package elte.java2_utikalauz5.crypto;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

/**
Rejtjelezett adatfolyamok.

@link.forrásfájl {@docRoot}/../data/crypto/src Crypt.java
@link.letöltés {@docRoot}/../data/crypto Crypt.jar
@since Java 2 Útikalauz programozóknak 5.0
*/
public class Crypt {
    private static final int ITERATION_COUNT = 42/2;

    private static final byte[] SALT = {0x42, 0x21, 0x42, 0x21, 0x42, 0x21, 0x42, 0x21};

    private final boolean   isEncrpyt;
    private final String    password;
    private final InputStream is;
    private final OutputStream os;

    public Crypt(boolean isEncrypt, String password, String inFileName, String outFileName) throws Exception {
        this.password   = password;
        this.isEncrpyt  = isEncrypt;

        FileInputStream fis = new FileInputStream(new File(inFileName));

        File outFile = new File(outFileName);
        outFile.createNewFile();
        FileOutputStream fos = new FileOutputStream(outFile);

        SecretKeyFactory skf = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        KeySpec keySpec = new PBEKeySpec(password.toCharArray());
        AlgorithmParameterSpec params = new PBEParameterSpec(SALT, ITERATION_COUNT);
        SecretKey key = skf.generateSecret(keySpec);

        Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");

        if( isEncrypt ) {
            cipher.init(Cipher.ENCRYPT_MODE, key, params);
            this.is = fis;
            this.os = new CipherOutputStream(fos,cipher);
        } else {
            cipher.init(Cipher.DECRYPT_MODE, key, params);
            this.os = fos;
            this.is = new CipherInputStream(fis,cipher);
        }
    }

    private void close() throws IOException {
        try {
            if( null != is ) {
                is.close();
            }
        } finally {
            if( null != os ) {
                os.close();
            }
        }
    }

    private void copy() throws IOException {
        byte[] buffer = new byte[10000];
        int i;
        while( (i = is.read(buffer )) > -1 ) {
            os.write(buffer,0,i);
        }
    }


    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws Exception {
        Crypt c = parseArgs(args);

        try {
            c.copy();
        } finally {
            c.close();
        }
    }

    private static final String PASSWORD_SWITCH = "--password:";
    private static final String DECRYPT_SWITCH = "-d";
    private static Crypt parseArgs(String[] args) throws Exception {
        String password = null;
        String inFileName = null;
        String outFileName = null;
        boolean isEncrypt  = true;

        for( String arg: args ) {
            if( arg.startsWith("-")) {
                if( arg.startsWith(PASSWORD_SWITCH)) {
                    password = arg.substring(PASSWORD_SWITCH.length());
                } else if( arg.equals(DECRYPT_SWITCH)) {
                    isEncrypt = false;
                } else {
                    error("Unrecognized option: " + arg, -1);
                }
            } else if( null == inFileName ) {
                inFileName = arg;
            } else if( null == outFileName ) {
                outFileName = arg;
            } else {
                error("Too many file names: " + arg, -1);
            }
        }
        if( (null == password) || (null == inFileName) || (null == outFileName) ) {
            error("Missing argument!", -1);
        }

        return new Crypt(isEncrypt, password, inFileName, outFileName);
    }
    private static void error(String message, int exitCode) {
        if( null != message ) {
            System.err.println(message+"\n");
        }
        System.err.println("Usage:");
        System.err.println("\tCrypt [-d] --password:<password> <inputfile> <outputfile>");
        System.exit(exitCode);
    }

}