Implement DictationScopeGuard with session state integration
epic-speech-to-text-input-foundation-task-012 — Implement DictationScopeGuard that inspects the current ActiveSessionState from Riverpod to enforce the business rule: dictation is only permitted outside of active peer mentoring sessions. Integrate with the session state provider to reactively block dictation if a session starts mid-dictation. Expose a Stream<ScopeGuardResult> for reactive UI binding. Register as a Riverpod provider.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Model ScopeGuardResult as a sealed class with two subclasses: ScopeGuardAllowed and ScopeGuardBlocked({required String reason}). Use Riverpod's StreamProvider or a StateNotifier that exposes a Stream internally. React to the ActiveSessionState provider using ref.listen inside a custom provider; emit new ScopeGuardResult values on each state change. Avoid polling — rely entirely on Riverpod reactivity.
The 'mid-dictation blocking' scenario is the most critical edge case: ensure the stream emits a blocked event even if dictation has already started, so the UI layer or DictationController can call stopListening() reactively. Do not embed any stopListening() logic inside the guard itself — it is the consumer's responsibility to react.
Testing Requirements
Unit tests must cover all state transition scenarios using mocked Riverpod providers (see task-013). Integration smoke test should verify that a real Riverpod container with a mock ActiveSessionState provider correctly drives stream output. No flutter_test widget tests are required for this task since it is a pure business-logic provider. Code coverage for this class should reach 100% of branching logic.
iOS 15 on-device speech recognition has a 1-minute session limit and requires network fallback for longer sessions. Peer mentor way-forward dictation may routinely exceed this limit, causing silent truncation of transcribed content without user feedback.
Mitigation & Contingency
Mitigation: Implement session-chunking logic in NativeSpeechApiBridge that automatically restarts recognition before the limit is reached, preserving continuity via partial concatenation. Document the iOS 15 vs iOS 16 on-device recognition behaviour difference in code comments.
Contingency: If chunking causes user-visible interruptions, surface a non-blocking informational banner on iOS 15 devices informing users that very long dictation sessions may need to be broken into segments, and use PartialTranscriptionRepository to persist each chunk immediately.
On iOS, speech recognition permission can only be requested once. If the user denies the permission, the app cannot re-request it. A poor first-impression permission flow will permanently disable dictation for those users, impacting the Blindeforbundet blind-user base who rely on dictation most.
Mitigation & Contingency
Mitigation: Design the NativeSpeechApiBridge permission flow to show a clear pre-permission rationale screen before the OS dialog. Implement a graceful degradation path that hides the microphone button and shows a settings deep-link when permission is permanently denied.
Contingency: If users have already denied permission before the rationale screen is added, provide a settings deep-link in DictationScopeGuard's denial message directing users to iOS Settings > Privacy > Speech Recognition to re-enable manually.
The approved field IDs and screen routes configuration in DictationScopeGuard may fall out of sync with the actual report form schema as new fields are added by org administrators, silently blocking dictation on legitimately approved fields.
Mitigation & Contingency
Mitigation: Source the approved field configuration from the same org-field-config-loader used by the report form, rather than a hardcoded list. Add a developer-time assertion that logs a warning when a dictation-eligible field type is rendered but not in the approved routes map.
Contingency: Provide a runtime override mechanism in the scope guard that coordinators or admins can use to temporarily whitelist a field ID while the config is updated, with an automatic expiry.