//
//  AccountSwitchViewController.swift
//  suixinkan
//

import SnapKit
import UIKit

// MARK: - Diffable 标识

private typealias AccountSwitchSection = Int
private typealias AccountSwitchItem = String

/// 账号切换列表空态标识。
private enum AccountSwitchItemID {
    static let empty = "accountSwitch:empty"
}

/// 账号切换页面，展示当前登录主体下可进入的景区账号和门店账号。
final class AccountSwitchViewController: UIViewController, UITableViewDelegate {

    private let viewModel = AccountSwitchViewModel()

    private lazy var tableView: UITableView = {
        let table = UITableView(frame: .zero, style: .plain)
        table.backgroundColor = UIColor(hex: 0xF5F7FB)
        table.separatorStyle = .none
        table.delegate = self
        table.register(AccountSwitchCell.self, forCellReuseIdentifier: AccountSwitchCell.reuseID)
        return table
    }()

    private lazy var confirmButton: UIButton = {
        let button = makePrimaryButton(title: "确认切换")
        button.addTarget(self, action: #selector(confirmTapped), for: .touchUpInside)
        return button
    }()

    /// Diffable 数据源，驱动账号列表与选中态刷新。
    private var tableDataSource: UITableViewDiffableDataSource<AccountSwitchSection, AccountSwitchItem>!

    /// 视图加载完成后的 UI 初始化与数据绑定。
    override func viewDidLoad() {
        super.viewDidLoad()
        title = "账号切换"
        view.backgroundColor = UIColor(hex: 0xF5F7FB)

        configureTableDataSource()
        view.addSubview(tableView)
        view.addSubview(confirmButton)
        tableView.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview()
            make.bottom.equalTo(confirmButton.snp.top).offset(-12)
        }
        confirmButton.snp.makeConstraints { make in
            make.leading.trailing.equalToSuperview().inset(16)
            make.bottom.equalTo(view.safeAreaLayoutGuide).inset(14)
            make.height.equalTo(50)
        }

        viewModel.onChange = { [weak self] in
            self?.applyTableSnapshot(reconfigure: true)
            self?.updateConfirmButton()
        }
        Task { await loadAccounts() }
    }

    /// 配置 Diffable 数据源。
    private func configureTableDataSource() {
        tableDataSource = UITableViewDiffableDataSource<AccountSwitchSection, AccountSwitchItem>(
            tableView: tableView
        ) { [weak self] (tableView: UITableView, indexPath: IndexPath, item: AccountSwitchItem) -> UITableViewCell? in
            guard let self else { return UITableViewCell() }
            if item == AccountSwitchItemID.empty {
                let cell = UITableViewCell()
                cell.selectionStyle = .none
                cell.backgroundColor = .clear
                cell.contentView.subviews.forEach { $0.removeFromSuperview() }
                let empty = makeEmptyStateView(
                    title: "暂无可切换账号",
                    message: "当前登录账号下没有其他可切换账号。",
                    systemImage: "person.crop.circle.badge.exclamationmark"
                )
                cell.contentView.addSubview(empty)
                empty.snp.makeConstraints { make in make.edges.equalToSuperview(); make.height.equalTo(280) }
                return cell
            }
            guard let account = self.viewModel.accounts.first(where: { $0.id == item }) else {
                return UITableViewCell()
            }
            let cell = tableView.dequeueReusableCell(withIdentifier: AccountSwitchCell.reuseID, for: indexPath) as! AccountSwitchCell
            cell.configure(
                account: account,
                selected: self.viewModel.selectedAccountId == account.id,
                isCurrent: account.isCurrent || self.isCurrentAccount(account)
            )
            return cell
        }
        applyTableSnapshot(animated: false)
    }

