package com.bage.study.cryption.github.lugeek;

import java.security.Key;
import java.security.SecureRandom;
import java.util.Base64;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/**
 * 来自：https://github.com/lugeek/Encryption/
 * @author bage
 *
 */
public class AES {
    public static final String ALGORITHM = "AES";
    
    public static byte[] decryptBASE64(String key) throws Exception {
        return Base64.getDecoder().decode(key);
    }

    public static String encryptBASE64(byte[] key) throws Exception {
        return Base64.getEncoder().encodeToString(key);
    }

    private static Key toKey(byte[] key) throws Exception {
        //DESKeySpec dks = new DESKeySpec(key);
        //SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
        //SecretKey secretKey = keyFactory.generateSecret(dks);

        // 当使用其他对称加密算法时，如AES、Blowfish等算法时，用下述代码替换上述三行代码
        SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);

        return secretKey;
    }

    public static byte[] decrypt(byte[] data, String key) throws Exception {
        Key k = toKey(decryptBASE64(key));

        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, k);

        return cipher.doFinal(data);
    }

    public static byte[] encrypt(byte[] data, String key) throws Exception {
        Key k = toKey(decryptBASE64(key));
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, k);

        return cipher.doFinal(data);
    }

    public static String initKey() throws Exception {
        return initKey(null);
    }

    public static String initKey(String seed) throws Exception {
        SecureRandom secureRandom = null;

        if (seed != null) {
            secureRandom = new SecureRandom(decryptBASE64(seed));
        } else {
            secureRandom = new SecureRandom();
        }

        KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM);
        kg.init(secureRandom);

        SecretKey secretKey = kg.generateKey();

        return encryptBASE64(secretKey.getEncoded());
    }
}