# Button System

## Objective

Replace the app's accumulated button variants with one predictable set of rules.

A single button contract covering hierarchy, size, icon placement, and the disabled and loading states.

## 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 every button-like control already in the app and record which visual treatment each one uses. Most codebases have three primary styles that were meant to be one.
2. Settle on a small hierarchy — primary, secondary, and quiet — and allow exactly one primary action per view or per dialog. If two actions both look primary, the hierarchy is not doing any work.
3. Define each size step with its own padding, text size, icon size, and minimum hit area, so a small button in a table row and a small button in a toolbar are genuinely the same size.
4. Keep buttons and links semantically distinct: something that navigates is a link and must be openable in a new tab, something that acts is a button and must respond to the space key. A button styled as a link is still a button.
5. Do not add a variant per screen. If a new context appears to need a fourth hierarchy level, the answer is almost always the wrong layout, and every extra variant permanently weakens the ones already there.

## 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

- Buttons and links must not be interchangeable in markup. A navigation styled as a button loses middle-click, right-click, and open-in-new-tab; an action wired as a link is skipped by the space key and reported wrongly to screen readers.
- An icon-only button has no visible text and therefore needs an accessible name supplied another way, or assistive technology announces nothing but the word button.
- Every size step must keep a hit area of at least 44 by 44 pixels on touch, even where the visible button is smaller. Shrink the padding, not the target.
- A button that swaps its label for a spinner changes width and pushes the rest of the row sideways. Reserve the resting width, or place the indicator without removing the label.
- Disabled buttons are typically skipped by keyboard navigation and give no explanation, so a permanently disabled primary action is a dead end unless the reason is stated nearby.
- Buttons carrying long or translated labels must wrap or truncate predictably rather than overflowing their container in German or Finnish.
- Focus rings must remain visible on every variant including the quiet one, where a subtle background often swallows the default outline.

## 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 button in the app resolves to one of the defined hierarchy levels and size steps.
- [ ] No view presents more than one primary action.
- [ ] Actions are buttons and navigations are links, regardless of how either is styled.
- [ ] Every size step meets the minimum touch target on a touch device.
- [ ] Entering the loading state does not change the button's width or shift adjacent content.
- [ ] Each variant has a visible focus state that passes contrast against its own background.
- [ ] 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.