# Daily Zone Check-in Integration

## Purpose

Campus staff log a daily self-regulation "Emotional Zone" (blue/green/yellow/red).
The same state drives three surfaces: the dashboard check-in card, the
`/zones-of-regulation` page (reminder banner + card), and a notification-dropdown
nudge when an eligible user has not checked in today.

## Backend contract

`/api/zone_checkins` (requires `ZONE_CHECKIN` — the four campus staff roles). The
client never computes the date; "today" is the campus-local date computed
server-side from `campuses.timezone`.

- `GET /today` → `{ date, zone, isCheckedInToday }`
- `POST /` `{ data: { zone } }` → record today's zone (upsert)
- `DELETE /today` → clear today's zone
- `GET /?from=&to=` → history `{ rows: [{ date, zone }], count }`

## Frontend Structure

- API/types: `shared/api/zoneCheckins.ts`, `shared/types/zoneCheckins.ts`
- Business: `business/zone-checkin/hooks.ts` (`useTodayZoneCheckIn`,
  `useZoneCheckInHistory`), `business/zone-checkin/selectors.ts`
  (`canZoneCheckIn`, `shouldNudgeZoneCheckIn`)
- Components: `components/zone-checkin/ZoneCheckInCard.tsx` (shared card),
  `ZoneCheckInReminder.tsx` (banner), `ZoneCheckInSection.tsx` (page section)

## Behavior

- **Eligibility/nudge gating** is role-based (`canZoneCheckIn` — the four campus
  staff roles), mirroring the backend grant. The dashboard card and the zones-page
  section render only for eligible roles; the nudge (red "Not checked in" badge,
  reminder banner, and notification) shows when an eligible user hasn't checked in
  today.
- **Dashboard**: the card is wired through `useDashboardPage` (which exposes
  `showZoneCheckIn` + `needsZoneCheckIn`) with an optimistic shell value for snappy
  selection.
- **Zones page**: `ZoneCheckInSection` is self-contained (`useTodayZoneCheckIn`)
  and renders above the regulation content.
- **Notifications**: `business/top-bar` derives a single unread notification from
  `shouldNudgeZoneCheckIn` (`buildTopBarNotifications`) — there is no backend
  notifications store. The notification carries an `href`
  (`APP_ROUTE_PATHS.zones`); clicking it navigates to `/zones-of-regulation`
  (a react-router `Link`) and closes the dropdown.
- The `useTodayZoneCheckIn` `error` surfaces **only** save/clear failures; the
  today-load query can 403 for an ineligible caller and must not render as an
  error in the widget. React Query dedupes the `/today` fetch across all three
  surfaces.

## Tests

- `business/zone-checkin/selectors.test.ts` (eligibility + nudge),
  `business/top-bar/selectors.test.ts` (notification builder + zones `href`).
- Seeded e2e: `frontend/tests/e2e/zone-checkins.seeded.e2e.ts` (record /
  read-back / clear today, invalid-zone rejection, external-role lockout).

## Verification

- `npm run typecheck`, `npm run lint`, `npm run test` pass.