import 'dart:async';

import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';

import 'carousel_controller.dart' as cs;
import 'carousel_options.dart';
import 'carousel_state.dart';
import 'utils.dart';

export 'carousel_controller.dart';
export 'carousel_options.dart';

typedef Widget ExtendedIndexedWidgetBuilder(
    BuildContext context, int index, int realIndex);

class CarouselSlider extends StatefulWidget {
  /// [CarouselOptions] to create a [CarouselState] with
  final CarouselOptions options;

  final bool? disableGesture;

  /// The widgets to be shown in the carousel of default constructor
  final List<Widget>? items;

  /// The widget item builder that will be used to build item on demand
  /// The third argument is the PageView's real index, can be used to cooperate
  /// with Hero.
  final ExtendedIndexedWidgetBuilder? itemBuilder;

  /// A [MapController], used to control the map.
  final cs.CarouselControllerImpl _carouselController;

  final int? itemCount;

  CarouselSlider(
      {required this.items,
        required this.options,
        this.disableGesture,
        cs.CarouselController? carouselController,
        Key? key})
      : itemBuilder = null,
        itemCount = items != null ? items.length : 0,
        _carouselController = carouselController != null
            ? carouselController as cs.CarouselControllerImpl
            : cs.CarouselController() as cs.CarouselControllerImpl,
        super(key: key);

  /// The on demand item builder constructor
  CarouselSlider.builder(
      {required this.itemCount,
        required this.itemBuilder,
        required this.options,
        this.disableGesture,
        cs.CarouselController? carouselController,
        Key? key})
      : items = null,
        _carouselController = carouselController != null
            ? carouselController as cs.CarouselControllerImpl
            : CarouselController() as cs.CarouselControllerImpl,
        super(key: key);

  @override
  CarouselSliderState createState() => CarouselSliderState(_carouselController);
}

class CarouselSliderState extends State<CarouselSlider>
    with TickerProviderStateMixin {
  final cs.CarouselControllerImpl carouselController;
  Timer? timer;

  CarouselOptions get options => widget.options;

  CarouselState? carouselState;

  PageController? pageController;

  /// mode is related to why the page is being changed
  CarouselPageChangedReason mode = CarouselPageChangedReason.controller;

  CarouselSliderState(this.carouselController);

  void changeMode(CarouselPageChangedReason _mode) {
    mode = _mode;
  }

  @override
  void didUpdateWidget(CarouselSlider oldWidget) {
    carouselState!.options = options;
    carouselState!.itemCount = widget.itemCount;

    // pageController needs to be re-initialized to respond to state changes
    pageController = PageController(
      viewportFraction: options.viewportFraction,
      initialPage: carouselState!.realPage,
    );
    carouselState!.pageController = pageController;

    // handle autoplay when state changes
    handleAutoPlay();

    super.didUpdateWidget(oldWidget);
  }

  @override
  void initState() {
    super.initState();
    carouselState =
        CarouselState(this.options, clearTimer, resumeTimer, this.changeMode);

    carouselState!.itemCount = widget.itemCount;
    carouselController.state = carouselState;
    carouselState!.initialPage = widget.options.initialPage;
    carouselState!.realPage = options.enableInfiniteScroll
        ? carouselState!.realPage + carouselState!.initialPage
        : carouselState!.initialPage;
    handleAutoPlay();

    pageController = PageController(
      viewportFraction: options.viewportFraction,
      initialPage: carouselState!.realPage,
    );

    carouselState!.pageController = pageController;
  }

  Timer? getTimer() {
    return widget.options.autoPlay
        ? Timer.periodic(widget.options.autoPlayInterval, (_) {
      if (!mounted) {
        clearTimer();
        return;
      }

      final route = ModalRoute.of(context);
      if (route?.isCurrent == false) {
        return;
      }

      CarouselPageChangedReason previousReason = mode;
      changeMode(CarouselPageChangedReason.timed);
      int nextPage = carouselState!.pageController!.page!.round() + 1;
      int itemCount = widget.itemCount ?? widget.items!.length;

      if (nextPage >= itemCount &&
          widget.options.enableInfiniteScroll == false) {
        if (widget.options.pauseAutoPlayInFiniteScroll) {
          clearTimer();
          return;
        }
        nextPage = 0;
      }

      carouselState!.pageController!
          .animateToPage(nextPage,
          duration: widget.options.autoPlayAnimationDuration,
          curve: widget.options.autoPlayCurve)
          .then((_) => changeMode(previousReason));
    })
        : null;
  }

  void clearTimer() {
    if (timer != null) {
      timer?.cancel();
      timer = null;
    }
  }

  void resumeTimer() {
    if (timer == null) {
      timer = getTimer();
    }
  }

  void handleAutoPlay() {
    bool autoPlayEnabled = widget.options.autoPlay;

    if (autoPlayEnabled && timer != null) return;

    clearTimer();
    if (autoPlayEnabled) {
      resumeTimer();
    }
  }

  Widget getGestureWrapper(Widget child) {
    Widget wrapper;
    if (widget.options.height != null) {
      wrapper = Container(height: widget.options.height, child: child);
    } else {
      wrapper =
          AspectRatio(aspectRatio: widget.options.aspectRatio, child: child);
    }

    if (true == widget.disableGesture) {
      return NotificationListener(
        onNotification: (Notification notification) {
          if (widget.options.onScrolled != null &&
              notification is ScrollUpdateNotification) {
            widget.options.onScrolled!(carouselState!.pageController!.page);
          }
          return false;
        },
        child: wrapper,
      );
    }

    return RawGestureDetector(
      behavior: HitTestBehavior.opaque,
      gestures: {
        _MultipleGestureRecognizer:
        GestureRecognizerFactoryWithHandlers<_MultipleGestureRecognizer>(
                () => _MultipleGestureRecognizer(),
                (_MultipleGestureRecognizer instance) {
              instance.onStart = (_) {
                onStart();
              };
              instance.onDown = (_) {
                onPanDown();
              };
              instance.onEnd = (_) {
                onPanUp();
              };
              instance.onCancel = () {
                onPanUp();
              };
            }),
      },
      child: NotificationListener(
        onNotification: (Notification notification) {
          if (widget.options.onScrolled != null &&
              notification is ScrollUpdateNotification) {
            widget.options.onScrolled!(carouselState!.pageController!.page);
          }
          return false;
        },
        child: wrapper,
      ),
    );
  }

