Update shutter speed based on illuminance

app/src/main/java/eu/wa5p/lightmeter/MainActivity.kt

@@ -57,11 +57,23 @@ class MainActivity : ComponentActivity(), SensorEventListener {
         illuminanceSensor = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT)
     }
 
+    fun updateLightmeterState(illuminance: Double) {
+        val iso = lightmeterState.value.iso
+        val aperture = lightmeterState.value.aperture
+        val shutterSpeed = (aperture * aperture) / (illuminance * (iso / 100))
+        lightmeterState.value = lightmeterState.value.copy(
+            illuminance = illuminance,
+            iso = iso,
+            aperture = aperture,
+            shutterSpeed = shutterSpeed
+        )
+    }
+
     override fun onSensorChanged(event: SensorEvent?) {
         event?.values?.let {
             for (v in it) {
                 Log.d(TAG, "sensor changed: $v lux")
-                lightmeterState.value = lightmeterState.value.copy(illuminance = v.toDouble())
+                updateLightmeterState(v.toDouble())
             }
         }
     }