import SnapKit
import UIKit

/// 线下收款登记页，按 9.7 视觉稿展示金额、支付方式和登记说明。
@MainActor
final class OfflineCollectionRegistrationViewController: BaseViewController {
    private let viewModel: OfflineCollectionRegistrationViewModel

    private let scrollView = UIScrollView()
    private let contentStack = UIStackView()
    private let amountCard = UIView()
    private let amountField = UITextField()
    private let methodCard = UIView()
    private let methodStack = UIStackView()
    private var methodButtons: [OfflineCollectionPaymentMethod: OfflinePaymentMethodButton] = [:]
    private let explanationCard = UIView()
    private let contextLabel = UILabel()
    private let bottomContainer = UIView()
    private let submitButton = OfflineCollectionGradientButton(
        startColor: UIColor(hex: 0x087BFF),
        endColor: UIColor(hex: 0x0067F4)
    )
    private var hasFocusedAmountField = false
    private var isShowingGlobalLoading = false

    init(
        context: OfflineCollectionContext = .current(),
        api: any OfflineCollectionServing = NetworkServices.shared.offlineCollectionAPI
    ) {
        viewModel = OfflineCollectionRegistrationViewModel(context: context, api: api)
        super.init(nibName: nil, bundle: nil)
    }

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

    override func setupNavigationBar() {
        title = "线下收款登记"
    }

    override func setupUI() {
        view.backgroundColor = UIColor(hex: 0xF7FAFF)
        configureScrollContent()
        configureAmountCard()
        configureMethodCard()
        configureExplanationCard()
        configureContextLabel()
        configureBottomBar()

        view.addSubview(scrollView)
        scrollView.addSubview(contentStack)
        [amountCard, methodCard, explanationCard, contextLabel].forEach(contentStack.addArrangedSubview)
        view.addSubview(bottomContainer)
        bottomContainer.addSubview(submitButton)
    }

    override func setupConstraints() {
        bottomContainer.snp.makeConstraints { make in
            make.leading.trailing.equalToSuperview()
            make.bottom.equalTo(view.keyboardLayoutGuide.snp.top)
        }
        submitButton.snp.makeConstraints { make in
            make.top.equalToSuperview().offset(16)
            make.leading.trailing.equalToSuperview().inset(18)
            make.height.equalTo(56)
            make.bottom.equalToSuperview().inset(16)
        }
        scrollView.snp.makeConstraints { make in
            make.top.leading.trailing.equalTo(view.safeAreaLayoutGuide)
            make.bottom.equalTo(bottomContainer.snp.top)
        }
        contentStack.snp.makeConstraints { make in
            make.edges.equalTo(scrollView.contentLayoutGuide).inset(UIEdgeInsets(top: 16, left: 16, bottom: 24, right: 16))
            make.width.equalTo(scrollView.frameLayoutGuide).offset(-32)
        }
    }

    override func bindActions() {
        amountField.addTarget(self, action: #selector(amountChanged), for: .editingChanged)
        submitButton.addTarget(self, action: #selector(submitTapped), for: .touchUpInside)
        viewModel.onStateChange = { [weak self] in Task { @MainActor in self?.applyState() } }
        viewModel.onShowMessage = { [weak self] message in Task { @MainActor in self?.showToast(message) } }
        viewModel.onRegistrationSuccess = { [weak self] receipt in Task { @MainActor in self?.showSuccess(receipt) } }
    }

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

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        guard !hasFocusedAmountField else { return }
        hasFocusedAmountField = true
        amountField.becomeFirstResponder()
        moveAmountCursorToEnd()
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        setGlobalLoadingVisible(false)
    }

    private func configureScrollContent() {
        scrollView.keyboardDismissMode = .interactive
        scrollView.alwaysBounceVertical = true
        scrollView.showsVerticalScrollIndicator = false
        contentStack.axis = .vertical
        contentStack.spacing = 16
    }

    private func configureAmountCard() {
        configureCard(amountCard)

        let titleLabel = makeTitleLabel("收款金额")
        let helperLabel = UILabel()
        helperLabel.text = "单笔金额 0.01～99,999.99 元"
        helperLabel.font = .systemFont(ofSize: 13)
        helperLabel.textColor = UIColor(hex: 0x7B8494)
        helperLabel.adjustsFontSizeToFitWidth = true
        helperLabel.minimumScaleFactor = 0.82

        let currencyLabel = UILabel()
        currencyLabel.text = "¥"
        currencyLabel.font = .systemFont(ofSize: 34, weight: .semibold)
        currencyLabel.textColor = UIColor(hex: 0x081739)

