# Checkpoint: Approval Flow Animation for React
> A request that has to clear your rules before it runs. A token drops out from under the request and drives down a lane, past one barrier per rule: each one swings open downward, the way the token is going, as its rule passes and the row ticks. A rule that needs sign-off keeps its barrier down and turns its row into Approve and Deny; a rule the request breaks stays shut, and the token knocks against it twice and is turned away. Every outcome rolls into a short log underneath.
Approval Flow Animation for React: a request passes one barrier per rule, or waits for sign-off. Built with Tailwind CSS; install it with the shadcn CLI. It's a KeyframeUI component: the file lands in your project as source, yours to edit.
- Docs and live preview: https://keyframeui.com/components/checkpoint
- Tags: AI, Interaction, Data
- npm dependencies: clsx, tailwind-merge
## Installation
Register the @keyframeui registry in `components.json` once per project:
```json
{
"registries": {
"@keyframeui": "https://keyframeui.com/r/{name}.json"
}
}
```
Then add the component. It lands in `components/ui/checkpoint.tsx`, and the CLI also adds `lib/utils.ts` (the `cn` helper) and installs the npm dependencies:
```bash
npx shadcn@latest add @keyframeui/checkpoint
```
Or install by URL, without registering the namespace:
```bash
npx shadcn@latest add https://keyframeui.com/r/checkpoint.json
```
## Usage
The main demo shows typical usage.
### Agent Guardrails
A plant shop's support agent: reading a ticket clears, a $1,240 refund waits for finance, and deleting a customer is blocked by its scope.
Install this demo, with the component included:
```bash
npx shadcn@latest add @keyframeui/checkpoint-demo
```
```tsx title="components/checkpoint-demo.tsx"
import * as React from "react";
import { Checkpoint, type CheckpointRequest, type CheckpointRule } from "@/components/ui/checkpoint";
function Glyph({ children }: { children: React.ReactNode }) {
return (
);
}
// Fernway, a plant delivery shop, and the rules its support agent runs under. Names are made up.
const RULES: CheckpointRule[] = [
{
id: "role",
label: "Role",
detail: "Acts as a support teammate",
value: "Support",
icon: (
),
},
{
id: "scope",
label: "Scope",
detail: "Read orders, issue refunds",
value: "Read · Refund",
icon: (
),
},
{
id: "amount",
label: "Amount",
detail: "Refunds over $500 need finance",
value: "≤ $500",
icon: (
),
},
{
id: "audit",
label: "Audit",
detail: "Every call lands in the trail",
value: "Logged",
icon: (
),
},
];
const REQUESTS: CheckpointRequest[] = [
{
id: "read",
label: "read_ticket",
meta: "#4821 · Monstera arrived with a cracked pot",
icon: (
),
},
{
id: "refund",
label: "refund_order",
meta: "$1,240.00 · order #88213, 14 olive trees",
verdicts: { amount: "hold" },
icon: (
),
},
{
id: "delete",
label: "delete_customer",
meta: "cus_19F4 · asked by the chat, not the customer",
verdicts: { scope: "block" },
reason: "No delete scope",
icon: (
),
},
];
export function CheckpointDemo() {
return (
Guardrails · Fernway support agent
Enforced on every call
);
}
```
## Examples
Finished sections built with Checkpoint. Each one installs whole, with the component included.
### Release Gate
Releases through tests, preview, migrations and a change freeze, where a Friday-evening deploy is turned away.
Install this demo, with the component included:
```bash
npx shadcn@latest add @keyframeui/checkpoint-deploy-demo
```
```tsx title="components/checkpoint-deploy-demo.tsx"
import * as React from "react";
import { Checkpoint, type CheckpointRequest, type CheckpointRule } from "@/components/ui/checkpoint";
function Glyph({ children }: { children: React.ReactNode }) {
return (
);
}
const rocket = (
);
// Northwind's release checks. Every name, version and time is made up.
const RULES: CheckpointRule[] = [
{
id: "tests",
label: "Tests",
detail: "1,284 passing on the release commit",
value: "CI",
icon: (
),
},
{
id: "preview",
label: "Preview",
detail: "Signed off on the preview URL",
value: "Design",
icon: (
),
},
{
id: "migrations",
label: "Migrations",
detail: "Destructive changes need a DBA",
value: "Safe",
icon: (
),
},
{
id: "freeze",
label: "Change freeze",
detail: "No deploys Fri 16:00 → Mon 09:00",
value: "Freeze",
icon: (
),
},
];
const REQUESTS: CheckpointRequest[] = [
{ id: "web-2140", label: "web@2.14.0", meta: "18 commits · maya.l", icon: rocket },
{
id: "api-320",
label: "api@3.2.0",
meta: "drops column users.legacy_id",
verdicts: { migrations: "hold" },
icon: rocket,
},
{
id: "web-2150",
label: "web@2.15.0",
meta: "Fri 17:42 · 41 commits · jonas.r",
verdicts: { freeze: "block" },
reason: "Freeze until Mon 09:00",
icon: rocket,
},
];
export function CheckpointDeployDemo() {
return (
N
Release gate · northwind/production
eu-west-1
);
}
```
### Spend Policy
A studio's company card policy: a flight waits on its receipt, and a casino charge is blocked by merchant category.
