package com.aelns.core.utils.security;

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

/**
 * RSA安全编码组件
 *
 * @author 梁栋
 * @version 1.0
 * @since 1.0
 */
public abstract class RSAUtil extends Coder {
    public static final String KEY_ALGORITHM = "RSA";
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    public static final String PUBLIC_KEY = "RSAPublicKey";
    public static final String PRIVATE_KEY = "RSAPrivateKey";

    /**
     * 用私钥对信息生成数字签名 
     *
     * @param data
     *            加密数据 
     * @param privateKey
     *            私钥 
     *
     * @return
     * @throws Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        // 解密由base64编码的私钥  
        byte[] keyBytes = decryptBASE64(privateKey);

        // 构造PKCS8EncodedKeySpec对象  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

        // KEY_ALGORITHM 指定的加密算法  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

        // 取私钥匙对象  
        PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 用私钥对信息生成数字签名  
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(priKey);
        signature.update(data);

        return encryptBASE64(signature.sign());
    }

    /**
     * 校验数字签名 
     *
     * @param data 加密数据
     *
     * @param publicKey
     *            公钥 
     * @param sign
     *            数字签名 
     *
     * @return 校验成功返回true 失败返回false 
     * @throws Exception
     *
     */
    public static boolean verify(byte[] data, String publicKey, String sign)
            throws Exception {

        // 解密由base64编码的公钥  
        byte[] keyBytes = decryptBASE64(publicKey);

        // 构造X509EncodedKeySpec对象  
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);

        // KEY_ALGORITHM 指定的加密算法  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

        // 取公钥匙对象  
        PublicKey pubKey = keyFactory.generatePublic(keySpec);

        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(pubKey);
        signature.update(data);

        // 验证签名是否正常  
        return signature.verify(decryptBASE64(sign));
    }

    /**
     * 解密<br> 
     * 用私钥解密 
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(byte[] data, String key)
            throws Exception {
        // 对密钥解密  
        byte[] keyBytes = decryptBASE64(key);

        // 取得私钥  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 对数据解密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);

        return cipher.doFinal(data);
    }

    /**
     * 解密<br> 
     * 用公钥解密 
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPublicKey(byte[] data, String key)
            throws Exception {
        // 对密钥解密  
        byte[] keyBytes = decryptBASE64(key);

        // 取得公钥  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);

        // 对数据解密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicKey);

        return cipher.doFinal(data);
    }

    /**
     * 加密<br> 
     * 用公钥加密 
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(byte[] data, String key)
            throws Exception {
        // 对公钥解密  
        byte[] keyBytes = decryptBASE64(key);

        // 取得公钥  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);

        // 对数据加密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);

        return cipher.doFinal(data);
    }

    /**
     * 加密<br> 
     * 用私钥加密 
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPrivateKey(byte[] data, String key)
            throws Exception {
        // 对密钥解密  
        byte[] keyBytes = decryptBASE64(key);

        // 取得私钥  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 对数据加密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);

        return cipher.doFinal(data);
    }

    /**
     * 取得私钥 
     *
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static String getPrivateKey(Map<String, Object> keyMap)
            throws Exception {
        Key key = (Key) keyMap.get(PRIVATE_KEY);

        return encryptBASE64(key.getEncoded());
    }

    /**
     * 取得公钥 
     *
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static String getPublicKey(Map<String, Object> keyMap)
            throws Exception {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return encryptBASE64(key.getEncoded());
    }

    /**
     * 初始化密钥 
     *
     * @return
     * @throws Exception
     */
    public static Map<String, Object> initKey() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator
                .getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(2048);

        KeyPair keyPair = keyPairGen.generateKeyPair();

        // 公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

        // 私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

        Map<String, Object> keyMap = new HashMap<>(2);

        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }

}