package elte.java2_utikalauz5.crypto;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SealedObject;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;

/**
Rejtjelezett objektumok.

@link.forrásfájl {@docRoot}/../data/crypto/src Codec.java
@link.letöltés {@docRoot}/../data/crypto Codec.jar
@since Java 2 Útikalauz programozóknak 5.0
*/
public class Codec {

    private static final String DECODE_COMMAND = "decode";

    private static final String ENCODE_COMMAND = "encode";

    public static void main(String[] args) throws Exception {
        parseArgs(args);
    }

    private static void parseArgs(String[] args) throws Exception {
        if (args.length < 1) {
            help(null, -1);
        }
        if (args[0].equalsIgnoreCase(ENCODE_COMMAND)) {
            if (args.length < 4) {
                help("Missing argument!", -1);
            }
            encode(args[1], args[2], args[3]);
        } else if (args[0].equalsIgnoreCase(DECODE_COMMAND)) {
            if (args.length < 3) {
                help("Missing argument!", -1);
            }
            decode(args[1], args[2]);

        } else {
            help("Unrecognized command: " + args[0], -1);
        }
    }

    private static void encode(String password, String outFileName,
            String message) throws Exception {
        SealedObject so = createSealedObject(password, message);
        File outFile = new File(outFileName);
        ObjectOutputStream oos = null;
        try {
            outFile.createNewFile();
            oos = new ObjectOutputStream(new FileOutputStream(outFile));
            oos.writeObject(so);
        } finally {
            if (null != oos) {
                oos.close();
            }
        }
    }

    private static void decode(String password, String inFileName) throws Exception {
        File inFile = new File(inFileName);
        ObjectInputStream ois = null;
        try {
            ois = new ObjectInputStream(new FileInputStream(inFile));
            SealedObject so = (SealedObject) ois.readObject();
            Object data = decrypSealedObject(password, so);
            System.out.println(data.toString());
        } finally {
            if( null != ois ) {
                ois.close();
            }
        }

    }

    private static Object decrypSealedObject(String password, SealedObject so) throws Exception {
        SecretKeyFactory skf = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        KeySpec keySpec = new PBEKeySpec(password.toCharArray());
        SecretKey key = skf.generateSecret(keySpec);
        return so.getObject(key);
    }

    private static SealedObject createSealedObject(String password,
            Serializable data) throws NoSuchAlgorithmException,
            InvalidKeySpecException, NoSuchPaddingException,
            IllegalBlockSizeException, IOException, InvalidKeyException {

        SecretKeyFactory skf = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        KeySpec keySpec = new PBEKeySpec(password.toCharArray());
        SecretKey key = skf.generateSecret(keySpec);
        Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        SealedObject so = new SealedObject(data, cipher);
        return so;
    }

    private static void help(String message, int exitCode) {
        if (null != message) {
            System.err.println(message);
        }
        System.err.println("Usage:");
        System.err.println("\tCodec encode <password> <outfile> <message>");
        System.err.println("or\tCodec decode <password> <infile>");
        System.exit(exitCode);
    }

}