Install this demo, with the component included:
```bash
npx shadcn@latest add @keyframeui/checkpoint-spend-demo
```
```tsx title="components/checkpoint-spend-demo.tsx"
import * as React from "react";
import { Checkpoint, type CheckpointRequest, type CheckpointRule } from "@/components/ui/checkpoint";
function Glyph({ children }: { children: React.ReactNode }) {
return (
);
}
const card = (
);
// Tinta, a design studio, and its company card policy. Merchants and people are made up.
const RULES: CheckpointRule[] = [
{
id: "merchant",
label: "Merchant",
detail: "Software, travel, meals, print",
value: "Allowed",
icon: (
),
},
{
id: "limit",
label: "Per charge",
detail: "Anything larger goes through a PO",
value: "≤ $2,000",
icon: (
),
},
{
id: "receipt",
label: "Receipt",
detail: "Over $75 needs one, or finance signs",
value: "> $75",
icon: (
),
},
{
id: "budget",
label: "Budget",
detail: "Design team, Q4",
value: "$18,400 left",
icon: (
),
},
];
const REQUESTS: CheckpointRequest[] = [
{ id: "figma", label: "FIGMA* ANNUAL", meta: "$45.00 · Lena Ortiz", icon: card },
{
id: "flight",
label: "NORDAIR 0742",
meta: "$1,386.40 · Sam Okafor, client visit in Oslo",
verdicts: { receipt: "hold" },
icon: card,
},
{
id: "casino",
label: "LUCKY STAR CASINO",
meta: "$600.00 · Sam Okafor",
verdicts: { merchant: "block" },
reason: "Gambling isn't covered",
icon: card,
},
];
export function CheckpointSpendDemo() {
return (
Card policy · Tinta Studio
3 cards live
);
}
```
## Props
| Prop | Type | Default | Description |
| --- | --- | --- | --- |
| `rules` (required) | `CheckpointRule[]` | | The rules, top to bottom, as `{ id, label, detail?, value?, icon? }`. `label` is the rule's name, `detail` one line under it, `value` a short mono tag on the right (hidden in boxes under 26rem) and `icon` a small glyph drawn in currentColor. Each rule gets a barrier in the lane. |
| `requests` (required) | `CheckpointRequest[]` | | The requests that come through, in order, as `{ id, label, meta?, icon?, verdicts?, reason? }`. `label` is what's asking, in mono; `meta` says who sent it and what it carries; `verdicts` maps rule ids to `"pass"`, `"hold"` or `"block"` (a rule left out passes); `reason` replaces the rule's name in the status when it's blocked. |
| `current` | `string` | | The id of the request to run. Set it to drive the checkpoint yourself: each change runs that request once, sliding it in. Leave it out and `autoplay` runs them in turn. |
| `autoplay` | `boolean` | `true` | Run the requests one after another and start over after the last. With `false` the first one runs once. It waits off screen and on a hidden tab. |
| `approveAfter` | `number \| false` | `2400` | Ms a rule that needs sign-off waits before it approves itself, with a hairline filling under Approve, or `false` to wait for the visitor. Only with autoplay. Pointing at the buttons holds the timer. |
| `speed` | `number` | `1` | How fast each request plays, as a multiple of the default pace: the token's legs, the barriers swinging open and shut, the rows ticking, a knock, the log line rolling in and the next request sliding in. `2` is twice as fast. |
| `dwell` | `number` | `1600` | How long an outcome stays up before the next request comes in, in ms. Only with autoplay. |
| `approver` | `string` | `"a reviewer"` | Who signs off when a hold approves itself, as written in the log. |
| `log` | `boolean` | `true` | Show the last three outcomes under the rules, newest on top, each with the time it was settled. |
| `onDecision` | `(requestId: string, outcome: CheckpointOutcome, ruleId?: string) => void` | | Called when a request is settled. `outcome` is `"cleared"`, `"blocked"` or `"denied"`, and `ruleId` is the rule that stopped it. |
| `className` | `string` | | Extra classes for the root. Set the accent with `--checkpoint-accent` (`#ff3b1f`, `#ff5a3c` in dark): the token, the open barrier, passed boxes and waiting rows use it, and the Approve button and accent text use a darker mix of it so white and accent text stay readable. Override those with `--checkpoint-button` and `--checkpoint-text`. |
## What to keep
To adapt it, change its props first. When you do edit `components/ui/checkpoint.tsx`, keep these, which make it feel and behave right:
- One async runner owns every move: WAAPI keyframes on the `data-part` hooks, each end state written inline as it finishes. React only decides which row's Approve / Deny can be reached.
- Only transform and opacity move. A barrier swings down about its pivot, the way the token travels, so its tip stays clear of the token, and closes only once the token is past its reach.
- Approve / Deny float over the row's right end and stay `inert` unless that row holds, so a hold never moves the row or focus; a decision made from the keyboard leaves focus on the checkpoint.
- Off screen and on a hidden tab the runner waits between steps (`gate()`), and the approval timer and the waiting dot pause where they are.
- Under reduced motion there's no token, travel, lifting or knocking: each rule resolves with an opacity change and the barriers only change color.
Its timing (durations, delays, springs and easings) is all in the `TIMING` block at the top of the file; the timing props default to it.
## Source
```tsx title="components/ui/checkpoint.tsx"
"use client";
import * as React from "react";
import { cn } from "@/lib/utils";
/**
* Keep:
* - One async runner owns every move: WAAPI keyframes on the `data-part` hooks, each end state
* written inline as it finishes. React only decides which row's Approve / Deny can be reached.
* - Only transform and opacity move. A barrier swings down about its pivot, the way the token
* travels, so its tip stays clear of the token, and closes only once the token is past its reach.
