import 'dart:async';
import 'package:mangayomi/utils/platform_utils.dart';
import 'package:extended_image/extended_image.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';
import 'package:mangayomi/main.dart';
import 'package:mangayomi/models/chapter.dart';
import 'package:mangayomi/models/settings.dart';
import 'package:mangayomi/modules/anime/widgets/desktop.dart';
import 'package:mangayomi/modules/manga/reader/mixins/reader_gestures.dart';
import 'package:mangayomi/modules/manga/reader/providers/crop_borders_provider.dart';
import 'package:mangayomi/modules/manga/reader/services/page_navigation_service.dart';
import 'package:mangayomi/modules/manga/reader/mixins/reader_memory_management.dart';
import 'package:mangayomi/modules/manga/reader/widgets/double_page_view.dart';
import 'package:mangayomi/modules/manga/reader/widgets/reader_app_bar.dart';
import 'package:mangayomi/modules/manga/reader/widgets/reader_bottom_bar.dart';
import 'package:mangayomi/modules/manga/reader/widgets/reader_gesture_handler.dart';
import 'package:mangayomi/modules/manga/reader/widgets/reader_settings_modal.dart';
import 'package:mangayomi/modules/manga/reader/widgets/auto_scroll_button.dart';
import 'package:mangayomi/modules/manga/reader/widgets/page_indicator.dart';
import 'package:mangayomi/modules/manga/reader/widgets/image_actions_dialog.dart';
import 'package:mangayomi/modules/more/settings/reader/providers/reader_state_provider.dart';
import 'package:mangayomi/providers/l10n_providers.dart';
import 'package:mangayomi/utils/extensions/others.dart';
import 'package:mangayomi/utils/riverpod.dart';
import 'package:mangayomi/modules/manga/reader/providers/push_router.dart';
import 'package:mangayomi/services/get_chapter_pages.dart';
import 'package:mangayomi/utils/extensions/build_context_extensions.dart';
import 'package:mangayomi/modules/manga/reader/image_view_paged.dart';
import 'package:mangayomi/modules/manga/reader/providers/reader_controller_provider.dart';
import 'package:mangayomi/modules/manga/reader/widgets/circular_progress_indicator_animate_rotate.dart';
import 'package:mangayomi/modules/manga/reader/widgets/transition_view_paged.dart';
import 'package:mangayomi/modules/more/settings/reader/reader_screen.dart';
import 'package:mangayomi/modules/manga/reader/providers/manga_reader_provider.dart';
import 'package:mangayomi/modules/manga/reader/image_view_webtoon.dart';
import 'package:mangayomi/modules/widgets/progress_center.dart';
import 'package:mangayomi/utils/system_ui.dart';
import 'package:photo_view/photo_view.dart';
import 'package:scrollable_positioned_list/scrollable_positioned_list.dart';
import 'package:wakelock_plus/wakelock_plus.dart';
import 'package:window_manager/window_manager.dart';

typedef DoubleClickAnimationListener = void Function();

class MangaReaderView extends ConsumerStatefulWidget {
  final int chapterId;
  const MangaReaderView({super.key, required this.chapterId});

  @override
  ConsumerState<MangaReaderView> createState() => _MangaReaderViewState();
}

class _MangaReaderViewState extends ConsumerState<MangaReaderView> {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      ref.invalidate(mangaReaderProvider(widget.chapterId));
    });
  }

  @override
  Widget build(BuildContext context) {
    final chapterData = ref.watch(mangaReaderProvider(widget.chapterId));

    return chapterData.when(
      loading: () => scaffoldWith(context, const ProgressCenter()),
      error: (error, _) =>
          scaffoldWith(context, Center(child: Text(error.toString()))),
      data: (data) {
        final chapter = data.chapter;
        final model = data.pages;

        if (model.pageUrls.isEmpty &&
            !(chapter.manga.value?.isLocalArchive ?? false)) {
          return scaffoldWith(
            context,
            const Center(child: Text('Error: no pages available')),
            restoreUi: true,
          );
        }

        return MangaChapterPageGallery(
          chapter: chapter,
          chapterUrlModel: model,
        );
      },
    );
  }

  Widget scaffoldWith(
    BuildContext context,
    Widget body, {
    bool restoreUi = false,
  }) {
    return Scaffold(
      backgroundColor: Theme.of(context).scaffoldBackgroundColor,
      appBar: AppBar(
        title: const Text(''),
        leading: BackButton(
          onPressed: () {
            if (restoreUi) {
              restoreSystemUI();
            }
            Navigator.of(context).pop();
          },
        ),
      ),
      body: body,
    );
  }
}

class MangaChapterPageGalleryState {
  static void setNavigatingToChapter() {
    _MangaChapterPageGalleryState._isNavigatingToChapter = true;
  }
}

class MangaChapterPageGallery extends ConsumerStatefulWidget {
  const MangaChapterPageGallery({
    super.key,
    required this.chapter,
    required this.chapterUrlModel,
  });
  final GetChapterPagesModel chapterUrlModel;

  final Chapter chapter;

  @override
  ConsumerState createState() {
    return _MangaChapterPageGalleryState();
  }
}

class _MangaChapterPageGalleryState
    extends ConsumerState<MangaChapterPageGallery>
    with
        TickerProviderStateMixin,
        WidgetsBindingObserver,
        ReaderMemoryManagement,
        PageNavigationMixin {
  late AnimationController _scaleAnimationController;
  late Animation<double> _animation;

  late ReaderController _readerController = ref.read(
    readerControllerProvider(chapter: chapter).notifier,
  );

  final ValueNotifier<bool> _isScrolling = ValueNotifier(false);
  Timer? _scrollIdleTimer;
  final Stopwatch _readingStopwatch = Stopwatch();

  /// Flag to prevent fullscreen from being disabled when navigating between
  /// chapters via pushReplacement. The old widget's dispose runs after the new
  /// widget is created, which would clobber the new reader's fullscreen state.
  static bool _isNavigatingToChapter = false;

