/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.spatial.prefix.tree;
import java.io.PrintStream;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Locale;
import org.locationtech.spatial4j.context.SpatialContext;
import org.locationtech.spatial4j.shape.Point;
import org.locationtech.spatial4j.shape.Rectangle;
import org.locationtech.spatial4j.shape.Shape;
import org.locationtech.spatial4j.shape.SpatialRelation;
import org.apache.lucene.util.BytesRef;
/**
* A {@link SpatialPrefixTree} which uses a
* <a href="http://en.wikipedia.org/wiki/Quadtree">quad tree</a> in which an
* indexed term will be generated for each cell, 'A', 'B', 'C', 'D'.
*
* @lucene.experimental
*/
public class QuadPrefixTree extends LegacyPrefixTree {
/**
* Factory for creating {@link QuadPrefixTree} instances with useful defaults
*/
public static class Factory extends SpatialPrefixTreeFactory {
@Override
protected int getLevelForDistance(double degrees) {
QuadPrefixTree grid = new QuadPrefixTree(ctx, MAX_LEVELS_POSSIBLE);
return grid.getLevelForDistance(degrees);
}
@Override
protected SpatialPrefixTree newSPT() {
return new QuadPrefixTree(ctx,
maxLevels != null ? maxLevels : MAX_LEVELS_POSSIBLE);
}
}
public static final int MAX_LEVELS_POSSIBLE = 50;//not really sure how big this should be
public static final int DEFAULT_MAX_LEVELS = 12;
protected final double xmin;
protected final double xmax;
protected final double ymin;
protected final double ymax;
protected final double xmid;
protected final double ymid;
protected final double gridW;
public final double gridH;
final double[] levelW;
final double[] levelH;
final int[] levelS; // side
final int[] levelN; // number
public QuadPrefixTree(
SpatialContext ctx, Rectangle bounds, int maxLevels) {
super(ctx, maxLevels);
this.xmin = bounds.getMinX();
this.xmax = bounds.getMaxX();
this.ymin = bounds.getMinY();
this.ymax = bounds.getMaxY();
levelW = new double[maxLevels];
levelH = new double[maxLevels];
levelS = new int[maxLevels];
levelN = new int[maxLevels];
gridW = xmax - xmin;
gridH = ymax - ymin;
this.xmid = xmin + gridW/2.0;
this.ymid = ymin + gridH/2.0;
levelW[0] = gridW/2.0;
levelH[0] = gridH/2.0;
levelS[0] = 2;
levelN[0] = 4;
for (int i = 1; i < levelW.length; i++) {
levelW[i] = levelW[i - 1] / 2.0;
levelH[i] = levelH[i - 1] / 2.0;
levelS[i] = levelS[i - 1] * 2;
levelN[i] = levelN[i - 1] * 4;
}
}
public QuadPrefixTree(SpatialContext ctx) {
this(ctx, DEFAULT_MAX_LEVELS);
}
public QuadPrefixTree(
SpatialContext ctx, int maxLevels) {
this(ctx, ctx.getWorldBounds(), maxLevels);
}
@Override
public Cell getWorldCell() {
return new QuadCell(BytesRef.EMPTY_BYTES, 0, 0);
}
public void printInfo(PrintStream out) {
NumberFormat nf = NumberFormat.getNumberInstance(Locale.ROOT);
nf.setMaximumFractionDigits(5);
nf.setMinimumFractionDigits(5);
nf.setMinimumIntegerDigits(3);
for (int i = 0; i < maxLevels; i++) {
out.println(i + "]\t" + nf.format(levelW[i]) + "\t" + nf.format(levelH[i]) + "\t" +
levelS[i] + "\t" + (levelS[i] * levelS[i]));
}
}
@Override
public int getLevelForDistance(double dist) {
if (dist == 0)//short circuit
return maxLevels;
for (int i = 0; i < maxLevels-1; i++) {
//note: level[i] is actually a lookup for level i+1
if(dist > levelW[i] && dist > levelH[i]) {
return i+1;
}
}
return maxLevels;
}
@Override
public Cell getCell(Point p, int level) {
List<Cell> cells = new ArrayList<>(1);
build(xmid, ymid, 0, cells, new BytesRef(maxLevels+1), ctx.makePoint(p.getX(),p.getY()), level);
return cells.get(0);//note cells could be longer if p on edge
}
private void build(
double x,
double y,
int level,
List<Cell> matches,
BytesRef str,
Shape shape,
int maxLevel) {
assert str.length == level;
double w = levelW[level] / 2;
