# Round-Robin Booking

## Objective

Spread incoming bookings across a team so the next available person takes the slot.

A shared booking page backed by a pool of team members, assigning each booking to one of them by an explicit rule.

## 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. Start with the minimum coherent version: a named pool of members, a merged availability view, and one assignment rule. Weighted pools, priority tiers, and per-member routing rules should be deferred until the simple pool is in use.
2. Compute the offered slots by merging every eligible member's real availability, and record which member a slot came from so the assignment at booking time is not a second, separate guess.
3. Assign on commit, not on render. Two people looking at the same slot must not both be promised the same member, and the assignment must be written in the same transaction that creates the booking.
4. Build on the app's existing calendar connections and on Time Zone-Aware Scheduling rather than adding a parallel availability system. If Calendly Booking Sync is present, treat its externally held busy time as authoritative when merging.
5. Do not assign by a simple rotating counter. A counter ignores cancellations, absences, and caps, and drifts into giving one person every booking within a week.

## 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

- Members who are away, off shift, or already at their daily cap must be excluded from the pool before slots are computed, not filtered out after a slot has already been offered.
- Distribution must stay fair once cancellations and no-shows are counted. If a cancelled booking still counts against the member's turn, whoever gets cancelled on most ends up with the least work.
- Availability from members in different zones must be merged as instants, not as local wall-clock times, or a slot will appear that is outside one member's actual working hours.
- When no member can honour a time, show no slot. Offering a slot and then reassigning or apologising afterwards is worse than an emptier calendar.
- If the assigned member becomes unavailable between booking and start, reassignment must follow a stated rule and notify both the attendee and the new member. Silent reassignment leaves the attendee expecting the wrong person.
- A booking that names a specific member directly must bypass the pool and still consume that member's availability and daily cap.
- Removing a member from the pool must not orphan their existing bookings. Decide explicitly whether those stay with them or are reassigned.
- Buffer time between bookings must be applied per member, so back-to-back slots are not offered against a member who needs a gap.

## 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

- [ ] A booking page backed by a member pool offers merged availability across the whole pool.
- [ ] Members who are away or at their daily cap contribute no slots.
- [ ] Assignment happens atomically at booking time and cannot give one slot to two attendees.
- [ ] Distribution stays balanced after cancellations and no-shows.
- [ ] Availability across zones merges correctly and no unhonourable slot is ever offered.
- [ ] Reassignment when a member drops out follows a documented rule and notifies both sides.
- [ ] The feature reuses the app's existing calendar connections and time zone handling.
- [ ] 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.