# OAuth Integration Connections

## Objective

Let users connect an external service so the app can read their data.

An OAuth connect flow for third-party data access, showing exactly which external account is attached and what it can reach.

## 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. Build the authorization flow with a single-use state value bound to the user's session, and PKCE where the provider supports it. Reject any callback whose state does not match — an unvalidated callback lets someone attach their account to another user's workspace.
2. Request the narrowest scopes that make the connection useful. Do not ask for write access to satisfy a read-only feature.
3. After connecting, display the external account identity — the email, handle, or workspace name the provider returned — not just 'Connected'.
4. Allow more than one connection to the same provider and keep each connection's tokens and data strictly separated. Store tokens encrypted and never render them in the UI or logs.
5. This feature is OAuth for data access only. OAuth used as a sign-in method is owned by Social Sign-In; extend that rather than building a second identity path. Ongoing health display is owned by Integration Connection Health, and refresh mechanics by OAuth Token Refresh Recovery.
6. Provide a disconnect action that revokes the token at the provider where the API allows it, rather than only deleting the local row.

## 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 user may approve some scopes and decline others. Detect partial consent and say which capability is missing, instead of treating the connection as complete.
- The user may connect the wrong external account. Show the identity before anything syncs and offer a one-step swap.
- Consent revoked at the provider's end will not tell you. The connection must degrade honestly the next time a call fails.
- A user who connects the same external account twice should be merged into one connection, not left with two that fight over the same data.
- The callback can arrive twice — from a refresh or a retried redirect. Treat the authorization code as single-use and make the second attempt idempotent, not an error page.
- When the connecting user leaves the workspace, decide up front whether the connection dies with them or transfers. A shared integration silently owned by an ex-employee is a time bomb.

## 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

- [ ] State is validated on every callback and PKCE is used where the provider supports it.
- [ ] Requested scopes are the minimum the feature needs, and are listed to the user before authorization.
- [ ] The connected external account is identified by name in the UI.
- [ ] Multiple connections to one provider coexist without sharing tokens or data.
- [ ] Partial or revoked consent produces a specific message, not a generic failure.
- [ ] Tokens are encrypted at rest and never appear in logs, exports, or the UI.
- [ ] 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.