A small hairline node/edge network where data pulses branch across random routes, easing along each edge with a fading tail — idle traffic, dense active traffic, or an error state where packets queue up at a congested hub node.
npx shadcn add https://design.helpmarq.comregistry/core/network-packet-trace/component.tsx"use client";
import { useEffect, useRef, useState } from "react";
// ---------------------------------------------------------------------------
// PacketTrace — a small fixed node/edge network (9 nodes, 13 hairline edges,
// deliberately irregular positions) with data pulses that travel edge-to-edge
// via random walks, easing along each segment with a short fading tail.
// Everything on the animation hot path (pulse head/tail positions) is a
// direct-DOM write of `cx`/`cy`/`opacity` on pre-mounted SVG circle refs
// inside a rAF loop — no React state per frame. Hovering (or focusing) a
// node is React state, since it only changes 9 edges' stroke + one node's
// radius, cheap enough to re-render.
//
// `state` drives traffic shape, not just a cosmetic tint:
// - idle: sparse ambient pulses (~3 concurrent), slow spawn.
// - active: dense traffic (~10 concurrent), fast spawn.
// - error: every new pulse takes the shortest path to a fixed hub node
// (the highest-degree node) and, on arrival, PARKS there instead of
// despawning — pulses stack visually above the node (newest on top,
// oldest evicted once the stack exceeds its cap) while the node itself
// blinks --error via a CSS keyframe (not JS) for as long as `state`
// stays "error". Switching away from "error" clears the queue.
//
// Reduced motion drops the whole rAF layer: no traveling pulses at all.
// Instead each edge's stroke-width is set from a fixed per-edge weight
// table (the network's inherent "which routes matter more" shape), so the
// static picture still communicates route frequency.
// ---------------------------------------------------------------------------
export type PacketTraceState = "idle" | "active" | "error";
export interface PacketTraceProps {
/** Traffic pattern. Default "idle". */
state?: PacketTraceState;
className?: string;
}
const VIEW_W = 320;
const VIEW_H = 180;
interface Node {
x: number;
y: number;
}
// Deliberately irregular — hand-placed, not a grid.
const NODES: Node[] = [
{ x: 38, y: 92 },
{ x: 98, y: 36 },
{ x: 92, y: 152 },
{ x: 163, y: 55 },
{ x: 156, y: 124 },
{ x: 228, y: 26 },
{ x: 222, y: 93 },
{ x: 230, y: 146 },
{ x: 282, y: 102 },
];
// Undirected edges; several cycles so a random walk actually branches.
const EDGES: [number, number][] = [
[0, 1],
[0, 2],
[1, 3],
[2, 3],
[2, 4],
[3, 5],
[3, 6],
[4, 6],
[4, 7],
[5, 6],
[6, 7],
[6, 8],
[7, 8],
];
// Fixed per-edge traffic weight for the reduced-motion static picture —
// edges touching the hub (node 6) run heavier than peripheral spurs.
const EDGE_WEIGHT: number[] = EDGES.map(([a, b]) => (a === 6 || b === 6 ? 2.4 : a === 3 || b === 3 ? 1.6 : 1));
// Node 6 is the highest-degree node (5 edges) — the natural congestion
// point, and where "error" traffic queues.
