// Author: fruit.com.cn

import 'package:flutter/material.dart';

/// 播放未就绪时沿进度轨道循环移动的加载高光。
class LoadingProgressTrack extends StatefulWidget {
  const LoadingProgressTrack({
    super.key = const Key('progress-loading'),
    required this.height,
    this.trackColor = Colors.white24,
    this.highlightColor = Colors.white,
  });

  final double height;
  final Color trackColor;
  final Color highlightColor;

  @override
  State<LoadingProgressTrack> createState() => _LoadingProgressTrackState();
}

class _LoadingProgressTrackState extends State<LoadingProgressTrack>
    with SingleTickerProviderStateMixin, WidgetsBindingObserver {
  late final AnimationController _controller;
  late final Animation<double> _position;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 1200),
    );
    _position = CurvedAnimation(parent: _controller, curve: Curves.easeInOut);
    WidgetsBinding.instance.addObserver(this);
    _syncAnimation();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    _syncAnimation();
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    _controller.dispose();
    super.dispose();
  }

  void _syncAnimation() {
    if (WidgetsBinding.instance.lifecycleState == AppLifecycleState.resumed) {
      if (!_controller.isAnimating) _controller.repeat();
    } else {
      _controller.stop();
    }
  }

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: widget.height,
      child: ClipRRect(
        borderRadius: BorderRadius.circular(widget.height / 2),
        child: LayoutBuilder(
          builder: (context, constraints) {
            final highlightWidth = constraints.maxWidth * 0.28;
            final travel = constraints.maxWidth + highlightWidth;
            return AnimatedBuilder(
              animation: _position,
              builder: (context, _) {
                final left = -highlightWidth + travel * _position.value;
                return Stack(
                  fit: StackFit.expand,
                  children: [
                    ColoredBox(
                      key: const Key('progress-loading-track'),
                      color: widget.trackColor,
                    ),
                    Positioned(
                      left: left,
                      top: 0,
                      bottom: 0,
                      width: highlightWidth,
                      child: ColoredBox(
                        key: const Key('progress-loading-highlight'),
                        color: widget.highlightColor,
                      ),
                    ),
                  ],
                );
              },
            );
          },
        ),
      ),
    );
  }
}