    /// 构建 Diffable snapshot。
    private func buildTableSnapshot() -> NSDiffableDataSourceSnapshot<AccountSwitchSection, AccountSwitchItem> {
        var snapshot = NSDiffableDataSourceSnapshot<AccountSwitchSection, AccountSwitchItem>()
        snapshot.appendSections([0])
        if viewModel.accounts.isEmpty, !viewModel.loading {
            snapshot.appendItems([AccountSwitchItemID.empty], toSection: 0)
        } else {
            snapshot.appendItems(viewModel.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ConfirmButton状态。
    private func updateConfirmButton() {
        let enabled = viewModel.selectedAccount != nil && !viewModel.loading && !viewModel.switching
        confirmButton.isEnabled = enabled
        confirmButton.alpha = enabled ? 1 : 0.5
    }

    /// 加载Accounts数据。
    private func loadAccounts(force: Bool = false) async {
        do {
            try await appServices.globalLoading.withOptionalLoading(!force && viewModel.accounts.isEmpty, message: "加载中...") {
                try await self.viewModel.load(
                    api: self.appServices.profileAPI,
                    force: force,
                    currentAccountId: self.currentAccountId
                )
            }
        } catch {
            showToast(error.localizedDescription)
        }
    }

    private var currentAccountId: String? {
        guard let current = appServices.accountContext.profile else { return nil }
        if let store = appServices.accountContext.currentStore {
            return "\(V9StoreUser.accountTypeValue)_\(store.id)"
        }
        if let scenic = appServices.accountContext.currentScenic {
            return "\(V9ScenicUser.accountTypeValue)_\(scenic.id)"
        }
        return current.userId.isEmpty ? nil : current.userId
    }

    /// 判断isCurrentAccount条件。
    private func isCurrentAccount(_ account: AccountSwitchAccount) -> Bool {
        viewModel.isCurrent(account, currentAccountId: currentAccountId)
    }

    /// 点击confirm的处理逻辑。
    @objc private func confirmTapped() {
        guard let account = viewModel.selectedAccount else { return }
        if account.isCurrent || isCurrentAccount(account) {
            navigationController?.popViewController(animated: true)
            return
        }
        Task { await switchAccount(account) }
    }

    /// switch账号相关逻辑。
    private func switchAccount(_ account: AccountSwitchAccount) async {
        do {
            let response = try await appServices.globalLoading.withLoading(message: "切换中...") {
                try await self.viewModel.switchAccount(account, api: self.appServices.authAPI)
            }
            let username = nonEmpty(appServices.accountContext.profile?.phone)
                ?? nonEmpty(account.phone)
                ?? ""
            try await appServices.authSessionCoordinator.completeLogin(
                with: response,
                username: username,
                privacyAgreementAccepted: appServices.authSessionCoordinator.loginPreferences().privacyAgreementAccepted,
                appSession: appServices.appSession,
                accountContext: appServices.accountContext,
                permissionContext: appServices.permissionContext,
                profileAPI: appServices.profileAPI,
                accountContextAPI: appServices.accountContextAPI
            )
            appServices.appNavigator.resetAllStacks()
            showToast("账号已切换")
            navigationController?.popToRootViewController(animated: true)
        } catch {
            showToast(error.localizedDescription)
        }
    }

    /// non空相关逻辑。
    private func nonEmpty(_ value: String?) -> String? {
        let text = value?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
        return text.isEmpty ? nil : text
    }

    /// 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),
              item != AccountSwitchItemID.empty,
              let account = viewModel.accounts.first(where: { $0.id == item }) else { return }
        viewModel.select(account)
    }

    /// UITableView 代理：行高。
    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        guard let item = tableDataSource.itemIdentifier(for: indexPath) else { return 92 }
        return item == AccountSwitchItemID.empty ? 280 : 92
    }
}

/// AccountSwitch列表或网格 Cell，负责单项内容展示。
private final class AccountSwitchCell: UITableViewCell {
    static let reuseID = "AccountSwitchCell"

    private let avatarView = UIImageView()
    private let titleLabel = UILabel()
    private let subtitleLabel = UILabel()
    private let phoneLabel = UILabel()
    private let tagLabel = UILabel()
    private let checkView = UIImageView()

