Integrate Supabase session token refresh on biometric success
epic-biometric-session-authentication-core-services-task-005 — Implement the Supabase session token refresh step within BiometricAuthService that executes immediately after a successful biometric verification. Calls SupabaseSessionManager to refresh the access token, ensuring the session is valid before returning BiometricAuthSuccess to the caller. Handles token refresh failures gracefully by returning a typed error result.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 4 - 323 tasks
Can start after Tier 3 completes
Implementation Notes
Inject SupabaseClient (or a SupabaseSessionManager abstraction) into BiometricAuthService via constructor for testability. Use a completer/mutex pattern to prevent concurrent refresh races — if a refresh is already in flight, await the same Future rather than issuing a second request. Catch GoTrueException specifically to differentiate session expiry from network failures. Store the refreshed access token and refresh token via flutter_secure_storage immediately after SupabaseClient updates its internal state — do not rely solely on the Supabase SDK's internal persistence since the app uses flutter_secure_storage as the authoritative store.
Log token refresh outcome at debug level only — never log token values.
Testing Requirements
Unit tests with mocked SupabaseClient covering: successful refresh returns new Session, AuthException on expired refresh token returns BiometricAuthSessionExpired, network timeout returns BiometricAuthTokenRefreshFailed. Integration test using a real Supabase test project verifying token rotation (new refresh token differs from old). Test that flutter_secure_storage is written with the new JWT after successful refresh. Test concurrent call guard: two simultaneous authenticate() calls should result in only one refreshSession() network request.
Multiple concurrent callers (e.g., SessionResumeManager and a background sync service) could simultaneously detect a near-expired token and each invoke SupabaseSessionManager.refreshSession(), causing duplicate refresh API calls and potentially a token invalidation race condition on the Supabase Auth server. This can result in one caller receiving a valid refreshed token while another receives a 401, causing intermittent authentication failures.
Mitigation & Contingency
Mitigation: Implement a single-flight pattern inside SupabaseSessionManager so that concurrent refresh calls coalesce into one in-flight request. Use a Dart Completer or AsyncMemoizer to ensure all waiters receive the same refreshed token. Write a concurrent integration test to validate the single-flight behaviour.
Contingency: If the single-flight pattern introduces deadlocks or timeout complexity, fall back to a mutex-based lock with a 10-second timeout, logging a warning if the lock is held longer than expected, and triggering a full re-login if the refresh ultimately fails.
Supabase Row-Level Security policies evaluate the JWT claims (user_id, role, org_id) on every query. If the refreshed token contains stale or changed claims — for example if a coordinator's role was updated server-side — RLS may silently block data access even though the session appears valid from the client's perspective, causing confusing empty screens rather than an authentication error.
Mitigation & Contingency
Mitigation: After every token refresh, decode the new JWT and compare key claims (role, org_id) with the cached values. If claims have changed, emit a session-claims-changed event that triggers a role re-resolution and navigation reset. Document this behaviour in the SupabaseSessionManager API contract.
Contingency: If claims drift is detected in production and causes data visibility issues, provide a force-refresh mechanism in the UI (pull-to-refresh on home screen) that clears cached role state and re-fetches from Supabase, accompanied by a user-visible toast indicating the session was refreshed.
Allowing session resumption from cached local token when offline introduces a window where a revoked or invalidated session can still grant app access. For example, if a coordinator deactivates a peer mentor's account while the mentor is offline, the mentor continues to have access until connectivity is restored and the token is validated server-side.
Mitigation & Contingency
Mitigation: Set a maximum offline grace period (e.g., 24 hours) stored alongside the token in SecureSessionStorage. If the grace period is exceeded, force a full credential re-login regardless of connectivity status. Scope offline access to read-only operations only, requiring connectivity for any write that reaches Supabase.
Contingency: If the offline grace period logic is found to be insufficient for compliance, implement remote session invalidation via a lightweight push notification that clears SecureSessionStorage even when the app is backgrounded, using FCM with a data-only message.