# Rich Text Editor

## Objective

Formatting tools that don't let pasted HTML wreck your app.

A WYSIWYG editor for long-form fields, with a fixed set of supported formats and server-side sanitisation of everything it produces.

## 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. Decide the supported format list first — headings, bold, italic, lists, links, quotes, code, images — and build the toolbar from it. An editor that accepts anything is an editor you cannot sanitise.
2. Sanitise on the server against an allowlist of tags and attributes, both on save and on render. Client-side sanitisation is a convenience, not a defence; the endpoint accepts whatever is posted to it.
3. Clean pasted content: strip inline styles, font tags, class names and comments from Word and Google Docs, and map what remains onto the supported formats.
4. Keep the editable region a real focusable control with a label, and make every toolbar action reachable by keyboard with its shortcut shown.
5. Do not store rendered HTML as the only copy if the app also needs plain text for search, previews or notifications — derive and store that too.

## 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

- Content that looks empty but is a stray break or empty paragraph must count as empty for validation.
- Links must be checked for scheme — javascript: and data: URLs are the whole attack.
- Pasted images arrive as base64 or as remote URLs; decide whether to upload, rewrite or reject them, and never hotlink silently.
- Undo must survive a paste-and-clean operation as a single step, not unwind character by character.
- Autosave and formatting must not fight: a save mid-edit should not move the caret or reset the selection.
- Content authored before this editor existed must still open and save without being mangled.

## 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

- [ ] Stored HTML is sanitised server-side against an explicit allowlist.
- [ ] Pasted Word and Docs content arrives clean and mapped to supported formats.
- [ ] Unsafe link schemes are rejected on save and on render.
- [ ] Every toolbar action has a keyboard path and headings produce real heading elements.
- [ ] Visually-empty content fails a required-field check.
- [ ] Legacy content round-trips through the editor unchanged.
- [ ] 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.