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    _readingStopwatch.stop();
    _readerController.setHistoryUpdate(
      elapsedSeconds: _readingStopwatch.elapsed.inSeconds,
    );
    _rebuildDetail.close();
    _doubleClickAnimationController.dispose();
    _scaleAnimationController.dispose();
    _failedToLoadImage.dispose();
    _autoScroll.value = false;
    _autoScroll.dispose();
    _autoScrollPage.dispose();
    _currentPageDisplayIndex.dispose();
    _scrollIdleTimer?.cancel();
    _isScrolling.dispose();
    _keyboardFocusNode.dispose();
    _itemPositionsListener.itemPositions.removeListener(_readProgressListener);
    _photoViewController.dispose();
    _photoViewScaleStateController.dispose();
    _extendedController.dispose();
    clearGestureDetailsCache();
    if (_isNavigatingToChapter) {
      _isNavigatingToChapter = false;
    } else if (isDesktop) {
      setFullScreen(value: false);
    } else {
      restoreSystemUI();
    }
    discordRpc?.showIdleText();
    final actualIdx = _pageViewToActualIndexSync(_currentIndex!);
    final index = pages[actualIdx].index;
    if (index != null) {
      _readerController.setPageIndex(
        _isDoublePageActiveSync ? index : _geCurrentIndex(index),
        true,
      );
    }
    disposePreloadManager();
    _readerController.keepAliveLink?.close();
    WakelockPlus.disable();
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.paused ||
        state == AppLifecycleState.detached) {
      _readingStopwatch.stop();
      final actualIdx = _pageViewToActualIndex(_currentIndex!);
      final index = pages[actualIdx].index;
      if (index != null) {
        _readerController.setPageIndex(
          _isDoublePageActive ? index : _geCurrentIndex(index),
          true,
        );
      }
    } else if (state == AppLifecycleState.resumed) {
      _readingStopwatch.start();
    }
  }

  late final _autoScroll = ValueNotifier(
    _readerController.autoScrollValues().$1,
  );
  late final _autoScrollPage = ValueNotifier(_autoScroll.value);
  late GetChapterPagesModel _chapterUrlModel = widget.chapterUrlModel;

  late Chapter chapter = widget.chapter;

  final _failedToLoadImage = ValueNotifier<bool>(false);

  late int? _currentIndex = _readerController.getPageIndex();
  late final ValueNotifier<int> _currentPageDisplayIndex = ValueNotifier(
    _readerController.getPageIndex(),
  );

  late final ItemScrollController _itemScrollController =
      ItemScrollController();
  final ScrollOffsetController _pageOffsetController = ScrollOffsetController();
  final ItemPositionsListener _itemPositionsListener =
      ItemPositionsListener.create();

  late AnimationController _doubleClickAnimationController;

  Animation<double>? _doubleClickAnimation;
  late DoubleClickAnimationListener _doubleClickAnimationListener;
  List<double> doubleTapScales = <double>[1.0, 2.0];
  final StreamController<double> _rebuildDetail =
      StreamController<double>.broadcast();
  @override
  void initState() {
    super.initState();
    _readingStopwatch.start();
    _doubleClickAnimationController = AnimationController(
      duration: _doubleTapAnimationDuration(),
      vsync: this,
    );
    _scaleAnimationController = AnimationController(
      duration: _doubleTapAnimationDuration(),
      vsync: this,
    );
    _animation = Tween(begin: 1.0, end: 2.0).animate(
      CurvedAnimation(curve: Curves.ease, parent: _scaleAnimationController),
    );
    _animation.addListener(() => _photoViewController.scale = _animation.value);
    _itemPositionsListener.itemPositions.addListener(_readProgressListener);
    initPageNavigation(
      itemScrollController: _itemScrollController,
      extendedController: _extendedController,
    );
    _initCurrentIndex();
    discordRpc?.showChapterDetails(ref, chapter);
    WidgetsBinding.instance.addObserver(this);
    _initWakelock();
  }

  void _initWakelock() {
    final keepOn = isar.settings.getSync(227)!.keepScreenOnReader ?? true;
    if (keepOn) {
      WakelockPlus.enable();
    }
  }

  // final double _horizontalScaleValue = 1.0;
  bool _isNextChapterPreloading = false;
  // bool _isPrevChapterPreloading = false;

  /// Guard flag: suppresses [_readProgressListener] during scroll position
  /// adjustment after prepending previous-chapter pages.
  bool _isAdjustingScroll = false;

  late int pagePreloadAmount = ref.read(pagePreloadAmountStateProvider);
  late bool _isBookmarked = _readerController.getChapterBookmarked();

  bool _isLastPageTransition = false;
  final _currentReaderMode = StateProvider<ReaderMode?>(() => null);
  PageMode? _pageMode;
  bool _isView = false;
  final _keyboardFocusNode = FocusNode();

  /// Cached reader mode to safely access in dispose without ref.read()
  ReaderMode? _cachedReaderMode;
  Alignment _scalePosition = Alignment.center;
  final PhotoViewController _photoViewController = PhotoViewController();
  final PhotoViewScaleStateController _photoViewScaleStateController =
      PhotoViewScaleStateController();
  final List<int> _cropBorderCheckList = [];

  void _onScaleEnd(
    BuildContext context,
    ScaleEndDetails details,
    PhotoViewControllerValue controllerValue,
  ) {
    if (controllerValue.scale! < 1) {
      _photoViewScaleStateController.reset();
    }
  }

  late final _extendedController = ExtendedPageController(
    initialPage: _currentIndex!,
  );

  double get pixelRatio => View.of(context).devicePixelRatio;

  Size get size => View.of(context).physicalSize / pixelRatio;
  Alignment _computeAlignmentByTapOffset(Offset offset) {
    return Alignment(
      (offset.dx - size.width / 2) / (size.width / 2),
      (offset.dy - size.height / 2) / (size.height / 2),
    );
  }

  Axis _scrollDirection = Axis.vertical;
  bool _isReverseHorizontal = false;

  Color _backgroundColor(BuildContext context) =>
      Theme.of(context).scaffoldBackgroundColor.withValues(alpha: 0.9);

  void _setFullScreen({bool? value}) async {
    if (isDesktop) {
      value = await windowManager.isFullScreen();
      setFullScreen(value: !value);
    }
    ref.read(fullScreenReaderStateProvider.notifier).set(!value!);
  }

  /// Goes to either next or previous chapter
  ///
  /// The [next] parameter determines the navigation direction:
  /// - `true` -> navigate to next chapter
  /// - `false` -> navigate to previous chapter
  ///
  /// If the reader is already at the first or last chapter (depending on
  /// the direction), the method returns without navigating.
  void _goToChapter(bool next) {
    if (next && !_readerController.hasNextChapter) return;
    if (!next && !_readerController.hasPreviousChapter) return;
    _isNavigatingToChapter = true;
    pushReplacementMangaReaderView(
      context: context,
      chapter: next
          ? _readerController.getNextChapter()
          : _readerController.getPrevChapter(),
    );
  }

