From 60e3f58307730ed11e1170f41db966626f410786 Mon Sep 17 00:00:00 2001
From: Kristin Cowalcijk <bo@wherobots.com>
Date: Wed, 7 Aug 2024 11:02:50 +0800
Subject: [PATCH] Fix linestring split accuracy problem

---
 .../sedona/common/utils/GeometrySplitter.java | 18 +++------
 .../apache/sedona/common/FunctionsTest.java   | 37 +++++++++++++++++++
 2 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/common/src/main/java/org/apache/sedona/common/utils/GeometrySplitter.java b/common/src/main/java/org/apache/sedona/common/utils/GeometrySplitter.java
index 89c6a08981..7045316fed 100644
--- a/common/src/main/java/org/apache/sedona/common/utils/GeometrySplitter.java
+++ b/common/src/main/java/org/apache/sedona/common/utils/GeometrySplitter.java
@@ -148,19 +148,12 @@ private MultiLineString splitLinesByPoints(Geometry lines, Geometry points) {
   }
 
   private MultiLineString splitLinesByLines(Geometry inputLines, Geometry blade) {
-    // compute the intersection of inputLines and blade
-    // and pass back to splitLines to handle as points
-    Geometry intersectionWithBlade = inputLines.intersection(blade);
-
-    if (intersectionWithBlade.isEmpty()) {
-      // blade and inputLines are disjoint so just return the input as a multilinestring
-      return (MultiLineString) ensureMultiGeometryOfDimensionN(inputLines, 1);
-    } else if (intersectionWithBlade.getDimension() != 0) {
-      logger.warn("Colinear sections detected between source and blade geometry. Returned null.");
-      return null;
+    Geometry diff = inputLines.difference(blade);
+    if (diff instanceof MultiLineString) {
+      return (MultiLineString) diff;
+    } else {
+      return geometryFactory.createMultiLineString(new LineString[] {(LineString) inputLines});
     }
-
-    return splitLines(inputLines, intersectionWithBlade);
   }
 
   private MultiPolygon splitPolygonsByLines(Geometry polygons, Geometry blade) {
@@ -197,6 +190,7 @@ private void splitLineStringAtCoordinates(
         Iterator<Coordinate> coordIterator =
             getIteratorForSegmentDirection(pointCoords, lineBuilder.getLastCoordinate(), endCoord);
 
+        // line.getPrecisionModel()
         applyCoordsToLineSegment(lineBuilder, coordIterator, endCoord);
       }
 
diff --git a/common/src/test/java/org/apache/sedona/common/FunctionsTest.java b/common/src/test/java/org/apache/sedona/common/FunctionsTest.java
index 74ec6b433a..8f0f13117b 100644
--- a/common/src/test/java/org/apache/sedona/common/FunctionsTest.java
+++ b/common/src/test/java/org/apache/sedona/common/FunctionsTest.java
@@ -33,6 +33,8 @@
 import org.geotools.referencing.operation.projection.ProjectionException;
 import org.junit.Test;
 import org.locationtech.jts.geom.*;
+import org.locationtech.jts.geom.prep.PreparedGeometry;
+import org.locationtech.jts.geom.prep.PreparedGeometryFactory;
 import org.locationtech.jts.io.ParseException;
 import org.locationtech.jts.io.WKTReader;
 import org.locationtech.jts.io.WKTWriter;
@@ -305,6 +307,41 @@ public void splitLineStringByPolygon() {
     assertEquals(actualResult, expectedResult);
   }
 
+  @Test
+  public void splitLineStringFpPrecisionIssue() {
+    LineString lineString =
+        GEOMETRY_FACTORY.createLineString(
+            coordArray(
+                -8.961173822708158, -3.93776773106963, -8.08908227533288, -3.8845245068873444));
+    Polygon polygon =
+        GEOMETRY_FACTORY.createPolygon(
+            coordArray(
+                -6.318936372442209, -6.44985859539768,
+                -8.669092633645995, -3.0659222341103956,
+                -6.264600073171498, -3.075347218794894,
+                -5.3654318906014495, -3.1019726170919877,
+                -5.488002156793005, -5.892626167859213,
+                -6.318936372442209, -6.44985859539768));
+
+    Geometry result = Functions.split(lineString, polygon);
+    assertEquals(2, result.getNumGeometries());
+    assertEquals(lineString.getLength(), result.getLength(), 1e-6);
+  }
+
+  @Test
+  public void tempTest() {
+    LineString lineString =
+        GEOMETRY_FACTORY.createLineString(
+            coordArray(
+                -8.961173822708158, -3.93776773106963, -8.08908227533288, -3.8845245068873444));
+    Point point =
+        GEOMETRY_FACTORY.createPoint(new Coordinate(-8.100103048843774, -3.885197350829553));
+    PreparedGeometryFactory factory = new PreparedGeometryFactory();
+    PreparedGeometry prepLineString = factory.create(lineString);
+    boolean intersects = prepLineString.intersects(point);
+    System.out.println(intersects);
+  }
+
   @Test
   public void splitPolygonByLineString() {
     Polygon polygon =