Define column mapper data models and interfaces
epic-bufdir-reporting-export-core-logic-task-001 — Define the Dart data models and abstract interfaces for the Bufdir column mapper, including ColumnMappingConfig, MappedRow, NullValuePolicy, and OrgColumnOverride. Establish the contract between the mapper and its config repository dependency.
Acceptance Criteria
Technical Requirements
Implementation Notes
Place all types under lib/features/bufdir_export/domain/models/. Use Dart sealed classes (Dart 3+) for NullValuePolicy — this enables compile-time exhaustive handling in the mapper engine. Do NOT use json_serializable for domain models; implement fromJson/toJson manually to avoid code generation coupling in the domain layer. Define BufdirColumnType as an enum covering: string, integer, decimal, date_iso8601, boolean.
ColumnMappingConfigRepository should be abstract so the infrastructure layer (Supabase) can be swapped. Keep MappedRow free of business logic — it is a pure data carrier. Follow clean architecture: domain layer must compile with zero external package imports beyond equatable.
Testing Requirements
Unit tests for all model constructors, equality checks, copyWith correctness, and JSON serialization round-trips. Test NullValuePolicy sealed class exhaustive switch coverage. Test OrgColumnOverride merging logic with NHF, Blindeforbundet, and HLF fixture configs. Target 100% line coverage on domain models.
No integration tests required at this layer.
Bufdir's column schema may have per-field business rules (conditional required fields, cross-field validation, organisation-specific category taxonomies) that cannot be expressed in a simple key-value mapping configuration. If the configuration model is too simple, supporting NHF's specific requirements will require hardcoded organisation logic, undermining the configuration-driven design.
Mitigation & Contingency
Mitigation: Design the column configuration schema as a full JSON document supporting field-level transformation rules, conditional expressions, and org-specific value enumerations. Validate the design against a real NHF Bufdir Excel template before implementation begins.
Contingency: If the configuration model cannot express all required rules, implement a thin transformation plugin interface where org-specific logic can be added as a named Dart class registered against the organisation ID, with the JSON config covering only the common cases.
For large organisations like NHF with potentially tens of thousands of activity records, the full export pipeline (query + map + generate + bundle + upload) may exceed Supabase Edge Function execution time limits (typically 150s), causing silent timeouts that leave audit records in a pending state indefinitely.
Mitigation & Contingency
Mitigation: Implement the orchestrator as a background Dart isolate with progress streaming rather than a synchronous Edge Function call. Use chunked processing for the query and mapping phases to reduce peak memory usage. Profile against realistic NHF data volumes in a staging environment.
Contingency: If processing time cannot be reduced below the timeout threshold, implement an asynchronous job model where the export is queued, processed in the background, and the user is notified via push notification when the download is ready — treating it as an eventual rather than synchronous operation.