Field Mapping Editor visual mapper widget
epic-external-system-integration-configuration-admin-ui-task-003 — Build the Field Mapping Editor widget providing a visual source-to-target column mapping interface. Support drag-and-drop or dropdown pairing of source fields from external system to internal data model fields, with Bufdir-specific override column support and per-row validation feedback.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Handles integration between different epics or system components. Requires coordination across multiple development streams.
Implementation Notes
Use Flutter's `LongPressDraggable` and `DragTarget` for the drag-and-drop interaction. The drag handle should be on the source field chip, and each row's right side should be a `DragTarget
Each entry: `{sourceFieldId, targetFieldId?, bufdirOverride?, validationStatus}`. Compute `validationStatus` reactively by comparing source field type to target field type from the schema. Implement a `FieldMappingRepository` that loads the external system's field schema from Supabase on widget initialization — cache it in memory for the session. For the Bufdir override: treat it as an additional optional field per row, not a separate mapping; render it as a small `AppTextField` that appears when the row is expanded or when a 'Bufdir' toggle is active.
Avoid `setState` in the parent — use fine-grained BLoC events (`MappingRowUpdated(rowIndex, targetFieldId)`) to update only affected rows.
Testing Requirements
Write flutter_test widget tests covering: (1) rendering 10 and 50 rows without overflow, (2) selecting a target via dropdown creates the mapping, (3) used fields are removed from other rows' dropdown options, (4) Bufdir override input appears and accepts text, (5) validation indicators show correct state for valid/warning/error rows, (6) Reset All dialog appears on button tap and restores prior state on confirm. Use `WidgetTester.drag` to test drag-and-drop mapping creation. Test keyboard navigation with `tester.sendKeyEvent`. Test serialization round-trip: create mappings in widget → extract JSON state → load into fresh widget → assert same mappings rendered.
Performance test with 50 rows using `benchmarkWidgetTester`.
The multi-step Integration Setup Wizard must render different credential fields, field mapping targets, and validation rules depending on the selected integration type. If the type-specific branching logic is implemented as conditional widget trees rather than driven by the Integration Type Registry, the wizard becomes unmaintainable and adding new integration types requires UI code changes.
Mitigation & Contingency
Mitigation: Design the wizard to be metadata-driven from the Integration Type Registry from day one. Credential form fields, required field validation, and mapping target lists are all fetched from the registry, not hardcoded in widgets. Implement one integration type end-to-end first (Xledger) to validate the pattern before building the others.
Contingency: If the metadata-driven approach proves too complex for the initial delivery, implement Xledger and Dynamics as hardcoded wizard variants and create a registry-driven refactor as a follow-up technical debt ticket with a fixed deadline.
The Excluded Features Configuration Panel must wire directly into the feature flag system to suppress HLF app features. If the feature flag system does not yet expose a writable admin interface, this panel cannot save its configuration, blocking the HLF-specific acceptance criteria.
Mitigation & Contingency
Mitigation: Verify that the Organization-scoped Feature Flags feature (a declared dependency) exposes a Dart API for programmatic flag writes before starting this panel. Coordinate with the feature flags team to ensure the write API is available. If needed, schedule this panel as the last item in the epic.
Contingency: If the feature flag write API is unavailable at implementation time, store excluded features in the integration's JSONB settings column and wire them into a local feature flag provider that merges database state with the standard flag system at app startup.
The Field Mapping Editor's usability for non-technical org admins is high-risk. If the visual mapping interface is confusing, admins will configure incorrect mappings that cause silent data corruption in accounting exports — a serious financial risk discovered only at month-end reconciliation.
Mitigation & Contingency
Mitigation: Conduct usability testing with at least one admin user from Blindeforbundet on the field mapping editor prototype before full implementation. Provide descriptive labels and sample data values for all fields. Add a 'test mapping' preview that shows a transformed sample record before saving.
Contingency: If usability testing reveals the visual editor is too complex, implement a simplified list-based mapping editor (select app field → select external field, one row at a time) as a fallback, deferring the drag-and-drop visual editor to a future iteration.
The Credential Management Form's masked fields and connection-test flow may conflict with screen reader requirements — VoiceOver and JAWS must be able to navigate the form, understand which fields are already configured, and receive feedback on connection test results without exposing credential values in accessible text.
Mitigation & Contingency
Mitigation: Design accessible semantics labels for masked fields (e.g., 'API key: configured, last 4 characters: abcd') from the start. Use Flutter's Semantics widget to provide screen-reader-specific text that differs from visual display. Test with VoiceOver on iOS and TalkBack on Android during development, not only at QA.
Contingency: If accessibility conflicts with security requirements for the credential form, implement a separate 'accessibility mode' flow where credential configuration is done through a separate confirmation step that provides more explicit semantic feedback without risk of value exposure.