interface Snowflake {
	x: number;
	y: number;
	size: number;
	opacity: number;
	speedY: number;
	speedX: number;
}

function createSnowfall() {
	const canvas = document.createElement("canvas");
	const ctx = canvas.getContext("2d")!;
	document.body.style.margin = "0";
	document.body.style.overflow = "hidden";
	canvas.style.position = "fixed";
	canvas.style.top = "0";
	canvas.style.left = "0";
	canvas.style.zIndex = "-1";

	document.body.appendChild(canvas);

	const resizeCanvas = () => {
		canvas.width = window.innerWidth;
		canvas.height = window.innerHeight;
	};
	resizeCanvas();
	window.addEventListener("resize", resizeCanvas);

	const NUM_SNOWFLAKES = 320;
	const snowflakes: Snowflake[] = [];

	let windStrength = 0;

	for (let i = 0; i < NUM_SNOWFLAKES; i++) {
		snowflakes.push(createSnowflake());
	}

	function createSnowflake(): Snowflake {
		const size = Math.random() * 3 + 1;
		return {
			x: Math.random() * canvas.width,
			y: Math.random() * canvas.height,
			size,
			opacity: Math.random() * 0.2 + 0.2,
			speedY: Math.random() * size * 0.6 + 0.4,
			speedX: Math.random() * 0.5 - 0.25,
		};
	}

	function updateWind() {
		windStrength += (Math.random() - 0.5) * 0.01;
		windStrength = Math.max(-0.5, Math.min(0.5, windStrength));
	}

	function updateSnowflakes() {
		ctx.clearRect(0, 0, canvas.width, canvas.height);

		updateWind();

		for (const flake of snowflakes) {
			flake.x += flake.speedX + windStrength;
			flake.y += flake.speedY;

			if (flake.y > canvas.height) {
				flake.y = -flake.size;
				flake.x = Math.random() * canvas.width;
				flake.speedY = Math.random() * flake.size * 0.5 + 0.5;
				flake.speedX = Math.random() * 0.5 - 0.25;
			}

			if (flake.x < -flake.size) {
				flake.x = canvas.width + flake.size;
			} else if (flake.x > canvas.width + flake.size) {
				flake.x = -flake.size;
			}

			ctx.beginPath();
			ctx.arc(flake.x, flake.y, flake.size, 0, Math.PI * 2);
			ctx.fillStyle = `rgba(255, 255, 255, ${flake.opacity})`;
			ctx.fill();
		}

		requestAnimationFrame(updateSnowflakes);
	}

	updateSnowflakes();
}

createSnowfall();