Implement StatsPeriodFilterBar widget
epic-coordinator-statistics-dashboard-ui-task-001 — Build the StatsPeriodFilterBar UI widget that allows coordinators to select time periods (week, month, quarter, year, custom) and emit filter change events to parent BLoC. Widget must support accessible touch targets (minimum 44x44pt) and include semantic labels for screen readers.
Acceptance Criteria
Technical Requirements
Implementation Notes
Keep this widget stateless. Accept a StatsPeriod selectedPeriod parameter and an onPeriodChanged callback (or use BlocProvider.of context to dispatch directly). Render options as a horizontal Row of PeriodOptionChip widgets wrapped in a SingleChildScrollView to handle narrow screens without overflow. Each PeriodOptionChip should be a GestureDetector wrapped in a Semantics widget; set the semanticsLabel to 'Filter statistics by [period name]' and semanticsSelected to selectedPeriod == thisPeriod.
Use design tokens from the project's token system for colors (e.g., AppColors.accentPrimary for the active chip, AppColors.textSecondary for inactive). For the custom date range, call showDateRangePicker with the current locale and emit a CustomPeriod(start, end) in the onDateRangeSelection callback. Ensure touch targets: wrap each chip in a SizedBox(height: 44) and use sufficient horizontal padding so the chip is at least 44 px wide.
Testing Requirements
Widget tests using flutter_test. Test groups: rendering (all five options visible, correct initial selection highlighted), interaction (tap each option emits correct BLoC event, custom option opens date picker), accessibility (each option has correct Semantics label and role, selected option has semanticsSelected=true, touch target size ≥ 44×44), responsive (no overflow at 320 px width). Use BlocProvider with a MockStatsDashboardBloc to capture emitted events. Run flutter test --coverage and assert ≥ 90 % line coverage for StatsPeriodFilterBar.
PeerMentorStatsList must handle rosters of 40+ mentors efficiently. A naive ListView implementation that re-renders all rows on filter change may cause frame drops on mid-range devices, degrading the experience for coordinators managing large chapters.
Mitigation & Contingency
Mitigation: Use ListView.builder with const constructors for row widgets. Profile the list with Flutter DevTools on a release build against a 60-mentor dataset before submitting for review. Implement sort in the BLoC layer, not in the widget.
Contingency: If frame drops persist, introduce pagination (load 20 mentors, scroll to load more) and add a search filter to reduce visible row count in practice.
The ActivityTypeDonutChart must render org-configured activity type labels from the org-labels system. If the terminology provider is not available or returns stale labels, chart segments will display raw key strings instead of human-readable organisation-specific names, confusing coordinators.
Mitigation & Contingency
Mitigation: Always resolve labels through the OrganizationLabelsProvider before passing data to the donut chart widget. Implement a fallback that formats the raw key as a readable string (e.g., 'peer_support' → 'Peer Support') if the provider returns null.
Contingency: If the org-labels system is unavailable, display the formatted fallback label and log a warning. Do not block chart rendering on label resolution — render with fallbacks immediately.
fl_chart widgets do not natively expose semantic labels for individual bars and donut segments. Without explicit Semantics wrappers, VoiceOver and TalkBack users will receive no meaningful chart information, failing accessibility requirements critical for Blindeforbundet and NHF deployments.
Mitigation & Contingency
Mitigation: Wrap each fl_chart widget in a Semantics widget with a descriptive label summarising the chart data. Implement the data table fallback toggle from the start, not as an afterthought. Validate with VoiceOver on iOS and TalkBack on Android during development.
Contingency: If fl_chart's rendering pipeline prevents semantic overlay from working reliably, replace chart widgets with a custom Canvas-based implementation that has full semantic control, or use a different charting library with better accessibility support.
The period filter state must be preserved when navigating away from the dashboard (e.g., drilling into a mentor's detail screen and pressing back). If the BLoC is re-created on navigation, the filter resets to default, forcing coordinators to re-select their period every time they drill down, degrading operational workflow efficiency.
Mitigation & Contingency
Mitigation: Provide the StatsBloc at a route level above the dashboard screen using a BlocProvider scoped to the statistics navigation shell, not inside the screen widget itself. Verify persistence with a widget integration test that navigates away and back.
Contingency: If route-level scoping is not achievable within the current navigation architecture, persist the last-used filter to a local session store and restore it on screen re-entry.