Compose child widgets in PeriodSelectionScreen
epic-bufdir-report-period-selection-ui-integration-task-009 — Assemble PeriodPresetList, CustomDateRangePicker, RecordCountBanner, and the confirm action button inside PeriodSelectionScreen's build method using a single scrollable Column. Pass BLoC state down via BlocBuilder. Ensure the confirm button is disabled while record count is loading or when validation errors are present.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 6 - 158 tasks
Can start after Tier 5 completes
Handles integration between different epics or system components. Requires coordination across multiple development streams.
Implementation Notes
Use BlocBuilder with a `buildWhen` predicate to avoid rebuilding on BLoC state transitions that don't affect the UI (e.g., intermediate loading sub-states). Pattern for confirm button disabled logic: `final canConfirm = state is PeriodValidState && state.validationErrors.isEmpty && !state.isLoading;`. Use AppButton's `enabled` parameter rather than conditionally passing null to onPressed, as AppButton should encapsulate the disabled visual state using design tokens. For spacing, use a ListView.separated with a fixed separatorBuilder returning SizedBox(height: AppSpacing.md) as an alternative to manual SizedBox insertion in Column — this reduces boilerplate.
Ensure CustomDateRangePicker and PeriodPresetList dispatch BLoC events on user interaction rather than calling callbacks up to the screen — keeps event handling local to each widget.
Testing Requirements
Widget tests: (1) all four child widgets present in widget tree when state is PeriodValidState; (2) confirm button disabled in PeriodLoadingState; (3) confirm button disabled when validationErrors non-empty; (4) confirm button enabled in PeriodValidState with no errors; (5) no RenderFlex overflow at 375pt width. Use MockPeriodSelectionBloc (via bloc_test/mocktail) to emit specific states. Test on small screen using tester.binding.setSurfaceSize.
The record count query is asynchronous and may take up to 1 second on a slow connection. If the BLoC does not manage loading states carefully, the UI may show a stale count or the confirm button may be briefly enabled during the loading transition, allowing premature submission.
Mitigation & Contingency
Mitigation: Define explicit BLoC states: PeriodSelectionLoading, PeriodSelectionCountLoaded, PeriodSelectionValidationError, and PeriodSelectionReady. The confirm button must only be enabled in PeriodSelectionReady. Add a debounce of 300ms on period-change events before triggering the count query to prevent excessive calls.
Contingency: If debouncing is insufficient to prevent UX degradation on slow connections, add an optimistic loading skeleton to the RecordCountBanner that clearly communicates a pending state, and keep the confirm button disabled until the count resolves.
The confirmedReportPeriodProvider Riverpod contract between this feature and the Bufdir Export feature may not be defined yet, causing integration failures when the downstream export screen attempts to read the provider.
Mitigation & Contingency
Mitigation: Define the confirmedReportPeriodProvider as a StateProvider<DateTimeRange?> in a shared providers file at the start of this epic, before any screen code is written. Communicate the provider contract to the Bufdir Export feature team so both sides align on the same provider reference.
Contingency: If the export feature consumes the period through a different mechanism (e.g., navigation arguments), add a thin adapter that writes the confirmed period to both the Riverpod provider and the navigation argument, ensuring backward compatibility.
Flutter's live region support for screen readers is inconsistent across platforms (iOS VoiceOver vs Android TalkBack), and the record count banner must be announced on every change — a pattern that has historically required platform-channel workarounds.
Mitigation & Contingency
Mitigation: Test the live region announcement on both iOS (VoiceOver) and Android (TalkBack) early in implementation using the accessibility_test harness. Reference the project's existing live-region-announcer component (664-accessibility-live-region-announcer) for a proven implementation pattern.
Contingency: If native live region support is insufficient, wrap the record count text in a Semantics widget with a programmatically updated label string, and trigger a SemanticsService.announce call on each count update as a platform-agnostic fallback.