Implement serialization for LinearRing.

Signed-off-by: dblock <dblock@amazon.com>

Author: dblock

server/src/main/java/org/opensearch/action/search/SearchTask.java

@@ -80,11 +80,7 @@ public SearchTask(
 
     @Override
     public final String getDescription() {
-        try {
-            return descriptionSupplier.get();
-        } catch(UnsupportedOperationException e) {
-            return e.getMessage();
-        }
+        return descriptionSupplier.get();
     }
 
     @Override

server/src/main/java/org/opensearch/common/geo/GeoJson.java

@@ -125,8 +125,13 @@ public XContentBuilder visit(Line line) throws IOException {
             }
 
             @Override
-            public XContentBuilder visit(LinearRing ring) {
-                throw new UnsupportedOperationException("linearRing cannot be serialized using GeoJson");
+            public XContentBuilder visit(LinearRing ring) throws IOException {
+                builder.field(ShapeParser.FIELD_COORDINATES.getPreferredName());
+                builder.startArray();
+                for (int i = 0; i < ring.length(); i++) {
+                    coordinatesToXContent(ring.getLat(i), ring.getLon(i), ring.getAlt(i));
+                }
+                return builder.endArray();
             }
 
             @Override
@@ -254,7 +259,18 @@ public Void visit(Line line) {
 
             @Override
             public Void visit(LinearRing ring) {
-                throw new UnsupportedOperationException("linearRing cannot be serialized using GeoJson");
+                List<Object> points = new ArrayList<>(ring.length());
+                for (int i = 0; i < ring.length(); i++) {
+                    List<Object> point = new ArrayList<>();
+                    point.add(ring.getX(i));
+                    point.add(ring.getY(i));
+                    if (ring.hasZ()) {
+                        point.add(ring.getZ(i));
+                    }
+                    points.add(point);
+                }
+                root.put(ShapeParser.FIELD_COORDINATES.getPreferredName(), points);
+                return null;
             }
 
             @Override
@@ -428,6 +444,9 @@ private static Geometry createGeometry(
             case LINESTRING:
                 verifyNulls(type, geometries, orientation, radius);
                 return coordinates.asLineString(coerce);
+            case LINEARRING:
+                verifyNulls(type, geometries, orientation, radius);
+                return coordinates.asLinearRing(orientation != null ? orientation : defaultOrientation, coerce);
             case MULTILINESTRING:
                 verifyNulls(type, geometries, orientation, radius);
                 return coordinates.asMultiLineString(coerce);
@@ -558,7 +577,7 @@ public String visit(Line line) {
 
             @Override
             public String visit(LinearRing ring) {
-                throw new UnsupportedOperationException("line ring cannot be serialized using GeoJson");
+                return "LinearRing";
             }
 
             @Override

server/src/test/java/org/opensearch/common/geo/GeoJsonSerializationTests.java

@@ -56,6 +56,7 @@
 import static org.opensearch.geo.GeometryTestUtils.randomCircle;
 import static org.opensearch.geo.GeometryTestUtils.randomGeometryCollection;
 import static org.opensearch.geo.GeometryTestUtils.randomLine;
+import static org.opensearch.geo.GeometryTestUtils.randomLinearRing;
 import static org.opensearch.geo.GeometryTestUtils.randomMultiLine;
 import static org.opensearch.geo.GeometryTestUtils.randomMultiPoint;
 import static org.opensearch.geo.GeometryTestUtils.randomMultiPolygon;
@@ -121,6 +122,10 @@ public void testLineString() throws IOException {
         xContentTest(() -> randomLine(randomBoolean()));
     }
 
+    public void testLinearRing() throws IOException {
+        xContentTest(() -> randomLinearRing(randomBoolean()));
+    }
+
     public void testMultiLineString() throws IOException {
         xContentTest(() -> randomMultiLine(randomBoolean()));
     }

test/framework/src/main/java/org/opensearch/geo/GeometryTestUtils.java

@@ -102,6 +102,30 @@ public static Line randomLine(boolean hasAlts) {
         return new Line(lons, lats);
     }
 
+    public static LinearRing randomLinearRing(boolean hasAlts) {
+        // we use nextPolygon because it guarantees no duplicate points
+        org.apache.lucene.geo.Polygon lucenePolygon = GeoTestUtil.nextPolygon();
+        int size = lucenePolygon.numPoints() - 1;
+        double[] lats = new double[size + 1];
+        double[] lons = new double[size + 1];
+        double[] alts = hasAlts ? new double[size + 1] : null;
+        for (int i = 0; i < size; i++) {
+            lats[i] = lucenePolygon.getPolyLat(i);
+            lons[i] = lucenePolygon.getPolyLon(i);
+            if (hasAlts) {
+                alts[i] = randomAlt();
+            }
+        }
+        // first and last points of the linear ring must be the same
+        lats[size] = lats[0];
+        lons[size] = lons[0];
+        if (hasAlts) {
+            alts[size] = alts[0];
+            return new LinearRing(lons, lats, alts);
+        }
+        return new LinearRing(lons, lats);
+    }
+
     public static Point randomPoint() {
         return randomPoint(OpenSearchTestCase.randomBoolean());
     }