Implement Wizard Draft Repository class
epic-cognitive-accessibility-foundation-task-002 — Build the WizardDraftRepository Dart class with full CRUD operations for draft state persistence. Implement saveDraft(), loadDraft(), deleteDraft(), and listDrafts() methods. Wire to Supabase with RLS policies so users can only access their own drafts. Include auto-save triggering on step transitions and optimistic local caching for offline resilience.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Use a single abstract WizardDraftRepository interface plus a SupabaseWizardDraftRepository concrete implementation — this allows a MockWizardDraftRepository for tests and future alternative backends. The debounce can be implemented with a simple Timer-based approach: cancel the previous timer on each saveDraft() call and fire after 500ms of inactivity. For the optimistic cache, a `Map
Do not persist the queue to disk in this task. WizardDraft serialization: implement toJson()/fromJson() manually or use json_serializable — ensure int keys in stepData survive JSON round-trip (JSON keys are strings, so deserialize '0', '1' back to int). Expose the repository via a Riverpod Provider, not a singleton, to support test override with ProviderContainer.overrideWith().
Testing Requirements
Unit tests: use flutter_test with a mock SupabaseClient (via mockito or mocktail) to test all four CRUD methods in isolation — cover happy paths, null returns, error propagation, and debounce behavior. Cache tests: verify that a second loadDraft() call within the same session does not trigger a second Supabase read (assert mock is called exactly once). Error handling tests: simulate SupabaseException (network error, RLS violation) and assert WizardDraftException is thrown with correct message. Debounce test: call saveDraft() five times in rapid succession and assert the mock upsert is called only once after the debounce delay.
Integration tests: run against a local Supabase Docker instance with real JWT tokens — test RLS (user A cannot read user B's draft), upsert idempotency, and null return on missing draft. Provider test: verify wizardDraftRepositoryProvider resolves without error in a ProviderContainer.
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.