Convert indefiniteArticle() to an extension method

deob/src/main/java/dev/openrs2/deob/remap/TypedRemapper.java

@@ -11,6 +11,7 @@ import dev.openrs2.asm.MemberRef;
 import dev.openrs2.asm.classpath.ClassMetadata;
 import dev.openrs2.asm.classpath.ClassPath;
 import dev.openrs2.util.StringUtils;
+import dev.openrs2.util.StringUtilsKt;
 import dev.openrs2.util.collect.DisjointSet;
 import org.objectweb.asm.Type;
 import org.objectweb.asm.commons.Remapper;
@@ -165,7 +166,7 @@ public final class TypedRemapper extends Remapper {
 				throw new IllegalArgumentException("Unknown field type " + type);
 			}
 
-			prefix = StringUtils.indefiniteArticle(prefix) + StringUtils.capitalize(prefix);
+			prefix = StringUtilsKt.indefiniteArticle(prefix) + StringUtils.capitalize(prefix);
 
 			var mappedName = generateName(prefixes, prefix);
 			for (var field : partition) {

util/src/main/java/dev/openrs2/util/StringUtils.kt

@@ -1,18 +1,16 @@
 package dev.openrs2.util
 
-object StringUtils {
-    // TODO(gpe): convert to an extension function
-    @JvmStatic
-    fun indefiniteArticle(str: String): String {
-        require(str.isNotEmpty())
+fun CharSequence.indefiniteArticle(): String {
+    require(isNotEmpty())
 
-        val first = str.first().toLowerCase()
+    val first = first().toLowerCase()
     return when (first) {
         'a', 'e', 'i', 'o', 'u' -> "an"
         else -> "a"
     }
 }
 
+object StringUtils {
     @JvmStatic
     fun capitalize(str: String): String {
         return str.capitalize()

util/src/test/java/dev/openrs2/util/StringUtilsTest.kt

@@ -1,7 +1,6 @@
 package dev.openrs2.util
 
 import dev.openrs2.util.StringUtils.capitalize
-import dev.openrs2.util.StringUtils.indefiniteArticle
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
@@ -9,10 +8,10 @@ import kotlin.test.assertFailsWith
 object StringUtilsTest {
     @Test
     fun testIndefiniteArticle() {
-        assertEquals("a", indefiniteArticle("book"))
-        assertEquals("an", indefiniteArticle("aeroplane"))
+        assertEquals("a", "book".indefiniteArticle())
+        assertEquals("an", "aeroplane".indefiniteArticle())
         assertFailsWith(IllegalArgumentException::class) {
-            indefiniteArticle("")
+            "".indefiniteArticle()
         }
     }