/*
 *  ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one or more
 *    contributor license agreements.  See the NOTICE file distributed with
 *    this work for additional information regarding copyright ownership.
 *    The ASF licenses this file to You under the Apache License, Version 2.0
 *    (the "License"); you may not use this file except in compliance with
 *    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.
 * ====================================================================
 */

package org.apache.poi.poifs.crypt.temp;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.spec.SecretKeySpec;

import org.apache.poi.poifs.crypt.ChainingMode;
import org.apache.poi.poifs.crypt.CipherAlgorithm;
import org.apache.poi.poifs.crypt.CryptoFunctions;
import org.apache.poi.util.Beta;
import org.apache.poi.xssf.streaming.SheetDataWriter;

@Beta
public class SheetDataWriterWithDecorator extends SheetDataWriter {
    static final CipherAlgorithm cipherAlgorithm = CipherAlgorithm.aes128;
    SecretKeySpec skeySpec;
    byte[] ivBytes;

    public SheetDataWriterWithDecorator() throws IOException {
        super();
    }

    void init() {
        if(skeySpec == null) {
            SecureRandom sr = new SecureRandom();
            ivBytes = new byte[16];
            byte[] keyBytes = new byte[16];
            sr.nextBytes(ivBytes);
            sr.nextBytes(keyBytes);
            skeySpec = new SecretKeySpec(keyBytes, cipherAlgorithm.jceId);
        }
    }

    @Override
    protected OutputStream decorateOutputStream(FileOutputStream fos) {
        init();
        Cipher ciEnc = CryptoFunctions.getCipher(skeySpec, cipherAlgorithm, ChainingMode.cbc, ivBytes, Cipher.ENCRYPT_MODE, "PKCS5Padding");
        return new CipherOutputStream(fos, ciEnc);
    }

    @Override
    protected InputStream decorateInputStream(FileInputStream fis) {
        Cipher ciDec = CryptoFunctions.getCipher(skeySpec, cipherAlgorithm, ChainingMode.cbc, ivBytes, Cipher.DECRYPT_MODE, "PKCS5Padding");
        return new CipherInputStream(fis, ciDec);
    }
}