# QR Code Generator

## Objective

Turn a link, some text, or a contact detail into a QR code people can print or download.

A QR code generator with live preview, optional branding, and downloads suitable for both screen and print.

## 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. Generate the code in the browser and update the preview as the user types, so they can see immediately when the content gets long enough to make the code too dense to be practical.
2. Support the kinds of content the app actually needs to encode: a link, plain text, and contact details. Do not ship a menu of a dozen formats where most produce codes nobody in this app will scan.
3. Offer both a raster download for screens and a vector download for print, and make the vector the default when the user's stated use is printing.
4. Where the app already has shareable or signed links, offer to generate the code from those rather than asking the user to paste a URL by hand. A short link also produces a much less dense code.
5. Do not let brand styling break scannability. Validate contrast and error correction against the current settings and refuse to export a code that will not scan, rather than exporting it with a warning nobody reads.

## 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 long link or a long block of text produces a dense code that phones fail to read at realistic sizes and print resolutions. Cap how much can be encoded, and suggest shortening the link rather than silently generating something unscannable.
- A logo placed over the centre destroys part of the code. Raise the error correction level automatically when a logo is added, and cap the logo size relative to the code so recovery is still possible.
- Exports must include the quiet-zone margin around the code. A code cropped tight to its edges fails to scan when it is placed against a coloured background or a page border.
- Print output must be vector, because a raster code scaled up to a poster blurs at the edge of every square and stops resolving.
- Brand colours frequently invert or flatten the contrast the code depends on. Enforce a minimum contrast between the modules and the background, and reject a light-on-dark inversion where scanners expect the opposite.
- Test the generated code by scanning it, not by looking at it. Verify at the smallest size the app offers for download, since that is where failures appear first.
- The code must have a text alternative wherever it is displayed, because a QR code is unusable to anyone who cannot point a second device at the screen. Show the underlying link as selectable text next to it.
- A code generated from a link that later expires or is revoked will already be printed somewhere. Warn the user before generating a code from a short-lived link.

## 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

- [ ] The preview updates live as the user edits the content being encoded.
- [ ] Links, plain text, and contact details all generate valid, scannable codes.
- [ ] Raster and vector downloads are both available, and print use gets vector.
- [ ] Adding a logo raises the error correction level and constrains the logo size.
- [ ] Exports include the quiet-zone margin.
- [ ] Colour combinations below the minimum contrast are rejected before export.
- [ ] Every displayed code is accompanied by the link or text it encodes, as selectable text.
- [ ] 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.