//
//  LoginViewController.swift
//  suixinkan
//

import SnapKit
import UIKit

@MainActor
/// 登录页，展示手机号/密码表单、协议勾选和多账号选择入口。
final class LoginViewController: UIViewController {

    private let services: AppServices
    private let viewModel = LoginViewModel()

    private let scrollView = UIScrollView()
    private let contentView = UIView()
    private let backgroundImageView = UIImageView(image: UIImage(named: "LoginBackground"))
    private let titleLabel = UILabel()
    private let cardView = UIView()
    private let usernameField = LoginInputField(iconName: "person", placeholder: "请输入手机号", isSecure: false)
    private let passwordField = LoginInputField(iconName: "lock", placeholder: "请输入密码", isSecure: true)
    private let privacyButton = UIButton(type: .custom)
    private let privacyLabel = UILabel()
    private let userAgreementButton = UIButton(type: .system)
    private let privacyPolicyButton = UIButton(type: .system)
    private let loginButton = UIButton(type: .system)

    /// 初始化实例。
    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")
    }

    /// 视图加载完成后的 UI 初始化与数据绑定。
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor(hex: 0x0B1220)
        configureViews()
        bindViewModel()
        viewModel.applyPreferences(services.authSessionCoordinator.loginPreferences())
    }

    /// 配置Views展示内容。
    private func configureViews() {
        backgroundImageView.contentMode = .scaleAspectFill
        backgroundImageView.clipsToBounds = true

        titleLabel.text = "欢迎使用\n随心瞰商家版"
        titleLabel.font = .systemFont(ofSize: AppMetrics.FontSize.largeTitle, weight: .semibold)
        titleLabel.textColor = .white
        titleLabel.numberOfLines = 0

        cardView.backgroundColor = .white
        cardView.layer.cornerRadius = AppMetrics.CornerRadius.card
        cardView.layer.shadowColor = UIColor.black.cgColor
        cardView.layer.shadowOpacity = 0.12
        cardView.layer.shadowRadius = 18
        cardView.layer.shadowOffset = CGSize(width: 0, height: 8)

        usernameField.textField.keyboardType = .phonePad
        usernameField.textField.textContentType = .telephoneNumber
        usernameField.textField.autocorrectionType = .no
        usernameField.textField.autocapitalizationType = .none
        usernameField.textField.returnKeyType = .next
        usernameField.textField.accessibilityIdentifier = "login.username"
        usernameField.textField.delegate = self
        usernameField.textField.addTarget(self, action: #selector(usernameChanged), for: .editingChanged)

        passwordField.textField.autocorrectionType = .no
        passwordField.textField.autocapitalizationType = .none
        passwordField.textField.returnKeyType = .go
        passwordField.textField.accessibilityIdentifier = "login.password"
        passwordField.textField.delegate = self
        passwordField.textField.addTarget(self, action: #selector(passwordChanged), for: .editingChanged)
        passwordField.onToggleVisibility = { [weak self] in
            self?.viewModel.showsPassword.toggle()
        }

        privacyButton.accessibilityIdentifier = "login.privacy"
        privacyButton.addTarget(self, action: #selector(togglePrivacy), for: .touchUpInside)

        configureAgreementText()

        loginButton.setTitle("登录", for: .normal)
        loginButton.titleLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.body, weight: .medium)
        loginButton.layer.cornerRadius = AppMetrics.CornerRadius.button
        loginButton.accessibilityIdentifier = "login.submit"
        loginButton.addTarget(self, action: #selector(loginTapped), for: .touchUpInside)

        view.addSubview(backgroundImageView)
        view.addSubview(scrollView)
        scrollView.addSubview(contentView)
        contentView.addSubview(titleLabel)
        contentView.addSubview(cardView)

        cardView.addSubview(usernameField)
        cardView.addSubview(passwordField)
        cardView.addSubview(privacyButton)
        cardView.addSubview(privacyLabel)
        cardView.addSubview(loginButton)

        backgroundImageView.snp.makeConstraints { make in
            make.edges.equalToSuperview()
        }

