import 'package:flutter/foundation.dart';

class MallWebHostState {
  const MallWebHostState({this.url, this.visible = false});
  final String? url;
  final bool visible;
}

/// 进程常驻的商城 WebView 状态，切换原生 Tab 时不销毁商城页面。
class MallWebHostController {
  MallWebHostController._();
  static final instance = MallWebHostController._();
  final state = ValueNotifier(const MallWebHostState());
  Future<void> Function()? _backHandler;

  void preload(String url) {
    final old = state.value;
    if (old.url == url) return;
    state.value = MallWebHostState(url: url, visible: old.visible);
  }

  void open(String url) =>
      state.value = MallWebHostState(url: url, visible: true);
  void dismiss() => state.value = MallWebHostState(url: state.value.url);
  void clear() => state.value = const MallWebHostState();
  void attachBackHandler(Future<void> Function() handler) =>
      _backHandler = handler;
  void detachBackHandler() => _backHandler = null;
  Future<void> handleBack() => _backHandler?.call() ?? Future.value();
}