Simple pig latin implementation

pglatin.kt

fun Char.isVowel(): Boolean {
    return "aeiou".contains(lowercaseChar())
}

fun String.toPigLatin(): String {
    if (isEmpty()) return this

    if (this[0].isVowel()) {
        return this + "way"
    }

    var index = -1
    // find first vowel occurrence
    for (i in this.indices) {
        if (this[i].isVowel()) {
            index = i
            break
        }
    }

    return if (index == -1) return this
    else substring(index) + substring(0, index) + "ay"
}


fun main() {
    println("human".toPigLatin()) //begins with a consonant
    println("egg".toPigLatin()) //begins with a vowel
    println("mist".toPigLatin()) //begins with a consonant
    println("cricket".toPigLatin()) //consonant cluster word
    println("extreme".toPigLatin()) //begins with a vowel
    println("stress".toPigLatin()) //consonant cluster word
    println("unit".toPigLatin()) //contains all vowels
    println("Psst".toPigLatin()) //contains no vowel
}