planetiler-openmaptiles/src/main/java/org/openmaptiles/layers/Water.java

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Design license: CC-BY 4.0

See https://github.com/openmaptiles/openmaptiles/blob/master/LICENSE.md for details on usage
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package org.openmaptiles.layers;

import com.onthegomap.planetiler.FeatureCollector;
import com.onthegomap.planetiler.FeatureMerge;
import com.onthegomap.planetiler.ForwardingProfile;
import com.onthegomap.planetiler.VectorTile;
import com.onthegomap.planetiler.config.PlanetilerConfig;
import com.onthegomap.planetiler.expression.MultiExpression;
import com.onthegomap.planetiler.geo.GeometryException;
import com.onthegomap.planetiler.geo.PolygonIndex;
import com.onthegomap.planetiler.reader.SimpleFeature;
import com.onthegomap.planetiler.reader.SourceFeature;
import com.onthegomap.planetiler.stats.Stats;
import com.onthegomap.planetiler.util.Translations;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Consumer;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.util.GeometryFixer;
import org.openmaptiles.OpenMapTilesProfile;
import org.openmaptiles.generated.OpenMapTilesSchema;
import org.openmaptiles.generated.Tables;
import org.openmaptiles.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Defines the logic for generating map elements for oceans and lakes in the {@code water} layer from source features.
 * <p>
 * This class is ported to Java from
 * <a href="https://github.com/openmaptiles/openmaptiles/tree/master/layers/water">OpenMapTiles water sql files</a>.
 */
public class Water implements
  OpenMapTilesSchema.Water,
  Tables.OsmWaterPolygon.Handler,
  OpenMapTilesProfile.NaturalEarthProcessor,
  OpenMapTilesProfile.OsmWaterPolygonProcessor,
  ForwardingProfile.LayerPostProcessor,
  ForwardingProfile.FinishHandler {

  /*
   * At low zoom levels, use natural earth for oceans and major lakes, and at high zoom levels
   * use OpenStreetMap data. OpenStreetMap data contains smaller bodies of water, but not
   * large ocean polygons. For oceans, use https://osmdata.openstreetmap.de/data/water-polygons.html
   * which infers ocean polygons by preprocessing all coastline elements.
   */

  private static final Logger LOGGER = LoggerFactory.getLogger(Water.class);
  // smallest NE lake is around 4.42E-13, smallest matching OSM lake is 9.34E-13, this is slightly bellow that
  // and approx. 33% of OSM features are smaller than this, hence to save some CPU cycles:
  private static final double OSM_ID_MATCH_AREA_LIMIT = Math.pow(4, -20);

  private final MultiExpression.Index<String> classMapping;
  private final PlanetilerConfig config;
  private final Stats stats;
  private PolygonIndex<LakeInfo> neLakeIndex = PolygonIndex.create();
  private final Map<String, Map<String, LakeInfo>> neLakeNameMaps = new ConcurrentHashMap<>();
  private final List<LakeInfo> neAllLakeInfos = new ArrayList<>();

  public Water(Translations translations, PlanetilerConfig config, Stats stats) {
    this.classMapping = FieldMappings.Class.index();
    this.config = config;
    this.stats = stats;
  }

  @Override
  public void processNaturalEarth(String table, SourceFeature feature, FeatureCollector features) {
    record WaterInfo(int minZoom, int maxZoom, String clazz) {}
    WaterInfo info = switch (table) {
      case "ne_110m_ocean" -> new WaterInfo(0, 1, FieldValues.CLASS_OCEAN);
      case "ne_50m_ocean" -> new WaterInfo(2, 4, FieldValues.CLASS_OCEAN);
      case "ne_10m_ocean" -> new WaterInfo(5, 5, FieldValues.CLASS_OCEAN);
      default -> null;
    };
    if (info != null) {
      setupNeWaterFeature(features, info.minZoom, info.maxZoom, info.clazz, null);
      return;
    }

    LakeInfo lakeInfo = switch (table) {
      case "ne_110m_lakes" -> new LakeInfo(0, 1, FieldValues.CLASS_LAKE);
      case "ne_50m_lakes" -> new LakeInfo(2, 3, FieldValues.CLASS_LAKE);
      case "ne_10m_lakes" -> new LakeInfo(4, 5, FieldValues.CLASS_LAKE);
      default -> null;
    };
    if (lakeInfo != null) {
      try {
        var geom = feature.worldGeometry();
        if (geom.isValid()) {
          lakeInfo.geom = geom;
        } else {
          LOGGER.trace("Fixing geometry of NE lake {}", feature.getLong("ne_id"));
          lakeInfo.geom = GeometryFixer.fix(geom);
        }
        lakeInfo.name = feature.getString("name");
        lakeInfo.neId = feature.getLong("ne_id");

        var neLakeNameMap = neLakeNameMaps.computeIfAbsent(table, t -> new ConcurrentHashMap<>());

        // need to externally synchronize inserts into ArrayList
        synchronized (this) {
          neAllLakeInfos.add(lakeInfo);
        }
        neLakeIndex.put(geom, lakeInfo);
        if (lakeInfo.name != null) {
          // on name collision, bigger lake gets on the name list
          neLakeNameMap.merge(lakeInfo.name, lakeInfo,
            (prev, next) -> next.geom.getArea() > prev.geom.getArea() ? next : prev);
        }
      } catch (GeometryException e) {
        e.log(stats, "omt_water_ne",
          "Error getting geometry for natural earth feature " + table + " " + feature.getTag("ogc_fid"));
        // make sure we have this NE lake even if without OSM ID
        setupNeWaterFeature(features, lakeInfo.minZoom, lakeInfo.maxZoom, lakeInfo.clazz, null);
      }
    }
  }

  private void setupNeWaterFeature(FeatureCollector features, int minZoom, int maxZoom, String clazz, Long osmId) {
    features.polygon(LAYER_NAME)
      .setBufferPixels(BUFFER_SIZE)
      .setZoomRange(minZoom, maxZoom)
      .setAttr(Fields.CLASS, clazz)
      .setAttr(Fields.ID, osmId);
  }

