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Next.js Proximity Prefetch (PPF)
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| "use client"; | |
| import { useRouter } from "next/navigation"; | |
| import type { ReactNode } from "react"; | |
| import { useCallback, useEffect, useState } from "react"; | |
| interface ProximityPrefetchProps { | |
| children: ReactNode; | |
| threshold?: number; | |
| predictionInterval?: number; | |
| } | |
| export function ProximityPrefetch({ | |
| children, | |
| threshold = 200, | |
| predictionInterval = 0, | |
| }: ProximityPrefetchProps) { | |
| const router = useRouter(); | |
| const [mousePosition, setMousePosition] = useState({ x: 0, y: 0 }); | |
| const [prefetchedRoutes, setPrefetchedRoutes] = useState<Set<string>>( | |
| new Set(), | |
| ); | |
| const [links, setLinks] = useState< | |
| { el: HTMLAnchorElement; href: string; rect: DOMRect }[] | |
| >([]); | |
| const updateLinks = useCallback(() => { | |
| const anchors = Array.from( | |
| document.querySelectorAll('a[href^="/"]'), | |
| ) as HTMLAnchorElement[]; | |
| setLinks( | |
| anchors | |
| .map((el) => { | |
| const href = el.getAttribute("href"); | |
| if (href?.startsWith("/") && !href.includes("#")) { | |
| return { | |
| el, | |
| href, | |
| rect: el.getBoundingClientRect(), | |
| }; | |
| } | |
| return null; | |
| }) | |
| .filter(Boolean) as { | |
| el: HTMLAnchorElement; | |
| href: string; | |
| rect: DOMRect; | |
| }[], | |
| ); | |
| }, []); | |
| const calculateDistance = ( | |
| x1: number, | |
| y1: number, | |
| x2: number, | |
| y2: number, | |
| ) => { | |
| return Math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2); | |
| }; | |
| const calculateCenterPoint = (rect: DOMRect) => { | |
| return { | |
| x: rect.left + rect.width / 2, | |
| y: rect.top + rect.height / 2, | |
| }; | |
| }; | |
| const prefetchNearbyRoutes = useCallback(async () => { | |
| if (!links.length) return; | |
| // Sort links by proximity to current mouse position | |
| const linksWithDistance = links.map((link) => { | |
| const center = calculateCenterPoint(link.rect); | |
| const distance = calculateDistance( | |
| mousePosition.x, | |
| mousePosition.y, | |
| center.x, | |
| center.y, | |
| ); | |
| return { ...link, distance }; | |
| }); | |
| // Sort by distance | |
| linksWithDistance.sort((a, b) => a.distance - b.distance); | |
| // Prefetch the closest links that are within threshold | |
| const closestLinks = linksWithDistance.filter( | |
| (link) => link.distance < threshold, | |
| ); | |
| const routesToPrefetch = closestLinks.map((link) => link.href); | |
| // Prefetch up to 3 routes at a time | |
| for (const route of routesToPrefetch.slice(0, 3)) { | |
| if (!prefetchedRoutes.has(route)) { | |
| console.log("prefetching", route); | |
| router.prefetch(route); | |
| setPrefetchedRoutes((prev) => new Set([...prev, route])); | |
| } | |
| } | |
| }, [links, mousePosition, prefetchedRoutes, router, threshold]); | |
| useEffect(() => { | |
| const handleMouseMove = (e: MouseEvent) => { | |
| setMousePosition({ x: e.clientX, y: e.clientY }); | |
| }; | |
| window.addEventListener("mousemove", handleMouseMove); | |
| return () => { | |
| window.removeEventListener("mousemove", handleMouseMove); | |
| }; | |
| }, []); | |
| useEffect(() => { | |
| // Update links on mount and when DOM changes | |
| updateLinks(); | |
| // Set up a MutationObserver to detect new links | |
| const observer = new MutationObserver(() => { | |
| updateLinks(); | |
| }); | |
| observer.observe(document.body, { | |
| childList: true, | |
| subtree: true, | |
| attributes: true, | |
| attributeFilter: ["href"], | |
| }); | |
| return () => { | |
| observer.disconnect(); | |
| }; | |
| }, [updateLinks]); | |
| useEffect(() => { | |
| const intervalId = setInterval(() => { | |
| if (mousePosition.x !== 0 || mousePosition.y !== 0) { | |
| prefetchNearbyRoutes(); | |
| } | |
| }, predictionInterval); | |
| return () => { | |
| clearInterval(intervalId); | |
| }; | |
| }, [mousePosition, prefetchNearbyRoutes, predictionInterval]); | |
| return children; | |
| } |
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