# Add-on Cart (Notchset): prompt.md (v1.0.0)

- id: `addon-cart` · version 1.0.0 · block · pro (Pro)
- category: Application UI
- build: Base UI (one set of files; its dependencies follow the build)
- install (this build): `npx shadcn@latest add @beautiful-ui-pro/addon-cart`
- npm dependencies: class-variance-authority@^0.7
- registry dependencies: utils, https://beautiful-ui.dev/r/notchset-foundation.json
- docs: https://beautiful-ui.dev/components/addon-cart
- The install command carries everything this item needs (files, CSS, tokens, npm and registry dependencies). Prefer it to copying source by hand.

Add capacity to a plan you already have, knowing what it costs today and from next month: add-on cards that become steppers up to each maximum (ones you have read ACTIVE), a cart chip with the count and monthly total, and a drawer with line items, REMOVE with a 4.5s UNDO, the next bill and the prorated amount due today, then ADD TO SUBSCRIPTION.

## Build it
- Stack: React 19 (`ref` is a plain prop), TypeScript, Tailwind CSS v4 utilities, a shadcn-initialised project with the `@/*` alias.
- Packages: `class-variance-authority@^0.7`.
- Files: `components/ui/notchset/blocks/addon-cart.tsx`; shared code: `lib/beautiful-ui/notchset/instrument.tsx`, `lib/beautiful-ui/notchset/root.ts`, `lib/beautiful-ui/notchset/button-variants.ts`.
- Registry dependencies, installed with it automatically: shadcn `utils` (cn), `notchset-foundation`.
- Builds: one set of files for both, but its dependencies come in Base UI and Radix builds. Install the one that matches the project (see Install): a free item's bare URL installs the Base UI build of it and its dependencies.
- Exports to keep: `AddonCart`, and every exported type.
- CSS: the install adds the notchset foundation (tokens, keyframes, motion levels) to your global stylesheet once. Nothing to import by hand.
- Re-running `add` (or `--overwrite`) re-applies those rules: put overrides in your own CSS, never in the installed rules.
- Tokens: retheme with the `--notchset-*` custom properties (`--notchset-check`, `--notchset-control-edge`, `--notchset-draw-from`, `--notchset-ease-bloom`, `--notchset-ease-glide`, `--notchset-ease-key-down`, `--notchset-ease-key-up`, `--notchset-ease-travel`, `--notchset-fade`, `--notchset-focus-color`, `--notchset-focus-inset`, `--notchset-grow-to`, `--notchset-key-down`, `--notchset-key-up`, `--notchset-life-from`, `--notchset-life-ms`, `--notchset-node-blink`, `--notchset-node-bloom`, `--notchset-node-delay`, `--notchset-plate-color`, `--notchset-rise-from`, `--notchset-rule`, `--notchset-scan-to`, `--notchset-scroll`, `--notchset-signal`, `--notchset-sweep-to`, `--notchset-travel`). Never add Tailwind colour classes inside the component.

```tsx
import { AddonCart } from "@/components/ui/notchset/blocks/addon-cart";
```

## Parts

| Part | data-slot | What it is for |
|---|---|---|
| `AddonCart` | `addon-cart` | Cards, cart chip and the drawer. |

Style a part with `[data-slot="<slot>"]` selectors or its `className`; keep the attributes when editing.

## Sound
- Keep every `data-slot` and `data-sound` attribute: the sound layer reads them.
- Installing this item adds no audio. Nothing plays until the app mounts `SoundProvider` once (install: `npx shadcn@latest add https://beautiful-ui.dev/r/notchset-sound.json`, import from `@/components/ui/notchset/sound-provider`); `useSound()` gives `muted` and `setMuted` for a mute control. Without a provider the audio engine never loads.

## Match the original
- Read `components/ui/notchset/blocks/addon-cart.tsx` as the reference implementation before changing or recreating anything, and match it: sizes, colours per theme, motion timings, copy and behaviour.
- If you deviate (a prop you can't honour, a style you changed, a dependency you swapped), say so in your reply, part by part.
- Keep the accessibility contract, the keyboard map and the motion levels listed below.