double h = levelH[level] / 2;
// Z-Order
// http://en.wikipedia.org/wiki/Z-order_%28curve%29
checkBattenberg('A', x - w, y + h, level, matches, str, shape, maxLevel);
checkBattenberg('B', x + w, y + h, level, matches, str, shape, maxLevel);
checkBattenberg('C', x - w, y - h, level, matches, str, shape, maxLevel);
checkBattenberg('D', x + w, y - h, level, matches, str, shape, maxLevel);
// possibly consider hilbert curve
// http://en.wikipedia.org/wiki/Hilbert_curve
// http://blog.notdot.net/2009/11/Damn-Cool-Algorithms-Spatial-indexing-with-Quadtrees-and-Hilbert-Curves
// if we actually use the range property in the query, this could be useful
}
protected void checkBattenberg(
char c,
double cx,
double cy,
int level,
List<Cell> matches,
BytesRef str,
Shape shape,
int maxLevel) {
assert str.length == level;
assert str.offset == 0;
double w = levelW[level] / 2;
double h = levelH[level] / 2;
int strlen = str.length;
Rectangle rectangle = ctx.makeRectangle(cx - w, cx + w, cy - h, cy + h);
SpatialRelation v = shape.relate(rectangle);
if (SpatialRelation.CONTAINS == v) {
str.bytes[str.length++] = (byte)c;//append
//str.append(SpatialPrefixGrid.COVER);
matches.add(new QuadCell(BytesRef.deepCopyOf(str), v.transpose()));
} else if (SpatialRelation.DISJOINT == v) {
// nothing
} else { // SpatialRelation.WITHIN, SpatialRelation.INTERSECTS
str.bytes[str.length++] = (byte)c;//append
int nextLevel = level+1;
if (nextLevel >= maxLevel) {
//str.append(SpatialPrefixGrid.INTERSECTS);
matches.add(new QuadCell(BytesRef.deepCopyOf(str), v.transpose()));
} else {
build(cx, cy, nextLevel, matches, str, shape, maxLevel);
}
}
str.length = strlen;
}
protected class QuadCell extends LegacyCell {
QuadCell(byte[] bytes, int off, int len) {
super(bytes, off, len);
}
QuadCell(BytesRef str, SpatialRelation shapeRel) {
this(str.bytes, str.offset, str.length);
this.shapeRel = shapeRel;
}
@Override
protected QuadPrefixTree getGrid() { return QuadPrefixTree.this; }
@Override
protected int getMaxLevels() { return maxLevels; }
@Override
protected Collection<Cell> getSubCells() {
BytesRef source = getTokenBytesNoLeaf(null);
List<Cell> cells = new ArrayList<>(4);
cells.add(new QuadCell(concat(source, (byte)'A'), null));
cells.add(new QuadCell(concat(source, (byte)'B'), null));
cells.add(new QuadCell(concat(source, (byte)'C'), null));
cells.add(new QuadCell(concat(source, (byte)'D'), null));
return cells;
}
protected BytesRef concat(BytesRef source, byte b) {
//+2 for new char + potential leaf
final byte[] buffer = Arrays.copyOfRange(source.bytes, source.offset, source.offset + source.length + 2);
BytesRef target = new BytesRef(buffer);
target.length = source.length;
target.bytes[target.length++] = b;
return target;
}
@Override
public int getSubCellsSize() {
return 4;
}
@Override
protected QuadCell getSubCell(Point p) {
return (QuadCell) QuadPrefixTree.this.getCell(p, getLevel() + 1);//not performant!
}
@Override
public Shape getShape() {
if (shape == null)
shape = makeShape();
return shape;
}
protected Rectangle makeShape() {
BytesRef token = getTokenBytesNoLeaf(null);
double xmin = QuadPrefixTree.this.xmin;
double ymin = QuadPrefixTree.this.ymin;
for (int i = 0; i < token.length; i++) {
byte c = token.bytes[token.offset + i];
switch (c) {
case 'A':
ymin += levelH[i];
break;
case 'B':
xmin += levelW[i];
ymin += levelH[i];
break;
case 'C':
break;//nothing really
case 'D':
xmin += levelW[i];
break;
default:
throw new RuntimeException("unexpected char: " + c);
}
}
int len = token.length;
double width, height;
if (len > 0) {
width = levelW[len-1];
height = levelH[len-1];
} else {
width = gridW;
height = gridH;
}
return ctx.makeRectangle(xmin, xmin + width, ymin, ymin + height);
}
}//QuadCell
}