/*
 * This file is part of FYReader.
 * FYReader is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * FYReader is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with FYReader.  If not, see <https://www.gnu.org/licenses/>.
 *
 * Copyright (C) 2020 - 2022 fengyuecanzhu
 */

package xyz.fycz.myreader.util;

import java.security.Key;
import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.Cipher;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;

/**
 * 加密解密工具包
 * @author lxp
 */
public class CyptoUtils {

	public static final String ALGORITHM_DES = "DES/CBC/PKCS5Padding";
	
    /**
     * DES算法，加密
     *
     * @param data 待加密字符串
     * @param key  加密私钥，长度不能够小于8位
     * @return 加密后的字节数组，一般结合Base64编码使用
     * @throws Exception
     */
    public static String encode(String key, String data) {
    	if(data == null)
    		return null;
    	try{
	    	DESKeySpec dks = new DESKeySpec(key.getBytes());
	    	SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
	        //key的长度不能够小于8位字节
	        Key secretKey = keyFactory.generateSecret(dks);
	        Cipher cipher = Cipher.getInstance(ALGORITHM_DES);
	        IvParameterSpec iv = new IvParameterSpec("12345678".getBytes());
	        AlgorithmParameterSpec paramSpec = iv;
	        cipher.init(Cipher.ENCRYPT_MODE, secretKey,paramSpec);
	        byte[] bytes = cipher.doFinal(data.getBytes());            
	        return byte2hex(bytes);
    	}catch(Exception e){
    		e.printStackTrace();
    		return data;
    	}
    }
	/**
	 * DES算法，加密
	 *
	 * @param data 待加密字符串
	 * @param key  加密私钥，长度不能够小于8位
	 * @return 加密后的字节数组，一般结合Base64编码使用
	 * @throws Exception
	 */
	public static byte[] encode(String key, byte[] data) {
		if(data == null)
			return null;
		try{
			DESKeySpec dks = new DESKeySpec(key.getBytes());
			SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
			//key的长度不能够小于8位字节
			Key secretKey = keyFactory.generateSecret(dks);
			Cipher cipher = Cipher.getInstance(ALGORITHM_DES);
			IvParameterSpec iv = new IvParameterSpec("12345678".getBytes());
			AlgorithmParameterSpec paramSpec = iv;
			cipher.init(Cipher.ENCRYPT_MODE, secretKey,paramSpec);
			byte[] bytes = cipher.doFinal(data);
			return bytes;
		}catch(Exception e){
			e.printStackTrace();
			return null;
		}
	}

    /**
     * DES算法，解密
     *
     * @param data 待解密字符串
     * @param key  解密私钥，长度不能够小于8位
     * @return 解密后的字节数组
     * @throws Exception 异常
     */
    public static String decode(String key, String data) {
    	if(data == null)
    		return null;
        try {
	    	DESKeySpec dks = new DESKeySpec(key.getBytes());
	    	SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
            //key的长度不能够小于8位字节
            Key secretKey = keyFactory.generateSecret(dks);
            Cipher cipher = Cipher.getInstance(ALGORITHM_DES);
            IvParameterSpec iv = new IvParameterSpec("12345678".getBytes());
            AlgorithmParameterSpec paramSpec = iv;
            cipher.init(Cipher.DECRYPT_MODE, secretKey, paramSpec);
            return new String(cipher.doFinal(hex2byte(data.getBytes())));
        } catch (Exception e){
    		e.printStackTrace();
    		return data;
        }
    }
	/**
	 * DES算法，解密
	 *
	 * @param data 待解密字符串
	 * @param key  解密私钥，长度不能够小于8位
	 * @return 解密后的字节数组
	 * @throws Exception 异常
	 */
	public static byte[] decodeToByte(String key, byte[] data) {
		if(data == null)
			return null;
		try {
			DESKeySpec dks = new DESKeySpec(key.getBytes());
			SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
			//key的长度不能够小于8位字节
			Key secretKey = keyFactory.generateSecret(dks);
			Cipher cipher = Cipher.getInstance(ALGORITHM_DES);
			IvParameterSpec iv = new IvParameterSpec("12345678".getBytes());
			AlgorithmParameterSpec paramSpec = iv;
			cipher.init(Cipher.DECRYPT_MODE, secretKey, paramSpec);
			return cipher.doFinal(hex2byte(data));
		} catch (Exception e){
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 二行制转字符串
	 * @param b
	 * @return
	 */
    private static String byte2hex(byte[] b) {
		StringBuilder hs = new StringBuilder();
		String stmp;
		for (int n = 0; b!=null && n < b.length; n++) {
			stmp = Integer.toHexString(b[n] & 0XFF);
			if (stmp.length() == 1)
				hs.append('0');
			hs.append(stmp);
		}
		return hs.toString().toUpperCase();
	}
    
    private static byte[] hex2byte(byte[] b) {
        if((b.length%2)!=0)
            throw new IllegalArgumentException();
		byte[] b2 = new byte[b.length/2];
		for (int n = 0; n < b.length; n+=2) {
		    String item = new String(b,n,2);
		    b2[n/2] = (byte) Integer.parseInt(item,16);
		}
        return b2;
    }
    
}