## Use it when
- add-ons, cart, extra seats, capacity, upsell, subscription add-ons, proration, billing drawer, Notchset
- Selling seats, runs or features on top of a subscription
- Upgrades where the prorated charge today should be clear

### Not when
- A first purchase: use Checkout
- Changing plans: use Plan Compare

## Mistakes
- Proration comes from your billing API; the block only multiplies for display
- Undo must restore the exact quantity removed

## Usage

```tsx
import { AddonCart } from "@/components/ui/notchset/blocks/addon-cart";

export function Capacity() {
  return (
    <AddonCart
      context="ACME LABS · TEAM PLAN"
      addons={[{ id: "seats", glyph: "+1", name: "Extra seat", description: "One more person.", price: 29, unit: "MO PER SEAT", max: 20 }]}
      planPrice={990}
      planLabel="TEAM PLAN"
      nextBill="NOV 01"
      proration={{ fraction: 0.6, label: "18 OF 30 DAYS" }}
      onCheckout={(lines) => fetch("/api/addons", { method: "POST", body: JSON.stringify(lines) })}
      confirmation={(n) => `Added ${n} to Acme Labs`}
    />
  );
}
```

## Props

| Prop | Type | Default | What it does |
|---|---|---|---|
| `addons` | `{ id, glyph, name, description, price, unit, max, active? }[]` |  | The cards; active means already on the plan. |
| `planPrice / planLabel / nextBill` | `number / string / string` |  | The plan's line and the next bill's date. |
| `proration` | `{ fraction, label }` |  | Today's share of the month ("18 OF 30 DAYS" → 0.6). |
| `onCheckout / confirmation / currency` | `(lines) => Promise / (count) => string / (n) => string` |  | Add the cart to the subscription (resolve to confirm), the confirmation line, money formatting. |

Full docs: https://beautiful-ui.dev/components/addon-cart

## Customising
- Colours: the component reads your shadcn tokens (`--background`, `--foreground`, `--border` …), refined by the `--notchset-*` tokens. The signal colour is `--notchset-signal` (it falls back to `--destructive`). Set tokens on `:root`, or on any container to retheme one area.
- Dark mode follows the `.dark` class on an ancestor (the shadcn and next-themes convention).
- Update later by re-running the install with `--overwrite` (review the diff if you edited it). Changelog: https://beautiful-ui.dev/r/changelog.json

## Keyboard

| Keys | Action |
|---|---|
| Esc | Close the drawer |
| Tab | Cards, the cart and the drawer's controls |

## Performance

- One timer for the undo bar; nothing else runs while idle.

## Responsive

- Cards wrap at 250px; the drawer is 380px or the full width.

## Motion inventory

| Interaction | What moves |
|---|---|
| Cart chip | Bumps when the count changes (260ms bloom) |
| Drawer | Opens over 420ms (unfold) and closes over 280ms |
| Amounts | Line totals, the next bill and today's charge roll |
| Remove | The line goes and UNDO stays for 4.5s |

## Accessibility contract (preserve when editing)
- The drawer is a modal dialog named Cart; focus moves into it and returns to the cart button when it closes (Esc, ×, or the scrim)
- Steppers name their action (More Extra seat); a capped + is aria-disabled
- Undo and the confirmation are announced

## Install

```bash
npx shadcn@latest add @beautiful-ui-pro/addon-cart
```

Pro item: needs the `@beautiful-ui-pro` registry in `components.json` and `BEAUTIFUL_UI_TOKEN` in `.env.local` (https://beautiful-ui.dev/account). Setup: https://beautiful-ui.dev/docs/pro. Your components.json `style` picks the build: radix-*, new-york and default get Radix, base-* gets Base UI.

## Credits
- Built on shadcn/ui (https://ui.shadcn.com)

The notchset foundation (the tokens listed above, keyframes and motion levels) installs once with the first component; its CSS is public at https://beautiful-ui.dev/r/notchset-foundation.json.