Add upperCamelCaseToSnakeCase()

2 files changed, 28 insertions, 0 deletions

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/util/Casing.java b/src/main/java/org/zwobble/hobgoblin/compiler/util/Casing.java
index 3705f99..ef002ba 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/util/Casing.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/util/Casing.java
@@ -42,4 +42,18 @@ public class Casing {
 
         return snakeCase.toString();
     }
+
+    public static String upperCamelCaseToSnakeCase(String lowerCamelCase) {
+        var snakeCase = new StringBuilder();
+
+        for (var characterIndex = 0; characterIndex < lowerCamelCase.length(); characterIndex++) {
+            var character = lowerCamelCase.charAt(characterIndex);
+            if (characterIndex != 0 && Character.isUpperCase(character) || Character.isDigit(character)) {
+                snakeCase.append('_');
+            }
+            snakeCase.append(Character.toLowerCase(character));
+        }
+
+        return snakeCase.toString();
+    }
 }
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/util/CasingTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/util/CasingTests.java
index 5893335..4d8c9c4 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/util/CasingTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/util/CasingTests.java
@@ -49,4 +49,18 @@ public class CasingTests {
 
         assertThat(result, equalTo(expectedUpperCase));
     }
+
+    @ParameterizedTest
+    @CsvSource({
+        "A,a",
+        "Abc,abc",
+        "AbcDef,abc_def",
+        "AbDeFg,ab_de_fg",
+        "A0,a_0",
+    })
+    public void upperCamelCaseToSnakeCase(String lowerCamelCase, String expectedUpperCase) {
+        var result = Casing.upperCamelCaseToSnakeCase(lowerCamelCase);
+
+        assertThat(result, equalTo(expectedUpperCase));
+    }
 }