Desafio codenation

Krypto.kt

package com.company

class Krypto {

    fun decrypt (textoOriginal: String, numeroCasas: Int = 10): String {
        return apply(textoOriginal, (numeroCasas * -1));
    }

    fun encrypt (textoOriginal: String, numeroCasas: Int = 10): String {
        return apply(textoOriginal, numeroCasas);
    }

    private fun apply(texto: String, fator: Int): String
    {
        val encriptedText = StringBuilder();

        for (x in texto.decapitalize().toCharArray()) {
            encriptedText.append(
                applyToChar(x, fator)
            );
        }

        return encriptedText.toString();
    }

    private fun applyToChar(char: Char, fator: Int): Char {
        if (!char.isLetter()) {
            return char;
        }

        val asciiCharStartsIn = 97;
        val minValue = 97;
        val maxValue = 122;

        var novoChar = ((char.toInt()-asciiCharStartsIn+fator));

        if (0 > novoChar) {
            novoChar += maxValue;
        } else if (novoChar < minValue) {
            novoChar += minValue
        }

        return novoChar.toChar();
    }

}

Main.kt

package com.company

import java.io.File
import java.net.URL

import org.json.JSONObject
import java.security.MessageDigest

// references:
// https://rosettacode.org/wiki/SHA-1#Kotlin
// https://www.javacodemonk.com/md5-and-sha256-in-java-kotlin-and-android-96ed9628
// http://www.asciitable.com/
// http://stleary.github.io/JSON-java/index.html

fun String.sha1(): String {
    val digestBytes = MessageDigest.getInstance("SHA-1").digest(this.toByteArray())
    return digestBytes.toHex()
}

fun ByteArray.toHex(): String {
    return joinToString("") { "%02x".format(it) }
}

object Main {
    @JvmStatic
    fun main(args: Array<String>) {

        val token = args[0] ?: "";

        val data = getData(token)

        val jsonData = JSONObject(data)

        val krypto = Krypto()

        println("## encriptando....")
        println(krypto.encrypt("a ligeira raposa marrom saltou sobre o cachorro cansado", 3))

        println("## decriptando....")
        println(krypto.decrypt("d oljhlud udsrvd pduurp vdowrx vreuh r fdfkruur fdqvdgr", 3))

        println("## descriptando pra valer....")

        val valorCifrado = jsonData.getString("cifrado")
        val numeroCasas = jsonData.getInt("numero_casas")
        val valorDecifrado = krypto.decrypt(valorCifrado, numeroCasas)

        println(valorCifrado)
        println(numeroCasas)
        println(valorDecifrado)

        println(valorDecifrado.sha1())

        jsonData.put("decifrado", valorDecifrado)
        jsonData.put("resumo_criptografico", valorDecifrado.sha1())

        println(jsonData.toString())
        val repo = RetrofitInitializer().codeNationService().generateData("1231231")
        repo.execute();
    }


    fun getData(token: String): String {
        val answerFile = File("answer.json")
        if (!answerFile.exists()) {
            val url = URL("https://api.codenation.dev/v1/challenge/dev-ps/generate-data?token=$token")
            answerFile.writeText(url.readText())
        }

        return answerFile.readText()
    }
}