        scrollView.snp.makeConstraints { make in
            make.edges.equalToSuperview()
        }

        contentView.snp.makeConstraints { make in
            make.edges.equalTo(scrollView.contentLayoutGuide)
            make.width.equalTo(scrollView.frameLayoutGuide)
        }

        titleLabel.snp.makeConstraints { make in
            make.top.equalTo(contentView.safeAreaLayoutGuide).offset(72)
            make.leading.trailing.equalToSuperview().inset(24)
        }
        titleLabel.accessibilityIdentifier = "login.title"

        cardView.snp.makeConstraints { make in
            make.top.equalTo(titleLabel.snp.bottom).offset(AppMetrics.Spacing.xxLarge)
            make.leading.trailing.equalToSuperview().inset(20)
            make.bottom.equalToSuperview().inset(AppMetrics.Spacing.xxLarge)
        }

        usernameField.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview().inset(AppMetrics.Spacing.medium)
            make.height.equalTo(AppMetrics.ControlSize.inputHeight)
        }

        passwordField.snp.makeConstraints { make in
            make.top.equalTo(usernameField.snp.bottom).offset(AppMetrics.Spacing.xSmall)
            make.leading.trailing.equalTo(usernameField)
            make.height.equalTo(AppMetrics.ControlSize.inputHeight)
        }

        privacyButton.snp.makeConstraints { make in
            make.top.equalTo(passwordField.snp.bottom).offset(AppMetrics.ControlSize.checkboxTapArea)
            make.leading.equalToSuperview().inset(AppMetrics.Spacing.medium)
            make.width.height.equalTo(AppMetrics.ControlSize.checkboxTapArea)
        }

        privacyLabel.snp.makeConstraints { make in
            make.leading.equalTo(privacyButton.snp.trailing)
            make.trailing.equalToSuperview().inset(AppMetrics.Spacing.medium)
            make.top.equalTo(privacyButton).offset(AppMetrics.Spacing.xxSmall)
        }

        loginButton.snp.makeConstraints { make in
            make.top.equalTo(privacyLabel.snp.bottom).offset(AppMetrics.Spacing.mediumLarge)
            make.leading.trailing.bottom.equalToSuperview().inset(AppMetrics.Spacing.medium)
            make.height.equalTo(AppMetrics.ControlSize.primaryButtonHeight)
        }

        let tap = UITapGestureRecognizer(target: self, action: #selector(dismissKeyboard))
        tap.cancelsTouchesInView = false
        view.addGestureRecognizer(tap)
    }

    /// 配置AgreementText展示内容。
    private func configureAgreementText() {
        privacyLabel.numberOfLines = 0
        privacyLabel.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline)

        userAgreementButton.setTitle("《用户协议》", for: .normal)
        userAgreementButton.titleLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline)
        userAgreementButton.setTitleColor(UIColor(hex: 0x208BFF), for: .normal)
        userAgreementButton.accessibilityIdentifier = "login.userAgreement"
        userAgreementButton.addTarget(self, action: #selector(openUserAgreement), for: .touchUpInside)

        privacyPolicyButton.setTitle("《隐私政策》", for: .normal)
        privacyPolicyButton.titleLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline)
        privacyPolicyButton.setTitleColor(UIColor(hex: 0x208BFF), for: .normal)
        privacyPolicyButton.accessibilityIdentifier = "login.privacyPolicy"
        privacyPolicyButton.addTarget(self, action: #selector(openPrivacyPolicy), for: .touchUpInside)

        let prefix = UILabel()
        prefix.text = "已阅读并同意"
        prefix.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline)
        prefix.textColor = UIColor(hex: 0x666666)

        let separator = UILabel()
        separator.text = "与"
        separator.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline)
        separator.textColor = UIColor(hex: 0x666666)

        let row = UIStackView(arrangedSubviews: [prefix, userAgreementButton, separator, privacyPolicyButton])
        row.axis = .horizontal
        row.spacing = 0
        row.alignment = .center
        privacyLabel.addSubview(row)
        row.snp.makeConstraints { make in
            make.edges.equalToSuperview()
        }
    }

