separate mutext for actual detection

ee/presencedetection/presencedetection.go

@@ -13,8 +13,8 @@ const (
 )
 
 type PresenceDetector struct {
-	lastDetection time.Time
-	mutex         sync.Mutex
+	lastDetection                      time.Time
+	lastDetectionMutex, detectionMutex sync.Mutex
 	// detector is an interface to allow for mocking in tests
 	detector detectorIface
 }
@@ -33,13 +33,8 @@ func (d *detector) Detect(reason string) (bool, error) {
 // DetectPresence checks if the user is present by detecting the presence of a user.
 // It returns the duration since the last detection.
 func (pd *PresenceDetector) DetectPresence(reason string, detectionInterval time.Duration) (time.Duration, error) {
-	// using try lock here because we don't want presence detections to queue up,
-	// in the event that the users presses cancel, if the request were queued up, it would
-	// request the presence detection again
-	if !pd.mutex.TryLock() {
-		return DetectionFailedDurationValue, errors.New("detection already in progress")
-	}
-	defer pd.mutex.Unlock()
+	pd.lastDetectionMutex.Lock()
+	defer pd.lastDetectionMutex.Unlock()
 
 	if pd.detector == nil {
 		pd.detector = &detector{}
@@ -50,6 +45,14 @@ func (pd *PresenceDetector) DetectPresence(reason string, detectionInterval time
 		return time.Since(pd.lastDetection), nil
 	}
 
+	// using try lock here because we don't want presence detections to queue up,
+	// in the event that the users presses cancel, if the request were queued up, it would
+	// request the presence detection again
+	if !pd.detectionMutex.TryLock() {
+		return DetectionFailedDurationValue, errors.New("detection already in progress")
+	}
+	defer pd.detectionMutex.Unlock()
+
 	success, err := pd.detector.Detect(reason)
 	if err != nil {
 		// if we got an error, we behave as if there have been no successful detections in the past