Preserve fluence by value when pulse duration changes

app/src/main/java/com/laseroptek/raman/ui/screens/main/MainViewModel.kt

@@ -134,6 +134,7 @@ import kotlinx.coroutines.joinAll
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import timber.log.Timber
+import kotlin.math.abs
 import javax.inject.Inject
 import kotlin.experimental.or
 import kotlin.time.Duration.Companion.milliseconds
@@ -2132,8 +2133,15 @@ class MainViewModel @Inject constructor(
             setFluenceList(newFluenceList)
         }
 
+        // 2-1. Resolve and apply fluence by value (not by old angle/index).
+        val resolvedFluence = newFluenceList.minByOrNull { abs(it - newFluence) } ?: 0f
+        val resolvedFluenceIndex = newFluenceList.indexOf(resolvedFluence).takeIf { it >= 0 } ?: 0
+        if (newFluenceList.isNotEmpty()) {
+            setFluenceAngle(resolvedFluenceIndex.stepToDegree(totalSteps = newFluenceList.size))
+        }
+
         // 3. Safely Update Repetition List (Prevents NullPointerException)
-        val newHzType = hzTable.value.getValue(newPulseDuration, newFluence)
+        val newHzType = hzTable.value.getValue(newPulseDuration, resolvedFluence)
         val newRepetitionList = RepetitionsByColorKey[newHzType] ?: RepetitionsByColorKey[KEY_YELLOW]!!
         if (newRepetitionList != repetitionList.value) {
             setRepetitionList(newRepetitionList)
@@ -2168,7 +2176,7 @@ class MainViewModel @Inject constructor(
         // 6. Any change invalidates the current preset selection.
         setSelectedPresetIndex(0)
 
-        Timber.d("Updated Laser Parameters: pulse=$newPulseDuration, fluence=$newFluence -> newRepListSize=${newRepetitionList.size}")
+        Timber.d("Updated Laser Parameters: pulse=$newPulseDuration, fluence=$resolvedFluence -> newRepListSize=${newRepetitionList.size}")
     }
 
     /**
@@ -2188,13 +2196,16 @@ class MainViewModel @Inject constructor(
         setPulseAngle(newPulseStep.stepToDegree(totalSteps = PulseDurations.size))
 
         val newPulseDuration = PulseDurations[newPulseStep]
-        // When pulse duration changes via slider, we use the first available fluence for the new list.
+        // Keep the current fluence value when pulse duration changes via slider.
-        val firstFluence = energyTable.value.getKey2ListForKey1(newPulseDuration).firstOrNull() ?: 0f
+        val currentFluenceStep = fluenceAngle.value.degreeToStep(totalSteps = fluenceList.value.size)
+        val currentFluence = fluenceList.value.getOrNull(currentFluenceStep)
+            ?: energyTable.value.getKey2ListForKey1(newPulseDuration).firstOrNull()
+            ?: 0f
 
-        // Call the centralized helper, resetting the fluence slider.
+        // Call the centralized helper using the preserved fluence value.
         updateLaserParameters(
             newPulseDuration = newPulseDuration,
-            newFluence = firstFluence,
+            newFluence = currentFluence,
         )
     }
 
@@ -2206,12 +2217,17 @@ class MainViewModel @Inject constructor(
             setPulseAngle(newStep.stepToDegree(totalSteps = PulseDurations.size))
 
             val newPulseDuration = PulseDurations[newStep]
-            val firstFluence = energyTable.value.getKey2ListForKey1(newPulseDuration).firstOrNull() ?: 0f
+            // Keep the current fluence value when pulse duration changes via slider.
+            val currentFluenceStep = fluenceAngle.value.degreeToStep(totalSteps = fluenceList.value.size)
+            val currentFluence = fluenceList.value.getOrNull(currentFluenceStep)
+                ?: energyTable.value.getKey2ListForKey1(newPulseDuration).firstOrNull()
+                ?: 0f
+
 
             // Call the centralized helper, resetting the fluence slider.
             updateLaserParameters(
                 newPulseDuration = newPulseDuration,
-                newFluence = firstFluence,
+                newFluence = currentFluence,
             )
         }
     }