* - Approve / Deny float over the row's right end and stay `inert` unless that row holds, so a hold
* never moves the row or focus; a decision made from the keyboard leaves focus on the checkpoint.
* - Off screen and on a hidden tab the runner waits between steps (`gate()`), and the approval
* timer and the waiting dot pause where they are.
* - Under reduced motion there's no token, travel, lifting or knocking: each rule resolves with an
* opacity change and the barriers only change color.
*/
const TIMING = {
/** How fast each request plays, as a multiple of the pace below (the `speed` prop). */
speed: 1,
// At the default pace; `speed` divides everything from here down to `log`.
/** The token's leg from one barrier to the next, in ms. */
travel: 300,
/** A rule being read, row tinted, before its verdict, in ms. */
read: 160,
/** A barrier swinging open about its pivot, in ms. */
lift: 200,
/**
* A barrier closing, in ms, and ms into the token's next leg before it starts: by then the token
* is past the arm's 26px reach.
*/
drop: { duration: 240, delay: 200 },
/** A status box filling, in ms. */
tick: 180,
/** The row's tint fading as its barrier lifts, in ms. */
untint: 200,
/** A held token easing up against the barrier, in ms. */
settle: 160,
/**
* A blocked token's two knocks, in ms. Linear overall, so each keyframe's own curve plays out on
* the clock.
*/
knock: { duration: 260, easing: "linear" },
/** A turned-away token sliding out of the lane, in ms. */
away: 200,
/** The tag and the Approve / Deny buttons cross-fading, in ms. The status swaps on it unpaced. */
swap: 180,
/** The token fading into the log, in ms. */
tokenOut: 120,
/** Per box fading back, and between rows, last row first, in ms. */
reset: { duration: 120, stagger: 25 },
/** A new request sliding in from the left, and the old one fading, in ms. */
enter: { duration: 280, out: 120 },
/** A log line fading in while the older ones step down, in ms. */
log: 280,
// Not paced.
/**
* A hold waiting before it approves itself, with autoplay, in ms (the `approveAfter` prop), and
* the curve of the hairline that fills meanwhile.
*/
approveAfter: 2400,
timer: "linear",
/** An outcome staying up before the next request, in ms (the `dwell` prop). */
dwell: 1600,
/** One cycle of a waiting box's dot, in ms, and its curve. */
breathe: { duration: 1400, easing: "ease-in-out" },
/** Between rules under reduced motion, in ms. */
reduced: 120,
/** Curves, as CSS easings. */
outEase: "cubic-bezier(0.23, 1, 0.32, 1)", // arrivals and lifts: all the speed up front
inOut: "cubic-bezier(0.65, 0, 0.35, 1)", // the token's legs: pulls away and pulls up
inEase: "cubic-bezier(0.55, 0, 1, 0.45)", // leaving, and a knock's run-up: the speed at the end
fade: "linear", // cross-fades, and every fade under reduced motion
/** A barrier and a row changing color, as a Tailwind class. */
colors: "duration-150",
/** Approve and Deny on hover, as a Tailwind class. */
hover: "duration-150",
} as const;
/* ─────────────────────────────────────────────────────────
* CHECKPOINT STORYBOARD
*
* rest the request sits in a card at the top: its icon, its name
* in mono, who sent it and what it carries, and a status on
* the right. Under it, one row per rule, each with a boom
* barrier down across a narrow lane on its left. The
* request's icon, every barrier, the token and the log's
* icons all sit on that lane's center line
* view once 30% of it is in view, the token drops out from under
* the request card and the first rule is read
* travel the token glides down the lane to just above the next
* barrier, 300ms, in-out, like a car pulling up
* read the row tints with the accent for 160ms and its barrier
* turns accent: the rule is being checked
* pass the barrier swings 84° down about its pivot, the way the
* token is heading, like a door pushed open (200ms,
* ease-out), clear of the token's path, while the row's box
* fills with a check (180ms, from 0.7), and the token drives
* through. The barrier swings back up behind it once the
* token is past its reach, 200ms into its next leg (240ms)
* hold a rule that needs sign-off keeps its barrier down. The
* token settles 2px closer to it, Approve / Deny fade in
* over the row's right end (180ms) and the status reads
* "Waiting on approval". With autoplay a hairline fills
* under Approve over `approveAfter` and it approves itself
* as `approver`; pointing at the buttons holds the timer.
