From 2fc7073c0161f4e25bebda675f1dd46b766e9e9e Mon Sep 17 00:00:00 2001
From: DBotThePony <dbotthepony@yandex.ru>
Date: Sat, 22 Oct 2022 12:22:08 +0700
Subject: [PATCH] Simplify integerDivisionDown and integerDivisionUp

---
 .../kotlin/ru/dbotthepony/mc/otm/core/Math.kt | 22 +---------
 .../ru/dbotthepony/mc/otm/tests/MathTests.kt  | 41 +++++++++++++++++++
 2 files changed, 43 insertions(+), 20 deletions(-)
 create mode 100644 src/test/kotlin/ru/dbotthepony/mc/otm/tests/MathTests.kt

diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/core/Math.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/core/Math.kt
index 8903ae352..a5955aa08 100644
--- a/src/main/kotlin/ru/dbotthepony/mc/otm/core/Math.kt
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/core/Math.kt
@@ -44,16 +44,7 @@ fun BigInteger.toIntSafe(): Int {
 @Suppress("SameParameterValue")
 fun integerDivisionDown(elements: Int, elementsPerRow: Int): Int {
 	require(elements >= 0) { "Invalid amount of elements $elements" }
-
-	if (elements == 0) {
-		return 0
-	}
-
-	if (elements % elementsPerRow == 0) {
-		return elements / elementsPerRow - 1
-	}
-
-	return elements / elementsPerRow
+	return (elements - 1) / elementsPerRow
 }
 
 /**
@@ -69,14 +60,5 @@ fun integerDivisionDown(elements: Int, elementsPerRow: Int): Int {
 @Suppress("SameParameterValue")
 fun integerDivisionUp(elements: Int, elementsPerRow: Int): Int {
 	require(elements >= 0) { "Invalid amount of elements $elements" }
-
-	if (elements == 0) {
-		return 0
-	}
-
-	if (elements % elementsPerRow == 0) {
-		return elements / elementsPerRow
-	}
-
-	return elements / elementsPerRow + 1
+	return (elements + elementsPerRow - 1) / elementsPerRow
 }
diff --git a/src/test/kotlin/ru/dbotthepony/mc/otm/tests/MathTests.kt b/src/test/kotlin/ru/dbotthepony/mc/otm/tests/MathTests.kt
new file mode 100644
index 000000000..4e96b646d
--- /dev/null
+++ b/src/test/kotlin/ru/dbotthepony/mc/otm/tests/MathTests.kt
@@ -0,0 +1,41 @@
+package ru.dbotthepony.mc.otm.tests
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+import ru.dbotthepony.mc.otm.core.integerDivisionDown
+import ru.dbotthepony.mc.otm.core.integerDivisionUp
+
+object MathTests {
+	@Test
+	@DisplayName("Integer divisions (round up and round down)")
+	fun integerDivision() {
+		assertEquals(0, integerDivisionDown(0, 9))
+		assertEquals(0, integerDivisionDown(1, 9))
+		assertEquals(0, integerDivisionDown(4, 9))
+		assertEquals(0, integerDivisionDown(5, 9))
+		assertEquals(0, integerDivisionDown(9, 9))
+		assertEquals(1, integerDivisionDown(10, 9))
+		assertEquals(1, integerDivisionDown(11, 9))
+		assertEquals(1, integerDivisionDown(12, 9))
+		assertEquals(1, integerDivisionDown(15, 9))
+		assertEquals(1, integerDivisionDown(16, 9))
+		assertEquals(1, integerDivisionDown(17, 9))
+		assertEquals(1, integerDivisionDown(18, 9))
+		assertEquals(2, integerDivisionDown(19, 9))
+
+		assertEquals(0, integerDivisionUp(0, 9))
+		assertEquals(1, integerDivisionUp(1, 9))
+		assertEquals(1, integerDivisionUp(4, 9))
+		assertEquals(1, integerDivisionUp(5, 9))
+		assertEquals(1, integerDivisionUp(9, 9))
+		assertEquals(2, integerDivisionUp(10, 9))
+		assertEquals(2, integerDivisionUp(11, 9))
+		assertEquals(2, integerDivisionUp(12, 9))
+		assertEquals(2, integerDivisionUp(15, 9))
+		assertEquals(2, integerDivisionUp(16, 9))
+		assertEquals(2, integerDivisionUp(17, 9))
+		assertEquals(2, integerDivisionUp(18, 9))
+		assertEquals(3, integerDivisionUp(19, 9))
+	}
+}