  @override
  Widget build(BuildContext context) {
    final backgroundColor = ref.watch(backgroundColorStateProvider);
    final fullScreenReader = ref.watch(fullScreenReaderStateProvider);
    final readerMode = ref.watch(_currentReaderMode);
    if (readerMode == null) return const SizedBox.shrink();
    final bool isHorizontalContinuous = readerMode.isHorizontalContinuous;

    final l10n = l10nLocalizations(context)!;
    return ReaderKeyboardHandler(
      onPreviousPage: () => _handlePageNavigation(forward: false),
      onNextPage: () => _handlePageNavigation(forward: true),
      onEscape: () => _goBack(context),
      onFullScreen: () => _setFullScreen(),
      onNextChapter: () => _goToChapter(true),
      onPreviousChapter: () => _goToChapter(false),
    ).wrapWithKeyboardListener(
      isReverseHorizontal: _isReverseHorizontal,
      focusNode: _keyboardFocusNode,
      child: NotificationListener<UserScrollNotification>(
        onNotification: (notification) {
          if (notification.direction == ScrollDirection.idle) {
            if (_isView) {
              _isViewFunction();
            }
          }

          return true;
        },
        child: Material(
          child: SafeArea(
            top: !fullScreenReader,
            bottom: false,
            child: ValueListenableBuilder(
              valueListenable: _failedToLoadImage,
              builder: (context, failedToLoadImage, child) {
                return Stack(
                  children: [
                    readerMode.isContinuous
                        ? ImageViewWebtoon(
                            pages: pages,
                            itemScrollController: _itemScrollController,
                            scrollOffsetController: _pageOffsetController,
                            itemPositionsListener: _itemPositionsListener,
                            scrollDirection: isHorizontalContinuous
                                ? Axis.horizontal
                                : Axis.vertical,
                            minCacheExtent: isHorizontalContinuous
                                ? pagePreloadAmount * context.width(1)
                                : pagePreloadAmount * context.height(1),
                            initialScrollIndex: _readerController
                                .getPageIndex(),
                            physics: const ClampingScrollPhysics(),
                            onLongPressData: (data) => ImageActionsDialog.show(
                              context: context,
                              data: data,
                              manga: widget.chapter.manga.value!,
                              chapterName: widget.chapter.name!,
                            ),
                            onFailedToLoadImage: (value) {
                              // TODO: Handle failed image loading
                              // if (_failedToLoadImage.value != value &&
                              //     context.mounted) {
                              //   _failedToLoadImage.value = value;
                              // }
                            },
                            backgroundColor: backgroundColor,
                            isDoublePageMode:
                                _pageMode == PageMode.doublePage &&
                                !isHorizontalContinuous,
                            isHorizontalContinuous: isHorizontalContinuous,
                            readerMode: ref.watch(_currentReaderMode)!,
                            photoViewController: _photoViewController,
                            photoViewScaleStateController:
                                _photoViewScaleStateController,
                            scalePosition: _scalePosition,
                            onScaleEnd: (details) => _onScaleEnd(
                              context,
                              details,
                              _photoViewController.value,
                            ),
                            onDoubleTapDown: (offset) => _toggleScale(offset),
                            onDoubleTap: () {},
                            webtoonSidePadding: ref.watch(
                              webtoonSidePaddingStateProvider,
                            ),
                            showPageGaps: ref.watch(showPageGapsStateProvider),
                            reverse: _isReverseHorizontal,
                            isScrolling: _isScrolling,
                          )
                        : Material(
                            color: getBackgroundColor(backgroundColor),
                            shadowColor: getBackgroundColor(backgroundColor),
                            child:
                                (_pageMode == PageMode.doublePage &&
                                    !isHorizontalContinuous)
                                ? ExtendedImageGesturePageView.builder(
                                    controller: _extendedController,
                                    scrollDirection: _scrollDirection,
                                    reverse: _isReverseHorizontal,
                                    physics: const ClampingScrollPhysics(),
                                    canScrollPage: (_) {
                                      return true;
                                    },
                                    itemBuilder: (context, index) {
                                      int index1 = index * 2;
                                      int index2 = index1 + 1;
                                      final pageList = [
                                        index1 < pages.length
                                            ? pages[index1]
                                            : null,
                                        index2 < pages.length
                                            ? pages[index2]
                                            : null,
                                      ];
                                      return DoublePageView.paged(
                                        pages: _isReverseHorizontal
                                            ? pageList.reversed.toList()
                                            : pageList,
                                        backgroundColor: backgroundColor,
                                        onFailedToLoadImage: (val) {
                                          if (_failedToLoadImage.value != val &&
                                              mounted) {
                                            _failedToLoadImage.value = val;
                                          }
                                        },
                                        onLongPressData: (datas) {
                                          ImageActionsDialog.show(
                                            context: context,
                                            data: datas,
                                            manga: widget.chapter.manga.value!,
                                            chapterName: widget.chapter.name!,
                                          );
                                        },
                                      );
                                    },
                                    itemCount: (pages.length / 2).ceil(),
                                    onPageChanged: _onPageChanged,
                                  )
                                : ExtendedImageGesturePageView.builder(
                                    controller: _extendedController,
                                    scrollDirection: _scrollDirection,
                                    reverse: _isReverseHorizontal,
                                    physics: const ClampingScrollPhysics(),
                                    canScrollPage: (gestureDetails) {
                                      return true;
                                    },
                                    itemBuilder: (BuildContext context, int index) {
                                      if (pages[index].isTransitionPage) {
                                        return TransitionViewPaged(
                                          data: pages[index],
                                        );
                                      }