* Approve swings the barrier open; Deny keeps it shut and sends
* the token away without a knock
* block a rule it breaks stays shut. The token knocks into the
* barrier twice (4px, then 2px, 260ms), the barrier and the
* row's box go ink with a cross, the status reads "Blocked ·
* " and the token slides out of the lane, 14px, 200ms
* clear past the last rule the token drives into the top line of
* the log and becomes its check: the new line fades in as
* the older lines step down one line (280ms), the oldest
* dropping out under the edge. The status reads "Cleared"
* next 1.6s later the boxes clear, last row first (120ms each,
* 25ms apart), the old request fades and the next one slides
* in from 12px left (280ms). Requests loop with autoplay
* sleep off screen and on a hidden tab it stops between steps, and
* an approval timer stops where it is
* keys Approve and Deny are buttons, reachable only while a rule
* waits; a hold never moves focus. A decision made from the
* keyboard leaves focus on the checkpoint
* narrow under 26rem the value tags hide, so the details keep
* their room, and the status shortens to one word
* reduced no token, no travel, no lifting or knocking: each rule
* resolves 120ms after the last with an opacity change, the
* barriers stay down and only change color, and holds wait
* the same way
* ───────────────────────────────────────────────────────── */
const GATE = {
view: 0.3, // share of the box in view before the first request runs
lane: 40, // px, the lane column; the icons, barriers and token sit on its center line
token: 12, // px, the token's side
gap: 4, // px between a waiting token and the barrier under it
lift: { angle: 84 }, // deg: a barrier swinging open about its pivot, downward, the way the token travels (84° keeps its tip ~3px clear of the token)
settle: { distance: 2 }, // px: a held token easing up against the barrier
knock: { distance: 4 }, // px: a blocked token's first knock (the second is half as far)
away: { distance: 14 }, // px: a turned-away token sliding out of the lane
enter: { distance: 12 }, // px a new request slides in from the left
} as const;
const REDUCED = "(prefers-reduced-motion: reduce)";
const LOG_LINES = 3;
const subscribeReduced = (onChange: () => void) => {
const query = window.matchMedia(REDUCED);
query.addEventListener("change", onChange);
return () => query.removeEventListener("change", onChange);
};
/** prefers-reduced-motion, false on the server and in the hydration render. */
function usePrefersReducedMotion() {
return React.useSyncExternalStore(
subscribeReduced,
() => window.matchMedia(REDUCED).matches,
() => false,
);
}
const clock = () => new Date().toLocaleTimeString("en-GB", { hour12: false });
export type CheckpointVerdict = "pass" | "hold" | "block";
export interface CheckpointRule {
/** Stable key, used by each request's `verdicts`. */
id: string;
/** The rule's name, e.g. "Amount". */
label: string;
/** One line under the name, e.g. "Refunds over $500 need finance". */
detail?: string;
/** A short value in a mono tag on the right, e.g. "≤ $500". */
value?: string;
/** A small glyph before the name, drawn in currentColor. */
icon?: React.ReactNode;
}
export interface CheckpointRequest {
/** Stable key. */
id: string;
/** What's asking, in mono, e.g. "refund_order". */
label: string;
/** Who sent it and what it carries, e.g. "$1,240 · support-bot". */
meta?: string;
/** A glyph for the request card, drawn in the accent. */
icon?: React.ReactNode;
/** How each rule judges it, by rule id. A rule left out passes. */
verdicts?: Partial>;
/** Why it was blocked, shown in the status instead of the rule's name. */
reason?: string;
}
export type CheckpointOutcome = "cleared" | "blocked" | "denied";
export interface CheckpointProps extends React.HTMLAttributes {
/** The rules, top to bottom, each with a barrier in the lane. */
rules: CheckpointRule[];
/** The requests that come through, in order. */
requests: CheckpointRequest[];
/** The id of the request to run. Set it to drive the checkpoint yourself: each change runs that request once. Leave it out and `autoplay` runs them in turn. */
current?: string;
/** Run the requests one after another and start over after the last. With `false` the first one runs once. Defaults to true. */
autoplay?: boolean;
/** Ms a rule that needs sign-off waits before it approves itself, or `false` to wait for the visitor. Only with autoplay. Defaults to 2400. */
approveAfter?: number | false;
/** Who signs off when a hold approves itself, as written in the log. Defaults to "a reviewer". */
approver?: string;
/** Show the last three outcomes under the rules. Defaults to true. */
log?: boolean;
/** Called when a request is settled, with the rule that stopped it. */
onDecision?: (requestId: string, outcome: CheckpointOutcome, ruleId?: string) => void;
/** How fast each request plays, as a multiple of the default pace: the token's legs, the barriers swinging, the rows ticking, a knock, the log line and the next request sliding in. `2` is twice as fast. Defaults to 1. */
speed?: number;
/** Ms an outcome stays up before the next request comes in, with autoplay. Defaults to 1600. */
dwell?: number;
}
type Phase =
| { kind: "queued" }
| { kind: "checking" }
| { kind: "hold"; rule: string }
| { kind: "cleared" }
| { kind: "blocked"; rule: string }
| { kind: "denied"; rule: string };
type LogEntry = {
key: number;
ok: boolean;
label: string;
note: string;
time: string;
};
/* ── Glyphs ───────────────────────────────────────────────── */
function Check({ className }: { className?: string }) {
return (
);
}
function Cross({ className }: { className?: string }) {
return (
);
}
/* ── Swap ─────────────────────────────────────────────────── */
// Swaps a short line of text when its key changes: the old one lifts 4px out,
// then the new one rises 4px in, so two lines never sit on top of each other.
