# Calendly Booking Sync

## Objective

Bring Calendly bookings and cancellations into the app so records stay current.

An inbound sync of Calendly booking, cancellation, and reschedule events onto the app's leads, contacts, and tasks.

## Before You Begin

This feature is being added to an application that already exists and already
works. Do not scaffold a new project, and do not assume a blank slate.

Inspect the codebase first and establish:

- The existing application structure and where code of this kind already lives.
- The framework and version in use.
- The existing design system — colours, spacing, typography, and component conventions.
- Existing UI components you can reuse instead of writing new ones.
- The existing database structure, if this feature needs to persist anything.
- The existing authentication and authorization system, if this feature is user-scoped.
- Dependencies already installed, so you don't add a library that duplicates one.
- The existing test setup and conventions.

Only start writing code once you understand the above. If the application
already implements part of this feature, extend it rather than replacing it.

## Implementation Instructions

1. Receive booking events on a dedicated endpoint that verifies the sender's signature before doing any work, and reject anything unsigned or stale. Do not identify the sender by source address alone.
2. Acknowledge receipt immediately and process the booking through the app's existing background-job system. A slow match against a large contact table will otherwise cause Calendly to time out and re-send.
3. Match each invitee to an existing user or lead by a defined rule — email first, then any identifier passed through the booking form — and when no confident match exists, create a clearly marked unmatched booking a human can resolve rather than guessing.
4. Treat booking, reschedule, and cancellation as states of one booking, not three unrelated records. Keep the original booking's identity through a reschedule and record the history against it.
5. Store every booking time as an instant with the named zone it occurs in, and keep the invitee's own zone separately so confirmations and reminders read correctly to them.

## UI and UX Requirements

Match the application's existing design system exactly. Reuse its components,
spacing, and typography. This feature should look like it was always there.

## Responsive Requirements

Works on mobile, tablet, and desktop. Touch targets are large enough to hit on a
phone, and nothing overflows horizontally at 320px.

## Accessibility Requirements

- Fully keyboard navigable.
- Correct semantic elements and ARIA roles.
- Visible focus states.
- Meets WCAG AA contrast.
- Dynamic changes are announced to screen readers.
- Respects prefers-reduced-motion.

## Edge Cases

- Invitees book with whatever email they feel like, so a naive match will attach a booking to the wrong person or to nobody. Define the match order explicitly, hold ambiguous cases in an unmatched queue with the raw booking details, and never merge two contacts automatically on the strength of a booking.
- Webhooks are re-sent on any doubt, and reschedules arrive as new events referencing an old one. Key on the provider's booking identifier so a repeat delivery updates rather than inserts, and process events for the same booking in order even when they arrive out of order.
- Cancellation and rescheduling are the same lifecycle as the original booking. A cancellation that creates an orphan record, or a reschedule that leaves the old slot marked active, will corrupt downstream tasks and reminders. Transition the existing booking instead.
- An account can span several organizations and many event types, and the app must not sync everything by default. Let the user select which organizations and event types are imported, and ignore the rest rather than filling the app with unrelated bookings.
- Times stored without an explicit zone display correctly to the host and wrongly to the invitee. Persist the canonical instant, the event's zone, and the invitee's zone, and render each audience in its own.
- A booking may arrive for a record that has since been deleted or that the connecting user no longer has access to. Retain it as unmatched with a clear reason instead of dropping it or attaching it to something the user cannot see.
- Tokens expire and a disconnected Calendly account will keep sending webhooks that can no longer be verified against a live connection. Mark the integration disconnected, stop processing, and tell the owner rather than accumulating silent failures.
- When Calendly is unavailable or a burst of webhooks arrives during a busy period, the endpoint must stay responsive. Bound per-account processing concurrency and let the queue absorb the burst rather than shedding events.

## Testing

Exercise the feature end to end in the running application. Cover every edge case
above, then run the existing test suite and confirm nothing regressed.

## Acceptance Criteria

- [ ] Incoming webhooks are signature-verified before any processing, and unverified requests are rejected.
- [ ] The endpoint acknowledges immediately and processes bookings in the background.
- [ ] Repeat deliveries key on the provider's booking identifier and update rather than duplicate.
- [ ] Booking, reschedule, and cancellation move one booking record through its lifecycle.
- [ ] Invitees with no confident match land in an unmatched queue rather than being attached to the wrong record.
- [ ] Users select which organizations and event types are imported.
- [ ] Times are stored canonically and displayed in both the host's and the invitee's zone correctly.
- [ ] The feature matches the existing design system.
- [ ] No existing functionality is broken.

## Adaptation Rules

- Match the existing design system. Do not introduce a new colour palette,
  spacing scale, or component library.
- Reuse existing components and utilities wherever they fit.
- Follow the naming, file layout, and code style already present.
- Do not upgrade, replace, or remove existing dependencies to make this
  feature fit. Adapt the feature to the app, not the app to the feature.
- Do not break existing functionality. If a change is genuinely required in
  existing code, make the smallest one that works and say so.
- If something in these instructions conflicts with how the application is
  built, follow the application and explain the deviation.

## Final Verification

Before you report the work as done:

1. Re-read the acceptance criteria above and check each one against what you
   actually built.
2. Run the application and exercise the feature end to end.
3. Run the existing test suite and confirm you have broken nothing.
4. Check the feature on mobile, tablet, and desktop widths.
5. Check keyboard navigation and focus handling.
6. Summarize what changed: files added, files modified, and anything you
   deliberately did differently because of how this application is built.

If any acceptance criterion is unmet, fix it before reporting completion.