smov/src/components/utils/Lightbar.tsx

import { useEffect, useRef } from "react";
import "./Lightbar.css";

class Particle {
  x = 0;

  y = 0;

  radius = 0;

  direction = 0;

  speed = 0;

  lifetime = 0;

  ran = 0;

  constructor(canvas: HTMLCanvasElement) {
    this.reset(canvas);
    this.initialize(canvas);
  }

  reset(canvas: HTMLCanvasElement) {
    this.x = Math.round((Math.random() * canvas.width) / 2 + canvas.width / 4);
    this.y = Math.random() * 100 + 5;

    this.radius = 1 + Math.floor(Math.random() * 0.5);
    this.direction = -((Math.random() * Math.PI) / 2) + Math.PI / 4;
    this.speed = 0.02 + Math.random() * 0.08;

    const second = 60;
    this.lifetime = second * 3 + Math.random() * (second * 30);

    this.ran = 0;
  }

  initialize(canvas: HTMLCanvasElement) {
    this.ran = Math.random() * this.lifetime;
    const baseSpeed = this.speed;
    this.speed = Math.random() * this.lifetime * baseSpeed;
    this.update(canvas);
    this.speed = baseSpeed;
  }

  update(canvas: HTMLCanvasElement) {
    this.ran += 1;

    const addX = this.speed * Math.sin(this.direction);
    const addY = this.speed * Math.cos(this.direction);
    this.x += addX;
    this.y += addY;

    if (this.ran > this.lifetime) {
      this.reset(canvas);
    }
  }

  render(canvas: HTMLCanvasElement) {
    const ctx = canvas.getContext("2d");
    if (!ctx) return;

    ctx.save();
    ctx.beginPath();

    const x = this.ran / this.lifetime;
    const o = (x - x * x) * 4;
    ctx.globalAlpha = Math.max(0, o * 0.8);

    ctx.ellipse(
      this.x,
      this.y,
      this.radius,
      this.radius * 1.5,
      this.direction,
      0,
      Math.PI * 2
    );
    ctx.fillStyle = "white";
    ctx.fill();
    ctx.restore();
  }
}

function ParticlesCanvas() {
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    if (!canvasRef.current) return;
    const canvas = canvasRef.current;
    const particles: Particle[] = [];

    canvas.width = canvas.scrollWidth;
    canvas.height = canvas.scrollHeight;

    for (let i = 0; i < 20; i += 1) {
      const particle = new Particle(canvas);
      particles.push(particle);
    }

    let shouldTick = true;
    let handle: ReturnType<typeof requestAnimationFrame> | null = null;
    function particlesLoop() {
      const ctx = canvas.getContext("2d");
      if (!ctx) return;

      if (shouldTick) {
        for (const particle of particles) {
          particle.update(canvas);
        }
        shouldTick = false;
      }

      canvas.width = canvas.scrollWidth;
      canvas.height = canvas.scrollHeight;
      for (const particle of particles) {
        particle.render(canvas);
      }

      handle = requestAnimationFrame(particlesLoop);
    }
    const interval = setInterval(() => {
      shouldTick = true;
    }, 1e3 / 120); // tick 120 times a sec

    particlesLoop();

    return () => {
      if (handle) cancelAnimationFrame(handle);
      clearInterval(interval);
    };
  }, []);

  return <canvas className="particles" ref={canvasRef} />;
}

export function Lightbar(props: { className?: string }) {
  return (
    <div className={props.className}>
      <div className="lightbar">
        <ParticlesCanvas />
      </div>
    </div>
  );
}