Geo: Refactors libs/geo parser to provide serialization logic as well (#43717)

Enables libs/geo parser to return a geometry format object that can
perform both serialization and deserialization functions. This can
be useful for ingest nodes that are trying to modify an existing
geometry in the source.

Relates to #43554

server/src/main/java/org/elasticsearch/common/geo/GeometryFormat.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.common.geo;
+
+import org.elasticsearch.common.xcontent.ToXContent;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.geo.geometry.Geometry;
+
+import java.io.IOException;
+import java.text.ParseException;
+
+/**
+ * Geometry serializer/deserializer
+ */
+public interface GeometryFormat {
+
+    /**
+     * Parser JSON representation of a geometry
+     */
+    Geometry fromXContent(XContentParser parser) throws IOException, ParseException;
+
+    /**
+     * Serializes the geometry into its JSON representation
+     */
+    XContentBuilder toXContent(Geometry geometry, XContentBuilder builder, ToXContent.Params params) throws IOException;
+
+}

server/src/main/java/org/elasticsearch/common/geo/GeometryParser.java

@@ -20,6 +20,8 @@
 package org.elasticsearch.common.geo;
 
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.common.xcontent.ToXContent;
+import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.geo.geometry.Geometry;
 import org.elasticsearch.geo.utils.GeographyValidator;
@@ -47,14 +49,64 @@ public final class GeometryParser {
     /**
      * Parses supplied XContent into Geometry
      */
-    public Geometry parse(XContentParser parser) throws IOException,
+    public Geometry parse(XContentParser parser) throws IOException, ParseException {
-        ParseException {
+        return geometryFormat(parser).fromXContent(parser);
+    }
+
+    /**
+     * Returns a geometry format object that can parse and then serialize the object back to the same format.
+     */
+    public GeometryFormat geometryFormat(XContentParser parser) {
         if (parser.currentToken() == XContentParser.Token.VALUE_NULL) {
-            return null;
+            return new GeometryFormat() {
+                @Override
+                public Geometry fromXContent(XContentParser parser) throws IOException {
+                    return null;
+                }
+
+                @Override
+                public XContentBuilder toXContent(Geometry geometry, XContentBuilder builder, ToXContent.Params params) throws IOException {
+                    if (geometry != null) {
+                        // We don't know the format of the original geometry - so going with default
+                        return GeoJson.toXContent(geometry, builder, params);
+                    } else {
+                        return builder.nullValue();
+                    }
+                }
+            };
         } else if (parser.currentToken() == XContentParser.Token.START_OBJECT) {
-            return geoJsonParser.fromXContent(parser);
+            return new GeometryFormat() {
+                @Override
+                public Geometry fromXContent(XContentParser parser) throws IOException {
+                    return geoJsonParser.fromXContent(parser);
+                }
+
+                @Override
+                public XContentBuilder toXContent(Geometry geometry, XContentBuilder builder, ToXContent.Params params) throws IOException {
+                    if (geometry != null) {
+                        return GeoJson.toXContent(geometry, builder, params);
+                    } else {
+                        return builder.nullValue();
+                    }
+                }
+            };
         } else if (parser.currentToken() == XContentParser.Token.VALUE_STRING) {
-            return wellKnownTextParser.fromWKT(parser.text());
+            return new GeometryFormat() {
+                @Override
+                public Geometry fromXContent(XContentParser parser) throws IOException, ParseException {
+                    return wellKnownTextParser.fromWKT(parser.text());
+                }
+
+                @Override
+                public XContentBuilder toXContent(Geometry geometry, XContentBuilder builder, ToXContent.Params params) throws IOException {
+                    if (geometry != null) {
+                        return builder.value(wellKnownTextParser.toWKT(geometry));
+                    } else {
+                        return builder.nullValue();
+                    }
+                }
+            };
+
         }
         throw new ElasticsearchParseException("shape must be an object consisting of type and coordinates");
     }

server/src/test/java/org/elasticsearch/common/geo/GeometryParserTests.java

@@ -20,6 +20,8 @@
 package org.elasticsearch.common.geo;
 