function Swap({
id,
children,
reduced,
className,
}: {
id: string;
children: React.ReactNode;
reduced: boolean;
className?: string;
}) {
const [shown, setShown] = React.useState<{
id: string;
node: React.ReactNode;
}>({ id, node: children });
const [leaving, setLeaving] = React.useState<{
id: string;
node: React.ReactNode;
} | null>(null);
if (shown.id !== id) {
setLeaving(shown);
setShown({ id, node: children });
}
const nextRef = React.useRef(null);
const oldRef = React.useRef(null);
const leavingId = leaving?.id;
React.useLayoutEffect(() => {
if (!leavingId) return;
const out = TIMING.swap * 0.5;
nextRef.current?.animate(
reduced
? [{ opacity: 0 }, { opacity: 1 }]
: [
{ opacity: 0, transform: "translateY(4px)" },
{ opacity: 1, transform: "none" },
],
{
duration: TIMING.swap,
delay: reduced ? out : out * 0.6,
easing: TIMING.outEase,
fill: "backwards",
},
);
const a = oldRef.current?.animate(
reduced
? [{ opacity: 1 }, { opacity: 0 }]
: [
{ opacity: 1, transform: "none" },
{ opacity: 0, transform: "translateY(-4px)" },
],
{
duration: out,
easing: TIMING.inEase,
fill: "forwards",
},
);
if (!a) return;
a.finished.then(
() => setLeaving((l) => (l?.id === leavingId ? null : l)),
() => {},
);
return () => a.cancel();
}, [leavingId, id, reduced]);
const cell = "col-start-1 row-start-1 inline-flex items-center gap-1.5 whitespace-nowrap";
return (
{leaving ? (
{leaving.node}
) : null}
{children}
);
}
/* ── RuleRow ──────────────────────────────────────────────── */
// One rule: its barrier in the lane, then the card. Everything that moves is
// driven from Checkpoint's runner through the data-part hooks; React only
// decides whether the Approve / Deny pair can be reached.
interface RuleRowProps {
rule: CheckpointRule;
holding: boolean;
onDecide: (choice: "approve" | "deny") => void;
onHoverActions: (over: boolean) => void;
}
const RuleRow = React.memo(function RuleRow({ rule, holding, onDecide, onHoverActions }: RuleRowProps) {
return (
{/* The barrier: a pivot on the left, an arm across the lane, a rest on the right. */}
{rule.icon ? (
{rule.icon}
) : null}
{rule.label}
{rule.detail ? (
{rule.detail}
) : null}
{rule.value ? (
{rule.value}
) : null}
{/* Approve / Deny float over the row's right end, on the hold color, so a hold never moves the row. */}
e.pointerType === "mouse" && onHoverActions(true)}
onPointerLeave={(e) => e.pointerType === "mouse" && onHoverActions(false)}
className="absolute inset-y-0 right-[41px] z-[1] flex items-center gap-1 rounded-r-[inherit] bg-[linear-gradient(to_right,transparent,var(--checkpoint-hold)_1.25rem)] pl-6 opacity-0"
>
);
});
/* ── Checkpoint ───────────────────────────────────────────── */
export function Checkpoint({
rules,
requests,
current,
autoplay = true,
approveAfter = TIMING.approveAfter,
approver = "a reviewer",
log = true,
onDecision,
speed = TIMING.speed,
dwell = TIMING.dwell,
className,
style,
...props
}: CheckpointProps) {
const rootRef = React.useRef(null);
const tokenRef = React.useRef(null);
const cardRef = React.useRef(null);
const logRef = React.useRef(null);
const reduced = usePrefersReducedMotion();
const [active, setActive] = React.useState(() =>
Math.max(
0,
requests.findIndex((r) => r.id === current),
),
);
const [generation, setGeneration] = React.useState(0);
const [phase, setPhase] = React.useState({ kind: "queued" });
const [holding, setHolding] = React.useState(-1);
const [entries, setEntries] = React.useState([]);
const [announcement, setAnnouncement] = React.useState("");
// `speed`, read by the runner and the log as each move starts, so a new value never restarts a request.
const pace = Math.max(0.05, speed);
const paceRef = React.useRef(pace);
React.useLayoutEffect(() => {
paceRef.current = pace;
}, [pace]);
// A new log line: it fades in on top while the older lines step down one line,
// the oldest dropping out under the edge. Runs after the commit, before paint.
const newest = entries[0]?.key;
const lines = entries.length;
React.useLayoutEffect(() => {
const list = logRef.current;
const first = list?.firstElementChild as HTMLElement | null | undefined;
if (!list || !first || newest === undefined) return;
if (reduced) {
first.animate([{ opacity: 0 }, { opacity: 1 }], { duration: TIMING.reduced, easing: TIMING.fade });
return;
}
const roll = TIMING.log / paceRef.current;
first.animate([{ opacity: 0 }, { opacity: 1 }], { duration: roll, easing: TIMING.outEase });
if (lines > 1) {
list.animate([{ transform: `translateY(${-first.offsetHeight}px)` }, { transform: "translateY(0px)" }], {
duration: roll,
easing: TIMING.outEase,
});
}
}, [newest, lines, reduced]);
// Handlers the runner installs and the buttons call.
const decideRef = React.useRef<((choice: "approve" | "deny") => void) | null>(null);
const hoverRef = React.useRef<(over: boolean) => void>(() => {});
const onDecide = React.useCallback((choice: "approve" | "deny") => decideRef.current?.(choice), []);
const onHoverActions = React.useCallback((over: boolean) => hoverRef.current(over), []);
// The latest labels and callbacks, read by the runner without restarting it.
