//
//  AccountSelectionViewController.swift
//  suixinkan
//

import SnapKit
import UIKit

// MARK: - Diffable 标识

private typealias AccountSelectionSection = Int
private typealias AccountSelectionItem = String

@MainActor
/// 多账号登录时的账号选择页，展示景区/门店账号列表并提交选择。
final class AccountSelectionViewController: UIViewController, UITableViewDelegate {

    private let payload: AccountSelectionPayload
    private var isLoading: Bool
    private let onCancel: () -> Void
    private let onConfirm: (AccountSwitchAccount) -> Void

    private var selectedAccountId: String?
    private let tableView = UITableView(frame: .zero, style: .plain)

    /// Diffable 数据源，驱动账号列表与选中态刷新。
    private var tableDataSource: UITableViewDiffableDataSource<AccountSelectionSection, AccountSelectionItem>!
    private let confirmButton = UIButton(type: .system)
    private let bottomBar = UIView()

    /// 初始化实例。
    init(
        payload: AccountSelectionPayload,
        isLoading: Bool,
        onCancel: @escaping () -> Void,
        onConfirm: @escaping (AccountSwitchAccount) -> Void
    ) {
        self.payload = payload
        self.isLoading = isLoading
        self.onCancel = onCancel
        self.onConfirm = onConfirm
        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()
        title = "选择账号"
        view.backgroundColor = UIColor(hex: 0xF5F7FB)
        navigationItem.leftBarButtonItem = UIBarButtonItem(title: "取消", style: .plain, target: self, action: #selector(cancelTapped))
        isModalInPresentation = isLoading

        selectedAccountId = payload.accounts.first?.id
        configureTableView()
        configureTableDataSource()
        configureBottomBar()
    }

    /// 配置 Diffable 数据源。
    private func configureTableDataSource() {
        tableDataSource = UITableViewDiffableDataSource<AccountSelectionSection, AccountSelectionItem>(
            tableView: tableView
        ) { [weak self] (tableView: UITableView, indexPath: IndexPath, item: AccountSelectionItem) -> UITableViewCell? in
            guard let self,
                  let cell = tableView.dequeueReusableCell(
                      withIdentifier: AccountSelectionCell.reuseIdentifier,
                      for: indexPath
                  ) as? AccountSelectionCell,
                  let account = self.payload.accounts.first(where: { $0.id == item }) else {
                return UITableViewCell()
            }
            cell.configure(account: account, selected: account.id == self.selectedAccountId)
            return cell
        }
        applyTableSnapshot(animated: false)
    }

    /// 构建 Diffable snapshot。
    private func buildTableSnapshot() -> NSDiffableDataSourceSnapshot<AccountSelectionSection, AccountSelectionItem> {
        var snapshot = NSDiffableDataSourceSnapshot<AccountSelectionSection, AccountSelectionItem>()
        snapshot.appendSections([0])
        snapshot.appendItems(payload.accounts.map(\.id), toSection: 0)
        return snapshot
    }

    /// 应用 snapshot 刷新列表。
    private func applyTableSnapshot(animated: Bool = true, reconfigure: Bool = false) {
        var snapshot = buildTableSnapshot()
        if reconfigure, !snapshot.itemIdentifiers.isEmpty {
            snapshot.reconfigureItems(snapshot.itemIdentifiers)
        }
        tableDataSource.apply(snapshot, animatingDifferences: animated)
    }

    /// 更新Loading状态。
    func updateLoading(_ loading: Bool) {
        isLoading = loading
        isModalInPresentation = loading
        confirmButton.isEnabled = canConfirm
        confirmButton.backgroundColor = canConfirm ? AppDesign.primary : UIColor(hex: 0xC9CED6)
    }

    private var selectedAccount: AccountSwitchAccount? {
        payload.accounts.first { $0.id == selectedAccountId }
    }

    private var canConfirm: Bool {
        selectedAccount != nil && !isLoading
    }

    /// 配置TableView展示内容。
    private func configureTableView() {
        tableView.backgroundColor = .clear
        tableView.separatorStyle = .none
        tableView.delegate = self
        tableView.register(AccountSelectionCell.self, forCellReuseIdentifier: AccountSelectionCell.reuseIdentifier)
        view.addSubview(tableView)
        tableView.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview()
            make.bottom.equalTo(view.safeAreaLayoutGuide).inset(90)
        }
    }

