Implement Period Selector — Custom Date Range Picker
epic-bufdir-reporting-export-ui-task-002 — Extend the BufdirPeriodSelectorWidget with a custom date-range picker fallback that opens a calendar dialog when the user taps 'Custom range'. Must enforce start-before-end validation, surface plain-language error messages, and announce date changes via accessibility live regions for VoiceOver and TalkBack compatibility.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Use Flutter's built-in showDateRangePicker or a two-step showDatePicker sequence — evaluate which gives better screen-reader UX on both platforms. If using showDateRangePicker, wrap it in a helper that posts a live-region Semantics announcement after the picker resolves. For the validation error, use a ValueNotifier
Ensure the 'Custom range' button uses the same PresetPeriodButton widget from task-001 with an isCustom flag that renders a calendar icon instead of a text date. Keep validation logic in a pure function (isValidDateRange) so it can be unit-tested without Flutter dependencies. Connect back to BufdirPeriodSelectorWidget via the existing onPeriodSelected callback — no new callback interface needed.
Testing Requirements
Write flutter_test widget tests: (1) tapping 'Custom range' opens dialog, (2) selecting end before start shows error message and disables Confirm, (3) selecting valid range closes dialog and fires onPeriodSelected with correct DateTimeRange, (4) Cancel closes dialog without firing callback, (5) previous preset selection is preserved on Cancel, (6) liveRegion Semantics node exists and updates on date change, (7) future dates are not selectable (Confirm disabled). Write unit tests for validation pure function: isValidRange(start, end) → true/false with edge cases (same day = invalid, start+1day = valid). Target 100% branch coverage on validation logic.
For large exports that run for 10–30 seconds, a static loading spinner will feel broken to users on slow mobile connections. If the UI cannot display meaningful progress during the export pipeline, coordinators may abandon the flow or trigger duplicate exports by pressing the button multiple times.
Mitigation & Contingency
Mitigation: Implement streaming progress events from the orchestrator BLoC through named pipeline stages (querying, mapping, generating, uploading). Display each stage label with a progress indicator on the trigger screen. Disable the generate button immediately on first tap to prevent duplicates.
Contingency: If streaming pipeline progress is not feasible in the first release, implement a deterministic stage-based progress animation (10% querying, 50% generating, 90% uploading) that gives users feedback without requiring real server events.
Custom date range pickers are among the most common accessibility failures in mobile apps. Blindeforbundet users rely on VoiceOver, and NHF users include people with cognitive impairments. A non-accessible period picker could make the entire export workflow unusable for a significant portion of the intended user base.
Mitigation & Contingency
Mitigation: Build the period picker using Flutter's native date picker semantics as the foundation, with preset shortcuts as primary navigation (reducing the need to interact with the custom range picker at all). Test with VoiceOver on iOS and TalkBack on Android before UI epic sign-off. Engage Blindeforbundet's test contact for accessibility validation.
Contingency: If the custom date range picker cannot be made fully accessible before release, ship only the preset period shortcuts (covering the majority of use cases) and add the custom range picker in a follow-up sprint after dedicated accessibility remediation.