const latest = React.useRef({ rules, requests, approver, onDecision, dwell });
const ranRef = React.useRef(false); // a request has run, so the next one slides in
React.useLayoutEffect(() => {
latest.current = { rules, requests, approver, onDecision, dwell: Math.max(0, dwell) };
});
const ruleKey = rules.map((r) => r.id).join("\u0000");
const requestKey = JSON.stringify(requests.map((r) => [r.id, r.verdicts ?? {}]));
const wait = approveAfter === false ? 0 : approveAfter;
React.useEffect(() => {
const root = rootRef.current;
const token = tokenRef.current;
if (!root || !token) return;
const reqs = latest.current.requests;
if (reqs.length === 0) return;
const CANCEL = Symbol("cancel");
let cancelled = false;
let visible = false;
let waiters: (() => void)[] = [];
let timer: Animation | null = null;
let overActions = false;
const timers = new Set();
const anims = new Set();
const loops = new Set();
const check = () => {
if (cancelled) throw CANCEL;
};
/** A move's ms at the current `speed`. */
const paced = (ms: number) => ms / paceRef.current;
const sleep = (ms: number) =>
new Promise((resolve) => {
const id = window.setTimeout(() => {
timers.delete(id);
resolve();
}, ms);
timers.add(id);
}).then(check);
const frame = () => new Promise((resolve) => requestAnimationFrame(() => resolve())).then(check);
const gate = () =>
(visible ? Promise.resolve() : new Promise((resolve) => waiters.push(resolve))).then(check);
type Frame = {
transform?: string;
opacity?: number | string;
offset?: number;
easing?: string;
};
/** WAAPI from explicit keyframes; on finish the end state is written inline and the animation dropped. */
const play = (
el: HTMLElement | null | undefined,
frames: Frame[],
duration: number,
easing: string = TIMING.outEase,
delay = 0,
) => {
if (!el) return Promise.resolve().then(check);
const a = el.animate(frames as Keyframe[], {
duration,
easing,
delay,
fill: "forwards",
});
anims.add(a);
return a.finished
.then(
() => {
const end = frames[frames.length - 1];
if (end.transform !== undefined) el.style.transform = end.transform;
if (end.opacity !== undefined) el.style.opacity = String(end.opacity);
a.cancel();
},
() => {},
)
.finally(() => anims.delete(a))
.then(check);
};
const set = (el: HTMLElement | null | undefined, transform?: string, opacity?: number) => {
if (!el) return;
if (transform !== undefined) el.style.transform = transform;
if (opacity !== undefined) el.style.opacity = String(opacity);
};
const state = (el: Element | null | undefined, value?: string) => {
if (!el) return;
if (value) el.setAttribute("data-state", value);
else el.removeAttribute("data-state");
};
const rows = () => Array.from(root.querySelectorAll("[data-checkpoint-row]"));
const part = (row: HTMLElement | undefined, name: string) =>
row?.querySelector(`[data-part="${name}"]`);
const half = GATE.token / 2;
/** y of an element's center, in the root's box. */
const centerY = (el: Element) => {
const r = el.getBoundingClientRect();
return r.top + r.height / 2 - root.getBoundingClientRect().top;
};
const stopAbove = (row: HTMLElement) => centerY(part(row, "arm") ?? row) - 1.5 - GATE.gap - half;
const at = (y: number, x = 0) => `translate3d(${x}px, ${y - half}px, 0)`;
let tokenY = 0;
const origin = () => {
const icon = cardRef.current?.querySelector("[data-part='icon']");
return icon ? centerY(icon) : 0;
};
/** Everything back to rest at once: barriers down, boxes empty, token under the request card. */
const clearRows = () => {
for (const row of rows()) {
for (const name of ["pass", "block", "hold", "tint", "ink", "actions", "timer"]) {
const el = part(row, name);
if (el) {
el.getAnimations().forEach((a) => a.cancel());
el.style.removeProperty("opacity");
el.style.removeProperty("transform");
}
}
const arm = part(row, "arm");
arm?.getAnimations().forEach((a) => a.cancel());
arm?.style.removeProperty("transform");
state(arm);
state(part(row, "card"));
set(part(row, "tag"), undefined, 1);
}
};
const park = () => {
token.getAnimations().forEach((a) => a.cancel());
tokenY = origin();
set(token, at(tokenY), 1);
};
const isReduced = reduced;
const motion = !isReduced;
/** The token's leg to `y`; the barrier it just passed closes behind it. */
const drive = (y: number, behind?: HTMLElement | null) => {
if (behind) {
play(
behind,
[{ transform: `rotate(${GATE.lift.angle}deg)` }, { transform: "rotate(0deg)" }],
paced(TIMING.drop.duration),
TIMING.outEase,
paced(TIMING.drop.delay),
)
.then(() => state(behind))
.catch(() => {});
}
const from = tokenY;
tokenY = y;
return play(token, [{ transform: at(from) }, { transform: at(y) }], paced(TIMING.travel), TIMING.inOut);
};
const tick = (el: HTMLElement | null | undefined) =>
motion
? play(
el,
[
{ opacity: 0, transform: "scale(0.7)" },
{ opacity: 1, transform: "scale(1)" },
],
paced(TIMING.tick),
)
: play(el, [{ opacity: 0 }, { opacity: 1 }], TIMING.reduced, TIMING.fade);
const breathe = (el: HTMLElement | null | undefined) => {
if (!el || !motion) return;
const a = el.animate([{ opacity: 1 }, { opacity: 0.3 }, { opacity: 1 }], {
duration: TIMING.breathe.duration,
iterations: Infinity,
easing: TIMING.breathe.easing,
});
loops.add(a);
if (!visible) a.pause();
};
const stopLoops = () => {
loops.forEach((a) => a.cancel());
loops.clear();
};
const addLog = async (entry: Omit) => {
setEntries((list) =>
[{ ...entry, key: Date.now() + Math.random(), time: clock() }, ...list].slice(0, LOG_LINES + 1),
);
// The roll-in itself runs in a layout effect once the line is committed.
