iOS and Android image picker platform implementations
epic-receipt-capture-and-attachment-foundation-task-009 — Implement concrete iOS and Android classes conforming to the ReceiptImagePickerIntegration interface using the image_picker Flutter package. Normalize platform differences in permission handling, file path resolution, and EXIF orientation correction. Return raw bytes without any compression — compression is handled separately by ReceiptImageCompressor. Handle user cancellation by returning null cleanly.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Use image_picker ^1.x. EXIF orientation correction can be done with the flutter_exif_rotation package or by reading the orientation tag and rotating using the image package before stripping. For EXIF stripping, use the flutter_image_compress package's stripExif option or the image package's encodeJpg (which drops EXIF by default). Be careful: readAsBytes() returns the raw file bytes including EXIF, so stripping must happen after readAsBytes().
The implementation class should be a single file shared between iOS and Android since image_picker abstracts the platform differences — only add conditional code if a genuine platform divergence is discovered. Register the implementation in ProviderScope overrides at app startup.
Testing Requirements
Unit tests using flutter_test with mockito to mock ImagePicker. Test scenarios: (1) mock returns valid XFile → assert ReceiptImageResult returned with correct MIME type, (2) mock returns null (cancellation) → assert null returned, (3) mock throws PlatformException with photo_access_denied → assert ReceiptPickerPermissionDeniedException thrown, (4) EXIF strip: provide a JPEG byte array with known EXIF orientation tag and assert it is absent in output. Widget tests not required for this task — UI integration tested in a later task.
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.