package stackoverflow;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

/**
 * @author TheLima
 */
public class Q_13271184 {

	private static final File DESKTOP =
					new File(System.getProperty("user.home") + "/Desktop");
	private static final File BASE_PDF = new File(DESKTOP, "Placas_teste.pdf");
	private static final byte[] SALT = {
		(byte) 0xde, (byte) 0x33, (byte) 0x10, (byte) 0x12,
		(byte) 0xde, (byte) 0x33, (byte) 0x10, (byte) 0x12,};
	private static final char[] KEY = "Just A Key For Testing".toCharArray();

	/**
	 * @param args the command line arguments
	 */
	public static void main(String[] args) throws GeneralSecurityException, IOException {
		byte[] content = readFile(BASE_PDF);
		System.out.println("ORIGINAL: " + new String(content).substring(0, 8));
		byte[] encrypted = encrypt(content);
		System.out.println("ENCRYPTED: " + new String(encrypted).substring(0, 8));
		File encryptedFile = new File(DESKTOP, "EncryptedPDF.pdf");
		saveFile(encrypted, encryptedFile);
		content = readFile(encryptedFile);
		byte[] decrypted = decrypt(content);
		System.out.println("DECRYPTED: " + new String(decrypted).substring(0, 8));
		File decryptedFile = new File(DESKTOP, "DecryptedPDF.pdf");
		saveFile(decrypted, decryptedFile);
	}

	private static byte[] encrypt(byte[] bytes) throws GeneralSecurityException {
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
		SecretKey key = keyFactory.generateSecret(new PBEKeySpec(KEY));
		Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
		pbeCipher.init(Cipher.ENCRYPT_MODE, key, new PBEParameterSpec(SALT, 20));

		//Encrypt and save to temporary storage.
		byte[] encrypted = pbeCipher.doFinal(bytes);

		//Cleanup data-sources - Leave no traces behind.
		for (int i = 0; i < bytes.length; i++) {
			bytes[i] = 0;
		}
		bytes = null;
		System.gc();

		//Return encryption result.
		return encrypted;
	}

	private static byte[] decrypt(byte[] bytes) throws GeneralSecurityException {
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
		SecretKey key = keyFactory.generateSecret(new PBEKeySpec(KEY));
		Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
		pbeCipher.init(Cipher.DECRYPT_MODE, key, new PBEParameterSpec(SALT, 20));
		return pbeCipher.doFinal(bytes);
	}

	private static byte[] readFile(File file) {
		byte[] content = null;
		InputStream is;
		try {
			is = new FileInputStream(file);
			BufferedInputStream vf = new BufferedInputStream(is);
			content = new byte[(file.length() <= Integer.MAX_VALUE)
							? (int) file.length() : Integer.MAX_VALUE];
//			content = new byte[is.available()];

			System.out.printf("file.length() : %d\nis.available() : %d",
							file.length(), is.available());

			vf.read(content);
			is.close();
		} catch (FileNotFoundException ex) {
			Logger.getLogger(Q_13271184.class.getName()).log(Level.SEVERE, null, ex);
		} catch (IOException ex) {
			Logger.getLogger(Q_13271184.class.getName()).log(Level.SEVERE, null, ex);
		}
		return content;
	}

	public static void saveFile(byte[] bytes, File file) throws IOException {
		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file));
		bos.write(bytes);
		bos.flush();
		bos.close();
	}
}