import 'package:flutter/material.dart';

class ShimmerEffect extends StatefulWidget {
  final Widget child;
  final Duration duration; // 光效滑动的时间
  final Duration delay; // 每轮动画结束后的延迟
  final Alignment begin; // 滑动起点
  final Alignment end; // 滑动终点
  final ImageProvider image; // 外部传入的光效图片
  final double shimmerWidthFactor; // 光效图片相对于 child 的宽度

  const ShimmerEffect({
    super.key,
    required this.child,
    required this.image,
    this.duration = const Duration(seconds: 2),
    this.delay = const Duration(seconds: 1),
    this.begin = const Alignment(-1, 0),
    this.end = const Alignment(1, 0),
    this.shimmerWidthFactor = 0.2,
  });

  @override
  State<ShimmerEffect> createState() => _ShimmerEffectState();
}

class _ShimmerEffectState extends State<ShimmerEffect>
    with SingleTickerProviderStateMixin {
  late final AnimationController _controller;
  late final Animation<double> _animation;

  @override
  void initState() {
    super.initState();

    _controller = AnimationController(
      vsync: this,
      duration: widget.duration,
    );

    _animation = Tween<double>(begin: -1.0, end: 1.0).animate(_controller);

    _startLoop();
  }

  void _startLoop() async {
    while (mounted) {
      await _controller.forward();
      _controller.reset();
      await Future.delayed(widget.delay);
    }
  }

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

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(builder: (context, constraints) {
      final width = constraints.maxWidth;
      final shimmerWidth = width * widget.shimmerWidthFactor;

      return Stack(
        children: [
          widget.child,
          AnimatedBuilder(
            animation: _controller,
            builder: (context, _) {
              final dx = _animation.value * (width + shimmerWidth);

              return Positioned(
                left: dx,
                top: 0,
                width: shimmerWidth,
                height: constraints.maxHeight,
                child: IgnorePointer(
                  child: Image(
                    image: widget.image,
                    fit: BoxFit.fill,
                  ),
                ),
              );
            },
          )
        ],
      );
    });
  }
}