                                      return ImageViewPaged(
                                        data: pages[index],
                                        loadStateChanged: (state) {
                                          if (state.extendedImageLoadState ==
                                              LoadState.loading) {
                                            final ImageChunkEvent?
                                            loadingProgress =
                                                state.loadingProgress;
                                            final double progress =
                                                loadingProgress
                                                        ?.expectedTotalBytes !=
                                                    null
                                                ? loadingProgress!
                                                          .cumulativeBytesLoaded /
                                                      loadingProgress
                                                          .expectedTotalBytes!
                                                : 0;
                                            return Container(
                                              color: getBackgroundColor(
                                                backgroundColor,
                                              ),
                                              height: context.height(0.8),
                                              child:
                                                  CircularProgressIndicatorAnimateRotate(
                                                    progress: progress,
                                                  ),
                                            );
                                          }
                                          if (state.extendedImageLoadState ==
                                              LoadState.completed) {
                                            if (_failedToLoadImage.value ==
                                                true) {
                                              Future.delayed(
                                                const Duration(
                                                  milliseconds: 10,
                                                ),
                                              ).then(
                                                (value) =>
                                                    _failedToLoadImage.value =
                                                        false,
                                              );
                                            }
                                            return ExtendedImageGesture(
                                              state,
                                              canScaleImage: (_) => true,
                                              imageBuilder:
                                                  (
                                                    Widget image, {
                                                    ExtendedImageGestureState?
                                                    imageGestureState,
                                                  }) {
                                                    return image;
                                                  },
                                            );
                                          }
                                          if (state.extendedImageLoadState ==
                                              LoadState.failed) {
                                            if (_failedToLoadImage.value ==
                                                false) {
                                              Future.delayed(
                                                const Duration(
                                                  milliseconds: 10,
                                                ),
                                              ).then(
                                                (value) =>
                                                    _failedToLoadImage.value =
                                                        true,
                                              );
                                            }
                                            return Container(
                                              color: getBackgroundColor(
                                                backgroundColor,
                                              ),
                                              height: context.height(0.8),
                                              child: Column(
                                                mainAxisAlignment:
                                                    MainAxisAlignment.center,
                                                children: [
                                                  Text(
                                                    l10n.image_loading_error,
                                                    style: TextStyle(
                                                      color: Colors.white
                                                          .withValues(
                                                            alpha: 0.7,
                                                          ),
                                                    ),
                                                  ),
                                                  Padding(
                                                    padding:
                                                        const EdgeInsets.all(
                                                          8.0,
                                                        ),
                                                    child: GestureDetector(
                                                      onLongPress: () {
                                                        state.reLoadImage();
                                                        _failedToLoadImage
                                                                .value =
                                                            false;
                                                      },
                                                      onTap: () {
                                                        state.reLoadImage();
                                                        _failedToLoadImage
                                                                .value =
                                                            false;
                                                      },
                                                      child: Container(
                                                        decoration: BoxDecoration(
                                                          color: context
                                                              .primaryColor,
                                                          borderRadius:
                                                              BorderRadius.circular(
                                                                30,
                                                              ),
                                                        ),
                                                        child: Padding(
                                                          padding:
                                                              const EdgeInsets.symmetric(
                                                                vertical: 8,
                                                                horizontal: 16,
                                                              ),
                                                          child: Text(
                                                            l10n.retry,
                                                          ),
                                                        ),
                                                      ),
                                                    ),
                                                  ),
                                                ],
                                              ),
                                            );
                                          }
                                          return const SizedBox.shrink();
                                        },
                                        initGestureConfigHandler: (state) {
                                          return GestureConfig(
                                            inertialSpeed: 200,
                                            inPageView: true,
                                            maxScale: 8,
                                            animationMaxScale: 8,
                                            cacheGesture: true,
                                            hitTestBehavior:
                                                HitTestBehavior.translucent,
                                          );
                                        },
                                        onDoubleTap: (state) {
                                          final Offset? pointerDownPosition =
                                              state.pointerDownPosition;
                                          final double? begin =
                                              state.gestureDetails!.totalScale;
                                          double end;

                                          //remove old
                                          _doubleClickAnimation?.removeListener(
                                            _doubleClickAnimationListener,
                                          );

                                          //stop pre
                                          _doubleClickAnimationController
                                              .stop();

                                          //reset to use
                                          _doubleClickAnimationController
                                              .reset();

                                          if (begin == doubleTapScales[0]) {
                                            end = doubleTapScales[1];
                                          } else {
                                            end = doubleTapScales[0];
                                          }

                                          _doubleClickAnimationListener = () {
                                            state.handleDoubleTap(
                                              scale:
                                                  _doubleClickAnimation!.value,
                                              doubleTapPosition:
                                                  pointerDownPosition,
                                            );
                                          };

                                          _doubleClickAnimation =
                                              Tween(
                                                begin: begin,
                                                end: end,
                                              ).animate(
                                                CurvedAnimation(
                                                  curve: Curves.ease,
                                                  parent:
                                                      _doubleClickAnimationController,
                                                ),
                                              );

                                          _doubleClickAnimation!.addListener(
                                            _doubleClickAnimationListener,
                                          );

