# Pagination

## Objective

Split long lists into numbered pages without losing filters or the user's place.

Discrete paged lists with an explicit page control, where page number, page size, filters, and sort all live in the URL.

## 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. Build a real page control: previous, next, and a way to jump to a specific page or the last page. This feature is for lists people navigate deliberately. If the list is a feed people graze, choose progressive appending instead.
2. Put page, page size, filters, and sort in the URL so every page is linkable, bookmarkable, and survives a refresh.
3. Show enough context to orient: current page, total pages or a clear next-page affordance, and the range of items shown out of the total.
4. Offer a page-size choice where rows vary in density, and persist the user's preference.
5. Keep filters and sort applied when the page changes, and reset to page one whenever a filter or sort changes.
6. Use cursor-based pagination for large or fast-moving datasets. Deep offsets get slow and skip records as rows shift underneath.
7. Do NOT compute an exact total count on every request for large tables. Either cache it, estimate it, or drop it in favour of a next-page indicator.

## 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

- Deleting the last item on the last page must land the user on a valid page, not an empty one with no way back.
- A page number beyond the end of the results should clamp to the last page rather than render a blank screen.
- Records inserted or removed between requests can duplicate or skip items under offset pagination. Sort on a stable tiebreaker such as the primary key.
- Filtered results of zero must show the empty state with a way to clear filters, not page one of nothing.
- Pagination controls need real labels for screen readers and must be reachable and operable by keyboard.
- Returning from a detail view should come back to the page the user left, not page one.
- Page size changes must recompute the current page so the user stays roughly where they were.

## 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

- [ ] Page, page size, filters, and sort are all reflected in the URL, and any page is directly linkable.
- [ ] An explicit page control offers previous, next, and a jump to a chosen page.
- [ ] Changing a filter resets to the first page and keeps the filter applied.
- [ ] Deleting the last item on the last page redirects to a valid page.
- [ ] Sorting includes a stable tiebreaker so records are neither skipped nor duplicated.
- [ ] Controls are keyboard operable and labelled for assistive technology.
- [ ] Returning from a detail view restores the previous page.
- [ ] 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.