Grasscutter/src/main/java/emu/grasscutter/scripts/SceneIndexManager.java

package emu.grasscutter.scripts;

import com.github.davidmoten.rtreemulti.Entry;
import com.github.davidmoten.rtreemulti.RTree;
import com.github.davidmoten.rtreemulti.geometry.Geometry;
import com.github.davidmoten.rtreemulti.geometry.Rectangle;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.function.Function;

public class SceneIndexManager {

    public static <T> RTree<T, Geometry> buildIndex(int dimensions, Collection<T> elements, Function<T, Geometry> extractor){
        RTree<T, Geometry> rtree = RTree.dimensions(dimensions).create();
        return rtree.add(elements.stream().map(e -> Entry.entry(e, extractor.apply(e))).toList());
    }
    public static <T> List<T> queryNeighbors(RTree<T, Geometry> tree, double[] position, int range){
        var result = new ArrayList<T>();
        Rectangle rectangle = Rectangle.create(calRange(position, -range), calRange(position, range));
        var queryResult = tree.search(rectangle);
        queryResult.forEach(q -> result.add(q.value()));
        return result;
    }
    private static double[] calRange(double[] position, int range){
        var newPos = position.clone();
        for(int i=0;i<newPos.length;i++){
            newPos[i] += range;
        }
        return newPos;
    }
}