Add share-sheet integration to screenshot utility
epic-annual-impact-summary-foundation-task-010 — Extend ScreenshotCaptureUtility with a shareWidget(globalKey, shareText) method that captures the widget, writes the PNG to a temporary file, and invokes the native share sheet via the share_plus package. Handle permission errors, empty byte arrays, and platform-specific file path requirements for iOS and Android. Provide a captureAsBase64(globalKey) helper for use cases that do not require file I/O.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Use share_plus's `Share.shareXFiles([XFile(filePath, mimeType: 'image/png')], subject: shareText)` API. Always wrap the share invocation in a try/catch for PlatformException. Build the temp file path as `'${tempDir.path}/${const Uuid().v4()}.png'` using the uuid package. Delete the file in a finally block using `File(filePath).deleteSync(ignoreIfAbsent: true)`.
For captureAsBase64, call captureWidget, then `base64Encode(bytes)` inside a `compute()` call: `await compute(_encodeBase64, bytes)` where `_encodeBase64` is a top-level function. On iPad, pass the `sharePositionOrigin` parameter to Share.shareXFiles using the GlobalKey's renderBox rect to anchor the popover correctly. Do not use deprecated `Share.share()` with file paths — always use shareXFiles with XFile.
Testing Requirements
Unit tests (flutter_test) with a mocked Share.shareXFiles() to verify: (1) correct XFile mime type and filename, (2) empty-byte guard throws ScreenshotCaptureException, (3) PlatformException is wrapped in ShareException, (4) temp file deletion in finally block. Widget test confirming captureAsBase64 output decodes to identical bytes as captureWidget. Integration test on device (see task-014) to verify share sheet appears and dismissal completes without error. Minimum 85% branch coverage on shareWidget and captureAsBase64.
Rive animation files may not be available at implementation time, blocking the wrapped-animation-controller from being fully tested. If asset delivery is delayed, the controller cannot be validated for memory-leak-free disposal.
Mitigation & Contingency
Mitigation: Implement the animation controller with stub/placeholder AnimationController instances first so the lifecycle and disposal logic can be unit-tested independently of Rive assets. Define a named animation registry interface early so UI components can reference animations by name without coupling to specific Rive files.
Contingency: If Rive assets are not delivered before Epic 3 begins, replace Rive animations with Flutter implicit animations (AnimatedOpacity, ScaleTransition) as a drop-in and schedule Rive integration as a follow-on task once assets arrive.
The annual_summaries Supabase RPC aggregating 12 months of activity records per mentor may exceed acceptable query latency (>2s) for mentors with high activity volumes such as the HLF mentor with 380 registrations cited in workshop notes.
Mitigation & Contingency
Mitigation: Design the RPC to materialise summary results into the annual_summaries table via a scheduled edge function rather than computing on demand. The repository reads pre-computed rows, keeping query latency constant regardless of activity volume.
Contingency: If on-demand queries are required for real-time period switching, add a PostgreSQL partial index on (mentor_id, activity_date) and implement a client-side loading skeleton so slow queries degrade gracefully rather than blocking the UI.
iOS requires photo library permission before saving a screenshot to the gallery. If the permission prompt is triggered at an unexpected point in the share flow, the UX breaks and users may deny permission permanently, making gallery save unavailable.
Mitigation & Contingency
Mitigation: Trigger the permission request only when the user explicitly chooses 'Save to gallery' in the share overlay, not on screen load. Implement a pre-prompt explanation screen following Apple HIG so users understand why the permission is needed before the system dialog appears.
Contingency: If permission is denied, gracefully fall back to clipboard copy and system share sheet options which do not require photo library access, and surface a non-blocking snackbar explaining the limitation.