Implement Report Field Validator
epic-structured-post-session-report-form-engine-task-006 — Build the service layer validator that evaluates field values against schema-defined rules: required, minLength, maxLength, pattern, min/max for numeric fields. Return typed ValidationResult objects with field-level error messages in Norwegian and English. Designed as a pure function class with no external dependencies, enabling fast unit testing of all validation paths.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 2 - 518 tasks
Can start after Tier 1 completes
Implementation Notes
Keep the validator stateless: `class ReportFieldValidator { const ReportFieldValidator(); }`. Use Dart's switch expression for clean rule dispatch. Pre-compile RegExp in a private cache: `static final _regexCache =
ValidationMessages class should be structured as static const strings grouped by errorCode: `class ValidationMessages { static const requiredNb = 'Dette feltet er obligatorisk'; static const requiredEn = 'This field is required'; ... }`. Do not use the Flutter localisation (intl) package here — the validator must remain a pure Dart library with zero Flutter dependencies. Error codes should be machine-readable snake_case strings (required, min_length, max_length, pattern, min_value, max_value, type_mismatch) for programmatic handling in the form BLoC.
Testing Requirements
Unit tests (flutter_test, no mocks needed): parametrized test table covering every rule × edge case combination. Required cases: (1) required=true, value=null → Invalid, (2) required=true, value='' → Invalid, (3) required=false, value=null → Valid, (4) minLength=3, value='ab' → Invalid, (5) minLength=3, value='abc' → Valid, (6) maxLength=5, value='toolong' → Invalid, (7) pattern='^\d+$', value='123' → Valid, (8) pattern='^\d+$', value='abc' → Invalid, (9) min=0, value=-1 → Invalid, (10) max=100, value=101 → Invalid, (11) multiple rules failing → single Invalid with multiple FieldValidationErrors, (12) validateAll with mixed valid/invalid fields → correct map. Assert both messageNb and messageEn are non-empty strings in every Invalid result. Minimum 100% branch coverage is achievable and expected for this pure logic class.
Dynamically rendered form fields built from runtime JSON schema are significantly harder to make accessible than statically declared widgets — Flutter's Semantics tree must be correct for every possible field type and every validation state. Failures here block the entire feature for Blindeforbundet's visually impaired peer mentors.
Mitigation & Contingency
Mitigation: Define WCAG 2.2 AA semantics requirements for each field type before implementation and write widget tests using Flutter's SemanticsController for every type. Include a real-device VoiceOver test session in the acceptance gate for this epic before marking it done.
Contingency: If dynamic semantics prove too difficult to get right generically, implement field-type-specific Semantics wrappers (one per supported field type) instead of a single generic renderer, accepting slightly more code duplication in exchange for reliable accessibility.
The report-form-orchestrator must manage a complex state machine — schema loading, draft persistence, per-field validation, submission retries, and error recovery — across multiple async operations. Incorrect state transitions could result in lost user data, double submissions, or UI freezes.
Mitigation & Contingency
Mitigation: Define all Bloc states and events explicitly as sealed classes before writing any logic. Use a state machine diagram reviewed by the team before implementation. Write exhaustive Bloc unit tests covering every state transition, including concurrent events and network interruption mid-submission.
Contingency: If Bloc complexity becomes unmanageable, extract draft persistence into a separate DraftManagerCubit and keep report-form-orchestrator focused solely on the submit workflow. The additional granularity makes each component independently testable.
Organisations may require field types beyond the five currently specified (text, multiline, checkbox group, radio, date). If a new type is discovered during pilot testing, the dynamic-field-renderer must be extended, potentially requiring changes across multiple layers.
Mitigation & Contingency
Mitigation: Design dynamic-field-renderer as a registry of field-type renderers with a clear extension point. Document the pattern for adding a new field type so that it can be done in one file without touching existing renderers.
Contingency: If an unhandled field type is encountered at runtime, dynamic-field-renderer renders a labelled plain-text fallback widget and logs a warning so the missing type is surfaced in monitoring, preventing a crash while making the gap visible.