const ERROR_NODE = 6;
const ADJACENCY: number[][] = NODES.map(() => []);
EDGES.forEach(([a, b]) => {
ADJACENCY[a].push(b);
ADJACENCY[b].push(a);
});
function randomWalk(start: number, hops: number): number[] {
const path = [start];
let prev = -1;
let cur = start;
for (let i = 0; i < hops; i++) {
const neighbors = ADJACENCY[cur];
const candidates = neighbors.filter((n) => n !== prev);
const pool = candidates.length > 0 ? candidates : neighbors;
const next = pool[Math.floor(Math.random() * pool.length)]!;
path.push(next);
prev = cur;
cur = next;
}
return path;
}
function bfsPath(start: number, target: number): number[] {
if (start === target) return [start];
const prev = new Array(NODES.length).fill(-1);
const visited = new Array(NODES.length).fill(false);
visited[start] = true;
const queue = [start];
while (queue.length) {
const cur = queue.shift()!;
if (cur === target) break;
for (const n of ADJACENCY[cur]) {
if (!visited[n]) {
visited[n] = true;
prev[n] = cur;
queue.push(n);
}
}
}
const path: number[] = [];
let cur = target;
while (cur !== -1) {
path.unshift(cur);
if (cur === start) break;
cur = prev[cur];
}
return path.length > 1 ? path : [start, target];
}
function easeInOutCubic(t: number): number {
return t < 0.5 ? 4 * t * t * t : 1 - Math.pow(-2 * t + 2, 3) / 2;
}
interface Pulse {
path: number[];
hop: number;
t: number;
speedPerMs: number;
queued: boolean;
}
const MAX_PULSES = 16;
const TAIL_COUNT = 3;
const QUEUE_CAP = 6;
const CONCURRENCY: Record<PacketTraceState, number> = { idle: 3, active: 10, error: 4 };
const SPAWN_RANGE: Record<PacketTraceState, [number, number]> = {
idle: [900, 1800],
active: [150, 400],
error: [400, 900],
};
export function PacketTrace({ state = "idle", className = "" }: PacketTraceProps) {
const dotRefs = useRef<(SVGCircleElement | null)[][]>(
Array.from({ length: MAX_PULSES }, () => Array(TAIL_COUNT + 1).fill(null))
);
const pulsesRef = useRef<(Pulse | null)[]>(Array(MAX_PULSES).fill(null));
const queueOrderRef = useRef<number[]>([]);
const nextSpawnAtRef = useRef(0);
const visitCountsRef = useRef<number[]>(Array(NODES.length).fill(0));
const stateRef = useRef<PacketTraceState>(state);
const [reducedMotion, setReducedMotion] = useState(false);
const [hoveredNode, setHoveredNode] = useState<number | null>(null);
const [tick, setTick] = useState(0);
const [announce, setAnnounce] = useState("");
useEffect(() => {
const mq = window.matchMedia("(prefers-reduced-motion: reduce)");
setReducedMotion(mq.matches);
const onChange = () => setReducedMotion(mq.matches);
mq.addEventListener("change", onChange);
return () => mq.removeEventListener("change", onChange);
}, []);
// Reset the simulation cleanly on every state transition.
useEffect(() => {
stateRef.current = state;
pulsesRef.current = Array(MAX_PULSES).fill(null);
queueOrderRef.current = [];
nextSpawnAtRef.current = 0;
for (const slot of dotRefs.current) {
for (const el of slot) {
if (el) el.style.opacity = "0";
}
}
const text =
state === "error"
? `Network error — packets queuing at node ${ERROR_NODE + 1}.`
: state === "active"
? "Network active — dense traffic."
: "Network idle.";
setAnnounce(text);
}, [state]);
useEffect(() => {
if (reducedMotion) return;
let raf = 0;
let last = performance.now();
const setDot = (el: SVGCircleElement | null, x: number, y: number, opacity: number) => {
if (!el) return;
el.setAttribute("cx", String(x));
el.setAttribute("cy", String(y));
el.style.opacity = String(opacity);
};
const step = (now: number) => {
const dt = now - last;
last = now;
const cur = stateRef.current;
const pulses = pulsesRef.current;
const concurrency = CONCURRENCY[cur];
const [minSpawn, maxSpawn] = SPAWN_RANGE[cur];
if (now >= nextSpawnAtRef.current) {
const traveling = pulses.filter((p) => p && !p.queued).length;
if (traveling < concurrency) {
const slot = pulses.findIndex((p) => p === null);
if (slot !== -1) {
let path: number[];
if (cur === "error") {
let start = Math.floor(Math.random() * NODES.length);
if (start === ERROR_NODE) start = (start + 1) % NODES.length;
path = bfsPath(start, ERROR_NODE);
} else {
const start = Math.floor(Math.random() * NODES.length);
path = randomWalk(start, 3 + Math.floor(Math.random() * 4));
}
const duration = 550 + Math.random() * 400;