    /// 初始化实例。
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        selectionStyle = .none
        backgroundColor = .clear

        let card = UIView()
        card.backgroundColor = .white
        card.layer.cornerRadius = 12
        contentView.addSubview(card)

        avatarView.layer.cornerRadius = 25
        avatarView.clipsToBounds = true
        avatarView.contentMode = .scaleAspectFill

        titleLabel.font = .systemFont(ofSize: 16, weight: .semibold)
        subtitleLabel.font = .systemFont(ofSize: 13)
        subtitleLabel.textColor = AppDesignUIKit.textSecondary
        phoneLabel.font = .systemFont(ofSize: 12)
        phoneLabel.textColor = UIColor(hex: 0x9AA1AA)
        tagLabel.font = .systemFont(ofSize: 11, weight: .semibold)
        tagLabel.textAlignment = .center
        tagLabel.layer.cornerRadius = 4
        tagLabel.clipsToBounds = true

        card.addSubview(avatarView)
        card.addSubview(titleLabel)
        card.addSubview(subtitleLabel)
        card.addSubview(phoneLabel)
        card.addSubview(tagLabel)
        card.addSubview(checkView)

        card.snp.makeConstraints { make in
            make.edges.equalToSuperview().inset(UIEdgeInsets(top: 6, left: 16, bottom: 6, right: 16))
        }
        avatarView.snp.makeConstraints { make in
            make.leading.centerY.equalToSuperview().inset(14)
            make.width.height.equalTo(50)
        }
        titleLabel.snp.makeConstraints { make in
            make.leading.equalTo(avatarView.snp.trailing).offset(13)
            make.top.equalTo(avatarView).offset(2)
            make.trailing.lessThanOrEqualTo(tagLabel.snp.leading).offset(-8)
        }
        subtitleLabel.snp.makeConstraints { make in
            make.leading.equalTo(titleLabel)
            make.top.equalTo(titleLabel.snp.bottom).offset(4)
        }
        phoneLabel.snp.makeConstraints { make in
            make.leading.equalTo(titleLabel)
            make.top.equalTo(subtitleLabel.snp.bottom).offset(4)
        }
        tagLabel.snp.makeConstraints { make in
            make.trailing.equalToSuperview().inset(14)
            make.top.equalToSuperview().offset(14)
            make.height.equalTo(22)
            make.width.greaterThanOrEqualTo(40)
        }
        checkView.snp.makeConstraints { make in
            make.trailing.equalToSuperview().inset(14)
            make.bottom.equalToSuperview().inset(14)
            make.width.height.equalTo(22)
        }
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) { fatalError() }

    /// 配置展示内容。
    func configure(account: AccountSwitchAccount, selected: Bool, isCurrent: Bool) {
        let title = account.title.trimmingCharacters(in: .whitespacesAndNewlines)
        titleLabel.text = title.isEmpty ? account.accountTypeLabel : title
        subtitleLabel.text = account.subtitle
        phoneLabel.text = account.phone
        tagLabel.text = account.isStoreUser ? "门店" : "景区"
        tagLabel.textColor = account.isStoreUser ? UIColor(hex: 0x0F9F6E) : UIColor(hex: 0x7C3AED)
        tagLabel.backgroundColor = account.isStoreUser ? UIColor(hex: 0xE8F8F1) : UIColor(hex: 0xF3ECFF)
        checkView.image = UIImage(systemName: selected ? "checkmark.circle.fill" : "circle")
        checkView.tintColor = selected ? AppDesignUIKit.primary : UIColor(hex: 0xB6BECA)
        avatarView.loadRemoteAvatar(urlString: account.avatar)
        if isCurrent {
            titleLabel.text = (titleLabel.text ?? "") + " (当前)"
        }
    }
}