/*
Copyright (c) 2021, MapTiler.com & OpenMapTiles contributors.
All rights reserved.

Code license: BSD 3-Clause License

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modification, are permitted provided that the following conditions are met:

* 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,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

* Neither the name of the copyright holder nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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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 com.onthegomap.planetiler.basemap.layers;

import com.onthegomap.planetiler.FeatureCollector;
import com.onthegomap.planetiler.FeatureMerge;
import com.onthegomap.planetiler.VectorTile;
import com.onthegomap.planetiler.basemap.BasemapProfile;
import com.onthegomap.planetiler.basemap.generated.OpenMapTilesSchema;
import com.onthegomap.planetiler.basemap.generated.Tables;
import com.onthegomap.planetiler.config.PlanetilerConfig;
import com.onthegomap.planetiler.expression.MultiExpression;
import com.onthegomap.planetiler.geo.GeometryException;
import com.onthegomap.planetiler.reader.SourceFeature;
import com.onthegomap.planetiler.stats.Stats;
import com.onthegomap.planetiler.util.Translations;
import com.onthegomap.planetiler.util.ZoomFunction;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Defines the logic for generating map elements for natural land cover polygons like ice, sand, and forest in the
 * {@code landcover} layer from source features.
 * <p>
 * This class is ported to Java from
 * <a href="https://github.com/openmaptiles/openmaptiles/tree/master/layers/landcover">OpenMapTiles landcover sql
 * files</a>.
 */
public class Landcover implements
  OpenMapTilesSchema.Landcover,
  BasemapProfile.NaturalEarthProcessor,
  Tables.OsmLandcoverPolygon.Handler,
  BasemapProfile.FeaturePostProcessor {

  /*
   * Large ice areas come from natural earth and the rest come from OpenStreetMap at higher zoom
   * levels. At render-time, postProcess() merges polygons into larger connected area based
   * on the number of points in the original area.  Since postProcess() only has visibility into
   * features on a single tile, process() needs to pass the number of points the original feature
   * had through using a temporary "_numpoints" attribute.
   */

  public static final ZoomFunction<Number> MIN_PIXEL_SIZE_THRESHOLDS = ZoomFunction.fromMaxZoomThresholds(Map.of(
    13, 8,
    10, 4,
    9, 2
  ));
  private static final String TEMP_NUM_POINTS_ATTR = "_numpoints";
  private static final Set<String> WOOD_OR_FOREST = Set.of(
    FieldValues.SUBCLASS_WOOD,
    FieldValues.SUBCLASS_FOREST
  );
  private final MultiExpression.Index<String> classMapping;

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

  private String getClassFromSubclass(String subclass) {
    return subclass == null ? null : classMapping.getOrElse(Map.of(Fields.SUBCLASS, subclass), null);
  }

  @Override
  public void processNaturalEarth(String table, SourceFeature feature,
    FeatureCollector features) {
    record LandcoverInfo(String subclass, int minzoom, int maxzoom) {}
    LandcoverInfo info = switch (table) {
      case "ne_110m_glaciated_areas" -> new LandcoverInfo(FieldValues.SUBCLASS_GLACIER, 0, 1);
      case "ne_50m_glaciated_areas" -> new LandcoverInfo(FieldValues.SUBCLASS_GLACIER, 2, 4);
      case "ne_10m_glaciated_areas" -> new LandcoverInfo(FieldValues.SUBCLASS_GLACIER, 5, 6);
      case "ne_50m_antarctic_ice_shelves_polys" -> new LandcoverInfo("ice_shelf", 2, 4);
      case "ne_10m_antarctic_ice_shelves_polys" -> new LandcoverInfo("ice_shelf", 5, 6);
      default -> null;
    };
    if (info != null) {
      String clazz = getClassFromSubclass(info.subclass);
      if (clazz != null) {
        features.polygon(LAYER_NAME).setBufferPixels(BUFFER_SIZE)
          .setAttr(Fields.CLASS, clazz)
          .setAttr(Fields.SUBCLASS, info.subclass)
          .setZoomRange(info.minzoom, info.maxzoom);
      }
    }
  }

  @Override
  public void process(Tables.OsmLandcoverPolygon element, FeatureCollector features) {
    String subclass = element.subclass();
    String clazz = getClassFromSubclass(subclass);
    if (clazz != null) {
      features.polygon(LAYER_NAME).setBufferPixels(BUFFER_SIZE)
        .setMinPixelSizeOverrides(MIN_PIXEL_SIZE_THRESHOLDS)
        .setAttr(Fields.CLASS, clazz)
        .setAttr(Fields.SUBCLASS, subclass)
        .setNumPointsAttr(TEMP_NUM_POINTS_ATTR)
        .setMinZoom(WOOD_OR_FOREST.contains(subclass) ? 9 : 7);
    }
  }

  @Override
  public List<VectorTile.Feature> postProcess(int zoom, List<VectorTile.Feature> items) throws GeometryException {
    if (zoom < 7 || zoom > 13) {
      for (var item : items) {
        item.attrs().remove(TEMP_NUM_POINTS_ATTR);
      }
      return items;
    } else { // z7-13
      // merging only merges polygons with the same attributes, so use this temporary key
      // to separate features into layers that will be merged separately
      String tempGroupKey = "_group";
      List<VectorTile.Feature> result = new ArrayList<>();
      List<VectorTile.Feature> toMerge = new ArrayList<>();
      for (var item : items) {
        Map<String, Object> attrs = item.attrs();
        Object numPointsObj = attrs.remove(TEMP_NUM_POINTS_ATTR);
        Object subclassObj = attrs.get(Fields.SUBCLASS);
        if (numPointsObj instanceof Number num && subclassObj instanceof String subclass) {
          long numPoints = num.longValue();
          if (zoom >= 10) {
            if (WOOD_OR_FOREST.contains(subclass) && numPoints < 300) {
              attrs.put(tempGroupKey, "<300");
              toMerge.add(item);
            } else { // don't merge
              result.add(item);
            }
          } else if (zoom == 9) {
            if (WOOD_OR_FOREST.contains(subclass)) {
              attrs.put(tempGroupKey, numPoints < 300 ? "<300" : ">300");
              toMerge.add(item);
            } else { // don't merge
              result.add(item);
            }
          } else { // zoom between 7 and 8
            toMerge.add(item);
          }
        } else {
          result.add(item);
        }
      }
      var merged = FeatureMerge.mergeOverlappingPolygons(toMerge, 4);
      for (var item : merged) {
        item.attrs().remove(tempGroupKey);
      }
      result.addAll(merged);
      return result;
    }
  }
}