import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:isekai_wiki/api/response/parse.dart';
import 'package:isekai_wiki/components/gesture_detector.dart';
import 'package:isekai_wiki/components/safearea_builder.dart';
import 'package:isekai_wiki/styles.dart';

class TOCStyles {
  static const double listPadding = 2;
  static const activeColor = Color.fromRGBO(51, 102, 204, 1);
}

class TOCList extends StatefulWidget {
  final String activedItem;
  final bool hasFirstSection;
  final List<MWParseSectionInfo> sections;
  final void Function(String anchor)? onSwitchTitle;

  const TOCList({
    super.key,
    required this.sections,
    this.activedItem = "",
    this.hasFirstSection = false,
    this.onSwitchTitle,
  });

  @override
  State<StatefulWidget> createState() => _TOCListState();
}

class _TOCListState extends State<TOCList> {
  String _activedItem = "";
  String _lastSelectedItem = "";
  double _listPaddingTop = 0;
  double _listPaddingBottom = 0;

  final ScrollController _scrollController = ScrollController();

  @override
  void didUpdateWidget(covariant TOCList oldWidget) {
    super.didUpdateWidget(oldWidget);

    if (_activedItem != widget.activedItem) {
      _activedItem = widget.activedItem;
      // Scroll to current item
      int activedIndex;
      if (_activedItem == "_firstSection") {
        activedIndex = 0;
      } else {
        activedIndex = widget.sections.indexWhere((element) => element.anchor == _activedItem);
        if (widget.hasFirstSection) {
          activedIndex += 1;
        }
        if (activedIndex == -1) {
          activedIndex = 0;
        }
      }
      scrollToTOCItem(activedIndex);
    }
  }

  void scrollToTOCItem(int index) {
    var listLength = widget.sections.length + (widget.hasFirstSection ? 1 : 0);
    var scrollInnerOffsetHeight =
        _scrollController.position.maxScrollExtent + _scrollController.position.viewportDimension;
    var scrollInnerHeight = scrollInnerOffsetHeight - _listPaddingTop - _listPaddingBottom;

    var itemHeight = scrollInnerHeight / listLength;
    var target = itemHeight * index;

    var scrollTop = _scrollController.position.pixels;
    var scrollOffsetBottom = scrollTop +
        _scrollController.position.viewportDimension -
        _listPaddingTop -
        _listPaddingBottom -
        itemHeight;

    if (target < scrollTop || target > scrollOffsetBottom) {
      _scrollController.jumpTo(clampDouble(target, _scrollController.position.minScrollExtent,
          _scrollController.position.maxScrollExtent));
    }
  }

  void handleTOCItemPressed(String anchor) {
    _lastSelectedItem = anchor;
    widget.onSwitchTitle?.call(_lastSelectedItem);
  }

  @override
  Widget build(BuildContext context) {
    final itemCount = widget.hasFirstSection ? widget.sections.length + 1 : widget.sections.length;

    List<Widget> tocItemList = [];
    if (widget.hasFirstSection) {
      // 创建首项
      tocItemList.add(
        TOCItem(
          text: "简介",
          anchor: "_firstSection",
          active: widget.activedItem == "_firstSection",
          onPressed: handleTOCItemPressed,
        ),
      );
    }

    for (var index = 0; index < widget.sections.length; index++) {
      var section = widget.sections[index];
      var isTopItem = !widget.hasFirstSection && index == 0;
      tocItemList.add(
        Container(
          decoration: BoxDecoration(
            border: Border(
                top: isTopItem
                    ? BorderSide.none
                    : const BorderSide(color: Color.fromRGBO(234, 236, 240, 1))),
          ),
          child: TOCItem(
            text: section.line,
            number: section.number,
            anchor: section.anchor,
            active: widget.activedItem == section.anchor,
            onPressed: handleTOCItemPressed,
          ),
        ),
      );
    }

    return DefaultTextStyle(
      style: CupertinoTheme.of(context).textTheme.textStyle,
      child: Container(
        color: Styles.themePageBackgroundColor,
        child: SafeAreaBuilder(builder: (context, padding) {
          _listPaddingTop = padding.top + TOCStyles.listPadding;
          _listPaddingBottom = padding.bottom + TOCStyles.listPadding;
          return ListView(
            controller: _scrollController,
            padding: EdgeInsets.only(
              top: _listPaddingTop,
              bottom: _listPaddingBottom,
              right: padding.right,
            ),
            children: tocItemList,
          );
        }),
      ),
    );
  }
}

class TOCItem extends StatelessWidget {
  final void Function(String anchor)? onPressed;
  final bool active;
  final String? number;
  final String anchor;
  final String text;

  const TOCItem(
      {super.key,
      this.onPressed,
      this.active = false,
      this.number,
      required this.text,
      required this.anchor});

  void handleTap() {
    onPressed?.call(anchor);
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        ClickableBuilder(
          builder: (context, mode, child) => GestureDetector(
            onTap: handleTap,
            child: Container(
              color: mode == PointerActiveMode.active
                  ? Styles.themeNormalActionActiveColor
                  : Styles.themeNormalActionColor,
              padding: const EdgeInsets.only(top: 12, right: 10, bottom: 12, left: 15),
              child: child,
            ),
          ),
          child: DefaultTextStyle(
            style: CupertinoTheme.of(context).textTheme.textStyle,
            child: Row(
              children: [
                if (number != null) Text(number!),
                if (number != null) const SizedBox(width: 10),
                Flexible(
                  child: Text(
                    text,
                    overflow: TextOverflow.fade,
                    maxLines: 1,
                    softWrap: false,
                  ),
                ),
              ],
            ),
          ),
        ),
        if (active)
          Positioned(
            top: 0,
            left: 0,
            bottom: 0,
            width: 4,
            child: Container(
              color: TOCStyles.activeColor,
            ),
          ),
      ],
    );
  }
}