//
//  BaseViewController.swift
//  suixinkan
//

import SnapKit
import UIKit

/// 业务 ViewController 基类，提供统一的 UI 搭建流程与通用 UI 能力。
class BaseViewController: UIViewController {

    private var loadingOverlay: UIView?
    private var loadingIndicator: UIActivityIndicatorView?

    // MARK: - Lifecycle

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBackground
        setupNavigationBar()
        setupUI()
        setupConstraints()
        bindActions()
        registerBaseNotifications()
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    // MARK: - Template Methods

    /// 配置导航栏，子类按需重写。
    func setupNavigationBar() {}

    /// 创建并添加子视图。
    func setupUI() {}

    /// 使用 SnapKit 设置约束。
    func setupConstraints() {}

    /// 绑定 target-action、delegate 等交互。
    func bindActions() {}

    /// Token 失效时回调，子类可重写处理跳转登录等逻辑。
    func onSessionDidExpire() {}

    // MARK: - Loading

    func showLoading() {
        if loadingOverlay == nil {
            let overlay = UIView()
            overlay.backgroundColor = UIColor.black.withAlphaComponent(0.1)

            let indicator = UIActivityIndicatorView(style: .large)
            indicator.hidesWhenStopped = true

            view.addSubview(overlay)
            overlay.addSubview(indicator)

            overlay.snp.makeConstraints { make in
                make.edges.equalToSuperview()
            }
            indicator.snp.makeConstraints { make in
                make.center.equalToSuperview()
            }

            loadingOverlay = overlay
            loadingIndicator = indicator
        }

        loadingOverlay?.isHidden = false
        loadingIndicator?.startAnimating()
        view.bringSubviewToFront(loadingOverlay!)
    }

    func hideLoading() {
        loadingIndicator?.stopAnimating()
        loadingOverlay?.isHidden = true
    }

    // MARK: - Toast / Alert

    func showToast(_ message: String, duration: TimeInterval = 2.0) {
        guard !message.isEmpty else { return }

        let container = UIView()
        container.backgroundColor = UIColor.black.withAlphaComponent(0.8)
        container.layer.cornerRadius = 8
        container.clipsToBounds = true
        container.alpha = 0

        let label = UILabel()
        label.text = message
        label.textColor = .white
        label.font = .systemFont(ofSize: 14)
        label.textAlignment = .center
        label.numberOfLines = 0

        container.addSubview(label)
        view.addSubview(container)

        label.snp.makeConstraints { make in
            make.edges.equalToSuperview().inset(UIEdgeInsets(top: 10, left: 16, bottom: 10, right: 16))
        }
        container.snp.makeConstraints { make in
            make.centerX.equalToSuperview()
            make.bottom.equalTo(view.safeAreaLayoutGuide).offset(-32)
            make.leading.greaterThanOrEqualToSuperview().offset(32)
            make.trailing.lessThanOrEqualToSuperview().offset(-32)
        }

        UIView.animate(withDuration: 0.25) {
            container.alpha = 1
        } completion: { _ in
            UIView.animate(withDuration: 0.25, delay: duration) {
                container.alpha = 0
            } completion: { _ in
                container.removeFromSuperview()
            }
        }
    }

    func showError(_ message: String) {
        showToast(message)
    }

    func showAlert(
        title: String?,
        message: String?,
        confirmTitle: String = "确定",
        confirmHandler: (() -> Void)? = nil
    ) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: confirmTitle, style: .default) { _ in
            confirmHandler?()
        })
        present(alert, animated: true)
    }

    // MARK: - Navigation

    func popViewController() {
        navigationController?.popViewController(animated: true)
    }

    // MARK: - Notifications

    private func registerBaseNotifications() {
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(handleSessionDidExpireNotification),
            name: NotificationName.sessionDidExpire,
            object: nil
        )
    }

    @objc private func handleSessionDidExpireNotification() {
        hideLoading()
        onSessionDidExpire()
    }
}