package app.utils;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Base64;

public class CryptoMethods {

    public static final String algorithm = "AES/CBC/PKCS5Padding";

    public static String generateIv() {
        byte[] iv = new byte[16];
        new SecureRandom().nextBytes(iv);
        return convertIvToString(new IvParameterSpec(iv));
    }

    public static String generateKey(int n){
        try {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(n);
            SecretKey key = keyGenerator.generateKey();
            return convertSecretKeyToString(key);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static String convertSecretKeyToString(SecretKey secretKey) throws NoSuchAlgorithmException {
        byte[] rawData = secretKey.getEncoded();
        return Base64.getEncoder().encodeToString(rawData);
    }

    public static String convertIvToString(IvParameterSpec iv) {
        byte[] rawData = iv.getIV();
        return Base64.getEncoder().encodeToString(rawData);
    }

    public static SecretKey convertStringToSecretKeyto(String encodedKey) {
        byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
        return new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES");
    }

    public static IvParameterSpec convertStringToIv(String iv) {
        byte[] decodedIv = Base64.getDecoder().decode(iv);
        return new IvParameterSpec(decodedIv, 0, decodedIv.length);
    }

    public static String encrypt(String input, String key, String iv) {
        return encrypt(algorithm, input, convertStringToSecretKeyto(key), convertStringToIv(iv));
    }

    public static String encrypt(String algorithm, String input, String key,
                                 String iv) {
        return encrypt(algorithm, input, convertStringToSecretKeyto(key), convertStringToIv(iv));
    }

    public static String encrypt(String algorithm, String input, SecretKey key,
                                 IvParameterSpec iv) {
        try {
            Cipher cipher = Cipher.getInstance(algorithm);
            cipher.init(Cipher.ENCRYPT_MODE, key, iv);
            byte[] cipherText = cipher.doFinal(input.getBytes());
            return Base64.getEncoder()
                    .encodeToString(cipherText);
        } catch (Exception e) {
            return null;
        }
    }

    public static String decrypt(String cipherText, String key, String iv) {
        return decrypt(algorithm, cipherText, convertStringToSecretKeyto(key), convertStringToIv(iv));
    }

    public static String decrypt(String algorithm, String cipherText, String key,
                                 String iv) {
        return decrypt(algorithm, cipherText, convertStringToSecretKeyto(key), convertStringToIv(iv));
    }

    public static String decrypt(String algorithm, String cipherText, SecretKey key,
                                 IvParameterSpec iv) {
        try {
            Cipher cipher = Cipher.getInstance(algorithm);
            cipher.init(Cipher.DECRYPT_MODE, key, iv);
            byte[] plainText = cipher.doFinal(Base64.getDecoder()
                    .decode(cipherText));
            return new String(plainText);
        } catch (Exception e) {
            return null;
        }
    }

}