// Copyright 2012 Citrix Systems, Inc. Licensed under the
// Apache License, Version 2.0 (the "License"); you may not use this
// file except in compliance with the License.  Citrix Systems, Inc.
// reserves all rights not expressly granted by the License.
// You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// 
// Automatically generated by addcopyright.py at 04/03/2012
package com.cloud.consoleproxy;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

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

import org.apache.commons.codec.binary.Base64;
import org.apache.log4j.Logger;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * 
 * @author Kelven Yang
 * A simple password based encyrptor based on DES. It can serialize simple POJO object into URL safe string
 * and deserialize it back.
 * 
 */
public class ConsoleProxyPasswordBasedEncryptor {
	private static final Logger s_logger = Logger.getLogger(ConsoleProxyPasswordBasedEncryptor.class);
	
	private String password;
	private Gson gson;
	
	public ConsoleProxyPasswordBasedEncryptor(String password) {
		this.password = password;
		gson = new GsonBuilder().create();
	}
	
	public String encryptText(String text) {
		if(text == null || text.isEmpty())
			return text;
		
		assert(password != null);
		assert(!password.isEmpty());
		
		try {
			Cipher cipher = Cipher.getInstance("DES");
			int maxKeySize = 8;
			SecretKeySpec keySpec = new SecretKeySpec(normalizeKey(password.getBytes(), maxKeySize), "DES");
			cipher.init(Cipher.ENCRYPT_MODE, keySpec);
			byte[] encryptedBytes = cipher.doFinal(text.getBytes());
			return Base64.encodeBase64URLSafeString(encryptedBytes);
		} catch (NoSuchAlgorithmException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (NoSuchPaddingException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (IllegalBlockSizeException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (BadPaddingException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (InvalidKeyException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		}
	}

	public String decryptText(String encryptedText) {
		if(encryptedText == null || encryptedText.isEmpty())
			return encryptedText;

		assert(password != null);
		assert(!password.isEmpty());

		try {
			Cipher cipher = Cipher.getInstance("DES");
            int maxKeySize = 8;
			SecretKeySpec keySpec = new SecretKeySpec(normalizeKey(password.getBytes(), maxKeySize), "DES");
			cipher.init(Cipher.DECRYPT_MODE, keySpec);
			
			byte[] encryptedBytes = Base64.decodeBase64(encryptedText);
			return new String(cipher.doFinal(encryptedBytes));
		} catch (NoSuchAlgorithmException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (NoSuchPaddingException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (IllegalBlockSizeException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (BadPaddingException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		} catch (InvalidKeyException e) {
			s_logger.error("Unexpected exception ", e);
			return null;
		}
	}
	
	public <T> String encryptObject(Class<?> clz, T obj) {
		if(obj == null)
			return null;
		
		String json = gson.toJson(obj);
		return encryptText(json);
	}
	
	@SuppressWarnings("unchecked")
	public <T> T decryptObject(Class<?> clz, String encrypted) {
		if(encrypted == null || encrypted.isEmpty())
			return null;
		
		String json = decryptText(encrypted);
		return (T)gson.fromJson(json, clz);
	}
	
	private static byte[] normalizeKey(byte[] keyBytes, int keySize) {
		assert(keySize > 0);
		byte[] key = new byte[keySize];
		
		for(int i = 0; i < keyBytes.length; i++)
			key[i%keySize] ^= keyBytes[i];
		
		return key;
	}
}