001// License: GPL. For details, see LICENSE file.
002package org.openstreetmap.josm.io;
003
004import java.io.StringWriter;
005import java.util.HashMap;
006import java.util.Iterator;
007import java.util.Map;
008import java.util.Map.Entry;
009
010import javax.json.Json;
011import javax.json.JsonArrayBuilder;
012import javax.json.JsonObjectBuilder;
013import javax.json.JsonWriter;
014import javax.json.stream.JsonGenerator;
015
016import org.openstreetmap.josm.data.Bounds;
017import org.openstreetmap.josm.data.coor.EastNorth;
018import org.openstreetmap.josm.data.coor.LatLon;
019import org.openstreetmap.josm.data.osm.DataSet;
020import org.openstreetmap.josm.data.osm.INode;
021import org.openstreetmap.josm.data.osm.IRelation;
022import org.openstreetmap.josm.data.osm.IWay;
023import org.openstreetmap.josm.data.osm.Node;
024import org.openstreetmap.josm.data.osm.OsmPrimitive;
025import org.openstreetmap.josm.data.osm.Way;
026import org.openstreetmap.josm.data.osm.visitor.PrimitiveVisitor;
027import org.openstreetmap.josm.data.projection.Projection;
028import org.openstreetmap.josm.gui.layer.OsmDataLayer;
029
030/**
031 * Writes OSM data as a GeoJSON string, using JSR 353: Java API for JSON Processing (JSON-P).
032 */
033public class GeoJSONWriter {
034
035    private final OsmDataLayer layer;
036    private final Projection projection;
037    private static final boolean skipEmptyNodes = true;
038
039    /**
040     * Constructs a new {@code GeoJSONWriter}.
041     * @param layer The OSM data layer to save
042     * @param projection The projection to use for coordinates
043     */
044    public GeoJSONWriter(OsmDataLayer layer, Projection projection) {
045        this.layer = layer;
046        this.projection = projection;
047    }
048
049    /**
050     * Writes OSM data as a GeoJSON string (prettified).
051     * @return The GeoJSON data
052     */
053    public String write() {
054        return write(true);
055    }
056
057    /**
058     * Writes OSM data as a GeoJSON string (prettified or not).
059     * @param pretty {@code true} to have pretty output, {@code false} otherwise
060     * @return The GeoJSON data
061     * @since 6756
062     */
063    public String write(boolean pretty) {
064        StringWriter stringWriter = new StringWriter();
065        Map<String, Object> config = new HashMap<>(1);
066        config.put(JsonGenerator.PRETTY_PRINTING, pretty);
067        try (JsonWriter writer = Json.createWriterFactory(config).createWriter(stringWriter)) {
068            JsonObjectBuilder object = Json.createObjectBuilder()
069                    .add("type", "FeatureCollection")
070                    .add("crs", Json.createObjectBuilder().add("type", "name").add("name", projection.toCode()))
071                    .add("generator", "JOSM");
072            appendLayerBounds(layer.data, object);
073            appendLayerFeatures(layer.data, object);
074            writer.writeObject(object.build());
075            return stringWriter.toString();
076        }
077    }
078
079    private class GeometryPrimitiveVisitor implements PrimitiveVisitor {
080
081        private final JsonObjectBuilder geomObj;
082
083        GeometryPrimitiveVisitor(JsonObjectBuilder geomObj) {
084            this.geomObj = geomObj;
085        }
086
087        @Override
088        public void visit(INode n) {
089            geomObj.add("type", "Point");
090            LatLon ll = n.getCoor();
091            if (ll != null) {
092                geomObj.add("coordinates", getCoorArray(Json.createArrayBuilder(), n.getCoor()));
093            }
094        }
095
096        @Override
097        public void visit(IWay w) {
098            geomObj.add("type", "LineString");
099            if (w instanceof Way) {
100                JsonArrayBuilder array = Json.createArrayBuilder();
101                for (Node n : ((Way) w).getNodes()) {
102                    LatLon ll = n.getCoor();
103                    if (ll != null) {
104                        array.add(getCoorArray(Json.createArrayBuilder(), ll));
105                    }
106                }
107                geomObj.add("coordinates", array);
108            }
109        }
110
111        @Override
112        public void visit(IRelation r) {
113        }
114    }
115
116    private JsonArrayBuilder getCoorArray(JsonArrayBuilder builder, LatLon c) {
117        return getCoorArray(builder, projection.latlon2eastNorth(c));
118    }
119
120    private static JsonArrayBuilder getCoorArray(JsonArrayBuilder builder, EastNorth c) {
121        return builder.add(c.getX()).add(c.getY());
122    }
123
124    protected void appendPrimitive(OsmPrimitive p, JsonArrayBuilder array) {
125        if (p.isIncomplete()) {
126            return;
127        } else if (skipEmptyNodes && p instanceof Node && p.getKeys().isEmpty()) {
128            return;
129        }
130
131        // Properties
132        final JsonObjectBuilder propObj = Json.createObjectBuilder();
133        for (Entry<String, String> t : p.getKeys().entrySet()) {
134            propObj.add(t.getKey(), t.getValue());
135        }
136
137        // Geometry
138        final JsonObjectBuilder geomObj = Json.createObjectBuilder();
139        p.accept(new GeometryPrimitiveVisitor(geomObj));
140
141        // Build primitive JSON object
142        array.add(Json.createObjectBuilder()
143                .add("type", "Feature")
144                .add("properties", propObj)
145                .add("geometry", geomObj));
146    }
147
148    protected void appendLayerBounds(DataSet ds, JsonObjectBuilder object) {
149        if (ds != null) {
150            Iterator<Bounds> it = ds.getDataSourceBounds().iterator();
151            if (it.hasNext()) {
152                Bounds b = new Bounds(it.next());
153                while (it.hasNext()) {
154                    b.extend(it.next());
155                }
156                appendBounds(b, object);
157            }
158        }
159    }
160
161    protected void appendBounds(Bounds b, JsonObjectBuilder object) {
162        if (b != null) {
163            JsonArrayBuilder builder = Json.createArrayBuilder();
164            getCoorArray(builder, b.getMin());
165            getCoorArray(builder, b.getMax());
166            object.add("bbox", builder);
167        }
168    }
169
170    protected void appendLayerFeatures(DataSet ds, JsonObjectBuilder object) {
171        JsonArrayBuilder array = Json.createArrayBuilder();
172        if (ds != null) {
173            for (Node n : ds.getNodes()) {
174                appendPrimitive(n, array);
175            }
176            for (Way w : ds.getWays()) {
177                appendPrimitive(w, array);
178            }
179        }
180        object.add("features", array);
181    }
182}