001// License: GPL. For details, see LICENSE file.
002package org.openstreetmap.josm.io;
003
004import java.io.StringWriter;
005import java.math.BigDecimal;
006import java.math.RoundingMode;
007import java.util.HashMap;
008import java.util.Iterator;
009import java.util.Map;
010import java.util.Map.Entry;
011
012import javax.json.Json;
013import javax.json.JsonArrayBuilder;
014import javax.json.JsonObjectBuilder;
015import javax.json.JsonWriter;
016import javax.json.stream.JsonGenerator;
017
018import org.openstreetmap.josm.data.Bounds;
019import org.openstreetmap.josm.data.coor.EastNorth;
020import org.openstreetmap.josm.data.coor.LatLon;
021import org.openstreetmap.josm.data.osm.DataSet;
022import org.openstreetmap.josm.data.osm.INode;
023import org.openstreetmap.josm.data.osm.IRelation;
024import org.openstreetmap.josm.data.osm.IWay;
025import org.openstreetmap.josm.data.osm.Node;
026import org.openstreetmap.josm.data.osm.OsmPrimitive;
027import org.openstreetmap.josm.data.osm.Way;
028import org.openstreetmap.josm.data.osm.visitor.PrimitiveVisitor;
029import org.openstreetmap.josm.data.projection.Projection;
030import org.openstreetmap.josm.gui.layer.OsmDataLayer;
031
032/**
033 * Writes OSM data as a GeoJSON string, using JSR 353: Java API for JSON Processing (JSON-P).
034 */
035public class GeoJSONWriter {
036
037    private final OsmDataLayer layer;
038    private final Projection projection;
039    private static final boolean skipEmptyNodes = true;
040
041    /**
042     * Constructs a new {@code GeoJSONWriter}.
043     * @param layer The OSM data layer to save
044     * @param projection The projection to use for coordinates
045     */
046    public GeoJSONWriter(OsmDataLayer layer, Projection projection) {
047        this.layer = layer;
048        this.projection = projection;
049    }
050
051    /**
052     * Writes OSM data as a GeoJSON string (prettified).
053     * @return The GeoJSON data
054     */
055    public String write() {
056        return write(true);
057    }
058
059    /**
060     * Writes OSM data as a GeoJSON string (prettified or not).
061     * @param pretty {@code true} to have pretty output, {@code false} otherwise
062     * @return The GeoJSON data
063     * @since 6756
064     */
065    public String write(boolean pretty) {
066        StringWriter stringWriter = new StringWriter();
067        Map<String, Object> config = new HashMap<>(1);
068        config.put(JsonGenerator.PRETTY_PRINTING, pretty);
069        try (JsonWriter writer = Json.createWriterFactory(config).createWriter(stringWriter)) {
070            JsonObjectBuilder object = Json.createObjectBuilder()
071                    .add("type", "FeatureCollection")
072                    .add("crs", Json.createObjectBuilder().add("type", "name").add(
073                            "properties", Json.createObjectBuilder().add("name", projection.toCode())))
074                    .add("generator", "JOSM");
075            appendLayerBounds(layer.data, object);
076            appendLayerFeatures(layer.data, object);
077            writer.writeObject(object.build());
078            return stringWriter.toString();
079        }
080    }
081
082    private class GeometryPrimitiveVisitor implements PrimitiveVisitor {
083
084        private final JsonObjectBuilder geomObj;
085
086        GeometryPrimitiveVisitor(JsonObjectBuilder geomObj) {
087            this.geomObj = geomObj;
088        }
089
090        @Override
091        public void visit(INode n) {
092            geomObj.add("type", "Point");
093            LatLon ll = n.getCoor();
094            if (ll != null) {
095                geomObj.add("coordinates", getCoorArray(Json.createArrayBuilder(), n.getCoor()));
096            }
097        }
098
099        @Override
100        public void visit(IWay w) {
101            geomObj.add("type", "LineString");
102            if (w instanceof Way) {
103                JsonArrayBuilder array = Json.createArrayBuilder();
104                for (Node n : ((Way) w).getNodes()) {
105                    LatLon ll = n.getCoor();
106                    if (ll != null) {
107                        array.add(getCoorArray(Json.createArrayBuilder(), ll));
108                    }
109                }
110                geomObj.add("coordinates", array);
111            }
112        }
113
114        @Override
115        public void visit(IRelation r) {
116            // Do nothing
117        }
118    }
119
120    private JsonArrayBuilder getCoorArray(JsonArrayBuilder builder, LatLon c) {
121        return getCoorArray(builder, projection.latlon2eastNorth(c));
122    }
123
124    private static JsonArrayBuilder getCoorArray(JsonArrayBuilder builder, EastNorth c) {
125        return builder
126                .add(BigDecimal.valueOf(c.getX()).setScale(11, RoundingMode.HALF_UP))
127                .add(BigDecimal.valueOf(c.getY()).setScale(11, RoundingMode.HALF_UP));
128    }
129
130    protected void appendPrimitive(OsmPrimitive p, JsonArrayBuilder array) {
131        if (p.isIncomplete()) {
132            return;
133        } else if (skipEmptyNodes && p instanceof Node && p.getKeys().isEmpty()) {
134            return;
135        }
136
137        // Properties
138        final JsonObjectBuilder propObj = Json.createObjectBuilder();
139        for (Entry<String, String> t : p.getKeys().entrySet()) {
140            propObj.add(t.getKey(), t.getValue());
141        }
142
143        // Geometry
144        final JsonObjectBuilder geomObj = Json.createObjectBuilder();
145        p.accept(new GeometryPrimitiveVisitor(geomObj));
146
147        // Build primitive JSON object
148        array.add(Json.createObjectBuilder()
149                .add("type", "Feature")
150                .add("properties", propObj)
151                .add("geometry", geomObj));
152    }
153
154    protected void appendLayerBounds(DataSet ds, JsonObjectBuilder object) {
155        if (ds != null) {
156            Iterator<Bounds> it = ds.getDataSourceBounds().iterator();
157            if (it.hasNext()) {
158                Bounds b = new Bounds(it.next());
159                while (it.hasNext()) {
160                    b.extend(it.next());
161                }
162                appendBounds(b, object);
163            }
164        }
165    }
166
167    protected void appendBounds(Bounds b, JsonObjectBuilder object) {
168        if (b != null) {
169            JsonArrayBuilder builder = Json.createArrayBuilder();
170            getCoorArray(builder, b.getMin());
171            getCoorArray(builder, b.getMax());
172            object.add("bbox", builder);
173        }
174    }
175
176    protected void appendLayerFeatures(DataSet ds, JsonObjectBuilder object) {
177        JsonArrayBuilder array = Json.createArrayBuilder();
178        if (ds != null) {
179            for (Node n : ds.getNodes()) {
180                appendPrimitive(n, array);
181            }
182            for (Way w : ds.getWays()) {
183                appendPrimitive(w, array);
184            }
185        }
186        object.add("features", array);
187    }
188}