pulses[slot] = { path, hop: 0, t: 0, speedPerMs: 1 / duration, queued: false };
}
}
nextSpawnAtRef.current = now + minSpawn + Math.random() * (maxSpawn - minSpawn);
}
for (let i = 0; i < pulses.length; i++) {
const p = pulses[i];
if (!p || p.queued) continue;
p.t += p.speedPerMs * dt;
if (p.t >= 1) {
const arrivedIdx = p.hop + 1;
const arrivedNode = p.path[arrivedIdx]!;
visitCountsRef.current[arrivedNode]! += 1;
if (arrivedIdx >= p.path.length - 1) {
if (cur === "error" && arrivedNode === ERROR_NODE) {
p.queued = true;
p.t = 1;
queueOrderRef.current.push(i);
if (queueOrderRef.current.length > QUEUE_CAP) {
const evict = queueOrderRef.current.shift()!;
pulses[evict] = null;
}
} else {
pulses[i] = null;
}
} else {
p.hop = arrivedIdx;
p.t = 0;
}
}
}
for (let i = 0; i < pulses.length; i++) {
const p = pulses[i];
const refs = dotRefs.current[i]!;
if (!p) {
for (const el of refs) if (el) el.style.opacity = "0";
continue;
}
if (p.queued) {
const qIdx = Math.max(0, queueOrderRef.current.indexOf(i));
const node = NODES[ERROR_NODE]!;
setDot(refs[0]!, node.x - 9, node.y - 12 - qIdx * 5, 1);
for (let k = 1; k <= TAIL_COUNT; k++) if (refs[k]) refs[k]!.style.opacity = "0";
continue;
}
const a = NODES[p.path[p.hop]!]!;
const b = NODES[p.path[p.hop + 1]!]!;
const eased = easeInOutCubic(p.t);
setDot(refs[0]!, a.x + (b.x - a.x) * eased, a.y + (b.y - a.y) * eased, 1);
for (let k = 1; k <= TAIL_COUNT; k++) {
const tt = Math.max(0, eased - k * 0.14);
const op = tt > 0 || eased > 0 ? Math.max(0.1, 1 - k * 0.3) : 0;
setDot(refs[k]!, a.x + (b.x - a.x) * tt, a.y + (b.y - a.y) * tt, op);
}
}
raf = requestAnimationFrame(step);
};
raf = requestAnimationFrame(step);
return () => cancelAnimationFrame(raf);
}, [reducedMotion]);
// Live-refresh the tooltip's throughput count while a node is hovered/focused.
useEffect(() => {
if (hoveredNode === null) return;
const id = window.setInterval(() => setTick((t) => t + 1), 500);
return () => window.clearInterval(id);
}, [hoveredNode]);
const openNode = (idx: number) => setHoveredNode(idx);
const closeNode = (idx: number) => setHoveredNode((cur) => (cur === idx ? null : cur));
const hovered = hoveredNode !== null ? NODES[hoveredNode] : null;
const throughput = hoveredNode !== null ? visitCountsRef.current[hoveredNode] : 0;
void tick; // read for the interval's re-render side effect only
return (
<div className={`relative inline-block ${className}`}>
<style>{CSS}</style>
<span role="status" aria-live="polite" aria-atomic="true" className="sr-only">
{announce}
</span>
<svg
viewBox={`0 0 ${VIEW_W} ${VIEW_H}`}
width="100%"
style={{ maxWidth: VIEW_W }}
focusable="false"
>
<g aria-hidden="true">
{EDGES.map(([a, b], i) => {
const na = NODES[a]!;
const nb = NODES[b]!;
const isHoverRoute = hoveredNode !== null && (a === hoveredNode || b === hoveredNode);
const width = reducedMotion ? 0.6 + EDGE_WEIGHT[i]! * 0.7 : isHoverRoute ? 1.6 : 1;
return (
<line
key={i}
x1={na.x}
y1={na.y}
x2={nb.x}
y2={nb.y}
stroke={isHoverRoute ? "var(--foreground)" : "var(--border)"}
strokeWidth={width}
strokeLinecap="round"
/>
);
})}
</g>
{!reducedMotion && (
<g aria-hidden="true">
{Array.from({ length: MAX_PULSES }, (_, i) => (
<g key={i}>
{Array.from({ length: TAIL_COUNT + 1 }, (_, k) => (
<circle
key={k}
ref={(el) => {
dotRefs.current[i]![k] = el;
}}
r={k === 0 ? 2 : 1.4}
fill="var(--foreground)"
opacity={0}
cx={-10}
cy={-10}
/>
))}
</g>
))}
</g>
)}
{reducedMotion && state === "error" && (
<g aria-hidden="true">
{[0, 1, 2].map((k) => (
<circle
key={k}
cx={NODES[ERROR_NODE]!.x - 9}
cy={NODES[ERROR_NODE]!.y - 12 - k * 5}
r={1.4}
fill="var(--foreground)"
opacity={1 - k * 0.25}
/>
))}
</g>
)}
{NODES.map((n, i) => {
const isHovered = hoveredNode === i;
const isError = state === "error" && i === ERROR_NODE;
return (
<circle
key={i}
role="button"
tabIndex={0}
aria-label={`Network node ${i + 1}${isError ? ", congested" : ""}`}
aria-describedby={isHovered ? "network-packet-trace-tip" : undefined}
cx={n.x}
cy={n.y}
r={isHovered ? 5.5 : 4}
fill={isError ? "var(--error)" : "var(--foreground)"}
className={isError ? "ns-pk-blink" : undefined}
style={{ cursor: "pointer", outline: "none" }}
onPointerEnter={() => openNode(i)}
onPointerLeave={() => closeNode(i)}
onFocus={() => openNode(i)}
onBlur={() => closeNode(i)}
onKeyDown={(e) => {
