Fix Line2D.TryIntersect to pass nullable Point2D (#187)

* Fix Line2D.TryIntersect to pass nullable Point2D

* Simplified TryIntersect

* Cleanup in LineSegment2DTests

---------

Co-authored-by: jkalias <[email protected]>

Author: f-frhs

src/Spatial.Tests/Euclidean/LineSegment2DTests.cs

@@ -32,10 +32,10 @@ public void ConstructorThrowsErrorOnSamePoint()
         [TestCase("0,0", "-1,0", 1)]
         [TestCase("0,-1", "0,1", 2)]
         [TestCase("-1,-1", "2,2", 4.24264068711)]
-        public void LineLength(string p1s, string p2s, double expected)
+        public void LineLength(string p1S, string p2S, double expected)
         {
-            var p1 = Point2D.Parse(p1s);
-            var p2 = Point2D.Parse(p2s);
+            var p1 = Point2D.Parse(p1S);
+            var p2 = Point2D.Parse(p2S);
             var line = new LineSegment2D(p1, p2);
             var len = line.Length;
 
@@ -46,10 +46,10 @@ public void LineLength(string p1s, string p2s, double expected)
         [TestCase("3,0", "0,0", "-1,0")]
         [TestCase("2.7,-2.7", "0,0", "-0.707106781,0.707106781")]
         [TestCase("11,-1", "11,1", "0,1")]
-        public void LineDirection(string p1s, string p2s, string exs)
+        public void LineDirection(string p1S, string p2S, string exs)
         {
-            var p1 = Point2D.Parse(p1s);
-            var p2 = Point2D.Parse(p2s);
+            var p1 = Point2D.Parse(p1S);
+            var p2 = Point2D.Parse(p2S);
             var ex = Vector2D.Parse(exs);
             var line = new LineSegment2D(p1, p2);
 
@@ -58,20 +58,20 @@ public void LineDirection(string p1s, string p2s, string exs)
 
         [TestCase("0,0", "10,10", "0,0", "10,10", true)]
         [TestCase("0,0", "10,10", "0,0", "10,11", false)]
-        public void EqualityOperator(string p1s, string p2s, string p3s, string p4s, bool expected)
+        public void EqualityOperator(string p1S, string p2S, string p3S, string p4S, bool expected)
         {
-            var l1 = LineSegment2D.Parse(p1s, p2s);
-            var l2 = LineSegment2D.Parse(p3s, p4s);
+            var l1 = LineSegment2D.Parse(p1S, p2S);
+            var l2 = LineSegment2D.Parse(p3S, p4S);
 
             Assert.AreEqual(expected, l1 == l2);
         }
 
         [TestCase("0,0", "10,10", "0,0", "10,10", false)]
         [TestCase("0,0", "10,10", "0,0", "10,11", true)]
-        public void InequalityOperator(string p1s, string p2s, string p3s, string p4s, bool expected)
+        public void InequalityOperator(string p1S, string p2S, string p3S, string p4S, bool expected)
         {
-            var l1 = new LineSegment2D(Point2D.Parse(p1s), Point2D.Parse(p2s));
-            var l2 = new LineSegment2D(Point2D.Parse(p3s), Point2D.Parse(p4s));
+            var l1 = new LineSegment2D(Point2D.Parse(p1S), Point2D.Parse(p2S));
+            var l2 = new LineSegment2D(Point2D.Parse(p3S), Point2D.Parse(p4S));
 
             Assert.AreEqual(expected, l1 != l2);
         }
@@ -139,17 +139,16 @@ public void IntersectWithTest(string s1, string e1, string s2, string e2, string
             Assert.AreEqual(e, result);
         }
 
-        [TestCase("0,0", "-2,-2", "1,0", "1,2", "1,1")]
-        [TestCase("0,0", "-2,-2", "0,1", "2,1", "1,1")]
-        [TestCase("0,0", "2,2", "-1,-5", "-1,0", "-1,-1")]
-        public void IntersectWithTest2(string s1, string e1, string s2, string e2, string expected)
+        [TestCase("0,0", "-2,-2", "1,0", "1,2")]
+        [TestCase("0,0", "-2,-2", "0,1", "2,1")]
+        [TestCase("0,0", "2,2", "-1,-5", "-1,0")]
+        public void IntersectWithTest2(string s1, string e1, string s2, string e2)
         {
             var line1 = LineSegment2D.Parse(s1, e1);
             var line2 = LineSegment2D.Parse(s2, e2);
-            var e = string.IsNullOrEmpty(expected) ? (Point2D?)null : Point2D.Parse(expected);
             bool success = line1.TryIntersect(line2, out var result, Angle.FromRadians(0.001));
             Assert.IsFalse(success);
-            Assert.AreEqual(e, result);
+            Assert.AreEqual(null, result);
         }
 
         [TestCase("0,0", "0,1", "1,1", "1,2", 0.0001, true)]

src/Spatial/Euclidean/LineSegment2D.cs

@@ -134,19 +134,19 @@ public Point2D ClosestPointTo(Point2D p)
         }
 
         /// <summary>
-        /// Compute the intersection between two lines if the angle between them is greater than a specified
+        /// Compute the intersection between two line segments if the angle between them is greater than a specified
         /// angle tolerance.
         /// </summary>
-        /// <param name="other">The other line to compute the intersection with</param>
-        /// <param name="intersection">When this method returns, contains the intersection point, if the conversion succeeded, or the default point if the conversion failed.</param>
-        /// <param name="tolerance">The tolerance used when checking if the lines are parallel</param>
+        /// <param name="other">The other line segment to compute the intersection with</param>
+        /// <param name="intersection">The intersection if it exists; otherwise null</param>
+        /// <param name="tolerance">The tolerance used when checking if the line segments are parallel</param>
         /// <returns>True if an intersection exists; otherwise false</returns>
         [Pure]
-        public bool TryIntersect(LineSegment2D other, out Point2D intersection, Angle tolerance)
+        public bool TryIntersect(LineSegment2D other, out Point2D? intersection, Angle tolerance)
         {
+            intersection = null;
             if (IsParallelTo(other, tolerance))
-            {
-                intersection = default(Point2D);
+            {   
                 return false;
             }
 
@@ -159,8 +159,13 @@ public bool TryIntersect(LineSegment2D other, out Point2D intersection, Angle to
             var t = (q - p).CrossProduct(s) / r.CrossProduct(s);
             var u = (p - q).CrossProduct(r) / s.CrossProduct(r);
 
-            intersection = p + (t * r);
-            return (0.0 <= t && t <= 1.0) && (0.0 <= u && u <= 1.0);
+            var isIntersected = (0.0 <= t && t <= 1.0) && (0.0 <= u && u <= 1.0);
+            if (isIntersected)
+            {
+                intersection = p + t * r;
+            }
+
+            return intersection != null;
         }
 
         /// <summary>