// Author: fruit.com.cn
// 职责：绘制收藏点赞周围的紧凑双向短线，无圆环或阴影，不参与手势。
import 'dart:math' as math;

import 'package:flutter/material.dart';

const int _rayCount = 8;
const double _startProgress = 0.1;
const double _radiusStart = 0.34;
const double _radiusTravel = 0.14;
const double _rayLength = 0.07;
const double _strokeFraction = 0.025;
const double _rayAlpha = 0.65;
const double _fullCircle = math.pi * 2;
const double _rayRotation = math.pi / _rayCount;

/// 收藏/点赞的装饰反馈：选中外扩，取消收束。
class RailTapBurst extends StatelessWidget {
  /// [progress] 来自按钮的点击动画，不创建独立计时器。
  const RailTapBurst({
    super.key,
    required this.progress,
    required this.color,
    required this.contracting,
  });

  final double progress;
  final Color color;
  final bool contracting;

  @override
  Widget build(BuildContext context) => IgnorePointer(
    child: CustomPaint(
      painter: _RailBurstPainter(
        progress: progress,
        color: color,
        contracting: contracting,
      ),
    ),
  );
}

class _RailBurstPainter extends CustomPainter {
  const _RailBurstPainter({
    required this.progress,
    required this.color,
    required this.contracting,
  });

  final double progress;
  final Color color;
  final bool contracting;

  @override
  void paint(Canvas canvas, Size size) {
    final phase = ((progress - _startProgress) / (1 - _startProgress)).clamp(
      0.0,
      1.0,
    );
    if (phase == 0 || phase == 1) return;
    final eased = Curves.easeOutCubic.transform(phase);
    final travel = contracting ? 1 - eased : eased;
    final base = size.shortestSide;
    final radius = base * (_radiusStart + _radiusTravel * travel);
    final alpha = math.sin(math.pi * phase);
    final paint = Paint()
      ..style = PaintingStyle.stroke
      ..strokeCap = StrokeCap.round
      ..strokeWidth = base * _strokeFraction
      ..color = color.withValues(alpha: alpha * _rayAlpha);
    final center = size.center(Offset.zero);
    final length = base * _rayLength * (1 - phase);
    for (var index = 0; index < _rayCount; index++) {
      final angle = _fullCircle * index / _rayCount + _rayRotation;
      canvas.drawLine(
        center + Offset.fromDirection(angle, radius),
        center + Offset.fromDirection(angle, radius + length),
        paint,
      );
    }
  }

  @override
  bool shouldRepaint(covariant _RailBurstPainter oldDelegate) =>
      oldDelegate.progress != progress ||
      oldDelegate.color != color ||
      oldDelegate.contracting != contracting;
}