    /// 配置BottomBar展示内容。
    private func configureBottomBar() {
        bottomBar.backgroundColor = .white

        let divider = UIView()
        divider.backgroundColor = UIColor.separator

        confirmButton.setTitle("进入系统", for: .normal)
        confirmButton.titleLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.body, weight: .semibold)
        confirmButton.setTitleColor(.white, for: .normal)
        confirmButton.layer.cornerRadius = AppMetrics.CornerRadius.button
        confirmButton.addTarget(self, action: #selector(confirmTapped), for: .touchUpInside)
        updateLoading(isLoading)

        view.addSubview(bottomBar)
        bottomBar.addSubview(divider)
        bottomBar.addSubview(confirmButton)

        bottomBar.snp.makeConstraints { make in
            make.leading.trailing.bottom.equalToSuperview()
        }

        divider.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview()
            make.height.equalTo(0.5)
        }

        confirmButton.snp.makeConstraints { make in
            make.top.equalTo(divider.snp.bottom).offset(AppMetrics.Spacing.medium)
            make.leading.trailing.equalToSuperview().inset(AppMetrics.Spacing.medium)
            make.bottom.equalTo(view.safeAreaLayoutGuide).inset(AppMetrics.Spacing.medium)
            make.height.equalTo(AppMetrics.ControlSize.primaryButtonHeight)
        }
    }

    /// 点击cancel的处理逻辑。
    @objc private func cancelTapped() {
        onCancel()
        dismiss(animated: true)
    }

    /// 点击confirm的处理逻辑。
    @objc private func confirmTapped() {
        guard let selectedAccount else { return }
        onConfirm(selectedAccount)
    }
}

extension AccountSelectionViewController {
    /// UITableView 代理：处理行选中。
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        guard let item = tableDataSource.itemIdentifier(for: indexPath) else { return }
        selectedAccountId = item
        applyTableSnapshot(animated: false, reconfigure: true)
        confirmButton.isEnabled = canConfirm
        confirmButton.backgroundColor = canConfirm ? AppDesign.primary : UIColor(hex: 0xC9CED6)
    }
}

/// 账号选择列表 Cell。
private final class AccountSelectionCell: UITableViewCell {
    static let reuseIdentifier = "AccountSelectionCell"

    private let avatarView = UIView()
    private let avatarLabel = UILabel()
    private let titleLabel = UILabel()
    private let subtitleLabel = UILabel()
    private let phoneLabel = UILabel()
    private let typeTag = UILabel()
    private let currentTag = UILabel()
    private let checkmark = UIImageView()

    /// 初始化实例。
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        selectionStyle = .none
        backgroundColor = .clear
        contentView.backgroundColor = .white
        contentView.layer.cornerRadius = AppMetrics.CornerRadius.button
        contentView.layer.masksToBounds = true

        avatarView.layer.cornerRadius = AppMetrics.ControlSize.primaryButtonHeight / 2
        avatarLabel.font = .systemFont(ofSize: AppMetrics.FontSize.callout, weight: .semibold)

        titleLabel.font = .systemFont(ofSize: AppMetrics.FontSize.body, weight: .semibold)
        titleLabel.textColor = AppDesign.textPrimary

        subtitleLabel.font = .systemFont(ofSize: AppMetrics.FontSize.footnote)
        subtitleLabel.textColor = AppDesign.textSecondary

        phoneLabel.font = .systemFont(ofSize: AppMetrics.FontSize.caption)
        phoneLabel.textColor = UIColor(hex: 0x9AA1AA)

        typeTag.font = .systemFont(ofSize: 11, weight: .semibold)
        typeTag.textAlignment = .center
        typeTag.layer.cornerRadius = AppMetrics.Spacing.xxSmall
        typeTag.clipsToBounds = true

        currentTag.font = .systemFont(ofSize: 11, weight: .semibold)
        currentTag.textAlignment = .center
        currentTag.text = "当前"
        currentTag.textColor = AppDesign.primary
        currentTag.backgroundColor = AppDesign.primarySoft
        currentTag.layer.cornerRadius = AppMetrics.Spacing.xxSmall
        currentTag.clipsToBounds = true
        currentTag.isHidden = true

