Add antipodal point unit test for distance calculator

app/src/test/java/org/nitri/opentopo/DistanceCalculatorTest.kt

@@ -1,5 +1,6 @@
 package org.nitri.opentopo
 
+import io.ticofab.androidgpxparser.parser.domain.Point
 import org.junit.Assert.assertEquals
 import org.junit.Test
 import org.nitri.opentopo.util.DistanceCalculator
@@ -30,4 +31,87 @@ class DistanceCalculatorTest {
 
         assertEquals(expectedDistanceMeters, distance, toleranceMeters)
     }
+
+    @Test
+    fun distanceBetweenPointsHandlesAntipodalLocations() {
+        val pointNearGreenwich = createPoint(0.0, 0.0)
+        val antipodalPoint = createPoint(0.0, 180.0)
+
+        val distance = DistanceCalculator.distance(pointNearGreenwich, antipodalPoint)
+
+        val expectedDistanceMeters = Math.PI * 6_371_000.0
+        val toleranceMeters = 10_000.0
+
+        assertEquals(expectedDistanceMeters, distance, toleranceMeters)
+    }
+
+    private fun createPoint(latitude: Double, longitude: Double): Point {
+        val constructors = Point::class.java.declaredConstructors
+
+        for (constructor in constructors) {
+            constructor.isAccessible = true
+            val parameterTypes = constructor.parameterTypes
+
+            var latAssigned = false
+            var lonAssigned = false
+
+            val arguments = Array<Any?>(parameterTypes.size) { index ->
+                val parameterType = parameterTypes[index]
+                when {
+                    !latAssigned && parameterType.isLatitudeLongitudeParameter() -> {
+                        latAssigned = true
+                        latitude
+                    }
+                    !lonAssigned && parameterType.isLatitudeLongitudeParameter() -> {
+                        lonAssigned = true
+                        longitude
+                    }
+                    else -> parameterType.defaultValue()
+                }
+            }
+
+            if (latAssigned && lonAssigned) {
+                try {
+                    val instance = constructor.newInstance(*arguments)
+                    if (instance is Point && instance.latitude == latitude && instance.longitude == longitude) {
+                        return instance
+                    }
+                } catch (ignored: ReflectiveOperationException) {
+                    // Try the next constructor
+                }
+            }
+        }
+
+        error("Unable to instantiate Point via reflection. Constructors: ${constructors.joinToString { it.toGenericString() }}")
+    }
+
+    private fun Class<*>.isLatitudeLongitudeParameter(): Boolean {
+        return this == java.lang.Double.TYPE || this == java.lang.Double::class.java
+    }
+
+    private fun Class<*>.defaultValue(): Any? = when (this) {
+        java.lang.Double.TYPE -> 0.0
+        java.lang.Float.TYPE -> 0f
+        java.lang.Long.TYPE -> 0L
+        java.lang.Integer.TYPE -> 0
+        java.lang.Boolean.TYPE -> false
+        java.lang.Short.TYPE -> 0.toShort()
+        java.lang.Byte.TYPE -> 0.toByte()
+        java.lang.Character.TYPE -> 0.toChar()
+        java.lang.String::class.java -> ""
+        java.util.Date::class.java -> java.util.Date(0)
+        java.math.BigDecimal::class.java -> java.math.BigDecimal.ZERO
+        java.lang.Double::class.java -> null
+        java.lang.Float::class.java -> null
+        java.lang.Long::class.java -> null
+        java.lang.Integer::class.java -> null
+        java.lang.Boolean::class.java -> null
+        java.lang.Short::class.java -> null
+        java.lang.Byte::class.java -> null
+        java.lang.Character::class.java -> null
+        else -> when (this.name) {
+            "kotlin.jvm.internal.DefaultConstructorMarker" -> null
+            else -> null
+        }
+    }
 }