                                          _doubleClickAnimationController
                                              .forward();
                                        },
                                        onLongPressData: (datas) {
                                          ImageActionsDialog.show(
                                            context: context,
                                            data: datas,
                                            manga: widget.chapter.manga.value!,
                                            chapterName: widget.chapter.name!,
                                          );
                                        },
                                      );
                                    },
                                    itemCount: pages.length,
                                    onPageChanged: _onPageChanged,
                                  ),
                          ),
                    Consumer(
                      builder: (context, ref, child) {
                        final usePageTapZones = ref.watch(
                          usePageTapZonesStateProvider,
                        );
                        final navigationLayout = ref.watch(
                          readerNavigationLayoutStateProvider,
                        );
                        return ReaderGestureHandler(
                          usePageTapZones: usePageTapZones,
                          navigationLayout: navigationLayout,
                          isRTL: _isReverseHorizontal,
                          hasImageError: failedToLoadImage,
                          isContinuousMode: readerMode.isContinuous,
                          onToggleUI: _isViewFunction,
                          onPreviousPage: () =>
                              _handlePageNavigation(forward: false),
                          onNextPage: () =>
                              _handlePageNavigation(forward: true),
                          onDoubleTapDown: (position) => _toggleScale(position),
                          onDoubleTap: () {},
                          onSecondaryTapDown: (position) =>
                              _toggleScale(position),
                          onSecondaryTap: () {},
                        );
                      },
                    ),
                    ReaderAppBar(
                      chapter: chapter,
                      mangaName: _readerController.getMangaName(),
                      chapterTitle: _readerController.getChapterTitle(),
                      isVisible: _isView,
                      isBookmarked: _isBookmarked,
                      backgroundColor: _backgroundColor,
                      onBackPressed: () => Navigator.pop(context),
                      onBookmarkPressed: () {
                        _readerController.setChapterBookmarked();
                        setState(() {
                          _isBookmarked = !_isBookmarked;
                        });
                      },
                      onWebViewPressed:
                          (chapter.manga.value!.isLocalArchive ?? false) ==
                              false
                          ? () {
                              final data = buildWebViewData(chapter);
                              if (data != null) {
                                context.push("/mangawebview", extra: data);
                              }
                            }
                          : null,
                    ),
                    ReaderBottomBar(
                      chapter: chapter,
                      isVisible: _isView,
                      hasPreviousChapter: _readerController.hasPreviousChapter,
                      hasNextChapter: _readerController.hasNextChapter,
                      onPreviousChapter: () => _goToChapter(false),
                      onNextChapter: () => _goToChapter(true),
                      onSliderChanged: (value, ref) {
                        _currentPageDisplayIndex.value = value;
                        ref
                            .read(currentIndexProvider(chapter).notifier)
                            .setCurrentIndex(value);
                      },
                      onSliderChangeEnd: (value) {
                        try {
                          final page = pages.firstWhere(
                            (element) =>
                                element.chapter == chapter &&
                                element.index == value,
                          );
                          int jumpIndex = page.pageIndex!;
                          // In double page mode, convert array index to page view index
                          if (_isDoublePageActive) {
                            jumpIndex = _actualToPageViewIndex(jumpIndex);
                          }
                          navigationService.jumpToPage(
                            index: jumpIndex,
                            readerMode: ref.read(_currentReaderMode)!,
                          );
                        } catch (_) {}
                      },
                      onReaderModeChanged: (mode, ref) {
                        ref.read(_currentReaderMode.notifier).state = mode;
                        _setReaderMode(mode, ref);
                      },
                      onPageModeToggle: () async {
                        final readerMode = ref.read(_currentReaderMode);
                        if (!(readerMode == ReaderMode.horizontalContinuous ||
                            readerMode == ReaderMode.horizontalContinuousRTL)) {
                          // Get the actual page index being viewed
                          final actualIdx = _pageViewToActualIndex(
                            _currentIndex!,
                          );
                          final pageIdx = pages[actualIdx].index ?? 0;
                          // Compute target index for the new mode
                          final int targetIndex;
                          if (_pageMode == PageMode.onePage) {
                            // Switching to double page: convert actual index to page view index
                            targetIndex = pageIdx ~/ 2;
                          } else {
                            // Switching to single page: use the actual page index
                            targetIndex = pageIdx;
                          }
                          navigationService.jumpToPage(
                            index: targetIndex,
                            readerMode: ref.read(_currentReaderMode)!,
                          );
                          PageMode newPageMode = _pageMode == PageMode.onePage
                              ? PageMode.doublePage
                              : PageMode.onePage;
                          _readerController.setPageMode(newPageMode);
                          if (mounted) {
                            setState(() {
                              _pageMode = newPageMode;
                            });
                          }
                        }
                      },
                      onSettingsPressed: () => ReaderSettingsModal.show(
                        context: context,
                        vsync: this,
                        currentReaderModeProvider: _currentReaderMode,
                        autoScroll: _autoScroll,
                        autoScrollPage: _autoScrollPage,
                        pageOffset: _pageOffset,
                        onAutoPageScroll: _autoPagescroll,
                        onReaderModeChanged: (mode, widgetRef) {
                          widgetRef.read(_currentReaderMode.notifier).state =
                              mode;
                          _setReaderMode(mode, widgetRef);
                        },
                        onAutoScrollSave: (enabled, offset) {
                          _readerController.setAutoScroll(enabled, offset);
                        },
                        onFullScreenToggle: () {
                          final fullScreen = ref.read(
                            fullScreenReaderStateProvider,
                          );
                          _setFullScreen(value: !fullScreen);
                        },
                      ),
                      currentReaderModeProvider: _currentReaderMode,
                      currentPageListenable: _currentPageDisplayIndex,
                      currentPageMode: _pageMode,
                      isReverseHorizontal: _isReverseHorizontal,
                      totalPages: _readerController.getPageLength(
                        _chapterUrlModel.pageUrls,
                      ),
                      currentIndexLabel: _currentIndexLabel,
                      backgroundColor: _backgroundColor,
                    ),
                    PageIndicator(
                      isUiVisible: _isView,
                      currentPageListenable: _currentPageDisplayIndex,
                      totalPages: _readerController.getPageLength(
                        _chapterUrlModel.pageUrls,
                      ),
                      formatCurrentIndex: _currentIndexLabel,
                    ),
                    ReaderAutoScrollButton(
                      isContinuousMode: readerMode.isContinuous,
                      isUiVisible: _isView,
                      autoScrollPage: _autoScrollPage,
                      autoScroll: _autoScroll,
                      onToggle: () {
                        _autoPagescroll();
                        _autoScroll.value = !_autoScroll.value;
                      },
                    ),
                  ],
                );
              },
            ),
          ),
        ),
      ),
    );
  }

  void _handlePageNavigation({required bool forward}) {
    final readerMode = ref.read(_currentReaderMode);
    final animatePageTransitions = ref.read(
      animatePageTransitionsStateProvider,
    );
    if (readerMode == null || _currentIndex == null) return;

    if (readerMode == ReaderMode.webtoon) {
      final viewportHeight = MediaQuery.sizeOf(context).height;
      final offset = viewportHeight * 0.60 * (forward ? 1 : -1);
      final duration = animatePageTransitions
          ? const Duration(milliseconds: 160)
          : const Duration(milliseconds: 10);
      _pageOffsetController.animateScroll(
        offset: offset,
        duration: duration,
        curve: Curves.easeInOut,
      );
      return;
    }

    if (forward) {
      navigationService.nextPage(
        readerMode: readerMode,
        currentIndex: _currentIndex!,
        maxPages: _pageViewPageCount,
        animate: animatePageTransitions,
      );
    } else {
      navigationService.previousPage(
        readerMode: readerMode,
        currentIndex: _currentIndex!,
        animate: animatePageTransitions,
      );
    }
  }