        amountField.placeholder = "0.00"
        amountField.font = .systemFont(ofSize: 42, weight: .bold)
        amountField.textColor = UIColor(hex: 0x081739)
        amountField.tintColor = AppColor.primary
        amountField.textAlignment = .right
        amountField.keyboardType = .decimalPad
        amountField.adjustsFontSizeToFitWidth = true
        amountField.minimumFontSize = 30
        amountField.delegate = self
        amountField.accessibilityLabel = "收款金额"
        amountField.accessibilityIdentifier = "offlineCollection.amount"

        let amountInputStack = UIStackView(arrangedSubviews: [currencyLabel, amountField])
        amountInputStack.axis = .horizontal
        amountInputStack.alignment = .center
        amountInputStack.spacing = 6

        let amountRow = UIView()
        amountRow.addSubview(helperLabel)
        amountRow.addSubview(amountInputStack)
        helperLabel.snp.makeConstraints { make in
            make.leading.centerY.equalToSuperview()
            make.trailing.lessThanOrEqualTo(amountInputStack.snp.leading).offset(-8)
        }
        amountInputStack.snp.makeConstraints { make in
            make.trailing.centerY.equalToSuperview()
            make.width.lessThanOrEqualTo(205)
        }
        amountField.snp.makeConstraints { make in
            make.height.equalTo(56)
            make.width.greaterThanOrEqualTo(98)
        }

        let underline = UIView()
        underline.backgroundColor = UIColor(hex: 0x1684FC)
        underline.snp.makeConstraints { make in make.height.equalTo(1) }

        let quickAmounts: [(String, Int)] = [("¥50", 5_000), ("¥100", 10_000), ("¥200", 20_000), ("¥500", 50_000)]
        let quickStack = UIStackView()
        quickStack.axis = .horizontal
        quickStack.distribution = .fillEqually
        quickStack.spacing = 12
        quickAmounts.forEach { title, fen in
            let button = UIButton(type: .system)
            button.tag = fen
            button.setTitle(title, for: .normal)
            button.setTitleColor(UIColor(hex: 0x1677FF), for: .normal)
            button.titleLabel?.font = .systemFont(ofSize: 15, weight: .medium)
            button.backgroundColor = UIColor(hex: 0xF5F8FD)
            button.layer.cornerRadius = 8
            button.layer.borderWidth = 1
            button.layer.borderColor = UIColor(hex: 0xE3E8F0).cgColor
            button.addTarget(self, action: #selector(quickAmountTapped(_:)), for: .touchUpInside)
            button.snp.makeConstraints { make in make.height.equalTo(36) }
            quickStack.addArrangedSubview(button)
        }

        let stack = UIStackView(arrangedSubviews: [titleLabel, amountRow, underline, quickStack])
        stack.axis = .vertical
        stack.setCustomSpacing(8, after: titleLabel)
        stack.setCustomSpacing(2, after: amountRow)
        stack.setCustomSpacing(22, after: underline)
        amountCard.addSubview(stack)
        stack.snp.makeConstraints { make in make.edges.equalToSuperview().inset(20) }
        amountRow.snp.makeConstraints { make in make.height.equalTo(56) }
    }

    private func configureMethodCard() {
        configureCard(methodCard)
        let titleLabel = makeTitleLabel("收款方式")
        methodStack.axis = .horizontal
        methodStack.distribution = .fillEqually
        methodStack.spacing = 12
        for method in OfflineCollectionPaymentMethod.allCases {
            let button = OfflinePaymentMethodButton(method: method)
            button.addTarget(self, action: #selector(methodTapped(_:)), for: .touchUpInside)
            methodButtons[method] = button
            methodStack.addArrangedSubview(button)
        }
        let stack = UIStackView(arrangedSubviews: [titleLabel, methodStack])
        stack.axis = .vertical
        stack.spacing = 20
        methodCard.addSubview(stack)
        stack.snp.makeConstraints { make in make.edges.equalToSuperview().inset(20) }
        methodStack.snp.makeConstraints { make in make.height.equalTo(120) }
    }

    private func configureExplanationCard() {
        configureCard(explanationCard)
        let iconView = UIImageView(image: UIImage(named: "offline_security_shield"))
        iconView.contentMode = .scaleAspectFit
        iconView.accessibilityLabel = "安全说明"

        let label = UILabel()
        label.text = "登记后计入今日待补缴，不生成订单"
        label.font = .systemFont(ofSize: 15)
        label.textColor = UIColor(hex: 0x22304D)
        label.numberOfLines = 0

