# Announcement Bar

## Objective

Put a timed message across the top of the site without shipping a deploy.

An operator-configured, dismissible strip at the top of public pages, with scheduling and a link.

## 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. Extend the existing Service Incident Banner rather than adding a second bar. It already handles scheduling, targeting, dismissal, and severity; this is a marketing-styled variant of the same component, and two independent bars will eventually stack on top of each other.
2. Let an operator set the message, an optional link, background and text colours, and a start and end time from an admin screen. Requiring a deploy to run a weekend promotion means it goes live late.
3. Insert the bar into the document flow so it pushes fixed headers and sticky navigation down. Overlaying it on top of the header hides navigation on exactly the pages people arrived on.
4. Define precedence when an announcement and an incident banner are both active. Show the incident and suppress the promotion; a sale strip above an outage notice looks negligent.
5. Do not make the bar a full-width interstitial or an auto-expanding panel. A strip a visitor can read in one line and dismiss in one click is the whole point.

## 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 dismissal must be remembered per visitor and per announcement, so closing one message does not suppress the next one, and editing the message brings the bar back for people who dismissed the old text.
- The bar must push fixed and sticky headers down rather than sitting over them, and must release that space cleanly when dismissed without leaving a gap or shifting the page under a scrolling reader.
- Scheduled start and end times must be entered in a stated zone and evaluated against real time, so a sale that ends at midnight ends at midnight for the audience it was set for, not for the server.
- Operators will choose colours that make the text unreadable. Compute contrast against the configured background and either warn in the admin screen or force a legible text colour.
- The bar must be announced to assistive technology as it appears without stealing focus from whatever the visitor is doing, and its close control must be reachable and labelled by keyboard.
- An anonymous visitor with no account still needs their dismissal remembered. Store it locally and key it to the announcement identifier, and accept that clearing site data brings it back.
- On a narrow screen a long message wraps to three lines and eats the viewport. Cap the length in the admin screen and truncate gracefully rather than letting it grow.
- An expired announcement must disappear on its own. A promotion still showing a week after the sale ended damages more than it ever earned.

## 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

- [ ] Operators can publish, schedule, edit, and expire an announcement without a deploy.
- [ ] The bar shares the existing banner component rather than being a second independent strip.
- [ ] Fixed and sticky headers are pushed down, not covered, and no layout shift occurs on dismissal.
- [ ] Dismissal is remembered per visitor and per announcement, and resets when the message is edited.
- [ ] Text contrast against any configured background meets the accessible minimum.
- [ ] The bar is announced to screen readers without moving focus, and its close control is keyboard-reachable.
- [ ] An active incident banner takes precedence over a promotional announcement.
- [ ] 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.