Implement StatsSummaryCards KPI row widget
epic-activity-statistics-dashboard-user-interface-task-003 — Build the StatsSummaryCards row consisting of three reactive KPI cards: session count, total hours, and reimbursement total. Cards must observe the stats Riverpod provider and rebuild when data changes. Each card must use the design token system for typography and spacing, carry Semantics labels with numeric values (e.g., 'Total sessions: 24'), and display a loading shimmer state while data is fetching.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Create a StatsSummary data class (or extend the freezed types from task-001) with fields: int sessionCount, double totalHours, double reimbursementTotal. The Riverpod provider should be a FutureProvider.family
Currency formatting should use the NumberFormat.currency(locale: 'nb_NO', symbol: 'kr') from the intl package. Place widget in lib/features/stats/presentation/widgets/stats_summary_cards.dart.
Testing Requirements
Widget tests in test/stats/stats_summary_cards_test.dart. Use ProviderScope with overridden provider to inject controlled AsyncValue states. Required scenarios: (1) AsyncLoading renders 3 shimmer placeholders with non-zero dimensions; (2) AsyncData renders correct session count, hours, and reimbursement values; (3) AsyncError renders error label on each card; (4) Semantics tree contains correct labels for each card in AsyncData state; (5) row does not overflow at 320dp width; (6) reimbursement card is hidden when role permission is absent (inject a mock permission provider). No golden tests required.
fl_chart renders chart elements on a Canvas, making individual bars and data points invisible to the Flutter Semantics tree by default. Without explicit Semantics wrappers, VoiceOver and TalkBack users receive no chart information, violating the WCAG 2.2 AA requirement mandated by all three partner organizations.
Mitigation & Contingency
Mitigation: Wrap the fl_chart widget in a Semantics node with a dynamically generated textual description of the chart data (e.g., 'Bar chart: January 12, February 8, March 15 sessions'). Implement a collapsible data table alternative beneath the chart that screen readers can navigate row by row. Validate with VoiceOver on iOS and TalkBack on Android before the epic is marked complete.
Contingency: If fl_chart's Canvas rendering cannot be made accessible within the epic timeline, ship the chart hidden from the Semantics tree with ExcludeSemantics and promote the data table alternative to first-class UI so screen reader users have full access to the information. Log a tech-debt item to revisit native chart accessibility in a future sprint.
Coordinators managing up to 5 chapters (NHF requirement) require the PeerMentorStatsList to display chapter affiliation labels for each row. With large chapter lists and many peer mentors, the list could become overwhelming and cause layout overflow or scrolling performance issues on lower-end Android devices.
Mitigation & Contingency
Mitigation: Implement chapter filtering as a segmented control above the list so coordinators can scope the list to one chapter at a time. Use ListView.builder (lazy rendering) rather than a Column of all rows. Profile scroll performance on a low-end Android device (Pixel 4a equivalent) with 50 peer mentors in scope during development.
Contingency: If multi-chapter display causes unacceptable performance, ship with single-chapter scope as the default view and a chapter switcher dropdown, deferring the combined cross-chapter list to a follow-up sprint.
Summary cards and the chart widget rebuilding simultaneously on provider state change could cause a visible jank frame on slower devices, degrading perceived quality especially since this screen is intended to feel motivating and polished for gamification purposes.
Mitigation & Contingency
Mitigation: Use AnimatedSwitcher with a short fade transition (150ms) on the stats cards and chart so that data replacement feels intentional rather than jarring. Profile with Flutter DevTools on a mid-range device and ensure no frame exceeds 16ms during a time-window switch.
Contingency: If animation introduces complexity that delays delivery, ship without animation and use a loading skeleton (shimmer effect) during re-fetch instead, which is simpler and equally effective at masking the data swap.
If the role-based screen dispatch is misconfigured, a peer mentor could navigate to the coordinator stats screen and see aggregated chapter data for all peer mentors, which is a data privacy violation and a compliance risk for all three organizations.
Mitigation & Contingency
Mitigation: Implement role guard at the router level using an existing role-route-guard component so the coordinator screen route is unreachable for peer mentor roles. Add a widget test that mounts the coordinator screen with a peer mentor session token and asserts that the guard redirects to the no-access screen.
Contingency: If a bypass is found in QA, add a secondary in-screen role assertion in the coordinator screen's initState that throws an AuthorizationException and navigates to the error screen, ensuring defence in depth regardless of router configuration.