# Expandable Text

## Objective

Shorten long text without making the full content hard to reach.

Long text clamped to a few lines, with an explicit control to show the rest and collapse it again.

## 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. Clamp by rendered lines, not by character count. Cutting a string at a fixed length breaks words, mangles markup, and truncates differently at every width.
2. Only show the expand control when the text is genuinely clipped. A 'Show more' on a two-line paragraph is noise.
3. Use a real button with an accessible label naming what expands, and expose the expanded state. An untagged 'more...' is invisible to a screen reader.
4. Keep the full text in the document and hide the overflow visually, so find-in-page, copy, and assistive technology see all of it.
5. Do not truncate anything the user must read to make a decision — error messages, warnings, legal terms, or the only description a record has.

## 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

- Re-measure after font load, container resize, and content change; a clamp decided once at mount will be wrong later.
- A link or interactive element in the clipped region must not be focusable while collapsed.
- Collapsing must not jump the page — keep the top of the block in view rather than the bottom.
- Rich text with lists, headings, or code blocks does not clamp cleanly; decide whether it collapses to a fixed height instead.
- Right-to-left and vertical text need the fade or ellipsis on the correct edge.
- Text with no spaces, such as a long URL or token, must wrap or truncate rather than forcing horizontal scroll.

## 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

- [ ] Truncation happens by rendered space and never breaks words or markup.
- [ ] The control appears only when content actually overflows.
- [ ] The trigger is a labelled button reporting its expanded state.
- [ ] Full text remains findable by browser search and copyable.
- [ ] Clamping is re-evaluated on resize and font load.
- [ ] Collapsing does not move the block out of view.
- [ ] 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.