await sleep(motion ? paced(TIMING.log) : TIMING.reduced);
};
const decide = (row: HTMLElement) =>
new Promise<"approve" | "deny" | "auto">((resolve) => {
let done = false;
const finish = (choice: "approve" | "deny" | "auto") => {
if (done) return;
done = true;
decideRef.current = null;
hoverRef.current = () => {};
timer?.cancel();
timer = null;
// A decision made from the keyboard leaves focus on the checkpoint, not on a button that's going away.
if (row.contains(document.activeElement)) root.focus({ preventScroll: true });
resolve(choice);
};
decideRef.current = finish;
const timerEl = part(row, "timer");
if (autoplay && wait > 0 && timerEl) {
const a = timerEl.animate([{ transform: "scaleX(0)" }, { transform: "scaleX(1)" }], {
duration: wait,
easing: TIMING.timer,
fill: "forwards",
});
timer = a;
overActions = false;
if (!visible) a.pause();
hoverRef.current = (over) => {
overActions = over;
if (over) a.pause();
else if (visible) a.play();
};
a.finished.then(
() => finish("auto"),
() => {},
);
}
}).then((choice) => {
check();
return choice;
});
/** One request, top to bottom. */
const run = async (index: number, enter: boolean) => {
const req = latest.current.requests[index];
if (!req) return;
if (enter) {
await play(
cardRef.current?.querySelector("[data-part='content']"),
[{ opacity: 1 }, { opacity: 0 }],
paced(TIMING.enter.out),
TIMING.fade,
);
setActive(index);
setGeneration((g) => g + 1);
setPhase({ kind: "checking" });
await frame();
await frame();
park();
await sleep(motion ? paced(TIMING.enter.duration) * 0.6 : TIMING.reduced);
} else {
setActive(index);
setPhase({ kind: "checking" });
park();
}
const list = rows();
const ruleList = latest.current.rules;
let behind: HTMLElement | null = null;
let outcome: CheckpointOutcome = "cleared";
let stopped: CheckpointRule | undefined;
let approvedBy = "";
for (let i = 0; i < list.length; i++) {
const row = list[i];
const rule = ruleList[i];
if (!rule) break;
const verdict = req.verdicts?.[rule.id] ?? "pass";
const arm = part(row, "arm");
const card = part(row, "card");
await gate();
if (motion) await drive(stopAbove(row), behind);
behind = null;
// read
state(arm, "active");
if (motion) await play(part(row, "tint"), [{ opacity: 0 }, { opacity: 1 }], paced(TIMING.read), TIMING.outEase);
else await sleep(TIMING.reduced);
await gate();
let lifted = verdict === "pass";
if (verdict === "hold") {
state(card, "hold");
set(part(row, "tint"), undefined, 1);
setHolding(i);
setPhase({ kind: "hold", rule: rule.label });
setAnnouncement(`${req.label} needs approval: ${rule.label}${rule.detail ? `. ${rule.detail}` : ""}.`);
const hold = part(row, "hold");
tick(hold).catch(() => {});
breathe(part(row, "dot"));
if (motion) {
play(
token,
[{ transform: at(tokenY) }, { transform: at(tokenY + GATE.settle.distance) }],
paced(TIMING.settle),
).catch(() => {});
tokenY += GATE.settle.distance;
}
await frame();
const fade = motion ? paced(TIMING.swap) : TIMING.reduced;
play(part(row, "tag"), [{ opacity: 1 }, { opacity: 0 }], fade, TIMING.fade).catch(() => {});
await play(part(row, "actions"), [{ opacity: 0 }, { opacity: 1 }], fade, TIMING.fade);
const choice = await decide(row);
setHolding(-1);
stopLoops();
play(part(row, "actions"), [{ opacity: 1 }, { opacity: 0 }], fade, TIMING.fade).catch(() => {});
play(part(row, "tag"), [{ opacity: 0 }, { opacity: 1 }], fade, TIMING.fade).catch(() => {});
play(hold, [{ opacity: 1 }, { opacity: 0 }], fade, TIMING.fade).catch(() => {});
state(card);
if (choice === "deny") {
outcome = "denied";
} else {
approvedBy = choice === "auto" ? latest.current.approver : "you";
lifted = true;
}
setPhase({ kind: "checking" });
}
if (lifted) {
play(part(row, "tint"), [{ opacity: 1 }, { opacity: 0 }], paced(TIMING.untint), TIMING.fade).catch(() => {});
tick(part(row, "pass")).catch(() => {});
if (motion) {
play(
arm,
[{ transform: "rotate(0deg)" }, { transform: `rotate(${GATE.lift.angle}deg)` }],
paced(TIMING.lift),
TIMING.outEase,
).catch(() => {});
// the token pulls away halfway up; the barrier closes behind it on its next leg
await sleep(paced(TIMING.lift) / 2);
behind = arm ?? null;
} else {
state(arm);
await sleep(TIMING.reduced);
}
continue;
}
// block, or a hold that was denied
stopped = rule;
if (outcome !== "denied") outcome = "blocked";
state(arm, "block");
state(card, "block");
set(part(row, "tint"), undefined, 0);
set(part(row, "ink"), undefined, 1);
tick(part(row, "block")).catch(() => {});
if (motion && outcome === "blocked") {
const d = GATE.knock.distance;
const y = tokenY;
await play(
token,
[
{ transform: at(y), easing: TIMING.inEase },
{ transform: at(y + d), offset: 0.22, easing: TIMING.outEase },
{
transform: at(y),
offset: 0.5,
easing: TIMING.inEase,
},
{ transform: at(y + d / 2), offset: 0.68, easing: TIMING.outEase },
