Prototype using builder strategy object and general purpose vector ma…

…p output format

src/community/vectortiles/src/main/java/org/geoserver/wms/topojson/TopoJSONBuilderFactory.java

@@ -0,0 +1,33 @@
+package org.geoserver.wms.topojson;
+
+import java.awt.Rectangle;
+import java.util.Set;
+
+import org.geoserver.wms.vector.VectorTileBuilder;
+import org.geoserver.wms.vector.VectorTileBuilderFactory;
+import org.geotools.geometry.jts.ReferencedEnvelope;
+
+import com.google.common.collect.ImmutableSet;
+
+public class TopoJSONBuilderFactory implements VectorTileBuilderFactory {
+
+    public static final String MIME_TYPE = "application/json;type=topojson";
+
+    public static final Set<String> OUTPUT_FORMATS = ImmutableSet.of(MIME_TYPE, "topojson");
+
+    @Override
+    public Set<String> getOutputFormats() {
+        return OUTPUT_FORMATS;
+    }
+
+    @Override
+    public String getMimeType() {
+        return MIME_TYPE;
+    }
+
+    @Override
+    public VectorTileBuilder newBuilder(Rectangle screenSize, ReferencedEnvelope mapArea) {
+        return new TopologyBuilder(screenSize, mapArea);
+    }
+
+}

src/community/vectortiles/src/main/java/org/geoserver/wms/topojson/TopoJSONEncoder.java

@@ -352,6 +352,9 @@ public static JsonArray quantize(final CoordinateSequence coords, PrecisionModel
                 buff.x = deltaX;
                 buff.y = deltaY;
                 precisionModel.makePrecise(buff);
+                if(buff.x == 0d && buff.y == 0d){
+                    continue;
+                }
                 addCoordinate(arc, buff);
             }
         }