From ecdf57be47e44e74a3c05c82bb07a32df302cdc1 Mon Sep 17 00:00:00 2001
From: Davi Dante <davi_donadelli@live.com>
Date: Sat, 19 Nov 2022 17:56:25 -0300
Subject: [PATCH 1/2] feat: creating tail-recursive call for factorial
 algorithm

---
 .idea/misc.xml                    |  2 +-
 src/main/kotlin/math/Factorial.kt | 18 ++++++++++++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/.idea/misc.xml b/.idea/misc.xml
index 4b49563..c23634d 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_9" project-jdk-name="9" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="corretto-1.8" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file
diff --git a/src/main/kotlin/math/Factorial.kt b/src/main/kotlin/math/Factorial.kt
index e33be00..95457b0 100644
--- a/src/main/kotlin/math/Factorial.kt
+++ b/src/main/kotlin/math/Factorial.kt
@@ -10,9 +10,19 @@ import java.security.InvalidParameterException
 fun getFactorial(number: Long): Long {
     if (number < 0L) {
         throw InvalidParameterException("The number of which to calculate the factorial must be greater or equal to zero.")
-    } else return when (number) {
-        0L -> 1
-        1L -> number
-        else -> number * getFactorial(number - 1)
+    } else return getFactorialOptimized(number, 1)
+}
+
+/**
+ * Calculates the factorial using tail recursion to optimize code.
+ * If the number is too high, the tail recursion returns 0.
+ * @param number The number of which to calculate the factorial.
+ * @param accumulator The accumulator of the factorial value
+ * @return The factorial of the number passed as parameter.
+ */
+private tailrec fun getFactorialOptimized(number: Long, accumulator: Long): Long {
+    return when (number) {
+        0L -> accumulator
+        else -> getFactorialOptimized(number - 1, number * accumulator)
     }
 }
\ No newline at end of file

From 414504dff91cd0639a59a6214e650b45365efed4 Mon Sep 17 00:00:00 2001
From: Davi Dante <davi_donadelli@live.com>
Date: Sat, 19 Nov 2022 17:58:33 -0300
Subject: [PATCH 2/2] feat: renaming packages and creating test for new
 tail-recursive function

---
 src/main/kotlin/math/Factorial.kt     |  2 +-
 src/test/kotlin/math/FactorialTest.kt | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/main/kotlin/math/Factorial.kt b/src/main/kotlin/math/Factorial.kt
index 95457b0..6058816 100644
--- a/src/main/kotlin/math/Factorial.kt
+++ b/src/main/kotlin/math/Factorial.kt
@@ -1,4 +1,4 @@
-package mathematics
+package math
 
 import java.security.InvalidParameterException
 
diff --git a/src/test/kotlin/math/FactorialTest.kt b/src/test/kotlin/math/FactorialTest.kt
index 7706828..4c6c92e 100644
--- a/src/test/kotlin/math/FactorialTest.kt
+++ b/src/test/kotlin/math/FactorialTest.kt
@@ -1,5 +1,6 @@
-package mathematics
+package math
 
+import math.getFactorial
 import org.junit.Test
 import java.security.InvalidParameterException
 
@@ -25,4 +26,11 @@ class FactorialTest {
         assert(getFactorial(input) == expectedFactorial)
     }
 
+    @Test
+    fun testFactorialOfHighValue() {
+        val input = 20000L
+        val expectedFactorial = 0L
+        assert(getFactorial(input) == expectedFactorial)
+    }
+
 }
\ No newline at end of file