import 'package:flutter/foundation.dart';

class MallWebHostState {
  const MallWebHostState({
    this.url,
    this.visible = false,
    this.isShowingQiyuPage = false,
    this.isQiyuKeyboardActive = false,
  });

  final String? url;
  final bool visible;
  final bool isShowingQiyuPage;
  final bool isQiyuKeyboardActive;
}

/// Process-lifetime presentation state for the resident mall WebView.
class MallWebHostController {
  MallWebHostController._();

  static final instance = MallWebHostController._();

  final state = ValueNotifier(const MallWebHostState());
  String? _pendingPreloadUrl;
  Future<void> Function()? _clearCache;
  Future<void> Function()? _handleSystemBack;

  void open(Uri url) {
    _pendingPreloadUrl = null;
    state.value = MallWebHostState(url: url.toString(), visible: true);
  }

  void preload(Uri url) {
    final current = state.value;
    if (current.visible) {
      if (current.url == null ||
          cacheKeyFor(current.url!) != cacheKeyFor(url.toString())) {
        _pendingPreloadUrl = url.toString();
      }
      return;
    }
    if (current.url != null &&
        cacheKeyFor(current.url!) == cacheKeyFor(url.toString())) {
      return;
    }
    state.value = MallWebHostState(
      url: url.toString(),
      visible: current.visible,
    );
  }

  void dismiss() {
    final current = state.value;
    final pending = _pendingPreloadUrl;
    _pendingPreloadUrl = null;
    state.value = MallWebHostState(url: pending ?? current.url);
  }

  void setShowingQiyuPage(bool isShowingQiyuPage) {
    final current = state.value;
    if (current.isShowingQiyuPage == isShowingQiyuPage) return;
    state.value = MallWebHostState(
      url: current.url,
      visible: current.visible,
      isShowingQiyuPage: isShowingQiyuPage,
      isQiyuKeyboardActive: isShowingQiyuPage
          ? current.isQiyuKeyboardActive
          : false,
    );
  }

  void setQiyuKeyboardActive(bool active) {
    final current = state.value;
    if (current.isQiyuKeyboardActive == active) return;
    state.value = MallWebHostState(
      url: current.url,
      visible: current.visible,
      isShowingQiyuPage: current.isShowingQiyuPage,
      isQiyuKeyboardActive: active,
    );
  }

  void attachCacheClearer(Future<void> Function() clearer) =>
      _clearCache = clearer;

  void detachCacheClearer() => _clearCache = null;

  Future<void> clear() async {
    await _clearCache?.call();
    _pendingPreloadUrl = null;
    state.value = const MallWebHostState();
  }

  static Uri uriForTheme(Uri uri, {required bool isDark}) {
    final query = Map<String, List<String>>.from(uri.queryParametersAll);
    query['isNight'] = [isDark ? '1' : '0'];
    return uri.replace(queryParameters: query);
  }

  void attachSystemBackHandler(Future<void> Function() handler) {
    _handleSystemBack = handler;
  }

  void detachSystemBackHandler() => _handleSystemBack = null;

  Future<void> handleSystemBack() =>
      _handleSystemBack?.call() ?? Future<void>.value();

  static String cacheKeyFor(String rawUrl) {
    final uri = Uri.tryParse(rawUrl);
    if (uri == null) return rawUrl;
    return uri
        .replace(
          queryParameters: uri.queryParameters['isNight'] == null
              ? const <String, String>{}
              : <String, String>{'isNight': uri.queryParameters['isNight']!},
          fragment: '',
        )
        .toString();
  }
}