NearbyParentFragment.kt: create method to update user location overlays

Before this commit, there was no easy way to update the user location overlays.

This commit adds the updateUserLocationOverlays() method, which will properly replace
the old user location overlays with new ones. It will also add the overlays if they
do not already exist.

app/src/main/java/fr/free/nrw/commons/nearby/fragments/NearbyParentFragment.kt

@@ -2700,16 +2700,65 @@ class NearbyParentFragment : CommonsDaggerSupportFragment(),
     private fun recenterMarkerToPosition(geoPoint: GeoPoint?) {
         geoPoint?.let {
             binding?.map?.controller?.setCenter(it)
+        }
+    }
+
+    /**
+     * Updates the user current location overlays (both the location and error overlays) by
+     * replacing any existing location overlays with new overlays at the given GeoPoint. If there
+     * are no existing location and error overlays, then new overlays are added.
+     *
+     * @param geoPoint The GeoPoint representing the user's current location.
+     * @param invalidate If true, the map overlays will be invalidated after the user
+     * location overlays are updated/added. If false, the overlays will not be invalidated.
+     */
+    private fun updateUserLocationOverlays(geoPoint: GeoPoint?, invalidate: Boolean) {
+        geoPoint?.let{
             val overlays = binding?.map?.overlays ?: return@let
 
-            // Remove markers and disks using index-based removal
-            var i = 0
-            while (i < overlays.size) {
-                when (overlays[i]) {
-                    is Marker, is ScaleDiskOverlay -> overlays.removeAt(i)
-                    else -> i++
+            // Multiply accuracy by 2 to get 95% confidence interval
+            val accuracy = getCurrentLocationAccuracy() * 2
+
+            // Create disk overlay
+            val errorOverlay = createCurrentLocationErrorOverlay(this.context, geoPoint,
+                (accuracy).toInt(), UnitOfMeasure.meter)
+
+            // Create current location overlay
+            val locationOverlay = createCurrentLocationOverlay(geoPoint)
+
+            var locationOverlayFound = false
+            var errorOverlayFound = false
+
+            // Find and replace overlays
+            for (i in overlays.indices) {
+                val overlay = overlays[i]
+                if (overlay is ScaleDiskOverlay) {
+                    overlays[i] = errorOverlay
+                    errorOverlayFound = true
+                }
+
+                if (overlay is Marker && overlay.icon.equals(locationOverlay.icon)) {
+                    overlays[i] = locationOverlay
+                    locationOverlayFound = true
+                }
+
+                if (errorOverlayFound && locationOverlayFound) {
+                    break
                 }
             }
+
+            // If the user location overlays were not found, add them
+            if (!errorOverlayFound) {
+                overlays.add(errorOverlay)
+            }
+
+            if (!locationOverlayFound) {
+                overlays.add(locationOverlay)
+            }
+        }
+
+        if (invalidate) {
+            binding!!.map.invalidate()
         }
     }