---
type: concept
tags: [parking, frontend, booth, realtime, ui]
sources: []
updated: 2026-06-18
status: open
---

# Booth Console (operator UI architecture)

The **operator console** — the real-time UI an attendant runs at a manned booth. Built 2026-06-17/18
on top of the [[react-vite-spa]]. This page covers the *architecture* (stack, live feed, layout);
the booth's *business flows* live in [[booth-exit-flow]], [[shift]], [[parking-session]].

## Stack (added 2026-06-17, beyond plain React)

The operator UI outgrew "plain React + useState" once it needed live updates and a real layout:

- **TanStack Query** owns SERVER state (fetch/cache/refetch/loading-error), wrapping the existing thin
  `apiFetch` client. Server data is never duplicated into client state.
- **TanStack Router** — real routes (`/booth`, `/shift`, `/setup`, `/tariff`, `/permits`, `/site`),
  role-guarded (admin-only routes redirect non-admins to `/booth`). Code-based route tree.
- **Zustand** — small CLIENT state only: the live WebSocket status + a rolling in-memory event feed +
  the latest pushed occupancy. Anything durable is re-fetched via Query.
- **Tailwind v4** with a **"Bloomberg-terminal" theme** (`apps/web/src/index.css`, `@theme`):
  near-black surfaces, amber/green/red/cyan status accents, monospace, dense/keyboard-first. **Radix**
  primitives (Dialog, etc.) for accessible unstyled components.
- **react-i18next** for [[i18n]] (Albanian default).

> This SUPERSEDES the original "plain React, no framework" note on [[react-vite-spa]] — that held
> while the UI was a few admin forms; the live booth console justified the additions.

## Live feed — one WebSocket (`/api/ws`)

The booth must reflect entries/exits/payments the instant they happen, so the console opens **one
authenticated WebSocket** app-wide instead of polling. See the WS tap in [[append-only-event-chain]]
(`EventLog.append` fires a read-side `onAppended` callback → the device bus `emitLedger` → the WS
route fans it out):

- On each signed **ledger** append (entry/exit/payment/void/anomaly/cash_movement/shift_*) the server
  pushes the event **plus the recomputed [[capacity-occupancy|occupancy]]** (a fold over the same
  ledger, always authoritative). Printer-status changes ([[printer-status-monitoring]]) ride the same
  socket.
- The client appends to the Zustand feed for the live ticker AND **invalidates the matching Query
  caches** (events, occupancy, active-sessions) — so Query stays the source of truth; the WS is the
  freshness trigger. Auto-reconnect with capped backoff survives a server restart.

### Auth — anti-CSWSH

The handshake is a normal GET through Fastify, so the **HttpOnly JWT cookie** that guards the REST API
guards the WS too. But a browser `WebSocket` can't send the CSRF double-submit header, which would
leave the socket open to **Cross-Site WebSocket Hijacking** (a malicious page opens
`ws://<booth>/api/ws`, the browser auto-attaches the cookie, the attacker reads the live feed). So the
WS route replaces CSRF with an **Origin allowlist** (same-origin always; extra origins via
`WS_ALLOWED_ORIGINS` for the dev SPA): a missing/cross origin is rejected before auth. The stream is
read-only — it can never mutate state. (Found + fixed by automated security review, 2026-06-17.)

## The booth screen (`/booth`)

Dense terminal layout: a **ticket input** (HID-scanner-friendly — types the id + Enter) spanning the
top; a left column with the **occupancy gauge** above the **[[booth-exit-flow|Active Sessions]]** list;
a right column with the **live event ticker**. Submitting/clicking a ticket opens the **pay/exit
modal** (entry/duration/total, tender, voucher checkbox, entry/exit snapshots). All live-refreshed via
the WS.

## The shift control (header) + the booth gate

The header carries a single **shift button** that expresses the [[shift|site-wide single-open
shift]] (added 2026-06-18):

- **No shift open** → "Open shift" (green, enabled).
- **My shift open** → "Close shift" (red, enabled — signs + prints the Z-report).
- **Another operator's shift open** → **disabled**, titled with who holds it. You can neither open
  yours nor close theirs until they hand over.

State comes from one shared Query (`useShift()` → `GET /api/shift/current`, returning `{ open:
{startedAt, operator} | null, isMine }`); the WS invalidates it on `shift_open` / `shift_z_report` /
`cash_movement`, so the button (and the per-shift log scope) update live without polling.

The **booth screen gates on this**: the pay/exit modal shows an "open a shift" banner (with a
one-click *Open shift now*) and disables pay/exit/voucher until **this operator's** shift is open;
the Active-Sessions "Open barrier" is disabled the same way. The server enforces it regardless
(`requireShift` 409 `no_shift`) — the UI just front-runs the rejection. The live feed is **scoped to
the open shift's window** (empty when no shift is open). See [[shift]] for the rule and the routes.

## The device-status footer

A **fixed footer** in the app shell shows the live status of every configured device — relays,
readers, cameras, printers — one chip each (coloured dot + name + fault detail), with an "all ready
/ N offline" roll-up. Fed by the unified [[device-status-monitoring|DeviceMonitor]] over the same
`/api/ws` socket (`hello` carries the initial set; a `device-status` frame per change), held in the
live store keyed by device id, with `GET /api/devices/status` as the seed/fallback. Visible on every
screen, so the operator always sees the barrier relay's reachability and the printer's paper state.

## Dev notes
- Vite proxies `/api/ws` (`ws: true`) to the backend; the backend's Origin allowlist must include the
  dev SPA origin (`WS_ALLOWED_ORIGINS=http://localhost:5173`). In production Fastify serves the SPA
  same-origin, so the allowlist isn't needed.
- Start the dev SPA via `pnpm dev` from `apps/web` (not `npx vite --host …`, which has mangled args
  and served 404s in this environment).

## Open
- **No automated frontend tests** — the booth/live-feed/modal logic is verified manually
  (Playwright + curl + DB inspection), not by a suite. The standing test-harness gap (see
  [[reconciliation]]-adjacent notes) now spans front and back.
- The pre-existing admin screens (Setup/Tariff/Permits/Site/Shift) still carry their **old inline
  styles** — reachable and functional, not yet on the terminal component system.