        explanationCard.addSubview(iconView)
        explanationCard.addSubview(label)
        iconView.snp.makeConstraints { make in
            make.leading.equalToSuperview().offset(20)
            make.centerY.equalToSuperview()
            make.width.height.equalTo(44)
        }
        label.snp.makeConstraints { make in
            make.leading.equalTo(iconView.snp.trailing).offset(14)
            make.trailing.equalToSuperview().inset(18)
            make.top.bottom.equalToSuperview().inset(20)
        }
        explanationCard.snp.makeConstraints { make in make.height.greaterThanOrEqualTo(72) }
    }

    private func configureContextLabel() {
        contextLabel.text = "当前：\(viewModel.context.collectorName) · \(viewModel.context.storeName) · \(viewModel.context.scenicName)"
        contextLabel.font = .systemFont(ofSize: 13)
        contextLabel.textColor = UIColor(hex: 0x7B8494)
        contextLabel.numberOfLines = 0
        contextLabel.textAlignment = .center
        contextLabel.snp.makeConstraints { make in make.height.greaterThanOrEqualTo(44) }
    }

    private func configureBottomBar() {
        bottomContainer.backgroundColor = .white
        bottomContainer.layer.shadowColor = UIColor(hex: 0x8090A8).cgColor
        bottomContainer.layer.shadowOpacity = 0.12
        bottomContainer.layer.shadowRadius = 12
        bottomContainer.layer.shadowOffset = CGSize(width: 0, height: -3)
        submitButton.setTitle("确认登记", for: .normal)
        submitButton.setTitleColor(.white, for: .normal)
        submitButton.titleLabel?.font = .systemFont(ofSize: 18, weight: .semibold)
        submitButton.layer.cornerRadius = 10
        submitButton.clipsToBounds = true
        submitButton.accessibilityIdentifier = "offlineCollection.submit"
    }

    @MainActor private func applyState() {
        setGlobalLoadingVisible(viewModel.isSubmitting)
        if amountField.text != viewModel.amountText {
            amountField.text = viewModel.amountText
            moveAmountCursorToEnd()
        }
        methodButtons.forEach { method, button in button.setSelected(method == viewModel.paymentMethod) }
        submitButton.isEnabled = viewModel.canSubmit && !viewModel.isSubmitting
        submitButton.alpha = viewModel.canSubmit || viewModel.isSubmitting ? 1 : 0.45
    }

    @MainActor private func showSuccess(_ receipt: OfflineCollectionRegistrationReceipt) {
        setGlobalLoadingVisible(false)
        amountField.resignFirstResponder()
        let totalText = receipt.summary.map { OfflineCollectionMoney.display($0.totalAmountFen) } ?? "—"
        let pendingText = receipt.summary.map { OfflineCollectionMoney.display($0.pendingAmountFen) } ?? "—"
        let message = """
        本次登记 \(OfflineCollectionMoney.display(receipt.record.amountFen))
        今日累计线下收款 \(totalText)
        今日待补缴 \(pendingText)
        """
        let alert = UIAlertController(title: "登记成功", message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "继续登记", style: .default) { [weak self] _ in
            self?.viewModel.startAnotherRegistration()
            self?.amountField.becomeFirstResponder()
            self?.moveAmountCursorToEnd()
        })
        alert.addAction(UIAlertAction(title: "查看今日明细", style: .default) { [weak self] _ in
            guard let self else { return }
            self.navigationController?.pushViewController(
                OfflineCollectionDailyViewController(
                    businessDate: receipt.businessDate,
                    context: self.viewModel.context,
                    api: self.viewModel.api
                ),
                animated: true
            )
        })
        present(alert, animated: true)
    }

    private func setGlobalLoadingVisible(_ visible: Bool) {
        guard visible != isShowingGlobalLoading else { return }
        isShowingGlobalLoading = visible
        visible ? showLoading() : hideLoading()
    }

    private func makeTitleLabel(_ text: String) -> UILabel {
        let label = UILabel()
        label.text = text
        label.font = .systemFont(ofSize: 17, weight: .semibold)
        label.textColor = UIColor(hex: 0x081739)
        return label
    }

    private func configureCard(_ card: UIView) {
        card.backgroundColor = .white
        card.layer.cornerRadius = 12
        card.layer.shadowColor = UIColor(hex: 0x8FA0B8).cgColor
        card.layer.shadowOpacity = 0.12
        card.layer.shadowRadius = 10
        card.layer.shadowOffset = CGSize(width: 0, height: 4)
    }

    private func moveAmountCursorToEnd() {
        guard amountField.isFirstResponder else { return }
        let end = amountField.endOfDocument
        amountField.selectedTextRange = amountField.textRange(from: end, to: end)
    }

