package com.httpsms

import timber.log.Timber

import java.security.MessageDigest

import java.util.Base64

import java.util.Random

import javax.crypto.Cipher

import javax.crypto.spec.IvParameterSpec

import javax.crypto.spec.SecretKeySpec

object Encrypter {

private const val ALGORITHM = "AES/CFB/NoPadding"

private const val IV_SIZE = 16

fun decrypt(key: String, cipherText: String): String {

val cipher = Cipher.getInstance(ALGORITHM)

val cipherBytes = Base64.getDecoder().decode(cipherText)

Timber.d("iv = ${Base64.getEncoder().encodeToString(cipherBytes.take(IV_SIZE).toByteArray())}")

Timber.d("cipher = ${Base64.getEncoder().encodeToString(cipherBytes.drop(IV_SIZE).toByteArray())}")

cipher.init(Cipher.DECRYPT_MODE, SecretKeySpec(hash(key), "AES"), IvParameterSpec(cipherBytes.take(IV_SIZE).toByteArray()))

val plainText = cipher.doFinal(cipherBytes.drop(IV_SIZE).toByteArray())

return String(plainText)

}

fun encrypt(key: String, inputText: String): String {

val cipher = Cipher.getInstance(ALGORITHM)

val iv = generateIv()

cipher.init(Cipher.ENCRYPT_MODE, SecretKeySpec(hash(key),"AES"), IvParameterSpec(iv))

val cipherBytes = iv + cipher.doFinal(inputText.toByteArray())

return Base64.getEncoder().encodeToString(cipherBytes)

}

private fun generateIv(): ByteArray {

val b = ByteArray(IV_SIZE)

Random().nextBytes(b)

return b

}

private fun hash(key: String): ByteArray {

val bytes = key.toByteArray()

val md = MessageDigest.getInstance("SHA-256")

return md.digest(bytes)

}

}