  Duration? _doubleTapAnimationDuration() {
    int doubleTapAnimationValue = isar.settings
        .getSync(227)!
        .doubleTapAnimationSpeed!;
    if (doubleTapAnimationValue == 0) {
      return const Duration(milliseconds: 10);
    } else if (doubleTapAnimationValue == 1) {
      return const Duration(milliseconds: 800);
    }
    return const Duration(milliseconds: 200);
  }

  void _readProgressListener() async {
    if (_isAdjustingScroll) return;
    final itemPositions = _itemPositionsListener.itemPositions.value;
    if (itemPositions.isEmpty) return;
    _currentIndex = itemPositions.first.index;
    if (!_isScrolling.value) _isScrolling.value = true;
    _scrollIdleTimer?.cancel();
    _scrollIdleTimer = Timer(const Duration(milliseconds: 150), () {
      if (mounted) _isScrolling.value = false;
    });
    final currentReaderMode = ref.read(_currentReaderMode);
    int pagesLength =
        (_pageMode == PageMode.doublePage &&
            currentReaderMode != ReaderMode.horizontalContinuous &&
            currentReaderMode != ReaderMode.horizontalContinuousRTL)
        ? (pages.length / 2).ceil()
        : pages.length;
    if (_currentIndex! >= 0 && _currentIndex! < pagesLength) {
      if (_readerController.chapter.id != pages[_currentIndex!].chapter!.id) {
        if (mounted) {
          setState(() {
            _readerController = ref.read(
              readerControllerProvider(
                chapter: pages[_currentIndex!].chapter!,
              ).notifier,
            );

            chapter = pages[_currentIndex!].chapter!;
            final chapterUrlModel = pages[_currentIndex!].chapterUrlModel;

            if (chapterUrlModel != null) {
              _chapterUrlModel = chapterUrlModel;
            }

            _isBookmarked = _readerController.getChapterBookmarked();
          });
        }
      }

      // ── Next-chapter preloading: trigger when near the end ──
      final distToEnd = pagesLength - 1 - itemPositions.last.index;
      if (distToEnd <= pagePreloadAmount && !_isLastPageTransition) {
        _triggerNextChapterPreload();
      }

      // // ── Previous-chapter preloading: trigger when near the start ──
      // if (itemPositions.first.index <= pagePreloadAmount) {
      //   _triggerPrevChapterPreload();
      // }

      final idx = pages[_currentIndex!].index;
      if (idx != null) {
        _currentPageDisplayIndex.value = idx;
        _readerController.setPageIndex(
          _isDoublePageActive ? idx : _geCurrentIndex(idx),
          false,
        );
        ref.read(currentIndexProvider(chapter).notifier).setCurrentIndex(idx);
      }
    }
  }

  void _addLastPageTransition(Chapter chap) {
    if (_isLastPageTransition) return;
    try {
      if (!mounted || pageCount == 0) return;
      if (pages.last.isLastChapter ?? false) return;

      final added = addLastChapterTransition(chap);
      if (added && mounted) {
        setState(() {
          _isLastPageTransition = true;
        });
      }
    } catch (_) {}
  }

  void _preloadNextChapter(GetChapterPagesModel chapterData, Chapter chap) {
    try {
      if (chapterData.uChapDataPreload.isEmpty || !mounted) return;

      final firstChapter = chapterData.uChapDataPreload.first.chapter;
      if (firstChapter == null) return;

      // Use mixin's method for memory-bounded preloading with auto-eviction
      preloadNextChapter(chapterData, chap).then((success) {
        if (success && mounted) {
          setState(() {});
        }
      });
    } catch (_) {}
  }

  // bidirectional proactive chapter preloading ──

  /// Proactively starts loading both adjacent chapters at reader init.
  void _proactivePreload() {
    _triggerNextChapterPreload();
    // _triggerPrevChapterPreload();
  }

  /// Fires off next-chapter page fetching if not already in progress.
  void _triggerNextChapterPreload() async {
    if (_isNextChapterPreloading || _isLastPageTransition) return;
    _isNextChapterPreloading = true;
    try {
      if (!mounted) {
        _isNextChapterPreloading = false;
        return;
      }
      final nextChapter = _readerController.getNextChapter();
      if (isChapterLoaded(nextChapter)) {
        _isNextChapterPreloading = false;
        return;
      }
      final value = await ref.read(
        getChapterPagesProvider(chapter: nextChapter).future,
      );
      if (mounted) {
        _preloadNextChapter(value, chapter);
      }
      _isNextChapterPreloading = false;
    } on RangeError {
      _isNextChapterPreloading = false;
      _addLastPageTransition(chapter);
    } catch (_) {
      _isNextChapterPreloading = false;
    }
  }
  // TODO: Need more optimization
  // /// Fires off previous-chapter page fetching and prepends pages.
  // void _triggerPrevChapterPreload() async {
  //   if (_isPrevChapterPreloading) return;
  //   _isPrevChapterPreloading = true;
  //   try {
  //     if (!mounted) return;
  //     final prevChapter = _readerController.getPrevChapter();
  //     if (isChapterLoaded(prevChapter)) {
  //       _isPrevChapterPreloading = false;
  //       return;
  //     }
  //     final value = await ref.read(
  //       getChapterPagesProvider(chapter: prevChapter).future,
  //     );
  //     if (mounted) {
  //       _handlePrevChapterPrepended(value, chapter);
  //     }
  //   } on RangeError {
  //     // No previous chapter — nothing to prepend
  //   } catch (_) {}
  //   _isPrevChapterPreloading = false;
  // }

  // /// Prepends previous-chapter pages and adjusts scroll position to avoid jump.
  // void _handlePrevChapterPrepended(
  //   GetChapterPagesModel chapterData,
  //   Chapter chap,
  // ) {
  //   try {
  //     if (chapterData.uChapDataPreload.isEmpty || !mounted) return;

  //     // Record the CURRENT visible top index BEFORE prepending
  //     final currentVisibleItems = _itemPositionsListener.itemPositions.value;
  //     final oldTopIndex = currentVisibleItems.isNotEmpty
  //         ? currentVisibleItems.first.index
  //         : _currentIndex ?? 0;

  //     preloadPreviousChapter(chapterData, chap).then((prependCount) {
  //       if (prependCount > 0 && mounted) {
  //         _isAdjustingScroll = true;

  //         // New index = old visible index + how many items we just prepended
  //         final newIndex = oldTopIndex + prependCount;

  //         // In double page mode, _currentIndex stores the page view index,
  //         // so convert the prepended page count to page view units.
  //         if (_isDoublePageActive) {
  //           // Recompute the page view index from the new actual index.
  //           final oldActual = _pageViewToActualIndex(oldTopIndex);
  //           final newActual = oldActual + prependCount;
  //           _currentIndex = _actualToPageViewIndex(newActual);
  //         } else {
  //           _currentIndex = newIndex;
  //         }
  //         setState(() {});
  //         WidgetsBinding.instance.addPostFrameCallback((_) {
  //           if (mounted) {
  //             if (_isContinuousMode()) {
  //               _itemScrollController.jumpTo(index: newIndex);
  //             } else if (_extendedController.hasClients) {
  //               _extendedController.jumpToPage(_currentIndex!);
  //             }
  //             _isAdjustingScroll = false;
  //           }
  //         });
  //       }
  //     });
  //   } catch (_) {}
  // }

  void _initCurrentIndex() async {
    if (ref.read(cropBordersStateProvider)) _processCropBorders();
    final readerMode = _readerController.getReaderMode();
    _currentPageDisplayIndex.value = _readerController.getPageIndex();

