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

class ConfettiOverlay extends StatefulWidget {
  const ConfettiOverlay({super.key});

  @override
  State<ConfettiOverlay> createState() => _ConfettiOverlayState();
}

class _ConfettiOverlayState extends State<ConfettiOverlay>
    with SingleTickerProviderStateMixin {
  late AnimationController _ctrl;
  final _rand = Random();
  late List<_Particle> _particles;

  @override
  void initState() {
    super.initState();
    _particles = List.generate(40, (_) => _Particle(_rand));
    _ctrl = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 2400),
    )..forward();
  }

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

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: _ctrl,
      builder: (_, __) => CustomPaint(
        painter: _ConfettiPainter(_particles, _ctrl.value),
        size: Size.infinite,
      ),
    );
  }
}

class _Particle {
  final double x;
  double y;
  final double speed;
  final double size;
  final Color color;
  final double rotation;
  final double rotSpeed;

  _Particle(Random r)
      : x = r.nextDouble(),
        y = -0.1 - r.nextDouble() * 0.3,
        speed = 0.3 + r.nextDouble() * 0.5,
        size = 6 + r.nextDouble() * 8,
        color = [
          const Color(0xFF5B4FCF),
          const Color(0xFFFF7EB3),
          const Color(0xFFFFD700),
          const Color(0xFF4CAF50),
          const Color(0xFF1CB0F6),
          const Color(0xFFFF7043),
        ][r.nextInt(6)],
        rotation = r.nextDouble() * 2 * pi,
        rotSpeed = (r.nextDouble() - 0.5) * 6;
}

class _ConfettiPainter extends CustomPainter {
  final List<_Particle> particles;
  final double t;

  _ConfettiPainter(this.particles, this.t);

  @override
  void paint(Canvas canvas, Size size) {
    for (final p in particles) {
      final y = (p.y + t * p.speed) * size.height;
      if (y > size.height) continue;
      final x = p.x * size.width;
      final rot = p.rotation + t * p.rotSpeed;

      canvas.save();
      canvas.translate(x, y);
      canvas.rotate(rot);

      final paint = Paint()..color = p.color;
      canvas.drawRect(
        Rect.fromCenter(center: Offset.zero, width: p.size, height: p.size * 0.5),
        paint,
      );
      canvas.restore();
    }
  }

  @override
  bool shouldRepaint(_ConfettiPainter old) => old.t != t;
}