Polygon merging incomplete

[davecraig]

If a feature has more than 1 duplicate, then they each just get merged with the first "original", but not with each other. I was using the golf course in testVectorToGeoJsonGrid as an example.

(I had added in a call to mergeAllPolygonsInFeatureCollection(featureCollection) to the test).

My attempts to fix this failed as the result of the first duplicate/original merge was failing validation attempts when going on to merge with subsequent duplicates. My changes (which could be wrong!) looked like this:

--- a/app/src/main/java/org/scottishtecharmy/soundscape/geoengine/utils/TileUtils.kt
+++ b/app/src/main/java/org/scottishtecharmy/soundscape/geoengine/utils/TileUtils.kt
@@ -1662,7 +1662,7 @@ fun mergeAllPolygonsInFeatureCollection(
         }
     }
 
-    val mergedPolygonsFeatureCollection = FeatureCollection()
+    val mergedPolygons = hashMapOf<Double, Feature>()
     val duplicateLineStringsAndPoints = FeatureCollection()
     val originalPolygonsUsedInMerge = mutableSetOf<Any>() // Track original polygons
 
@@ -1674,7 +1674,23 @@ fun mergeAllPolygonsInFeatureCollection(
 
         // Merge duplicate polygons
         if (originalFeature != null && originalFeature.geometry.type == "Polygon" && duplicate.geometry.type == "Polygon") {
-            mergedPolygonsFeatureCollection.features.add(mergePolygons(originalFeature, duplicate))
+
+            originalFeature.foreign?.get("osm_ids")?.let {
+                val osmIdArray = it as ArrayList<Double>
+                if(!mergedPolygons.containsKey(osmIdArray[0])) {
+                    mergedPolygons[osmIdArray[0]] = mergePolygons(
+                        originalFeature,
+                        duplicate
+                    )
+                } else {
+                    mergedPolygons[osmIdArray[0]] = mergePolygons(
+                        mergedPolygons[osmIdArray[0]]!!,
+                        duplicate
+                    )
+                }
+                if(osmIdArray[0] == 2191281972.0)
+                    println("Golf!")
+            }
             // Add to the set
             originalFeature.foreign?.get("osm_ids")?.let { originalPolygonsUsedInMerge.add(it) }
             // Add to the set
@@ -1690,8 +1706,9 @@ fun mergeAllPolygonsInFeatureCollection(
     val finalFeatureCollection = FeatureCollection()
 
     // Add merged Polygons
-    finalFeatureCollection.features.addAll(mergedPolygonsFeatureCollection.features)
-
+    for(feature in mergedPolygons) {
+        finalFeatureCollection.addFeature(feature.value)
+    }