ofSize: 16, weight: .semibold)
        titleLabel.textColor = AppColor.textPrimary
        titleLabel.textAlignment = .center
        detailLabel.text = "完成线下收款后，请及时登记"
        detailLabel.font = .systemFont(ofSize: 13)
        detailLabel.textColor = AppColor.textSecondary
        detailLabel.textAlignment = .center
        registerButton.setTitle("去登记", for: .normal)
        registerButton.titleLabel?.font = .systemFont(ofSize: 14, weight: .semibold)
        registerButton.addTarget(self, action: #selector(registerTapped), for: .touchUpInside)

        let stack = UIStackView(arrangedSubviews: [titleLabel, detailLabel, registerButton])
        stack.axis = .vertical
        stack.spacing = AppSpacing.sm
        stack.alignment = .center
        contentView.addSubview(stack)
        stack.snp.makeConstraints { make in
            make.top.equalToSuperview().inset(48)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.screenHorizontalInset)
            make.bottom.equalToSuperview().inset(32)
        }
    }

    @objc private func registerTapped() {
        onRegister?()
    }
}

private extension Collection {
    /// 安全按下标读取元素，超出范围时返回 nil。
    subscript(safe index: Index) -> Element? {
        indices.contains(index) ? self[index] : nil
    }
}