Add a spatial function to convert WKT to Geo-JSON

src/main/java/org/neo4j/gis/spatial/functions/SpatialFunctions.java

@@ -20,8 +20,12 @@
 
 package org.neo4j.gis.spatial.functions;
 
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.io.ParseException;
+import org.locationtech.jts.io.WKTReader;
 import org.neo4j.gis.spatial.Layer;
 import org.neo4j.gis.spatial.procedures.SpatialProcedures.GeometryResult;
+import org.neo4j.gis.spatial.utilities.GeoJsonUtils;
 import org.neo4j.gis.spatial.utilities.SpatialApiBase;
 import org.neo4j.graphdb.Node;
 import org.neo4j.procedure.Description;
@@ -55,4 +59,14 @@ public Object asGeometry(@Name("geometry") Object geometry) {
 	}
 
 
+	@UserFunction("spatial.convert.wktToGeoJson")
+	@Description("Converts a WKT to GeoJson structure")
+	public Object wktToGeoJson(@Name("wkt") String wkt) throws ParseException {
+		if (wkt == null) {
+			return null;
+		}
+		WKTReader wktReader = new WKTReader();
+		Geometry geometry = wktReader.read(wkt);
+		return GeoJsonUtils.toGeoJsonStructure(geometry);
+	}
 }

src/main/java/org/neo4j/gis/spatial/utilities/GeoJsonUtils.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j Spatial.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.neo4j.gis.spatial.utilities;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.geom.GeometryCollection;
+import org.locationtech.jts.geom.LineString;
+import org.locationtech.jts.geom.Point;
+import org.locationtech.jts.geom.Polygon;
+
+
+public class GeoJsonUtils {
+
+	private GeoJsonUtils() {
+	}
+
+	public static Map<String, Object> toGeoJsonStructure(Geometry geometry) {
+		return Map.of(
+				"type", geometry.getGeometryType(),
+				"coordinates", getCoordinates(geometry)
+		);
+	}
+
+	private static List<?> getCoordinates(Geometry geometry) {
+		if (geometry instanceof Point point) {
+			return getPoint(point.getCoordinate());
+		}
+		if (geometry instanceof LineString lineString) {
+			return Arrays.stream(lineString.getCoordinates()).map(GeoJsonUtils::getPoint).toList();
+		}
+		if (geometry instanceof Polygon polygon) {
+			return Stream.concat(
+							Stream.of(polygon.getExteriorRing()),
+							IntStream.range(0, polygon.getNumInteriorRing())
+									.mapToObj(polygon::getInteriorRingN)
+					)
+					.map(GeoJsonUtils::getCoordinates)
+					.toList();
+		}
+		if (geometry instanceof GeometryCollection geometryCollection) {
+			return IntStream.range(0, geometryCollection.getNumGeometries())
+					.mapToObj(geometryCollection::getGeometryN)
+					.map(GeoJsonUtils::getCoordinates)
+					.toList();
+		}
+		throw new IllegalArgumentException("Unsupported geometry type: " + geometry.getGeometryType());
+	}
+
+	private static List<Object> getPoint(Coordinate coordinate) {
+		if (Double.isNaN(coordinate.getZ())) {
+			return List.of(coordinate.getX(), coordinate.getY());
+		}
+		return List.of(
+				coordinate.getX(),
+				coordinate.getY(),
+				coordinate.getZ());
+	}
+}

src/test/java/org/neo4j/gis/spatial/functions/SpatialFunctionsTest.java

@@ -20,9 +20,12 @@
 
 package org.neo4j.gis.spatial.functions;
 
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.closeTo;
+import static org.hamcrest.Matchers.equalTo;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 
+import java.util.List;
 import java.util.Map;
 import org.hamcrest.MatcherAssert;
 import org.junit.jupiter.api.Test;
@@ -69,4 +72,24 @@ public void literal_geometry_return() {
 				"WITH spatial.asGeometry({latitude: 5.0, longitude: 4.0}) AS geometry RETURN geometry", "geometry");
 		assertInstanceOf(Geometry.class, geometry, "Should be Geometry type");
 	}
+
+	@Test
+	public void wktToGeoJson() {
+		String wkt = "MULTIPOLYGON(((15.3 60.2, 15.3 60.4, 15.7 60.4, 15.7 60.2, 15.3 60.2)))";
+		Object json = executeObject("return spatial.convert.wktToGeoJson($wkt) as json", Map.of("wkt", wkt), "json");
+		assertThat(json, equalTo(Map.of(
+				"type", "MultiPolygon",
+				"coordinates", List.of( // MultiPolygon
+						List.of( // Polygon
+								List.of( // LineString
+										List.of(15.3, 60.2),
+										List.of(15.3, 60.4),
+										List.of(15.7, 60.4),
+										List.of(15.7, 60.2),
+										List.of(15.3, 60.2)
+								)
+						)
+				)
+		)));
+	}
 }