package org.theyeasy.weixin.util;

import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider; 

import javax.crypto.BadPaddingException; 
import javax.crypto.Cipher; 
import javax.crypto.IllegalBlockSizeException; 
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException; 
import javax.crypto.spec.IvParameterSpec; 
import javax.crypto.spec.SecretKeySpec; 

import java.io.UnsupportedEncodingException; 
import java.security.*; 
import java.security.spec.InvalidParameterSpecException;


import java.security.AlgorithmParameters;
import java.security.Key;
import java.security.Security;

import org.bouncycastle.jce.provider.symmetric.ARC4.Base;
import org.bouncycastle.util.*;

/*微信小程序的解密算法*/
public class WxMiniAES128Util {
	// 算法名
	public static final String KEY_NAME = "AES";
	// 加解密算法/模式/填充方式
	// ECB模式只用密钥即可对数据进行加密解密，CBC模式需要添加一个iv
	public static final String CIPHER_ALGORITHM = "AES/CBC/PKCS7Padding";
	
	static { 
	    //BouncyCastle是一个开源的加解密解决方案，主页在http://www.bouncycastle.org/ 
	    Security.addProvider(new BouncyCastleProvider()); 
	  } 

	/**
	 * 微信 数据解密<br/>
	 * 对称解密使用的算法为 AES-128-CBC，数据采用PKCS#7填充<br/>
	 * 对称解密的目标密文:encrypted=Base64_Decode(encryptData)<br/>
	 * 对称解密秘钥:key = Base64_Decode(session_key),aeskey是16字节<br/>
	 * 对称解密算法初始向量:iv = Base64_Decode(iv),同样是16字节<br/>
	 *
	 * @param encrypted 目标密文
	 * @param session_key 会话ID
	 * @param iv 加密算法的初始向量
	 */
	public static String wxDecrypt(String encrypted, String session_key, String iv) {
		String json = null;
	
		byte[] encrypted64 = Base64.decodeBase64(encrypted.getBytes());
		byte[] key64 = Base64.decodeBase64(session_key.getBytes());
		byte[] iv64 = Base64.decodeBase64(iv.getBytes());
		byte[] data;
		try {
			init();
			json = new String(decrypt(encrypted64, key64, generateIV(iv64)));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return json;
	}

	/**
	 * 初始化密钥
	 */
	public static void init() throws Exception {
		Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
		KeyGenerator.getInstance(KEY_NAME).init(128);
	}

	/**
	 * 生成iv
	 */
	public static AlgorithmParameters generateIV(byte[] iv) throws Exception {
		// iv 为一个 16 字节的数组，这里采用和 iOS 端一样的构造方法，数据全为0
		// Arrays.fill(iv, (byte) 0x00);
		AlgorithmParameters params = AlgorithmParameters.getInstance(KEY_NAME);
		params.init(new IvParameterSpec(iv));
		return params;
	}

	/**
	 * 生成解密
	 */
	public static byte[] decrypt(byte[] encryptedData, byte[] keyBytes, AlgorithmParameters iv)
			throws Exception {
		Key key = new SecretKeySpec(keyBytes, KEY_NAME);
		Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
		// 设置为解密模式
		cipher.init(Cipher.DECRYPT_MODE, key, iv);
		return cipher.doFinal(encryptedData);
	}

	public static void main(String[] args) {
		// 微信demo中的测试数据
		String encrypted = "CiyLU1Aw2KjvrjMdj8YKliAjtP4gsMZM" + "QmRzooG2xrDcvSnxIMXFufNstNGTyaGS" + "9uT5geRa0W4oTOb1WT7fJlAC+oNPdbB+" + "3hVbJSRgv+4lGOETKUQz6OYStslQ142d" + "NCuabNPGBzlooOmB231qMM85d2/fV6Ch" + "evvXvQP8Hkue1poOFtnEtpyxVLW1zAo6" + "/1Xx1COxFvrc2d7UL/lmHInNlxuacJXw" + "u0fjpXfz/YqYzBIBzD6WUfTIF9GRHpOn" + "/Hz7saL8xz+W//FRAUid1OksQaQx4CMs" + "8LOddcQhULW4ucetDf96JcR3g0gfRK4P" + "C7E/r7Z6xNrXd2UIeorGj5Ef7b1pJAYB" + "6Y5anaHqZ9J6nKEBvB4DnNLIVWSgARns" + "/8wR2SiRS7MNACwTyrGvt9ts8p12PKFd" + "lqYTopNHR1Vf7XjfhQlVsAJdNiKdYmYV" + "oKlaRv85IfVunYzO0IKXsyl7JCUjCpoG" + "20f0a04COwfneQAGGwd5oa+T8yO5hzuy" + "Db/XcxxmK01EpqOyuxINew==";
		String session_key = "tiihtNczf5v6AKRyjwEUhQ==";
		String iv = "r7BXXKkLb8qrSNn05n0qiA==";
		String json = wxDecrypt(encrypted, session_key, iv);
		System.out.println(json);
	}
}