  @Override
  public void processOsmWater(SourceFeature feature, FeatureCollector features) {
    features.polygon(LAYER_NAME)
      .setBufferPixels(BUFFER_SIZE)
      .setAttr(Fields.CLASS, FieldValues.CLASS_OCEAN)
      .setMinZoom(6);
  }

  @Override
  public void process(Tables.OsmWaterPolygon element, FeatureCollector features) {
    if (!"bay".equals(element.natural())) {
      String clazz = classMapping.getOrElse(element.source(), FieldValues.CLASS_LAKE);
      features.polygon(LAYER_NAME)
        .setBufferPixels(BUFFER_SIZE)
        .setMinPixelSizeBelowZoom(11, 2)
        .setMinZoom(6)
        .setAttr(Fields.ID, element.source().id())
        .setAttr(Fields.INTERMITTENT, element.isIntermittent() ? 1 : 0)
        .setAttrWithMinzoom(Fields.BRUNNEL, Utils.brunnel(element.isBridge(), element.isTunnel()), 12)
        .setAttr(Fields.CLASS, clazz);

      try {
        attemptNeLakeIdMapping(element);
      } catch (GeometryException e) {
        e.log(stats, "omt_water",
          "Unable to add OSM ID to natural earth water feature", config.logJtsExceptions());
      }
    }
  }

  void attemptNeLakeIdMapping(Tables.OsmWaterPolygon element) throws GeometryException {
    // if OSM lake is too small for Z6 (e.g. area bellow ~4px) we assume there is no matching NE lake
    var geom = element.source().worldGeometry();
    if (geom.getArea() < OSM_ID_MATCH_AREA_LIMIT) {
      return;
    }

    if (!geom.isValid()) {
      geom = GeometryFixer.fix(geom);
      stats.dataError("omt_fix_water_before_ne_intersect");
      LOGGER.trace("Fixing geometry of OSM element {} before attempt to add ID to natural earth water feature",
        element.source().id());
    }

    // match by name:
    boolean match = false;
    if (element.name() != null) {
      for (var map : neLakeNameMaps.values()) {
        var lakeInfo = map.get(element.name());
        if (lakeInfo != null) {
          match = true;
          fillOsmIdIntoNeLake(element, geom, lakeInfo, true);
        }
      }
    }
    if (match) {
      return;
    }

    // match by intersection:
    List<LakeInfo> items = neLakeIndex.getIntersecting(geom);
    for (var lakeInfo : items) {
      fillOsmIdIntoNeLake(element, geom, lakeInfo, false);
    }
  }

  /*
   * When we match lakes with `neLakeIndexes` then `intersetsCheckNeeded` should be `false`,
   * otherwise `true`, to make sure we DO check the intersection but to avoid checking it twice.
   */
  void fillOsmIdIntoNeLake(Tables.OsmWaterPolygon element, Geometry geom, LakeInfo lakeInfo,
    boolean intersetsCheckNeeded) {
    final Geometry neGeom = lakeInfo.geom;
    if (intersetsCheckNeeded && !neGeom.intersects(geom)) {
      return;
    }
    final var intersection = neGeom.intersection(geom);

    // Should match following in OpenMapTiles: Distinct on keeps just the first occurence -> order by 'area_ratio DESC'
    // With a twist: NE geometry is always the same, hence we can make it a little bit faster by dropping "ratio"
    // and compare only the intersection area: bigger area -> bigger ratio.
    double area = intersection.getArea();
    lakeInfo.mergeId(element.source().id(), area);
  }

  @Override
  public void finish(String sourceName, FeatureCollector.Factory featureCollectors,
    Consumer<FeatureCollector.Feature> emit) {
    if (OpenMapTilesProfile.OSM_SOURCE.equals(sourceName)) {
      var timer = stats.startStage("ne_lakes");
      for (var item : neAllLakeInfos) {
        var features = featureCollectors.get(SimpleFeature.fromWorldGeometry(item.geom));
        setupNeWaterFeature(features, item.minZoom, item.maxZoom, item.clazz, item.osmId);
        for (var feature : features) {
          emit.accept(feature);
        }
      }
      neLakeNameMaps.clear();
      neLakeIndex = null;
      neAllLakeInfos.clear();
      timer.stop();
    }
  }

  @Override
  public List<VectorTile.Feature> postProcess(int zoom, List<VectorTile.Feature> items) throws GeometryException {
    return items.size() > 1 ? FeatureMerge.mergeOverlappingPolygons(items, config.minFeatureSize(zoom)) : items;
  }

  /**
   * Information to hold onto from processing an NE lake to determine OSM ID later.
   */
  private static class LakeInfo {
    String name;
    int minZoom;
    int maxZoom;
    String clazz;
    Geometry geom;
    Long osmId;
    long neId;
    double area;

    public LakeInfo(int minZoom, int maxZoom, String clazz) {
      this.name = null;
      this.minZoom = minZoom;
      this.maxZoom = maxZoom;
      this.clazz = clazz;
      this.osmId = null;
      this.neId = -1;
      this.area = 0;
    }

    public synchronized void mergeId(Long newId, double newArea) {
      if (newArea > area) {
        osmId = newId;
        area = newArea;
      }
    }
  }
}