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.xcontent.ToXContent;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentParseException;
@@ -44,7 +46,11 @@ public class GeometryParserTests extends ESTestCase {
 
         try (XContentParser parser = createParser(pointGeoJson)) {
             parser.nextToken();
-            assertEquals(new Point(0, 100), new GeometryParser(true, randomBoolean(), randomBoolean()).parse(parser));
+            GeometryFormat format = new GeometryParser(true, randomBoolean(), randomBoolean()).geometryFormat(parser);
+            assertEquals(new Point(0, 100), format.fromXContent(parser));
+            XContentBuilder newGeoJson = XContentFactory.jsonBuilder();
+            format.toXContent(new Point(10, 100), newGeoJson, ToXContent.EMPTY_PARAMS);
+            assertEquals("{\"type\":\"Point\",\"coordinates\":[100.0,10.0]}", Strings.toString(newGeoJson));
         }
 
         XContentBuilder pointGeoJsonWithZ = XContentFactory.jsonBuilder()
@@ -77,7 +83,7 @@ public class GeometryParserTests extends ESTestCase {
                     .endArray()
                 .endObject();
 
-        Polygon p = new Polygon(new LinearRing(new double[] {1d, 1d, 0d, 0d, 1d}, new double[] {100d, 101d, 101d, 100d, 100d}));
+        Polygon p = new Polygon(new LinearRing(new double[]{1d, 1d, 0d, 0d, 1d}, new double[]{100d, 101d, 101d, 100d, 100d}));
         try (XContentParser parser = createParser(polygonGeoJson)) {
             parser.nextToken();
             // Coerce should automatically close the polygon
@@ -101,7 +107,12 @@ public class GeometryParserTests extends ESTestCase {
             parser.nextToken(); // Start object
             parser.nextToken(); // Field Name
             parser.nextToken(); // Field Value
-            assertEquals(new Point(0, 100), new GeometryParser(true, randomBoolean(), randomBoolean()).parse(parser));
+            GeometryFormat format = new GeometryParser(true, randomBoolean(), randomBoolean()).geometryFormat(parser);
+            assertEquals(new Point(0, 100), format.fromXContent(parser));
+            XContentBuilder newGeoJson = XContentFactory.jsonBuilder().startObject().field("val");
+            format.toXContent(new Point(10, 100), newGeoJson, ToXContent.EMPTY_PARAMS);
+            newGeoJson.endObject();
+            assertEquals("{\"val\":\"point (100.0 10.0)\"}", Strings.toString(newGeoJson));
         }
     }
 
@@ -115,7 +126,20 @@ public class GeometryParserTests extends ESTestCase {
             parser.nextToken(); // Start object
             parser.nextToken(); // Field Name
             parser.nextToken(); // Field Value
-            assertNull(new GeometryParser(true, randomBoolean(), randomBoolean()).parse(parser));
+            GeometryFormat format = new GeometryParser(true, randomBoolean(), randomBoolean()).geometryFormat(parser);
+            assertNull(format.fromXContent(parser));
+
+            XContentBuilder newGeoJson = XContentFactory.jsonBuilder().startObject().field("val");
+            // if we serialize non-null value - it should be serialized as geojson
+            format.toXContent(new Point(10, 100), newGeoJson, ToXContent.EMPTY_PARAMS);
+            newGeoJson.endObject();
+            assertEquals("{\"val\":{\"type\":\"Point\",\"coordinates\":[100.0,10.0]}}", Strings.toString(newGeoJson));
+
+            newGeoJson = XContentFactory.jsonBuilder().startObject().field("val");
+            format.toXContent(null, newGeoJson, ToXContent.EMPTY_PARAMS);
+            newGeoJson.endObject();
+            assertEquals("{\"val\":null}", Strings.toString(newGeoJson));
+
         }
     }