From b28c192d1b6505b57f0d290f6349cf296cc24f6c Mon Sep 17 00:00:00 2001
From: Tuan Pham <103537251+phantumcode@users.noreply.github.com>
Date: Wed, 10 Jan 2024 16:14:43 +0000
Subject: [PATCH] fix: resolve race condition when starting AVCaptureSession
 (#93)

---
 Sources/FaceLiveness/AV/LivenessCaptureSession.swift       | 7 +++----
 .../Views/Liveness/FaceLivenessDetectionView.swift         | 3 +++
 .../Views/Liveness/LivenessViewController.swift            | 7 +++++++
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/Sources/FaceLiveness/AV/LivenessCaptureSession.swift b/Sources/FaceLiveness/AV/LivenessCaptureSession.swift
index 9cd8eccf..f8400262 100644
--- a/Sources/FaceLiveness/AV/LivenessCaptureSession.swift
+++ b/Sources/FaceLiveness/AV/LivenessCaptureSession.swift
@@ -11,6 +11,7 @@ import AVFoundation
 class LivenessCaptureSession {
     let captureDevice: LivenessCaptureDevice
     private let captureQueue = DispatchQueue(label: "com.amazonaws.faceliveness.cameracapturequeue")
+    private let configurationQueue = DispatchQueue(label: "com.amazonaws.faceliveness.sessionconfiguration", qos: .userInitiated)
     let outputDelegate: AVCaptureVideoDataOutputSampleBufferDelegate
     var captureSession: AVCaptureSession?
     
@@ -43,6 +44,7 @@ class LivenessCaptureSession {
         else { throw LivenessCaptureSessionError.cameraUnavailable }
 
         let cameraInput = try AVCaptureDeviceInput(device: camera)
+        let videoOutput = AVCaptureVideoDataOutput()
 
         teardownExistingSession(input: cameraInput)
         captureSession = AVCaptureSession()
@@ -53,13 +55,10 @@ class LivenessCaptureSession {
 
         try setupInput(cameraInput, for: captureSession)
         captureSession.sessionPreset = captureDevice.preset
-
-        let videoOutput = AVCaptureVideoDataOutput()
         try setupOutput(videoOutput, for: captureSession)
-
         try captureDevice.configure()
 
-        DispatchQueue.global().async {
+        configurationQueue.async {
             captureSession.startRunning()
         }
 
diff --git a/Sources/FaceLiveness/Views/Liveness/FaceLivenessDetectionView.swift b/Sources/FaceLiveness/Views/Liveness/FaceLivenessDetectionView.swift
index 64098e5f..320da58e 100644
--- a/Sources/FaceLiveness/Views/Liveness/FaceLivenessDetectionView.swift
+++ b/Sources/FaceLiveness/Views/Liveness/FaceLivenessDetectionView.swift
@@ -172,6 +172,9 @@ public struct FaceLivenessDetectorView: View {
                     UIScreen.main.brightness = 1.0
                 }
             }
+            .onDisappear() {
+                viewModel.stopRecording()
+            }
             .onReceive(viewModel.$livenessState) { output in
                 switch output.state {
                 case .completed:
diff --git a/Sources/FaceLiveness/Views/Liveness/LivenessViewController.swift b/Sources/FaceLiveness/Views/Liveness/LivenessViewController.swift
index 0189c3c8..5e5111a7 100644
--- a/Sources/FaceLiveness/Views/Liveness/LivenessViewController.swift
+++ b/Sources/FaceLiveness/Views/Liveness/LivenessViewController.swift
@@ -37,6 +37,12 @@ final class _LivenessViewController: UIViewController {
             }
         }
     }
+    
+    deinit {
+        self.previewLayer.removeFromSuperlayer()
+        (self.previewLayer as? AVCaptureVideoPreviewLayer)?.session = nil
+        self.previewLayer = nil
+    }
 
     override func viewDidLoad() {
         super.viewDidLoad()
@@ -110,6 +116,7 @@ extension _LivenessViewController: FaceLivenessViewControllerPresenter {
             imageView.frame = self.previewLayer.frame
             self.view.addSubview(imageView)
             self.previewLayer.removeFromSuperlayer()
+            (self.previewLayer as? AVCaptureVideoPreviewLayer)?.session = nil
             self.viewModel.stopRecording()
         }
     }