    /// 绑定ViewModel回调或数据。
    private func bindViewModel() {
        viewModel.onChange = { [weak self] in
            self?.renderViewModel()
        }
        renderViewModel()
    }

    /// render视图模型相关逻辑。
    private func renderViewModel() {
        if usernameField.textField.text != viewModel.username {
            usernameField.textField.text = viewModel.username
        }
        if passwordField.textField.text != viewModel.password {
            passwordField.textField.text = viewModel.password
        }

        passwordField.setSecureEntry(!viewModel.showsPassword)

        let checkboxImage = viewModel.privacyChecked ? "LoginCheckboxChecked" : "LoginCheckboxUnchecked"
        privacyButton.setImage(UIImage(named: checkboxImage), for: .normal)

        loginButton.isEnabled = viewModel.canSubmit && !viewModel.isLoading
        loginButton.backgroundColor = viewModel.canSubmit ? AppDesign.primary : .gray
        loginButton.setTitleColor(.white, for: .normal)
        loginButton.alpha = viewModel.isLoading ? 0.7 : 1

        if viewModel.showsAgreementSheet {
            viewModel.showsAgreementSheet = false
            presentAgreementSheet()
        }

        if let payload = viewModel.pendingAccountSelection {
            if let controller = accountSelectionController {
                controller.updateLoading(viewModel.isSelectingAccount)
            } else if presentedViewController == nil {
                presentAccountSelection(payload)
            }
        } else if accountSelectionController != nil {
            dismiss(animated: true)
            accountSelectionController = nil
        }
    }

    private weak var accountSelectionController: AccountSelectionViewController?

    /// username变更相关逻辑。
    @objc private func usernameChanged() {
        viewModel.username = usernameField.textField.text ?? ""
        viewModel.normalizeUsernameCountryCodeIfNeeded()
        services.toastCenter.dismiss()
    }

    /// password变更相关逻辑。
    @objc private func passwordChanged() {
        viewModel.password = passwordField.textField.text ?? ""
        services.toastCenter.dismiss()
    }

    /// togglePrivacy相关逻辑。
    @objc private func togglePrivacy() {
        viewModel.privacyChecked.toggle()
    }

    /// openUserAgreement相关逻辑。
    @objc private func openUserAgreement() {
        showToast("用户协议页面待接入")
    }

    /// openPrivacyPolicy相关逻辑。
    @objc private func openPrivacyPolicy() {
        showToast("隐私政策页面待接入")
    }

    /// 点击login的处理逻辑。
    @objc private func loginTapped() {
        view.endEditing(true)
        performLogin()
    }

    /// dismiss键盘相关逻辑。
    @objc private func dismissKeyboard() {
        view.endEditing(true)
    }

    /// perform登录相关逻辑。
    private func performLogin() {
        if let validationError = viewModel.validateForLogin() {
            if validationError == .privacyUnchecked {
                presentAgreementSheet()
            } else {
                showToast(validationError.message)
                if validationError.focusField == .username {
                    usernameField.textField.becomeFirstResponder()
                } else if validationError.focusField == .password {
                    passwordField.textField.becomeFirstResponder()
                }
            }
            return
        }

        Task {
            do {
                try await services.globalLoading.withLoading(message: "登录中...") {
                    let resolution = try await viewModel.login(authAPI: services.authAPI)
                    switch resolution {
                    case let .completed(response):
                        await completeLogin(with: response)
                    case .needsAccountSelection:
                        break
                    }
                }
            } catch is CancellationError {
                return
            } catch {
                showToast(error.localizedDescription)
            }
        }
    }

    /// 弹出AgreementSheet页面。
    private func presentAgreementSheet() {
        let controller = LoginAgreementConsentViewController(
            onOpenAgreement: { [weak self] title in
                self?.showToast("\(title)页面待接入")
            },
            onAgreeAndContinue: { [weak self] in
                self?.viewModel.acceptAgreement()
                self?.performLogin()
            }
        )
        if let sheet = controller.sheetPresentationController {
            sheet.detents = [.custom(resolver: { _ in 240 })]
            sheet.prefersGrabberVisible = true
        }
        present(controller, animated: true)
    }

