# External Attendee Dish Self-Selection — Design Spec

**Date:** 2026-06-05
**Status:** Approved (design), pending implementation plan
**Author:** Matt + Claude

## Problem

External lunch attendees (e.g. partners, VIPs added by an admin in the logistics
screen) currently have **no way to choose their own dish**. The admin is expected
to set each external's `dishId` inline. There is no email and no self-service page.

This surfaced when an admin (Marine Jacq-Pietri, `marine@monaco-impact.org`) added
herself as an external attendee expecting to receive an email to pick a dish, and
never got one — because the flow does not exist. Verified in prod 2026-06-05:
the `ExternalAttendee` row exists with `dishId = null`, and no email path targets
externals.

### Current behaviour (verified in code + prod)

- `lunch.createExternal` / `lunch.updateExternal` write the row and send **no email**.
- The only "Pick your lunch dish" email (`sendLunchReminderEmail`) is driven by
  `selectUnpickedAttendees`, which queries **`AttendingMember` rows tied to a
  CONFIRMED `FinalistConfirmation`** — finalist team members only. Externals are
  never in that set.
- `sendLunchRecapEmail` goes to admins + `extraRecipients` only (a manifest, not a picker).
- Externals' dishes are meant to be set by the admin inline via `dishId`.

## Goal

External attendees with an email on file receive a dish-selection email containing
a tokenized link to a dedicated, no-login page where they choose a dish, declare
allergens, and add allergen notes — mirroring the finalist team-member picker.

## Design decisions (locked)

1. **Email trigger:** auto-send on add (when the external has an email) **plus** a
   per-row "Resend invite" button in the logistics screen.
2. **Reminders:** unpicked externals are included in both the reminder cron and the
   manual "Send reminders" action.
3. **Page fields:** dish + allergens + allergen notes (mirror the member picker).
4. **Dish write precedence:** last-write-wins. Both the inline admin `dishId` field
   and the self-service page can write the dish; the admin can always override.

## Reference pattern

This feature mirrors the existing **finalist confirmation flow**:

- `src/lib/finalist-token.ts` — HMAC-signed token (`{ confirmationId, exp }`) via
  `NEXTAUTH_SECRET`.
- `src/app/(public)/finalist/confirm/[token]/page.tsx` — public, tokenized, no-login page.
- `finalist.getByToken` / `finalist.confirm` / `finalist.decline` — `publicProcedure`s.

We replicate this shape for externals.

## Architecture

### 1. Data model

`prisma/schema.prisma` — `ExternalAttendee` gains one nullable field:

```prisma
inviteSentAt  DateTime?   // when the dish-selection email was last sent
```

- Drives an "invited ✓" indicator in the admin UI.
- Does **not** gate resends or reminders (those are intentionally repeatable).
- Nullable, so the migration is additive with no backfill.

**No `token` column.** The link is a stateless HMAC-signed token; the external is
loaded by the `externalId` embedded in the verified payload. Trade-off accepted:
individual links can't be revoked without rotating `NEXTAUTH_SECRET` — acceptable
for low-stakes dish picking. (This is the one intentional divergence from the
finalist flow, which stores a DB token for supersede/rotation scenarios that
externals don't have.)

Migration: single additive column. Apply in prod via `prisma migrate deploy`
(runs automatically on container start per the entrypoint). **Do not** run
`migrate dev` against the drifted dev DB — create the migration SQL and use
`db execute` + `migrate resolve` if needed locally.

### 2. Token helper — `src/lib/external-lunch-token.ts`

Mirror `finalist-token.ts`:

```ts
export type ExternalLunchTokenPayload = { externalId: string; exp: number }
export function signExternalLunchToken(payload): string
export function verifyExternalLunchToken(token): ExternalLunchTokenPayload  // throws on bad sig / expired
```

- HMAC-SHA256 over base64url payload, `timingSafeEqual` comparison.
- `exp` = `eventAt + 24h` when `eventAt` is set, else `now + 30d`. Generous so the
  link outlives the change deadline (the deadline is enforced separately at write time).

### 3. tRPC — `src/server/routers/lunch.ts`

- **`getExternalByToken`** (`publicProcedure`, input `{ token }`):
  verify token → load external (+ its `LunchEvent`, ordered `dishes`, current
  `dish`/`allergens`/`allergenOther`) → return payload incl. computed
  `changeDeadline = eventAt − changeCutoffHours`. Throws map to the page's friendly
  error states (`expired` / `signature` / not found).

