Implement Coordinator Stats BLoC Core
epic-coordinator-statistics-dashboard-core-logic-task-009 — Implement StatsBloc (flutter_bloc Bloc) with LoadCoordinatorStats and FilterChanged events, and StatsLoading / StatsLoaded / StatsError states. StatsBloc delegates to CoordinatorStatsService and maps results to state. StatsLoaded must carry CoordinatorStatsViewModel including all view model fields needed by KPI cards, bar chart, donut chart, and peer mentor stats list widgets.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 3 - 413 tasks
Can start after Tier 2 completes
Implementation Notes
StatsBloc is the primary BLoC for the coordinator dashboard screen — it will be extended in tasks 010 and 011. Design the class with extension points in mind: use protected-style comments marking where the Realtime subscription (task-010) and filter propagation (task-011) will be added. For FilterChanged debouncing, use `on
Keep event handlers small — the actual logic lives in CoordinatorStatsService. Use `on
Testing Requirements
Unit tests using flutter_test + bloc_test. Scenarios: (1) initial state is StatsInitial, (2) LoadCoordinatorStats → [StatsLoading, StatsLoaded] on service success, (3) LoadCoordinatorStats → [StatsLoading, StatsError] on service failure, (4) FilterChanged → [StatsLoading, StatsLoaded] with updated filter, (5) FilterChanged while already loading — handled gracefully (no duplicate states), (6) StatsLoaded.viewModel is fully populated (no null fields), (7) StatsError carries a displayable string message not a raw exception, (8) default filter is last30Days. Mock CoordinatorStatsService with mocktail. Verify transformer behavior: send two FilterChanged events in rapid succession and assert only one load completes.
fl_chart's default colour palette may not meet WCAG 2.2 AA contrast requirements when rendered on the app's dark or light backgrounds. If segment colours are insufficient, the donut chart will fail accessibility audits, which is a compliance blocker for all three organisations.
Mitigation & Contingency
Mitigation: Define all chart colours in the design token system with pre-validated contrast ratios. Run the contrast-ratio-validator against every chart colour during the adapter's unit tests. Use the contrast-safe-color-palette as the source palette.
Contingency: If a colour fails validation, replace with the nearest compliant token. If activity types exceed the available token set, implement a deterministic hashing algorithm that maps activity type IDs to compliant colours.
StatsBloc subscribing to the activity registration stream creates a long-lived subscription. If the subscription is not disposed correctly when the dashboard is closed, it will cause a stream leak and potentially trigger re-fetches on a disposed BLoC, resulting in uncaught errors in production.
Mitigation & Contingency
Mitigation: Implement subscription disposal in the BLoC's close() override. Write a widget test that navigates away from the dashboard and asserts no BLoC events are emitted after disposal.
Contingency: If leaks are detected in QA, add a mounted check guard before emitting states from async callbacks, and audit all other BLoC stream subscriptions in the codebase for the same pattern.
PersonalStatsService's Phase 4 gamification data structure is designed against an assumed future schema. If the Phase 4 Spotify Wrapped feature defines a different data contract when it is developed, the structure built now will require a breaking change and migration.
Mitigation & Contingency
Mitigation: Document the contribution data structure with explicit field semantics and versioning comments. Keep the Phase 4 fields as optional/nullable so they do not break existing consumers if the schema evolves.
Contingency: If the Phase 4 schema diverges significantly, the personal stats data can be re-mapped in a thin adapter layer without changing PersonalStatsService's core implementation.