    // Initialize the preload manager with bounded memory (from ReaderMemoryManagement mixin)
    initializePreloadManager(
      _chapterUrlModel,
      onPagesUpdated: () {
        if (mounted) {
          setState(() {});
          if (ref.read(cropBordersStateProvider)) _processCropBorders();
        }
      },
    );

    // Kick off ordered prefetch before the first frame so lower-indexed pages
    // win the HTTP race against the simultaneous widget-driven loads.
    _prefetchPagesInOrder(); // intentionally not awaited

    // proactively start loading adjacent chapters in background
    _proactivePreload();

    _readerController.setHistoryUpdate();
    // Use post-frame callback instead of Future.delayed(1ms) timing hack
    await Future(() {});
    final fullScreenReader = ref.watch(fullScreenReaderStateProvider);
    if (fullScreenReader) {
      if (isDesktop) {
        setFullScreen(value: true);
      } else {
        SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
      }
    }
    ref.read(_currentReaderMode.notifier).state = readerMode;
    if (mounted) {
      setState(() {
        _pageMode = _readerController.getPageMode();
      });
    }
    _setReaderMode(readerMode, ref);

    if (readerMode != ReaderMode.verticalContinuous &&
        readerMode != ReaderMode.webtoon) {
      _autoScroll.value = false;
    }
    _autoPagescroll();
    if (_readerController.getPageLength(_chapterUrlModel.pageUrls) == 1 &&
        (readerMode == ReaderMode.ltr ||
            readerMode == ReaderMode.rtl ||
            readerMode == ReaderMode.vertical)) {
      _onPageChanged(0);
    }
  }

  /// Warms Flutter's [ImageCache] in page order before the widget tree renders.
  ///
  /// [ScrollablePositionedList] builds all items within [minCacheExtent] in a
  /// single frame, firing every network request simultaneously, which means
  /// pages complete in arbitrary (server-response) order.  By resolving each
  /// provider sequentially here — starting before that first frame — we seed
  /// the cache so that earlier pages win the HTTP race: lower-indexed pages
  /// start their requests first and are therefore ready sooner.
  ///
  /// For pages already within the cache extent the widget will attach to the
  /// already-pending Future (Flutter deduplicates by provider key), so no
  /// extra requests are made.  Pages beyond the cache extent are fetched
  /// strictly one at a time in reading order, so the reader never sees a
  /// later page appear before an earlier one.
  ///
  /// This is fully async — [await] inside a fire-and-forget call — so the
  /// UI stays interactive throughout.
  Future<void> _prefetchPagesInOrder() async {
    final startIdx = (_currentIndex ?? 0).clamp(0, pages.length - 1);

    // Visit pages from the opening position forward, then backward.
    final indices = [
      for (var i = startIdx; i < pages.length; i++) i,
      for (var i = startIdx - 1; i >= 0; i--) i,
    ];

    for (final i in indices) {
      if (!mounted) return;
      final page = pages[i];
      if (page.isTransitionPage) continue;
      try {
        // Awaiting ensures page[i] finishes (or fails) before page[i+1]
        // starts downloading, giving strict reading-order priority.
        await precacheImage(page.getImageProvider(ref, true), context);
      } catch (_) {
        // Swallow errors: network failures, widget disposal, etc.
      }
    }
  }

  Future<void> _onPageChanged(int index) async {
    // In non-continuous double page mode, convert page view index to actual
    // pages array index for correct lookups.
    final int actualIndex = _pageViewToActualIndex(index);
    final int prevActualIndex = _pageViewToActualIndex(_currentIndex!);
    final cropBorders = ref.watch(cropBordersStateProvider);
    if (cropBorders) {
      _processCropBordersByIndex(index);
    }
    final idx = pages[prevActualIndex].index;
    if (idx != null) {
      _readerController.setPageIndex(
        _isDoublePageActive ? idx : _geCurrentIndex(idx),
        false,
      );
    }
    if (_readerController.chapter.id != pages[actualIndex].chapter!.id) {
      if (mounted) {
        setState(() {
          _readerController = ref.read(
            readerControllerProvider(
              chapter: pages[actualIndex].chapter!,
            ).notifier,
          );
          chapter = pages[actualIndex].chapter!;
          final chapterUrlModel = pages[actualIndex].chapterUrlModel;
          if (chapterUrlModel != null) {
            _chapterUrlModel = chapterUrlModel;
          }
          _isBookmarked = _readerController.getChapterBookmarked();
        });
      }
    }
    // Reset zoom of the previous page so user can swipe back freely (#443).
    clearGestureDetailsCache();
    _currentIndex = index;
    if (pages[actualIndex].index != null) {
      _currentPageDisplayIndex.value = pages[actualIndex].index!;
      ref
          .read(currentIndexProvider(chapter).notifier)
          .setCurrentIndex(pages[actualIndex].index!);
    }

    // ── Next-chapter preloading: trigger when near the end ──
    final distToEnd = pages.length - 1 - actualIndex;
    if (distToEnd <= pagePreloadAmount && !_isLastPageTransition) {
      _triggerNextChapterPreload();
    }

    // // ── Previous-chapter preloading: trigger when near the start ──
    // if (actualIndex <= pagePreloadAmount) {
    //   _triggerPrevChapterPreload();
    // }
  }

  late final _pageOffset = ValueNotifier(
    _readerController.autoScrollValues().$2,
  );

  void _autoPagescroll() async {
    if (_isContinuousMode()) {
      for (int i = 0; i < 1; i++) {
        await Future.delayed(const Duration(milliseconds: 100));
        if (!_autoScroll.value) {
          return;
        }
        _pageOffsetController.animateScroll(
          offset: _pageOffset.value,
          duration: const Duration(milliseconds: 100),
        );
      }
      _autoPagescroll();
    }
  }

  void _toggleScale(Offset tapPosition) {
    if (mounted) {
      setState(() {
        if (_scaleAnimationController.isAnimating) {
          return;
        }

        if (_photoViewController.scale == 1.0) {
          _scalePosition = _computeAlignmentByTapOffset(tapPosition);

          if (_scaleAnimationController.isCompleted) {
            _scaleAnimationController.reset();
          }

