one/dist/esm/link/prefetchIntent.mjs

One is a React framework for web, iOS, and Android apps.

function createPrefetchIntent(options) {
	const { onPrefetch, maxReach = 500, perpWeight = 5, minSpeed = 8 } = options;
	const done = /* @__PURE__ */ new Set();
	let rects = [];
	let px = 0, py = 0, vx = 0, vy = 0;
	let moveCount = 0;
	let lastPrefetchMove = 0;
	function setRects(newRects) {
		rects = newRects.filter((r) => !done.has(r.h));
	}
	function move(x, y, dx, dy) {
		moveCount++;
		const smooth = moveCount < 3 ? .3 : .6;
		vx = vx * smooth + dx * (1 - smooth);
		vy = vy * smooth + dy * (1 - smooth);
		px = x;
		py = y;
		const speed = Math.sqrt(vx * vx + vy * vy);
		if (speed < minSpeed) return;
		const ux = vx / speed;
		const uy = vy / speed;
		let best = Infinity;
		let href = "";
		for (const { r, h } of rects) {
			const cx = (r.left + r.right) / 2 - px;
			const cy = (r.top + r.bottom) / 2 - py;
			const dist = Math.sqrt(cx * cx + cy * cy);
			const along = cx * ux + cy * uy;
			if (along < 0) continue;
			const perpX = cx - along * ux;
			const perpY = cy - along * uy;
			const perp = Math.sqrt(perpX * perpX + perpY * perpY);
			const baseRadius = Math.max(r.width, r.height) / 2 + 30;
			const distanceFactor = Math.max(.2, 1 - dist / 1e3);
			const radius = baseRadius * distanceFactor + 20;
			if (perp > radius) continue;
			const score = along + perp * perpWeight;
			if (score < best) {
				best = score;
				href = h;
			}
		}
		if (href && best < maxReach && moveCount - lastPrefetchMove > 1) {
			done.add(href);
			rects = rects.filter((r) => r.h !== href);
			lastPrefetchMove = moveCount;
			onPrefetch(href);
		}
	}
	const nodes = /* @__PURE__ */ new Map();
	function observe(el, href) {
		nodes.set(el, href);
		return () => {
			nodes.delete(el);
			done.delete(href);
		};
	}
	return {
		setRects,
		move,
		observe,
		nodes,
		done
	};
}
let instance = null;
let started = false;
function startPrefetchIntent(onPrefetch) {
	if (started) return instance;
	started = true;
	instance = createPrefetchIntent({ onPrefetch });
	let frame = 0;
	let px = 0, py = 0;
	function measure() {
		if (!instance.nodes.size) return setTimeout(measure, 300);
		const io = new IntersectionObserver((entries) => {
			io.disconnect();
			instance.setRects(entries.filter((e) => e.isIntersecting).map((e) => ({
				r: e.boundingClientRect,
				h: instance.nodes.get(e.target)
			})).filter((x) => x.h));
			setTimeout(measure, 300);
		});
		instance.nodes.forEach((_, el) => io.observe(el));
	}
	measure();
	document.addEventListener("mousemove", (e) => {
		if (++frame % 4) return;
		const dx = e.clientX - px;
		const dy = e.clientY - py;
		px = e.clientX;
		py = e.clientY;
		instance.move(px, py, dx, dy);
	}, { passive: true });
	return instance;
}
function observePrefetchIntent(el, href) {
	if (!instance) return () => {};
	return instance.observe(el, href);
}

export { createPrefetchIntent, observePrefetchIntent, startPrefetchIntent };
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