    @objc private func amountChanged() {
        viewModel.updateAmount(amountField.text ?? "")
        moveAmountCursorToEnd()
    }

    @objc private func quickAmountTapped(_ sender: UIButton) {
        viewModel.updateAmount(OfflineCollectionMoney.apiAmount(sender.tag))
        amountField.becomeFirstResponder()
        moveAmountCursorToEnd()
    }

    @objc private func methodTapped(_ sender: OfflinePaymentMethodButton) {
        viewModel.selectPaymentMethod(sender.method)
    }

    @objc private func submitTapped() {
        Task { await viewModel.submit() }
    }
}

extension OfflineCollectionRegistrationViewController: UITextFieldDelegate {
    func textField(
        _ textField: UITextField,
        shouldChangeCharactersIn range: NSRange,
        replacementString string: String
    ) -> Bool {
        guard let current = textField.text, let swiftRange = Range(range, in: current) else { return false }
        return OfflineCollectionMoney.acceptsEditingText(current.replacingCharacters(in: swiftRange, with: string))
    }
}

/// 登记页的收款方式单选卡，展示生成的品牌图标和右上角选中标记。
@MainActor
final class OfflinePaymentMethodButton: UIControl {
    let method: OfflineCollectionPaymentMethod

    private let iconView = UIImageView()
    private let titleLabel = UILabel()
    private let checkmarkView = UIImageView(image: UIImage(systemName: "checkmark"))

    init(method: OfflineCollectionPaymentMethod) {
        self.method = method
        super.init(frame: .zero)
        setupUI()
    }

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

    func setSelected(_ selected: Bool) {
        isSelected = selected
        backgroundColor = selected ? UIColor(hex: 0xF1F7FF) : .white
        layer.borderColor = (selected ? UIColor(hex: 0x1684FC) : UIColor(hex: 0xE2E7EF)).cgColor
        layer.borderWidth = selected ? 1.5 : 1
        checkmarkView.isHidden = !selected
        titleLabel.textColor = UIColor(hex: 0x081739)
        accessibilityTraits = selected ? [.button, .selected] : .button
    }

    private func setupUI() {
        layer.cornerRadius = 10
        clipsToBounds = false
        accessibilityLabel = method.displayName
        iconView.image = UIImage(named: method.assetName)?.withRenderingMode(.alwaysOriginal)
        iconView.contentMode = .scaleAspectFit
        titleLabel.text = method.displayName
        titleLabel.font = .systemFont(ofSize: 16, weight: .semibold)
        titleLabel.textAlignment = .center
        checkmarkView.tintColor = .white
        checkmarkView.backgroundColor = UIColor(hex: 0x1684FC)
        checkmarkView.layer.cornerRadius = 11
        checkmarkView.contentMode = .center
        checkmarkView.isHidden = true

        let stack = UIStackView(arrangedSubviews: [iconView, titleLabel])
        stack.axis = .vertical
        stack.alignment = .center
        stack.spacing = 12
        stack.isUserInteractionEnabled = false
        addSubview(stack)
        addSubview(checkmarkView)
        stack.snp.makeConstraints { make in make.center.equalToSuperview() }
        iconView.snp.makeConstraints { make in make.width.height.equalTo(46) }
        checkmarkView.snp.makeConstraints { make in
            make.width.height.equalTo(22)
            make.top.trailing.equalToSuperview().inset(-2)
        }
        setSelected(false)
    }
}

/// 线下收款页面共用的双端色渐变按钮。
@MainActor
final class OfflineCollectionGradientButton: UIButton {
    private let gradientLayer = CAGradientLayer()

    init(startColor: UIColor, endColor: UIColor) {
        super.init(frame: .zero)
        gradientLayer.colors = [startColor.cgColor, endColor.cgColor]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0.5)
        gradientLayer.endPoint = CGPoint(x: 1, y: 0.5)
        layer.insertSublayer(gradientLayer, at: 0)
    }

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

    override func layoutSubviews() {
        super.layoutSubviews()
        gradientLayer.frame = bounds
        gradientLayer.cornerRadius = layer.cornerRadius
    }

    override var isEnabled: Bool {
        didSet { gradientLayer.opacity = isEnabled ? 1 : 0.45 }
    }
}