fix: update no match timeout check from frame count to elapsed time (#41)

* fix: update no match timeout check from frame count to elapsed time

* chore: fix spacing

* fix: resolve build errors in latest fix

* add unit test

* fix failed unit test

Author: phantumcode

Sources/FaceLiveness/Views/Liveness/FaceLivenessDetectionViewModel+FaceDetectionResultHandler.swift

@@ -90,9 +90,12 @@ extension FaceLivenessDetectionViewModel: FaceDetectionResultHandler {
     }
 
     func handleNoMatch(instruction: Instructor.Instruction, percentage: Double) {
+        let noMatchTimeoutInterval: TimeInterval = 7
         self.livenessState.awaitingFaceMatch(with: instruction, nearnessPercentage: percentage)
-        noMatchCount += 1
-        if noMatchCount >= 210 {
+        if noMatchStartTime == nil {
+            noMatchStartTime = Date()
+        }
+        if let elapsedTime = noMatchStartTime?.timeIntervalSinceNow, abs(elapsedTime) >= noMatchTimeoutInterval {
             self.livenessState
                 .unrecoverableStateEncountered(.timedOut)
             self.captureSession.stopRunning()
@@ -112,7 +115,7 @@ extension FaceLivenessDetectionViewModel: FaceDetectionResultHandler {
                 self.livenessViewControllerDelegate?.displayFreshness(colorSequences: colorSequences)
                 let generator = UINotificationFeedbackGenerator()
                 generator.notificationOccurred(.success)
-                self.noMatchCount = 0
+                self.noMatchStartTime = nil
 
             case .tooClose(_, let percentage),
                     .tooFar(_, let percentage),

Sources/FaceLiveness/Views/Liveness/FaceLivenessDetectionViewModel.swift

@@ -39,8 +39,8 @@ class FaceLivenessDetectionViewModel: ObservableObject {
     var faceGuideRect: CGRect!
     var initialClientEvent: InitialClientEvent?
     var faceMatchedTimestamp: UInt64?
-    var noMatchCount = 0
-
+    var noMatchStartTime: Date?
+    
     init(
         faceDetector: FaceDetector,
         faceInOvalMatching: FaceInOvalMatching,

Tests/FaceLivenessTests/LivenessTests.swift

@@ -38,6 +38,13 @@ final class FaceLivenessDetectionViewModelTestCase: XCTestCase {
         self.videoChunker = videoChunker
         self.viewModel = viewModel
     }
+    
+    override func tearDown() {
+        self.faceDetector = nil
+        self.livenessService = nil
+        self.videoChunker = nil
+        self.viewModel = nil
+    }
 
     /// Given:  A `FaceLivenessDetectionViewModel`
     /// When: The viewModel is first initialized
@@ -100,4 +107,20 @@ final class FaceLivenessDetectionViewModelTestCase: XCTestCase {
             "initializeLivenessStream(withSessionID:userAgent:)"
         ])
     }
+    
+    /// Given:  A `FaceLivenessDetectionViewModel`
+    /// When: The viewModel handles a no match event over a duration of 7 seconds
+    /// Then: The end state is `.encounteredUnrecoverableError(.timedOut)`
+    func testNoMatchTimeoutCheck() async throws {
+        viewModel.livenessService = self.livenessService
+        self.viewModel.handleNoMatch(instruction: .tooFar(nearnessPercentage: 0.2), percentage: 0.2)
+        
+        XCTAssertNotEqual(self.viewModel.livenessState.state, .encounteredUnrecoverableError(.timedOut))
+        try await Task.sleep(seconds: 6)
+        self.viewModel.handleNoMatch(instruction: .tooFar(nearnessPercentage: 0.2), percentage: 0.2)
+        XCTAssertNotEqual(self.viewModel.livenessState.state,  .encounteredUnrecoverableError(.timedOut))
+        try await Task.sleep(seconds: 1)
+        self.viewModel.handleNoMatch(instruction: .tooFar(nearnessPercentage: 0.2), percentage: 0.2)
+        XCTAssertEqual(self.viewModel.livenessState.state,  .encounteredUnrecoverableError(.timedOut))
+    }
 }