Wizard State Manager service implementation
epic-cognitive-accessibility-foundation-task-012 — Implement the WizardStateManager service using BLoC/Cubit pattern to manage multi-step wizard state across the ≤5 step flow. Integrates with WizardDraftRepository for auto-save on every step transition. Exposes methods for nextStep(), previousStep(), jumpToStep(), and abandonDraft(). Emits typed state events for progress indicator synchronization. Enforces the step limit constraint via CognitiveLoadRuleEngine before allowing step additions.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 3 - 413 tasks
Can start after Tier 2 completes
Implementation Notes
Use a sealed class hierarchy for WizardState to enforce exhaustive pattern matching at call sites — this prevents missed state handling as the wizard evolves. The auto-save should use a debounce strategy only if transitions happen faster than 300ms in sequence (e.g., rapid taps); otherwise save immediately. Keep WizardStateManager free of any UI dependencies — it should be a pure Dart class with no Flutter imports except for foundation.dart if needed. Scope the Cubit using a Riverpod AutoDisposeNotifierProvider so it is torn down when the wizard screen is popped, preventing memory leaks.
If CognitiveLoadRuleEngine returns a violation, do NOT swallow it silently — surface it as a WizardError state so the UI can display an accessible error message via PlainLanguageErrorDisplay. Avoid storing step widget instances inside the state — store only step indices and data payloads; the UI layer owns rendering.
Testing Requirements
Write flutter_test unit tests covering: (1) all six state transitions including guard conditions, (2) auto-save invocation count per transition using a mock WizardDraftRepository, (3) CognitiveLoadRuleEngine rejection path when step index would exceed 5, (4) abandonDraft() completes even if the delete RPC returns an error (graceful degradation), (5) stream deduplication — identical state emitted twice should result in one downstream event. Write an integration test using a real Supabase test project that verifies auto-save round-trips correctly and draft restoration after simulated app restart. Target ≥90% line coverage on WizardStateManager. Use bloc_test package for BLoC/Cubit state assertion helpers.
The error message registry and help content registry both depend on bundled JSON assets loaded at startup. If asset loading fails silently (e.g. malformed JSON, missing pubspec asset declaration), the entire plain-language layer falls back to empty strings or raw error codes, breaking the accessibility guarantee app-wide.
Mitigation & Contingency
Mitigation: Implement eager validation of both assets during app initialisation with an assertion failure in debug mode and a structured error log in release mode. Add integration tests that verify asset loading in the Flutter test harness on every CI run.
Contingency: Ship a hardcoded minimum-viable fallback message set directly in Dart code so the app always has at least a safe generic message, preventing a blank or code-only error surface.
The AccessibilityDesignTokenEnforcer relies on dart_code_metrics custom lint rules. If the lint toolchain is not already configured in the project's CI pipeline, integrating a new linting plugin may cause unexpected build failures or require significant CI configuration work beyond the estimated scope.
Mitigation & Contingency
Mitigation: Audit the existing dart_code_metrics configuration in the project before starting implementation. Scope the lint rules to a separate Dart package that can be integrated incrementally, starting with the most critical rule (hard-coded colors) and adding others in subsequent iterations.
Contingency: Fall back to Flutter test-level assertions (using the cognitive-accessibility-audit utility) to catch violations in CI if the lint plugin integration is delayed, preserving enforcement coverage without blocking the epic.
WizardDraftRepository must choose between shared_preferences and Hive for local persistence. Choosing the wrong store for the data volume (e.g. shared_preferences for complex nested wizard state) can lead to serialisation bugs or performance degradation, particularly on lower-end Android devices used by some NHF members.
Mitigation & Contingency
Mitigation: Define a clean repository interface first and implement shared_preferences as the initial backend. Profile serialisation round-trip time with a realistic wizard state payload (≈10 fields) before committing to either store.
Contingency: Swap the persistence backend behind the repository interface without touching wizard UI code, which is possible precisely because the repository abstraction isolates the storage detail.
The AccessibilityDesignTokenEnforcer scope could expand significantly if a large portion of existing widgets use hard-coded values. Discovering widespread violations during this epic would force either a major refactor or a decision to exclude legacy components, potentially reducing the enforcer's coverage and value.
Mitigation & Contingency
Mitigation: Run a preliminary audit of existing widgets using a simple grep for hard-coded hex colors and raw pixel values before implementation begins. Use the results to set a realistic remediation boundary for this epic and log all out-of-scope violations as tracked tech-debt items.
Contingency: Scope the enforcer to new and modified components only (via file-path filters in dart_code_metrics config), shipping a partial but immediately valuable coverage rather than blocking the epic on full-codebase remediation.