Park.java

/*
Copyright (c) 2021, MapTiler.com & OpenMapTiles contributors.
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Code license: BSD 3-Clause License

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* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
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  this software without specific prior written permission.

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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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Design license: CC-BY 4.0

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

import static com.onthegomap.planetiler.collection.FeatureGroup.SORT_KEY_BITS;
import static org.openmaptiles.util.Utils.coalesce;
import static org.openmaptiles.util.Utils.nullIfEmpty;

import com.carrotsearch.hppc.LongIntMap;
import com.onthegomap.planetiler.FeatureCollector;
import com.onthegomap.planetiler.FeatureMerge;
import com.onthegomap.planetiler.VectorTile;
import com.onthegomap.planetiler.collection.Hppc;
import com.onthegomap.planetiler.config.PlanetilerConfig;
import com.onthegomap.planetiler.geo.GeoUtils;
import com.onthegomap.planetiler.geo.GeometryException;
import com.onthegomap.planetiler.geo.GeometryType;
import com.onthegomap.planetiler.stats.Stats;
import com.onthegomap.planetiler.util.SortKey;
import com.onthegomap.planetiler.util.Translations;
import java.util.List;
import java.util.Locale;
import org.openmaptiles.OpenMapTilesProfile;
import org.openmaptiles.generated.OpenMapTilesSchema;
import org.openmaptiles.generated.Tables;
import org.openmaptiles.util.OmtLanguageUtils;

/**
 * Defines the logic for generating map elements for designated parks polygons and their label points in the {@code
 * park} layer from source features.
 * <p>
 * This class is ported to Java from
 * <a href="https://github.com/openmaptiles/openmaptiles/tree/master/layers/park">OpenMapTiles park sql files</a>.
 */
public class Park implements
  OpenMapTilesSchema.Park,
  Tables.OsmParkPolygon.Handler,
  OpenMapTilesProfile.FeaturePostProcessor {

  // constants for packing the minimum zoom ordering of park labels into the sort-key field
  private static final int PARK_NATIONAL_PARK_BOOST = 1 << (SORT_KEY_BITS - 1);
  private static final int PARK_WIKIPEDIA_BOOST = 1 << (SORT_KEY_BITS - 2);

  // constants for determining the minimum zoom level for a park label based on its area
  private static final double WORLD_AREA_FOR_70K_SQUARE_METERS =
    Math.pow(GeoUtils.metersToPixelAtEquator(0, Math.sqrt(70_000)) / 256d, 2);
  private static final double LOG2 = Math.log(2);
  private static final int PARK_AREA_RANGE = 1 << (SORT_KEY_BITS - 3);
  private static final double SMALLEST_PARK_WORLD_AREA = Math.pow(4, -26); // 2^14 tiles, 2^12 pixels per tile

  private final Translations translations;
  private final Stats stats;

  public Park(Translations translations, PlanetilerConfig config, Stats stats) {
    this.stats = stats;
    this.translations = translations;
  }

  @Override
  public void process(Tables.OsmParkPolygon element, FeatureCollector features) {
    String protectionTitle = element.protectionTitle();
    if (protectionTitle != null) {
      protectionTitle = protectionTitle.replace(' ', '_').toLowerCase(Locale.ROOT);
    }
    String clazz = coalesce(
      nullIfEmpty(protectionTitle),
      nullIfEmpty(element.boundary()),
      nullIfEmpty(element.leisure())
    );

    // park shape
    var outline = features.polygon(LAYER_NAME).setBufferPixels(BUFFER_SIZE)
      .setAttrWithMinzoom(Fields.CLASS, clazz, 5)
      .setMinPixelSize(2)
      .setMinZoom(4);

    // park name label point (if it has one)
    if (element.name() != null) {
      try {
        double area = element.source().area();
        int minzoom = getMinZoomForArea(area);

        var names = OmtLanguageUtils.getNamesWithoutTranslations(element.source().tags());

        outline.putAttrsWithMinzoom(names, 5);

        features.pointOnSurface(LAYER_NAME).setBufferPixels(256)
          .setAttr(Fields.CLASS, clazz)
          .putAttrs(names)
          .putAttrs(OmtLanguageUtils.getNames(element.source().tags(), translations))
          .setPointLabelGridPixelSize(14, 100)
          .setSortKey(SortKey
            .orderByTruesFirst("national_park".equals(clazz))
            .thenByTruesFirst(element.source().hasTag("wikipedia") || element.source().hasTag("wikidata"))
            .thenByLog(area, 1d, SMALLEST_PARK_WORLD_AREA, 1 << (SORT_KEY_BITS - 2) - 1)
            .get()
          ).setMinZoom(minzoom);
      } catch (GeometryException e) {
        e.log(stats, "omt_park_area", "Unable to get park area for " + element.source().id());
      }
    }
  }

  private int getMinZoomForArea(double area) {
    // sql filter:    area > 70000*2^(20-zoom_level)
    // simplifies to: zoom_level > 20 - log(area / 70000) / log(2)
    int minzoom = (int) Math.floor(20 - Math.log(area / WORLD_AREA_FOR_70K_SQUARE_METERS) / LOG2);
    minzoom = Math.clamp(minzoom, 5, 14);
    return minzoom;
  }

  @Override
  public List<VectorTile.Feature> postProcess(int zoom, List<VectorTile.Feature> items) throws GeometryException {
    // infer the "rank" attribute from point ordering within each label grid square
    LongIntMap counts = Hppc.newLongIntHashMap();
    for (VectorTile.Feature feature : items) {
      if (feature.geometry().geomType() == GeometryType.POINT && feature.hasGroup()) {
        int count = counts.getOrDefault(feature.group(), 0) + 1;
        feature.attrs().put("rank", count);
        counts.put(feature.group(), count);
      }
    }
    if (zoom <= 4) {
      items = FeatureMerge.mergeOverlappingPolygons(items, 0);
    }
    return items;
  }
}