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

class LineTabSwitcher extends StatefulWidget {
  const LineTabSwitcher({
    super.key,
    required this.tabs,
    required this.onTabChange,
    required this.selectedTab,
  });

  final List<String> tabs;
  final void Function(int index) onTabChange;
  final int selectedTab;

  @override
  State<LineTabSwitcher> createState() => _LineTabSwitcherState();
}

class _LineTabSwitcherState extends State<LineTabSwitcher> {
  List<GlobalKey> textWidgetKeys = [];
  List<Size> textWidgetSizes = [];
  double totalWidth = 0;
  final double itemPadding = 16;
  final double barPadding = 8;
  bool textWidgetsMeasured = false;

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

    if (oldWidget.tabs.length != widget.tabs.length) {
      textWidgetKeys = List.generate(widget.tabs.length, (_) => GlobalKey());
      textWidgetSizes = [];
      totalWidth = 0;
      textWidgetsMeasured = false;

      WidgetsBinding.instance.addPostFrameCallback((_) => measure());
    }
  }

  double _calcBarLeft() {
    double left = 0;

    if (textWidgetKeys.isEmpty || textWidgetSizes.isEmpty) {
      return 0;
    }

    for (int i = 0; i < widget.selectedTab; i++) {
      left += textWidgetSizes[i].width + itemPadding;
    }

    left += barPadding;

    return left;
  }

  @override
  void initState() {
    super.initState();
    textWidgetKeys = List.generate(widget.tabs.length, (index) => GlobalKey());
    WidgetsBinding.instance.addPostFrameCallback((_) => measure());
  }

  void measure() {
    if(textWidgetsMeasured) return;
    setState(() {
      textWidgetSizes = textWidgetKeys
          .map((k) => k.currentContext!.size)
          .whereType<Size>()
          .toList();

      for(final size in textWidgetSizes) {
        totalWidth += size.width+itemPadding;
      }
      totalWidth += barPadding;
      textWidgetsMeasured = true;
    });
  }

  @override
  Widget build(BuildContext context) {
    if (!textWidgetsMeasured) {
      WidgetsBinding.instance.addPostFrameCallback((_) => measure());
    }

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      mainAxisAlignment: MainAxisAlignment.start,
      children: [
        Container(
          height: 28,
          child: Row(
            children: widget.tabs.map((item){

              final index = widget.tabs.indexOf(item);

              return GestureDetector(
                onTap: () {
                  widget.onTabChange(index);
                },
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: [
                    AnimatedDefaultTextStyle(
                      duration: Duration(milliseconds: 150),
                      style: DefaultTextStyle.of(context).style.copyWith(
                        inherit: true,
                        fontSize: 16,
                        fontWeight: FontWeight.w500,
                        color: widget.selectedTab == index
                            ? Theme.of(context).colorScheme.onSurface
                            : Theme.of(context).colorScheme.onSurfaceVariant,
                      ),
                      child: Padding(
                        padding: EdgeInsets.symmetric(horizontal: itemPadding/2),
                        child: Text(
                          item,
                          key: textWidgetKeys[index],
                        ),
                      ),
                    ),
                  ],
                ),
              );
            }).toList()
          )
        ),
        Container(
          width: totalWidth,
          height: 2,
          child: Stack(
            children: [
              AnimatedPositioned(
                curve: Curves.easeOut,
                left: _calcBarLeft(),
                bottom: 0,
                duration: Duration(milliseconds: 150),
                child: AnimatedSize(
                  duration: Duration(milliseconds: 150),
                  child: Container(
                    height: 2,
                    width: textWidgetSizes.isEmpty
                        ? 0
                        : textWidgetSizes[widget.selectedTab].width,
                    color: Theme.of(context).colorScheme.onSurface,
                  ),
                ),
              ),
            ],
          ),
        ),
      ],
    );
  }
}