Compose sub-widgets and coordinate distance state in form
epic-mileage-reimbursement-entry-user-interface-task-010 — Embed DistanceInputFieldWidget, RouteInputFieldsWidget, and RealtimeReimbursementDisplayWidget into MileageEntryForm. Lift the current distance value into form state and pass it down as the distanceKm prop to RealtimeReimbursementDisplay via onChanged from DistanceInputField so the display updates on every keystroke. Ensure the form scrolls correctly when the keyboard appears and focus management moves logically between fields.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 4 - 323 tasks
Can start after Tier 3 completes
Implementation Notes
State lifting pattern: declare `double? _distanceKm` and `final _distanceController = TextEditingController()` in MileageEntryForm state. Pass `onChanged: (val) => setState(() => _distanceKm = double.tryParse(val))` to DistanceInputFieldWidget. double.tryParse returns null for non-numeric input, which correctly triggers the placeholder.
For orgRateNok: use `ref.watch(orgReimbursementRateProvider)` if the form is a ConsumerStatefulWidget (Riverpod), or read from the nearest BLoC state. Do not hardcode the rate — it varies per organisation (HLF vs Blindeforbundet). FocusNode management: create FocusNodes in initState, dispose in dispose(). Pass TextInputAction.next to each field and use `_routeFocusNode.requestFocus()` in onFieldSubmitted.
For scroll-to-focused-field behaviour, consider using Scrollable.ensureVisible() in a post-frame callback after focus changes, or rely on Flutter's built-in keyboard avoidance if SingleChildScrollView + viewInsets padding is correctly implemented from task-009.
Testing Requirements
Write flutter_test widget tests: (1) Pump MileageEntryForm, enter '23' in DistanceInputField, verify RealtimeReimbursementDisplay text contains '23'. (2) Enter a non-numeric string, verify display shows placeholder. (3) Enter '0', verify display shows placeholder. (4) Verify FocusNode transitions: after entering distance, textInputAction next moves focus to first RouteInputField (use tester.testTextInput).
(5) Verify orgRateNok is correctly passed by checking display math: if rate=4.90 and distance=10, display must show 'NOK 49.00'. Use ProviderScope with overrideWithValue for Riverpod rate provider in tests.
Triggering MileageCalculationService on every keystroke in the distance field could cause frame drops on lower-end Android devices if the widget rebuild chain is too broad. Jank during real-time calculation would degrade the peer-mentor experience, particularly for users with motor impairments who may type slowly and need immediate feedback.
Mitigation & Contingency
Mitigation: Keep the reimbursement calculation inside the RealtimeReimbursementDisplay widget subtree only, using a StatefulWidget with a local state variable rather than lifting state to the BLoC. This limits rebuilds to a single widget. Profile on a low-end device (Qualcomm Snapdragon 450 class) before code review.
Contingency: If profiling shows frame drops, debounce the onChanged callback by 50ms using a Timer before updating the local state, which remains imperceptible to the user while eliminating excessive rebuilds.
The optional destination field requires balancing two competing requirements: WCAG 2.2 AA demands a clear label association for screen readers, while the privacy requirement means the label must communicate optionality and privacy sensitivity without exposing the user to undue pressure to fill it in. A poorly worded label could cause screen-reader users to misunderstand the field's optional nature or feel compelled to enter private location data.
Mitigation & Contingency
Mitigation: Draft label text and hint text with input from at least one screen-reader user during the accessibility review. Use Flutter's Semantics widget to provide a separate semantic label that is more descriptive than the visual placeholder. Test with TalkBack and VoiceOver before sign-off.
Contingency: If user testing reveals confusion, replace the inline hint with a tappable information icon that opens a brief explanation of why the field is optional and how the data is used, reducing cognitive load on the field label itself.
If OrgRateConfigRepository has not yet resolved the org rate when the form loads (e.g. slow network, first launch with empty cache), the reimbursement display cannot show a meaningful value. Showing '0' or an error state could confuse mentors and undermine trust in the feature.
Mitigation & Contingency
Mitigation: Display a loading skeleton in the reimbursement display widget until the rate is available. Once loaded, animate the value in. Show a subtle 'rate unavailable' message if the fetch times out, but allow form completion and submission (rate will be fetched server-side at submission time).
Contingency: If rate unavailability is frequent due to connectivity issues, store the last successfully fetched rate in SharedPreferences as an additional fallback so the widget can render a stale-but-indicative value with a caveat label.