Refactor ProjectViewModel resource cleanup to use addCloseable

[harrydbarnes]

Replaces the GlobalScope.launch based cleanup in ProjectViewModel.onCleared with the idiomatic addCloseable mechanism. Modified FaceRecognitionHelper to implement Closeable and updated its close method to be non-suspending using runBlocking, ensuring safe resource release.

[gemini-code-assist]

Summary of Changes

Hello @harrydbarnes, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves resource management within the application by transitioning the ProjectViewModel's cleanup strategy from a manual, potentially error-prone GlobalScope.launch implementation to the more robust and integrated addCloseable mechanism. This change ensures that the FaceRecognitionHelper's resources are reliably released when the ViewModel is no longer needed, enhancing application stability and preventing resource leaks.

Highlights

• Resource Cleanup Refactor: The pull request refactors the resource cleanup mechanism in ProjectViewModel to utilize the idiomatic addCloseable method, replacing the previous GlobalScope.launch based approach.
• FaceRecognitionHelper implements Closeable: The FaceRecognitionHelper class now implements the java.io.Closeable interface, making it compatible with the addCloseable mechanism.
• Non-suspending Close Method: The close() method within FaceRecognitionHelper has been modified to be non-suspending by wrapping its coroutine logic in runBlocking, ensuring it adheres to the Closeable interface contract for synchronous resource release.
• Simplified ViewModel Lifecycle: The manual cleanup logic in ProjectViewModel.onCleared() has been removed, as addCloseable now automatically handles the faceRecognitionHelper's lifecycle, leading to cleaner and more robust code.

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[gemini-code-assist]

Code Review

This pull request refactors the resource cleanup for ProjectViewModel to use the idiomatic addCloseable mechanism, which is a cleaner approach for ViewModel lifecycle management and removes GlobalScope.launch for cleanup. However, a critical threading issue and potential Denial of Service (DoS) vulnerability have been identified in FaceRecognitionHelper.close(). The use of runBlocking on the main thread to acquire a mutex, especially when background tasks might be holding it, risks triggering ANR (Application Not Responding) errors and creating a performance bottleneck. It is recommended to perform the cleanup asynchronously or ensure the close() operation does not block the UI thread.

[gemini-code-assist]

The use of runBlocking within the close() method, which is called on the main thread via addCloseable in ProjectViewModel, introduces a potential Denial of Service (DoS) vulnerability. If a background task is performing face recognition and holding the mutex, the main thread will be blocked until the computationally intensive TFLite inference completes, leading to Application Not Responding (ANR) errors. This also presents a significant performance bottleneck, as runBlocking on the main thread should generally be avoided for potentially blocking or intensive operations. Consider if interpreter?.close() or gpuDelegate?.close() are truly fast and non-blocking; if not, a different resource management strategy or offloading these operations to a background thread within close() might be more appropriate.