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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.common.geo;
import org.elasticsearch.geometry.Line;
import org.elasticsearch.geometry.MultiLine;
import java.util.Arrays;
import java.util.List;
import static org.elasticsearch.common.geo.GeoUtils.normalizePoint;
/**
* Splits lines by datelines.
*/
public class GeoLineDecomposer {
private static final double DATELINE = 180;
private GeoLineDecomposer() {
// no instances
}
public static void decomposeMultiLine(MultiLine multiLine, List collector) {
for (Line line : multiLine) {
decomposeLine(line, collector);
}
}
/**
* Splits the specified line by datelines and adds them to the supplied lines array
*/
public static void decomposeLine(Line line, List collector) {
if (line.isEmpty()) {
return;
}
double[] lons = new double[line.length()];
double[] lats = new double[lons.length];
for (int i = 0; i < lons.length; i++) {
double[] lonLat = new double[] {line.getX(i), line.getY(i)};
normalizePoint(lonLat,false, true);
lons[i] = lonLat[0];
lats[i] = lonLat[1];
}
decompose(lons, lats, collector);
}
/**
* Decompose a linestring given as array of coordinates by anti-meridian.
*/
private static void decompose(double[] lons, double[] lats, List collector) {
int offset = 0;
double shift = 0;
int i = 1;
while (i < lons.length) {
// Check where the line is going east (+1), west (-1) or directly north/south (0)
int direction = Double.compare(lons[i], lons[i - 1]);
double newShift = calculateShift(lons[i - 1], direction < 0);
// first point lon + shift is always between -180.0 and +180.0
if (i - offset > 1 && newShift != shift) {
// Jumping over anti-meridian - we need to start a new segment
double[] partLons = Arrays.copyOfRange(lons, offset, i);
double[] partLats = Arrays.copyOfRange(lats, offset, i);
performShift(shift, partLons);
shift = newShift;
offset = i - 1;
collector.add(new Line(partLons, partLats));
} else {
// Check if new point intersects with anti-meridian
shift = newShift;
double t = intersection(lons[i - 1] + shift, lons[i] + shift);
if (Double.isNaN(t) == false) {
// Found intersection, all previous segments are now part of the linestring
double[] partLons = Arrays.copyOfRange(lons, offset, i + 1);
double[] partLats = Arrays.copyOfRange(lats, offset, i + 1);
lons[i - 1] = partLons[partLons.length - 1] = (direction > 0 ? DATELINE : -DATELINE) - shift;
lats[i - 1] = partLats[partLats.length - 1] = lats[i - 1] + (lats[i] - lats[i - 1]) * t;
performShift(shift, partLons);
offset = i - 1;
collector.add(new Line(partLons, partLats));
} else {
// Didn't find intersection - just continue checking
i++;
}
}
}
if (offset == 0) {
performShift(shift, lons);
collector.add(new Line(lons, lats));
} else if (offset < lons.length - 1) {
double[] partLons = Arrays.copyOfRange(lons, offset, lons.length);
double[] partLats = Arrays.copyOfRange(lats, offset, lats.length);
performShift(shift, partLons);
collector.add(new Line(partLons, partLats));
}
}
/**
* shifts all coordinates by shift
*/
private static void performShift(double shift, double[] lons) {
if (shift != 0) {
for (int j = 0; j < lons.length; j++) {
lons[j] = lons[j] + shift;
}
}
}
/**
* Calculates how many degres the given longitude needs to be moved east in order to be in -180 - +180. +180 is inclusive only
* if include180 is true.
*/
private static double calculateShift(double lon, boolean include180) {
double normalized = GeoUtils.centeredModulus(lon, 360);
double shift = Math.round(normalized - lon);
if (!include180 && normalized == 180.0) {
shift = shift - 360;
}
return shift;
}
/**
* Checks it the segment from p1x to p2x intersects with anti-meridian
* p1x must be with in -180 +180 range
*/
private static double intersection(double p1x, double p2x) {
if (p1x == p2x) {
return Double.NaN;
}
final double t = ((p1x < p2x ? DATELINE : -DATELINE) - p1x) / (p2x - p1x);
if (t >= 1 || t <= 0) {
return Double.NaN;
} else {
return t;
}
}
}