Generate lexicographically ordered IDs for writeGeojson features

#1565

Author: koperagen

dataframe-geo/src/main/kotlin/org/jetbrains/kotlinx/dataframe/geo/geotools/toSimpleFeatureCollection.kt

@@ -40,14 +40,16 @@ fun GeoDataFrame<*>.toSimpleFeatureCollection(
     val featureCollection = ListFeatureCollection(featureType)
 
     val featureBuilder = SimpleFeatureBuilder(featureType)
-
+    // if ID is present, SortedMap in DefaultFeatureCollection sorts rows by ID lexicographically
+    // I couldn't disable writing it, so let's generate lexicographically sorted IDs
+    val format = "f%0${df.rowsCount().toString().length}d"
     df.forEach { row ->
         val geometry = row["geometry"]
         featureBuilder.add(geometry)
         df.columnNames().filter { it != "geometry" }.forEach { colName ->
             featureBuilder.add(row[colName])
         }
-        val feature: SimpleFeature = featureBuilder.buildFeature(null)
+        val feature: SimpleFeature = featureBuilder.buildFeature(String.format(format, index()))
         featureCollection.add(feature)
     }
 

dataframe-geo/src/test/kotlin/org/jetbrains/kotlinx/dataframe/geo/io/IOTest.kt

@@ -1,5 +1,6 @@
 package org.jetbrains.kotlinx.dataframe.geo.io
 
+import org.geotools.referencing.CRS
 import org.jetbrains.kotlinx.dataframe.api.dataFrameOf
 import org.jetbrains.kotlinx.dataframe.geo.GeoDataFrame
 import org.jetbrains.kotlinx.dataframe.geo.toGeo
@@ -35,17 +36,18 @@ class IOTest {
         assert(geodf.crs == null)
     }
 
-    /*
-    TODO: doesn't work for now - writers adds ids that breaks order when read features
     @Test
     fun writeGeoJson() {
         val tempFile = Files.createTempFile("simple_points", ".json").toFile()
         simplePointsGeoDf.writeGeoJson(tempFile)
 
-        assertEquals(simplePointsGeoDf, GeoDataFrame.readGeoJson(tempFile.toURI().toURL()))
+        val loadedGeoDataFrame = GeoDataFrame.readGeoJson(tempFile.toURI().toURL())
+        assertEquals(simplePointsGeoDf.df, loadedGeoDataFrame.df)
+        // TODO: Doesn't work because of how equality between CRS is checked by geotools
+        // assertEquals(simplePointsGeoDf, loadedGeoDataFrame)
 
         tempFile.deleteOnExit()
-    }*/
+    }
 
     @Test
     fun readShapefile() {