Expense Form BLoC — state and event model
epic-travel-expense-registration-ui-task-005 — Implement the ExpenseFormBloc using the flutter_bloc package. Define all form states (initial, editing, validating, submitting, submitted, error) and events (typeSelected, amountChanged, receiptAttached, receiptRemoved, submit, reset). The BLoC must coordinate type selection with dynamic field visibility rules: selecting a mileage type shows the distance field; selecting a fixed-amount type hides it.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 2 - 518 tasks
Can start after Tier 1 completes
Implementation Notes
Use flutter_bloc 8.x Bloc
Delegate conflict rule evaluation to the same ConflictRuleEngine used by the selector widget to keep logic DRY. Register the BLoC with a BlocProvider at the expense form screen level, not globally, so it is disposed when the screen is popped. Use emit.forEach() or on
Testing Requirements
Unit tests (flutter_test / bloc_test): use bloc_test's blocTest() helper for every event/state transition. Test: initial state is ExpenseFormInitial; TypeSelected with mileage type → showDistanceField true; TypeSelected with fixed-amount type → showDistanceField false; AmountChanged below threshold → receiptRequired false; AmountChanged above threshold → receiptRequired true; ReceiptAttached → receipt set in state; ReceiptRemoved → receipt null; SubmitExpense with missing required fields → ExpenseFormEditing with validationErrors; SubmitExpense with all valid fields → ExpenseFormSubmitting → ExpenseFormSubmitted (mock repository success); SubmitExpense with repository error → ExpenseFormError; ResetForm → ExpenseFormInitial. Target 100% event-handler coverage.
The image_picker Flutter plugin requires platform-specific permissions (NSPhotoLibraryUsageDescription, camera permission) and behaves differently across iOS and Android versions. Permission denial or plugin misconfiguration can silently prevent receipt attachment.
Mitigation & Contingency
Mitigation: Configure all required permission strings in Info.plist and AndroidManifest.xml during initial plugin setup. Use the permission_handler package to check and request permissions before launching the picker, with clear user-facing explanations. Test on both platforms across at least two OS versions.
Contingency: If image_picker proves unreliable on a specific platform version, fall back to file_picker as an alternative that uses the OS document picker interface, which requires fewer permissions on some Android versions.
The expense form BLoC manages interconnected state across expense type selection, field visibility, receipt requirement, threshold evaluation, and submission flow. Incorrect state transitions can cause UI inconsistencies such as required receipt indicator not updating after amount change, or form appearing valid when mutual exclusion is violated.
Mitigation & Contingency
Mitigation: Model BLoC states as sealed classes with exhaustive pattern matching. Write state transition unit tests covering every combination of: type selection change, amount field change above/below threshold, receipt attachment/removal, and offline mode toggle. Use bloc_test for comprehensive state sequence assertions.
Contingency: If BLoC complexity becomes unmanageable, split into two BLoCs — one for type selection/exclusion state and one for field values/submission — coordinating via a parent provider, accepting the small overhead of inter-BLoC communication.
The expense type selector must enforce mutual exclusion visually by disabling options and showing conflict tooltips, while remaining fully accessible to screen reader users who cannot perceive visual disable states. Incorrect semantics labelling will fail WCAG 2.2 AA requirements critical for Blindeforbundet and HLF users.
Mitigation & Contingency
Mitigation: Use Flutter Semantics widgets to explicitly set disabled state and provide conflict explanations as semanticLabel strings on disabled options. Run accessibility audits with TalkBack and VoiceOver during widget development, not post-completion. Reference the project's accessibility test harness for required test coverage.
Contingency: If custom widget accessibility is difficult to certify, implement the selector as a standard Flutter Radio/Checkbox group with built-in accessibility semantics and an explanatory Text widget below each conflicting option, sacrificing visual elegance for guaranteed WCAG compliance.