    /// 弹出AccountSelection页面。
    private func presentAccountSelection(_ payload: AccountSelectionPayload) {
        let controller = AccountSelectionViewController(
            payload: payload,
            isLoading: viewModel.isSelectingAccount,
            onCancel: { [weak self] in
                self?.viewModel.clearPendingAccountSelection()
                self?.accountSelectionController = nil
            },
            onConfirm: { [weak self] account in
                self?.selectAccount(account)
            }
        )
        accountSelectionController = controller
        let navigation = UINavigationController(rootViewController: controller)
        navigation.modalPresentationStyle = .formSheet
        present(navigation, animated: true)
    }

    /// select账号相关逻辑。
    private func selectAccount(_ account: AccountSwitchAccount) {
        Task {
            do {
                try await services.globalLoading.withLoading(message: "账号切换中...") {
                    let response = try await viewModel.selectAccount(account, authAPI: services.authAPI)
                    await completeLogin(with: response)
                    accountSelectionController = nil
                    dismiss(animated: true)
                }
            } catch is CancellationError {
                return
            } catch {
                showToast(error.localizedDescription)
            }
        }
    }

    /// complete登录相关逻辑。
    private func completeLogin(with response: V9AuthResponse) async {
        do {
            try await services.authSessionCoordinator.completeLogin(
                with: response,
                username: viewModel.normalizedUsername,
                privacyAgreementAccepted: viewModel.privacyChecked,
                appSession: services.appSession,
                accountContext: services.accountContext,
                permissionContext: services.permissionContext,
                profileAPI: services.profileAPI,
                accountContextAPI: services.accountContextAPI
            )
        } catch {
            showToast(error.localizedDescription)
        }
    }
}

extension LoginViewController: UITextFieldDelegate {
    /// text字段ShouldReturn相关逻辑。
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if textField === usernameField.textField {
            passwordField.textField.becomeFirstResponder()
        } else if viewModel.canSubmit, !viewModel.isLoading {
            performLogin()
        }
        return true
    }
}

/// 登录输入框，包含图标、文本框和密码可见切换。
private final class LoginInputField: UIView {
    let textField = UITextField()
    var onToggleVisibility: (() -> Void)?

    private let toggleButton = UIButton(type: .custom)
    private var isSecure = false

    /// 初始化实例。
    init(iconName: String, placeholder: String, isSecure: Bool) {
        self.isSecure = isSecure
        super.init(frame: .zero)
        backgroundColor = UIColor(hex: 0xF1F5F9)
        layer.cornerRadius = AppMetrics.CornerRadius.input
        layer.borderWidth = 1
        layer.borderColor = UIColor(hex: 0xDDE3EA).cgColor

        let icon = UIImageView(image: UIImage(systemName: iconName))
        icon.tintColor = AppDesign.textSecondary
        icon.contentMode = .scaleAspectFit

        textField.placeholder = placeholder
        textField.font = .systemFont(ofSize: AppMetrics.FontSize.body)
        textField.textColor = AppDesign.textPrimary
        textField.tintColor = AppDesign.primary
        textField.borderStyle = .none
        textField.isSecureTextEntry = isSecure

        addSubview(icon)
        addSubview(textField)

        icon.snp.makeConstraints { make in
            make.leading.equalToSuperview().inset(AppMetrics.Spacing.medium)
            make.centerY.equalToSuperview()
            make.width.height.equalTo(AppMetrics.ControlSize.smallIcon)
        }

