UY CI validation for kotlin

UYDocValidations.kt

fun getUyValDigit(externCi: String): Int{
    if(externCi.isEmpty() || externCi.length > 7) return 0

    var ci = externCi
    val validationArray = arrayOf(2,9,8,7,6,3,4)
    var resp = 0

    while (ci.length <= 6) {
        ci = "0$ci"
    }

    for(i in ci.indices){
        val char = ci[i]

        if(char.isDigit()){
            resp += (Character.getNumericValue(ci[i]) * validationArray[i]) % 10
        }
    }

    return if(resp % 10 == 0) 0 else 10 - resp % 10
}

fun validateUyCi(ci: String): Boolean{
    if(ci.isEmpty()) return false

    var cleanCi = cleanUyCi(ci)
    val dig = ci.last()
    cleanCi = cleanCi.replace(Regex.fromLiteral("/[0-9]$/"), "")

    return dig.isDigit() && Character.getNumericValue(dig) == getUyValDigit(cleanCi)
}

fun cleanUyCi(ci: String): String{
    return if(ci.isEmpty()) ci else ci.dropLast(1)
}