if (e.key === "Escape") closeNode(i);
}}
/>
);
})}
{hoveredNode !== null && (
<circle
cx={NODES[hoveredNode]!.x}
cy={NODES[hoveredNode]!.y}
r={8}
fill="none"
stroke="var(--foreground)"
strokeWidth={1}
opacity={0.35}
aria-hidden="true"
/>
)}
</svg>
{hovered && (
<div
id="network-packet-trace-tip"
role="tooltip"
aria-live="off"
className="pointer-events-none absolute z-10 -translate-x-1/2 -translate-y-full whitespace-nowrap rounded-[6px] border border-border bg-background px-2 py-1 font-mono text-[11px] text-foreground shadow-sm"
style={{
left: `${(hovered.x / VIEW_W) * 100}%`,
top: `${(hovered.y / VIEW_H) * 100 - 4}%`,
}}
>
Node {hoveredNode! + 1} — {throughput} routed
</div>
)}
</div>
);
}
const CSS = `
@keyframes ns-pk-blink { 0%, 100% { opacity: 1; } 50% { opacity: 0.35; } }
.ns-pk-blink { animation: ns-pk-blink 1.1s ease-in-out infinite; }
@media (prefers-reduced-motion: reduce) {
.ns-pk-blink { animation: none; }
}
`;
Build an activity/status visualization as a small fixed node network: 9 SVG nodes at hand-placed (not grid-aligned) coordinates inside a 320x180 viewBox, joined by 13 hairline edges (var(--border), ~1px stroke, round linecap) forming a graph with several cycles so routes actually branch rather than forming a single tree. One node (the highest-degree node in the graph, acting as a hub) is the designated congestion point. A `state` prop (idle | active | error, default idle) drives a rAF-based particle simulation: pulses are small circles (2px radius head + a 3-segment fading tail, all var(--foreground), tail opacity stepping down ~0.3 per segment) that travel along the graph via random walks — from a random start node, hop to a random neighbor (avoiding immediate backtrack unless at a dead end) for 3-6 hops, then despawn and eventually respawn elsewhere. idle keeps ~3 pulses concurrently alive with slow (900-1800ms) spawn spacing; active keeps ~10 alive with fast (150-400ms) spacing. In error, every new pulse's route is instead the shortest path (BFS over the adjacency graph) to the hub node; on arrival it does NOT despawn — it parks there, stacking visually above the node (each queued pulse offset a few px higher than the last, newest on top), capped at 6 concurrent queued pulses with the oldest evicted once the cap is exceeded so the stack keeps turning over. While `state==="error"` the hub node itself blinks between full opacity and 35% opacity using a CSS keyframe animation (not JS per-frame) tinted var(--error). All per-frame position writes (pulse head/tail cx/cy, opacity) are direct DOM writes via refs to pre-mounted SVG circle elements inside one requestAnimationFrame loop — never React state per frame. React state is reserved for the cheap, infrequent stuff: which node is hovered/focused (used to brighten every edge incident to that node to var(--foreground) at a heavier stroke-width and enlarge the node's radius), and the tooltip's open/closed state. Each node is a focusable SVG circle (role="button", tabIndex=0, aria-label naming it e.g. "Network node 3", plus ", congested" appended when it's the error-state hub) so both pointer hover and keyboard focus open the same highlight + a Geist Mono tooltip (role="tooltip", aria-live="off", positioned via percentage offsets derived from the node's viewBox coordinates) reading "Node N — K routed", where K is a running per-node visit counter incremented in the simulation loop every time a pulse's hop advances onto that node (a real live count, refreshed every 500ms while a tooltip is open via a small interval driving a re-render, not a decorative number). A dedicated sr-only span (role="status", aria-live="polite", aria-atomic="true") announces the traffic mode in plain language on every `state` change (e.g. "Network error — packets queuing at node 7."), separate from the tooltip and node elements so it can't pick up their text on an atomic re-read. prefers-reduced-motion removes the entire pulse layer: instead each edge's stroke-width is set from a fixed per-edge weight table (edges touching the hub render heavier) so the static picture still communicates which routes matter most, and the error state renders three small static stacked dots above the hub instead of an animated queue. No canvas anywhere — pure SVG + rAF. Zero dependencies.