        if isSecure {
            toggleButton.addTarget(self, action: #selector(toggleVisibility), for: .touchUpInside)
            addSubview(toggleButton)
            toggleButton.snp.makeConstraints { make in
                make.trailing.equalToSuperview().inset(AppMetrics.Spacing.small)
                make.centerY.equalToSuperview()
                make.width.height.equalTo(AppMetrics.ControlSize.iconTapArea)
            }
            textField.snp.makeConstraints { make in
                make.leading.equalTo(icon.snp.trailing).offset(AppMetrics.Spacing.xSmall)
                make.trailing.equalTo(toggleButton.snp.leading)
                make.centerY.equalToSuperview()
            }
        } else {
            textField.snp.makeConstraints { make in
                make.leading.equalTo(icon.snp.trailing).offset(AppMetrics.Spacing.xSmall)
                make.trailing.equalToSuperview().inset(AppMetrics.Spacing.medium)
                make.centerY.equalToSuperview()
            }
        }
    }

    required init?(coder: NSCoder) {
        nil
    }

    /// setSecureEntry相关逻辑。
    func setSecureEntry(_ secure: Bool) {
        textField.isSecureTextEntry = secure
        let imageName = secure ? "LoginPwdInvisible" : "LoginPwdVisible"
        toggleButton.setImage(UIImage(named: imageName), for: .normal)
    }

    /// toggleVisibility相关逻辑。
    @objc private func toggleVisibility() {
        onToggleVisibility?()
    }
}

/// 协议确认弹窗，引导用户勾选协议后继续登录。
private final class LoginAgreementConsentViewController: UIViewController {

    private let onOpenAgreement: (String) -> Void
    private let onAgreeAndContinue: () -> Void

    /// 初始化实例。
    init(onOpenAgreement: @escaping (String) -> Void, onAgreeAndContinue: @escaping () -> Void) {
        self.onOpenAgreement = onOpenAgreement
        self.onAgreeAndContinue = onAgreeAndContinue
        super.init(nibName: nil, bundle: nil)
    }

    required init?(coder: NSCoder) {
        nil
    }

    /// 视图加载完成后的 UI 初始化与数据绑定。
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBackground

        let titleLabel = UILabel()
        titleLabel.text = "请先阅读并同意相关协议"
        titleLabel.font = .systemFont(ofSize: AppMetrics.FontSize.title3, weight: .semibold)
        titleLabel.textColor = AppDesign.textPrimary
        titleLabel.textAlignment = .center

        let descriptionLabel = UILabel()
        descriptionLabel.text = "为了保障你的账号安全和服务体验，请阅读并同意用户协议和隐私政策。"
        descriptionLabel.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline)
        descriptionLabel.textColor = AppDesign.textSecondary
        descriptionLabel.numberOfLines = 0
        descriptionLabel.textAlignment = .center

        let continueButton = UIButton(type: .system)
        continueButton.setTitle("同意并继续", for: .normal)
        continueButton.titleLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.body, weight: .medium)
        continueButton.backgroundColor = AppDesign.primary
        continueButton.setTitleColor(.white, for: .normal)
        continueButton.layer.cornerRadius = AppMetrics.CornerRadius.button
        continueButton.accessibilityIdentifier = "login.agreement.continue"
        continueButton.addTarget(self, action: #selector(continueTapped), for: .touchUpInside)

        view.addSubview(titleLabel)
        view.addSubview(descriptionLabel)
        view.addSubview(continueButton)

        titleLabel.snp.makeConstraints { make in
            make.top.equalTo(view.safeAreaLayoutGuide).offset(AppMetrics.Spacing.sheet)
            make.leading.trailing.equalToSuperview().inset(AppMetrics.Spacing.large)
        }

        descriptionLabel.snp.makeConstraints { make in
            make.top.equalTo(titleLabel.snp.bottom).offset(AppMetrics.Spacing.small)
            make.leading.trailing.equalTo(titleLabel)
        }

        continueButton.snp.makeConstraints { make in
            make.leading.trailing.equalTo(titleLabel)
            make.bottom.equalTo(view.safeAreaLayoutGuide).inset(AppMetrics.Spacing.mediumLarge)
            make.height.equalTo(AppMetrics.ControlSize.sheetButtonHeight)
        }
    }

    /// 点击continue的处理逻辑。
    @objc private func continueTapped() {
        dismiss(animated: true) { [onAgreeAndContinue] in
            onAgreeAndContinue()
        }
    }
}