- **`setExternalPick`** (`publicProcedure`, input
  `{ token, dishId: string | null, allergens, allergenOther }`):
  verify token → if `eventAt` set and `now > changeDeadline` → `PRECONDITION_FAILED`
  → update the external's `dishId` / `allergens` / `allergenOther`. No audit row
  (no authenticated user on a public pick).

- **`sendExternalInvite`** (`adminProcedure`, input `{ externalId }`):
  load external (must have an email, else `PRECONDITION_FAILED`) → sign token →
  `sendExternalDishInviteEmail(...)` → stamp `inviteSentAt = now` → audit
  `LUNCH_EXTERNAL_INVITE_SENT`. Returns the updated row.

- **`createExternal`** (existing, modified): after insert, if `input.email` present,
  fire-and-forget send the invite (sign token, send email, stamp `inviteSentAt`)
  wrapped in `try/catch` — **never throws** (per the "round notifications never
  throw" project constraint). A failed send leaves `inviteSentAt = null` so the
  admin can resend.

### 4. Email — `src/lib/email.ts`

```ts
export async function sendExternalDishInviteEmail(opts: {
  to: string
  name: string
  eventAt: Date | null
  venue: string | null
  notes: string | null
  changeDeadline: Date | null
  pickUrl: string
}): Promise<void>
```

- Uses the existing branded wrapper.
- Subject: `Choose your lunch dish — MOPC grand finale`.
- Body: greeting, event date (Europe/Monaco), venue, optional notes, deadline, CTA
  button → `pickUrl`.
- One template serves both the initial invite and reminders.

### 5. Reminders — extend existing flow

- **`src/server/services/lunch-reminders.ts`**: add
  `selectUnpickedExternals(prisma, event)` → externals where `email` is set and
  `dishId IS NULL` for the event.
- **`src/app/api/cron/lunch-reminders/route.ts`** and **`lunch.sendReminders`**:
  after the existing `AttendingMember` loop, also loop unpicked externals and send
  `sendExternalDishInviteEmail` with a freshly signed token URL. External links go
  to `/lunch/pick/<token>` (not `/applicant`). Per-send errors are caught and
  logged, consistent with the member loop.

### 6. Public page — `src/app/(public)/lunch/pick/[token]/page.tsx`

Mirror `(public)/finalist/confirm/[token]/page.tsx`:

- `'use client'`, reads `token` from params, queries `lunch.getExternalByToken`.
- States: loading skeleton; invalid/expired/not-found friendly cards (reuse the
  `FriendlyError` pattern with `info@monaco-opc.com` fallback).
- Header card: event date, venue, notes, deadline countdown (reuse `CountdownLabel`).
- Form: dish radio list with dietary-tag badges, allergen checkboxes, allergen-notes
  textarea. Submit → `lunch.setExternalPick`.
- Success state: "Your dish is saved", editable until the deadline.
- Past deadline: read-only with "contact an admin" message.

### 7. Admin UI — logistics externals table

- Per-row status chip: `no email` / `Invited` / `Picked`.
- Per-row **Resend invite** button → `lunch.sendExternalInvite` (disabled when no email).
- The inline `dishId` editor stays (admin override path).

### Manifest / recap

No change. `lunch-recap.ts` already includes externals, so self-service picks flow
into the manifest, CSV export, and recap email automatically.

## Edge cases

- **No email on external:** auto-send skipped; resend button disabled; reminders skip.
- **Tampered / expired link:** friendly error card; no data leak.
- **Pick after deadline:** `PRECONDITION_FAILED`; page shows read-only state.
- **Admin and external both set a dish:** last-write-wins (intended).
- **Email added later via `updateExternal`:** no auto-send on update; admin uses the
  resend button (keeps `updateExternal` side-effect-free).

## Testing

- Unit: token sign/verify roundtrip + tamper + expiry rejection (`external-lunch-token`).
- Unit: `selectUnpickedExternals` returns only emailed + unpicked externals.
- Integration: `getExternalByToken` happy path; bad/expired token errors.
- Integration: `setExternalPick` happy path; deadline rejection.
- Integration: `createExternal` with email stamps `inviteSentAt` (mocked email send);
  without email leaves it null.

## Out of scope

- External attendee decline / RSVP (this is dish-only).
- Reworking the member picker.
- Audience-window / live-voting rework (tracked separately).
```
