# Component Acceptance Criteria

## Objective

Give every shared component a written bar it must clear before anyone uses it.

A per-component specification of required behaviour, keyboard handling, responsive limits, and theming, written so each line can be checked.

## 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. Inventory the components other parts of the app depend on — buttons, inputs, selects, dialogs, tables, menus, toasts — and write criteria for those first rather than for every file in the tree.
2. Write each criterion as a statement of an observable end state, not a task. A line that says the component supports keyboard use is untestable; a line that says Escape closes it and returns focus to the trigger is not.
3. Cover both the controlled and the uncontrolled shape of every component that has one, including what happens when a parent changes the value underneath an interaction already in progress.
4. Enumerate the variants and sizes each component claims to support, and state which combinations are unsupported, so an invalid pairing fails loudly instead of rendering something half-broken.
5. Do not write the criteria as a generic checklist copied to every component. A shared list gets ticked without reading; each component's document should name its own states, its own keyboard contract, and its own failure modes.

## 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

- A component used both controlled and uncontrolled behaves differently in each mode, and the difference is where the bugs live — the criteria must state what happens when the parent supplies a value, when it does not, and when it starts supplying one mid-life.
- Keyboard behaviour has to be written out key by key: which key moves focus, which commits, which cancels, whether arrow keys wrap at the ends, and where focus lands when the component closes or unmounts.
- Every declared variant and size needs coverage, and so do the combinations nobody intends — a destructive ghost button, a loading disabled input, an icon-only control with no accessible name — each should have a stated outcome rather than being left undefined.
- Stress content belongs in the criteria: a forty-word label, a single unbroken string with no spaces, right-to-left text, and a translated string two or three times longer than the English one all have to be handled without the layout collapsing.
- Criteria written once and never revisited rot quietly. Tie the document to the component so a change to the component's props or states is not considered done until the criteria are updated.
- Reduced motion, forced colours, and a doubled root font size are part of the component's contract, not separate concerns, and each should have at least one line saying what stays usable.
- A component with an asynchronous state needs a criterion for the slow case and one for the failed case, not only for the resolved one.

## 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

- [ ] Every shared component has its own criteria document rather than a shared generic list.
- [ ] Each criterion states an observable end state that can be checked by inspection.
- [ ] Controlled and uncontrolled use are both specified, including a parent changing the value mid-interaction.
- [ ] The full keyboard contract is written key by key, including where focus lands on close.
- [ ] Supported variant and size combinations are enumerated and unsupported ones are named.
- [ ] Long, unbroken, translated, and right-to-left content is covered by explicit criteria.
- [ ] Changing a component's props or states without updating its criteria is treated as incomplete work.
- [ ] 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.