  Widget getCenterWrapper(Widget child) {
    if (widget.options.disableCenter) {
      return Container(
        child: child,
      );
    }
    return Center(child: child);
  }

  Widget getEnlargeWrapper(Widget? child,
      {double? width,
        double? height,
        double? scale,
        required double itemOffset}) {
    if (widget.options.enlargeStrategy == CenterPageEnlargeStrategy.height) {
      return SizedBox(child: child, width: width, height: height);
    }
    if (widget.options.enlargeStrategy == CenterPageEnlargeStrategy.zoom) {
      late Alignment alignment;
      final bool horizontal = options.scrollDirection == Axis.horizontal;
      if (itemOffset > 0) {
        alignment = horizontal ? Alignment.centerRight : Alignment.bottomCenter;
      } else {
        alignment = horizontal ? Alignment.centerLeft : Alignment.topCenter;
      }
      return Transform.scale(child: child, scale: scale!, alignment: alignment);
    }
    return Transform.scale(
        scale: scale!,
        child: Container(child: child, width: width, height: height));
  }

  void onStart() {
    changeMode(CarouselPageChangedReason.manual);
  }

  void onPanDown() {
    if (widget.options.pauseAutoPlayOnTouch) {
      clearTimer();
    }

    changeMode(CarouselPageChangedReason.manual);
  }

  void onPanUp() {
    if (widget.options.pauseAutoPlayOnTouch) {
      resumeTimer();
    }
  }

  @override
  void dispose() {
    super.dispose();
    clearTimer();
  }

  @override
  Widget build(BuildContext context) {
    return getGestureWrapper(PageView.builder(
      padEnds: widget.options.padEnds,
      scrollBehavior: ScrollConfiguration.of(context).copyWith(
        scrollbars: false,
        overscroll: false,
        dragDevices: {
          PointerDeviceKind.touch,
          PointerDeviceKind.mouse,
        },
      ),
      clipBehavior: widget.options.clipBehavior,
      physics: widget.options.scrollPhysics,
      scrollDirection: widget.options.scrollDirection,
      pageSnapping: widget.options.pageSnapping,
      controller: carouselState!.pageController,
      reverse: widget.options.reverse,
      itemCount: widget.options.enableInfiniteScroll ? null : widget.itemCount,
      key: widget.options.pageViewKey,
      onPageChanged: (int index) {
        int currentPage = getRealIndex(index + carouselState!.initialPage,
            carouselState!.realPage, widget.itemCount);
        if (widget.options.onPageChanged != null) {
          widget.options.onPageChanged!(currentPage, mode);
        }
      },
      itemBuilder: (BuildContext context, int idx) {
        final int index = getRealIndex(idx + carouselState!.initialPage,
            carouselState!.realPage, widget.itemCount);

        return AnimatedBuilder(
          animation: carouselState!.pageController!,
          child: (widget.items != null)
              ? (widget.items!.length > 0 ? widget.items![index] : Container())
              : widget.itemBuilder!(context, index, idx),
          builder: (BuildContext context, child) {
            double distortionValue = 1.0;
            // if `enlargeCenterPage` is true, we must calculate the carousel item's height
            // to display the visual effect
            double itemOffset = 0;
            if (widget.options.enlargeCenterPage != null &&
                widget.options.enlargeCenterPage == true) {
              // pageController.page can only be accessed after the first build,
              // so in the first build we calculate the itemoffset manually
              var position = carouselState?.pageController?.position;
              if (position != null &&
                  position.hasPixels &&
                  position.hasContentDimensions) {
                var _page = carouselState?.pageController?.page;
                if (_page != null) {
                  itemOffset = _page - idx;
                }
              } else {
                BuildContext storageContext = carouselState!
                    .pageController!.position.context.storageContext;
                final double? previousSavedPosition =
                PageStorage.of(storageContext)?.readState(storageContext)
                as double?;
                if (previousSavedPosition != null) {
                  itemOffset = previousSavedPosition - idx.toDouble();
                } else {
                  itemOffset =
                      carouselState!.realPage.toDouble() - idx.toDouble();
                }
              }

              final double enlargeFactor =
              options.enlargeFactor.clamp(0.0, 1.0);
              final num distortionRatio =
              (1 - (itemOffset.abs() * enlargeFactor)).clamp(0.0, 1.0);
              distortionValue =
                  Curves.easeOut.transform(distortionRatio as double);
            }

            final double height = widget.options.height ??
                MediaQuery.of(context).size.width *
                    (1 / widget.options.aspectRatio);

            if (widget.options.scrollDirection == Axis.horizontal) {
              return getCenterWrapper(getEnlargeWrapper(child,
                  height: distortionValue * height,
                  scale: distortionValue,
                  itemOffset: itemOffset));
            } else {
              return getCenterWrapper(getEnlargeWrapper(child,
                  width: distortionValue * MediaQuery.of(context).size.width,
                  scale: distortionValue,
                  itemOffset: itemOffset));
            }
          },
        );
      },
    ));
  }
}

class _MultipleGestureRecognizer extends PanGestureRecognizer {}