Notes

class SecuirtyActivity : AppCompatActivity() {

private val encryptedPrefs by lazy {
EncryptedSharedPreferences.create(
PREFS_FILE_NAME,
masterKeyAlias,
applicationContext,
EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
)
}

private val file by lazy { File(filesDir, ENCRYPTED_FILE_NAME) }
private val encryptedFile by lazy {
EncryptedFile.Builder(file,
applicationContext,
masterKeyAlias,
EncryptedFile.FileEncryptionScheme.AES256_GCM_HKDF_4KB
).build()
}

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_secuirty)

handleClickListeners()


}

fun handleClickListeners(){

btn_save_pref.setOnClickListener {
saveIntoSharedPreferences(ed_input_information.text.toString())
}
btn_load_pref.setOnClickListener {
val result = getDataFromSharedPreferences() ?: "No Data Found"
tv_result.text = result
}

btn_download.setOnClickListener { downloadAndEncryptFile() }
btn_delete.setOnClickListener {
val deleteStatus = deleteFile()
tv_result.text = if(deleteStatus) {"File deleted"} else { "File is not available" }
}
btn_encrypted_data.setOnClickListener {
readFile{file.inputStream()}
}
btn_decrypted_data.setOnClickListener {
readFile { encryptedFile.openFileInput() }
}

}

fun saveIntoSharedPreferences(value: String){
encryptedPrefs.edit().putString(ENC_KEY, value).apply()
tv_result.text = "Data Save in to shared Prefs with ($value)"
}

fun getDataFromSharedPreferences(): String? = encryptedPrefs.getString(ENC_KEY, null)

fun deleteFile(): Boolean{
var success: Boolean = false
if(file.exists()){
file.delete()
success = true
}
return success
}

private fun downloadAndEncryptFile() {
if (file.exists()) {
Log.i("TAG", "Encrypted file already exists!")
tv_result.text = "file already Exist"
} else {
Log.i("TAG", "Encrypted file does not exist exists! Downloading...")
val request = Request.Builder().url(FILE_URL).build()
okHttpClient.newCall(request).enqueue(
object : Callback {
override fun onFailure(call: Call, e: IOException) {
runOnUiThread { tv_result.text = e.message }
Log.e("TAG", "Error occurred!", e)
}

override fun onResponse(call: Call, response: Response) {
val result = response.body!!.bytes()
runOnUiThread { onFileDownloaded(result) }
}
}
)
}
}

private fun onFileDownloaded(bytes: ByteArray) {
var encryptedOutputStream: FileOutputStream? = null
try {
encryptedOutputStream = encryptedFile.openFileOutput().apply {
write(bytes)
}
tv_result.text = "File Downloaded and Encrypted"
} catch (e: Exception) {
Log.e("TAG", "Could not open encrypted file", e)
tv_result.text = e.message
} finally {
encryptedOutputStream?.close()
}
}

private fun readFile(fileInput: () -> FileInputStream) {
Log.i("TAG", "Loading file...")
var fileInputStream: FileInputStream? = null
try {
fileInputStream = fileInput()
val reader = BufferedReader(InputStreamReader(fileInputStream))
val stringBuilder = StringBuilder()
reader.forEachLine { line -> stringBuilder.appendln(line) }
tv_result.text = stringBuilder.toString()
} catch (e: Exception) {
Log.e("TAG", "Error occurred when reading file", e)
tv_result.text = e.message
} finally {
fileInputStream?.close()
}
}



companion object{

val masterKeyAlias = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC)
val okHttpClient: OkHttpClient = OkHttpClient.Builder().build()
const val ENC_KEY = "ENCRYPT_KEY"
const val PREFS_FILE_NAME = "MY_ENCRYPTED_PRERS_FILE_NAME"
const val ENCRYPTED_FILE_NAME = "MY_ENCRYPT_FILE_NAME"
const val FILE_URL = "https://raw.githubusercontent.com/salmanyaqoob/react-monster-app/master/README.md"

}

}