ReceiptImagePicker abstraction interface definition
epic-receipt-capture-and-attachment-foundation-task-008 — Define the ReceiptImagePickerIntegration abstract class with a pickFromGallery() method and a pickFromCamera() method, both returning a Future<ReceiptImageResult?> containing the raw image bytes and detected MIME type. The interface must be platform-agnostic so iOS and Android implementations can be swapped via Riverpod provider override.
Acceptance Criteria
Technical Requirements
Implementation Notes
Keep this file to under 60 lines — it is a pure interface definition. Use @immutable on ReceiptImageResult and provide a const constructor where possible (though Uint8List is not const, so use final fields). Define the Riverpod provider as a Provider
The UnimplementedError default forces each platform entry point to register the correct implementation, preventing silent fallback to a no-op.
Testing Requirements
Unit tests using flutter_test. Verify: (1) ReceiptImageResult can be constructed with valid bytes and MIME type, (2) ReceiptImageResult constructor throws AssertionError or ArgumentError for empty bytes, (3) ReceiptImageResult constructor throws for unsupported MIME type, (4) equality operator returns true for two ReceiptImageResult instances with identical bytes and MIME type, (5) a mock implementation of ReceiptImagePickerIntegration can be created inline (verifying the abstract contract is implementable). No platform channel calls in these tests.
Supabase Storage RLS policies using org/user/claim path scoping may not enforce correctly if claim ownership is not present in the JWT or if path segments are constructed differently at upload vs. read time, leading to data leakage or access denial for legitimate users.
Mitigation & Contingency
Mitigation: Define and test RLS policies in isolation before wiring to app code. Write integration tests that assert cross-org and cross-user access is denied. Use service-role key only in edge functions, never in client code.
Contingency: If client-side RLS proves insufficient, route all storage reads through a Supabase Edge Function that validates ownership before generating signed URLs, adding a controlled server-side enforcement layer.
Aggressive image compression may reduce receipt legibility below the threshold required for financial auditing, causing claim rejections or compliance failures despite technically successful uploads.
Mitigation & Contingency
Mitigation: Define minimum legibility requirements with HLF finance team before implementation. Set compression targets conservatively (e.g., max 1MB, min 80% JPEG quality) and validate with sample receipt images. Provide compression statistics in verbose/debug mode.
Contingency: If post-compression quality is disputed by auditors, increase the quality floor at the cost of larger file sizes, and add a manual override allowing users to skip compression for PDFs and high-quality scans.
The Flutter image_picker package behaves differently on iOS 17+ (PHPicker) vs older Android (Intent-based), particularly for file types, permission flows, and PDF selection, which may cause platform-specific failures not caught in development.
Mitigation & Contingency
Mitigation: Test image picker integration on physical devices for both platforms early in the sprint. Pin the image_picker package version and review changelogs before updates. Write widget tests using mock file results for each platform branch.
Contingency: If PHPicker or Android Intent differences cause blocking issues, implement separate platform-specific picker delegates behind the unified interface, allowing platform-specific fixes without breaking the shared API.