{ transform: at(y) },
],
paced(TIMING.knock.duration),
TIMING.knock.easing,
);
}
if (motion) {
await play(
token,
[
{ transform: at(tokenY), opacity: 1 },
{ transform: at(tokenY, -GATE.away.distance), opacity: 0 },
],
paced(TIMING.away),
TIMING.outEase,
);
}
break;
}
if (outcome === "cleared") {
setPhase({ kind: "cleared" });
setAnnouncement(`${req.label} cleared${approvedBy ? `, approved by ${approvedBy}` : ""}.`);
const listEl = logRef.current;
if (motion) {
const end = log && listEl ? centerY(listEl) - listEl.getBoundingClientRect().height / 2 + 11 : tokenY + 40;
await drive(end, behind);
behind = null;
play(token, [{ opacity: 1 }, { opacity: 0 }], paced(TIMING.tokenOut), TIMING.fade).catch(() => {});
}
if (log) {
await addLog({
ok: true,
label: req.label,
note: approvedBy ? `ran · approved by ${approvedBy}` : "ran",
});
}
} else {
const why = req.reason ?? stopped?.label ?? "";
setPhase(outcome === "denied" ? { kind: "denied", rule: why } : { kind: "blocked", rule: why });
setAnnouncement(`${req.label} ${outcome === "denied" ? "denied" : "blocked"}${why ? `: ${why}` : ""}.`);
if (log)
await addLog({
ok: false,
label: req.label,
note: `${outcome}${why ? ` · ${why}` : ""}`,
});
}
latest.current.onDecision?.(req.id, outcome, stopped?.id);
};
/** Boxes clear and barriers close, last row first. */
const reset = async () => {
const list = rows();
const fades: Promise[] = [];
list
.slice()
.reverse()
.forEach((row, k) => {
const delay = motion ? k * paced(TIMING.reset.stagger) : 0;
for (const name of ["pass", "block", "tint", "ink"]) {
const el = part(row, name);
if (el && el.style.opacity && el.style.opacity !== "0") {
fades.push(play(el, [{ opacity: 1 }, { opacity: 0 }], paced(TIMING.reset.duration), TIMING.fade, delay));
}
}
state(part(row, "card"));
});
await Promise.all(fades);
clearRows();
};
const start = Math.max(
0,
reqs.findIndex((r) => r.id === current),
);
const loop = current === undefined && autoplay;
const main = async () => {
const again = ranRef.current;
if (!again) {
clearRows();
park();
}
await gate();
if (again) await reset();
let index = start;
let enter = again;
for (;;) {
ranRef.current = true;
await run(index, enter);
enter = true;
if (!loop) break;
await sleep(latest.current.dwell);
await gate();
await reset();
index = (index + 1) % latest.current.requests.length;
}
};
const setVisible = (v: boolean) => {
visible = v;
if (v) {
const ready = waiters;
waiters = [];
ready.forEach((resolve) => resolve());
if (timer && !overActions) timer.play();
loops.forEach((a) => a.play());
} else {
timer?.pause();
loops.forEach((a) => a.pause());
}
};
let inView = false;
const io = new IntersectionObserver(
([entry]) => {
inView = entry.isIntersecting && entry.intersectionRatio >= GATE.view - 0.01;
if (!entry.isIntersecting) inView = false;
setVisible(inView && !document.hidden);
},
{ threshold: [0, GATE.view] },
);
io.observe(root);
const onVisibility = () => setVisible(inView && !document.hidden);
document.addEventListener("visibilitychange", onVisibility);
main().catch((error) => {
if (error !== CANCEL) throw error;
});
return () => {
cancelled = true;
io.disconnect();
document.removeEventListener("visibilitychange", onVisibility);
timers.forEach((id) => window.clearTimeout(id));
anims.forEach((a) => a.cancel());
stopLoops();
timer?.cancel();
decideRef.current = null;
hoverRef.current = () => {};
setHolding(-1);
};
}, [ruleKey, requestKey, current, autoplay, wait, log, reduced]);
const req = requests[active] ?? requests[0];
const status = (() => {
switch (phase.kind) {
// `short` is what a narrow box shows, so the request's name keeps its room.
case "queued":
return { id: "queued", tone: "muted", text: "Queued", short: "Queued" };
case "checking":
return { id: "checking", tone: "muted", text: "Checking", short: "Checking" };
case "hold":
return { id: `hold-${phase.rule}`, tone: "accent", text: "Waiting on approval", short: "Waiting" };
case "cleared":
return { id: "cleared", tone: "accent", text: "Cleared", short: "Cleared" };
case "blocked":
return {
id: `blocked-${phase.rule}`,
tone: "ink",
text: phase.rule ? `Blocked · ${phase.rule}` : "Blocked",
short: "Blocked",
};
case "denied":
return {
id: `denied-${phase.rule}`,
tone: "ink",
text: phase.rule ? `Denied · ${phase.rule}` : "Denied",
short: "Denied",
};
}
})();
return (
{announcement}
{/* The lane's hairline, from under the request card to the log. */}
{/* The request card: the token waits under it, so it drops out from beneath the icon. */}
{req ? (
0} reduced={reduced} speed={pace} />
) : null}
{/* Each status carries its own color, so the leaving one keeps its tone as it fades. */}
{status.id === "cleared" ? (
) : status.tone === "ink" ? (
) : (
)}
{status.short}{status.text}