          _scaleAnimationController.forward();
          return;
        }

        if (_photoViewController.scale == 2.0) {
          _scaleAnimationController.reverse();
          return;
        }

        _photoViewScaleStateController.reset();
      });
    }
  }

  void _setReaderMode(ReaderMode value, WidgetRef ref) async {
    if (value != ReaderMode.verticalContinuous && value != ReaderMode.webtoon) {
      _autoScroll.value = false;
    } else {
      if (_autoScrollPage.value) {
        _autoPagescroll();
        _autoScroll.value = true;
      }
    }

    _failedToLoadImage.value = false;
    _readerController.setReaderMode(value);

    // Cache the reader mode for safe access in dispose
    _cachedReaderMode = value;

    int index = _pageViewToActualIndex(_currentIndex!);
    ref.read(_currentReaderMode.notifier).state = value;
    if (value == ReaderMode.vertical) {
      if (mounted) {
        setState(() {
          _scrollDirection = Axis.vertical;
          _isReverseHorizontal = false;
        });
        // Wait for the next frame so the PageView rebuilds with new direction
        await WidgetsBinding.instance.endOfFrame;

        _extendedController.jumpToPage(index);
      }
    } else if (value == ReaderMode.ltr || value == ReaderMode.rtl) {
      if (mounted) {
        setState(() {
          if (value == ReaderMode.rtl) {
            _isReverseHorizontal = true;
          } else {
            _isReverseHorizontal = false;
          }

          _scrollDirection = Axis.horizontal;
        });
        // Wait for the next frame so the PageView rebuilds with new direction
        await WidgetsBinding.instance.endOfFrame;

        _extendedController.jumpToPage(index);
      }
    } else {
      if (mounted) {
        setState(() {
          _isReverseHorizontal = value == ReaderMode.horizontalContinuousRTL;
        });
        // Wait for the next frame so the scroll view rebuilds
        await WidgetsBinding.instance.endOfFrame;
        _itemScrollController.scrollTo(
          index: index,
          duration: const Duration(milliseconds: 1),
          curve: Curves.ease,
        );
      }
    }
  }

  void _processCropBordersByIndex(int index) async {
    if (!_cropBorderCheckList.contains(index)) {
      _cropBorderCheckList.add(index);
      if (!mounted) return;
      final value = await ref.read(
        cropBordersProvider(data: pages[index], cropBorder: true).future,
      );
      if (mounted) {
        updatePageCropImage(index, value);
      }
    }
  }

  bool _isCropBordersProcessing = false;
  void _processCropBorders() async {
    if (_isCropBordersProcessing ||
        _cropBorderCheckList.length == pages.length) {
      return;
    }
    _isCropBordersProcessing = true;

    try {
      for (var i = 0; i < pages.length; i++) {
        if (!_cropBorderCheckList.contains(i)) {
          _cropBorderCheckList.add(i);
          if (!mounted) return;
          final value = await ref.read(
            cropBordersProvider(data: pages[i], cropBorder: true).future,
          );
          if (mounted) {
            updatePageCropImage(i, value);
          }
        }
      }
    } finally {
      _isCropBordersProcessing = false;
    }
  }

  void _goBack(BuildContext context) {
    restoreSystemUI();
    Navigator.pop(context);
  }

  void _isViewFunction() {
    final fullScreenReader = ref.watch(fullScreenReaderStateProvider);
    if (context.mounted) {
      setState(() {
        _isView = !_isView;
      });
    }
    if (fullScreenReader) {
      if (_isView) {
        restoreSystemUI();
      } else {
        SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
      }
    }
  }

  String _currentIndexLabel(int index) {
    if (_pageMode != PageMode.doublePage) {
      return "${index + 1}";
    }
    int pageLength = _readerController.getPageLength(_chapterUrlModel.pageUrls);
    int page1 = index + 1;
    int page2 = index + 2;
    return page2 > pageLength ? "$pageLength" : "$page1-$page2";
  }

  int _geCurrentIndex(int index) {
    return index;
  }

  /// Whether double page mode is active (continuous or paged).
  /// Horizontal continuous mode does NOT use double page layout.
  /// Uses ref.read() so cannot be called during dispose.
  bool get _isDoublePageActive =>
      _pageMode == PageMode.doublePage &&
      ref.read(_currentReaderMode) != ReaderMode.horizontalContinuous &&
      ref.read(_currentReaderMode) != ReaderMode.horizontalContinuousRTL;

  /// Safe version of _isDoublePageActive that uses cached reader mode.
  /// Safe to call during dispose without Riverpod assertion errors.
  bool get _isDoublePageActiveSync =>
      _pageMode == PageMode.doublePage &&
      _cachedReaderMode != ReaderMode.horizontalContinuous &&
      _cachedReaderMode != ReaderMode.horizontalContinuousRTL;

  /// Converts a page view index (from ExtendedPageController) to the actual
  /// index in the [pages] array for double page mode.
  ///
  /// In double page mode:
  ///   PV 0 → pages[0] (first page shown solo)
  ///   PV n (n>0) → pages[2n-1] (first page of the pair)
  int _pageViewToActualIndex(int pageViewIndex) {
    if (!_isDoublePageActive) return pageViewIndex;
    return (pageViewIndex * 2).clamp(0, pages.length - 1);
  }

  /// Safe version that uses cached reader mode for use in dispose.
  int _pageViewToActualIndexSync(int pageViewIndex) {
    if (!_isDoublePageActiveSync) return pageViewIndex;
    return (pageViewIndex * 2).clamp(0, pages.length - 1);
  }

  /// Converts an actual [pages] array index to a page view index
  /// for double page mode.
  int _actualToPageViewIndex(int actualIndex) {
    if (!_isDoublePageActive) return actualIndex;
    return actualIndex ~/ 2;
  }

  /// Total page count as seen by the page view controller.
  /// In double page mode, each PV page shows 2 actual pages.
  int get _pageViewPageCount =>
      _isDoublePageActive ? (pages.length / 2).ceil() : pages.length;

  bool _isContinuousMode([ReaderMode? mode]) {
    final readerMode = mode ?? ref.read(_currentReaderMode);
    return readerMode!.isContinuous;
  }
}