Add EnumHelper

src/main/kotlin/net/shadowfacts/cacao/util/EnumHelper.kt

@@ -0,0 +1,20 @@
+package net.shadowfacts.cacao.util
+
+/**
+ * @author shadowfacts
+ */
+object EnumHelper {
+
+	fun <E: Enum<E>> next(value: E): E {
+		val constants = value.declaringClass.enumConstants
+		val index = constants.indexOf(value) + 1
+		return if (index < constants.size) constants[index] else constants.first()
+	}
+
+	fun <E: Enum<E>> previous(value: E): E {
+		val constants = value.declaringClass.enumConstants
+		val index = constants.indexOf(value) - 1
+		return if (index >= 0) constants[index] else constants.last()
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/util/EnumHelperTests.kt

@@ -0,0 +1,27 @@
+package net.shadowfacts.cacao.util
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class EnumHelperTests {
+
+	enum class MyEnum {
+		ONE, TWO
+	}
+
+	@Test
+	fun testNext() {
+		assertEquals(MyEnum.TWO, EnumHelper.next(MyEnum.ONE))
+		assertEquals(MyEnum.ONE, EnumHelper.next(MyEnum.TWO))
+	}
+
+	@Test
+	fun testPrev() {
+		assertEquals(MyEnum.ONE, EnumHelper.previous(MyEnum.TWO))
+		assertEquals(MyEnum.TWO, EnumHelper.previous(MyEnum.ONE))
+	}
+
+}