        checkmark.contentMode = .scaleAspectFit

        contentView.addSubview(avatarView)
        avatarView.addSubview(avatarLabel)
        contentView.addSubview(titleLabel)
        contentView.addSubview(subtitleLabel)
        contentView.addSubview(phoneLabel)
        contentView.addSubview(typeTag)
        contentView.addSubview(currentTag)
        contentView.addSubview(checkmark)

        avatarView.snp.makeConstraints { make in
            make.leading.equalToSuperview().inset(AppMetrics.FontSize.subheadline)
            make.centerY.equalToSuperview()
            make.width.height.equalTo(AppMetrics.ControlSize.primaryButtonHeight)
        }

        avatarLabel.snp.makeConstraints { make in
            make.center.equalToSuperview()
        }

        titleLabel.snp.makeConstraints { make in
            make.top.equalToSuperview().inset(AppMetrics.FontSize.subheadline)
            make.leading.equalTo(avatarView.snp.trailing).offset(AppMetrics.FontSize.footnote)
            make.trailing.lessThanOrEqualTo(checkmark.snp.leading).offset(-8)
        }

        currentTag.snp.makeConstraints { make in
            make.leading.equalTo(titleLabel.snp.trailing).offset(AppMetrics.Spacing.xSmall)
            make.centerY.equalTo(titleLabel)
            make.height.equalTo(AppMetrics.Spacing.sheet)
        }

        subtitleLabel.snp.makeConstraints { make in
            make.top.equalTo(titleLabel.snp.bottom).offset(AppMetrics.Spacing.xxSmall)
            make.leading.equalTo(titleLabel)
            make.trailing.equalTo(checkmark.snp.leading).offset(-8)
        }

        phoneLabel.snp.makeConstraints { make in
            make.top.equalTo(subtitleLabel.snp.bottom).offset(AppMetrics.Spacing.xxSmall)
            make.leading.equalTo(titleLabel)
            make.bottom.equalToSuperview().inset(AppMetrics.FontSize.subheadline)
        }

        typeTag.snp.makeConstraints { make in
            make.trailing.equalTo(checkmark.snp.leading).offset(-AppMetrics.Spacing.xSmall)
            make.top.equalTo(titleLabel)
            make.height.equalTo(AppMetrics.Spacing.sheet)
        }

        checkmark.snp.makeConstraints { make in
            make.trailing.equalToSuperview().inset(AppMetrics.FontSize.subheadline)
            make.centerY.equalToSuperview()
            make.width.height.equalTo(AppMetrics.ControlSize.passwordIcon)
        }
    }

    required init?(coder: NSCoder) {
        nil
    }

    /// 配置展示内容。
    func configure(account: AccountSwitchAccount, selected: Bool) {
        titleLabel.text = account.title.isEmpty ? account.accountTypeLabel : account.title
        subtitleLabel.text = account.subtitle
        subtitleLabel.isHidden = account.subtitle.isEmpty
        phoneLabel.text = account.phone
        phoneLabel.isHidden = account.phone.isEmpty
        currentTag.isHidden = !account.isCurrent

        if account.isStoreUser {
            avatarView.backgroundColor = UIColor(hex: 0xE8F8F1)
            avatarLabel.text = "店"
            avatarLabel.textColor = UIColor(hex: 0x0F9F6E)
            typeTag.text = " 门店 "
            typeTag.textColor = UIColor(hex: 0x0F9F6E)
            typeTag.backgroundColor = UIColor(hex: 0xE8F8F1)
        } else {
            avatarView.backgroundColor = UIColor(hex: 0xF3ECFF)
            avatarLabel.text = "景"
            avatarLabel.textColor = UIColor(hex: 0x7C3AED)
            typeTag.text = " 景区 "
            typeTag.textColor = UIColor(hex: 0x7C3AED)
            typeTag.backgroundColor = UIColor(hex: 0xF3ECFF)
        }

        let symbolName = selected ? "checkmark.circle.fill" : "circle"
        checkmark.image = UIImage(systemName: symbolName)
        checkmark.tintColor = selected ? AppDesign.primary : UIColor(hex: 0xB6BECA)

        contentView.layer.borderWidth = selected ? 1.4 : 1
        contentView.layer.borderColor = (selected ? AppDesign.primary : UIColor(hex: 0xE6ECF4)).cgColor
    }
}