/*
 * [Wrap.java]
 *
 * Summary: Prepares an object for shipping via HTTP CGI-POST.
 *
 * Copyright: (c) 2004-2017 Roedy Green, Canadian Mind Products, http://mindprod.com
 *
 * Licence: This software may be copied and used freely for any purpose but military.
 *          http://mindprod.com/contact/nonmil.html
 *
 * Requires: JDK 1.8+
 *
 * Created with: JetBrains IntelliJ IDEA IDE http://www.jetbrains.com/idea/
 *
 * Version History:
 *  1.4 2006-03-05 reformat with IntelliJ and add Javadoc.
 */
package com.mindprod.transporter;

import com.mindprod.base64.Base64u;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.zip.GZIPOutputStream;

/**
 * Prepares an object for shipping via HTTP CGI-POST.
 * <p/>
 * Serialised, compressed, and Base64u armoured.
 * No encryption or signing. See Transporter.java for example of use.
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 1.4 2006-03-05 reformat with IntelliJ and add Javadoc.
 * @since 2004-06-06
 */
public class Wrap
    {
    /**
     * used to add armouring
     */
    final Base64u armourer;

    /**
     * constructor
     */
    public Wrap()
        {
        armourer = new Base64u();
        armourer.setLineLength( Integer.MAX_VALUE );
        armourer.setLineSeparator( "\n" );
        }

    /**
     * add ASCII base64u armouring to a message of bytes to prepare it for transport.
     *
     * @param raw raw bytes.
     *
     * @return Printable ASCII armoured message.
     */
    protected String armour( byte[] raw )
        {
        return armourer.encode( raw );
        }

    /**
     * Compress message with GZIP compression.
     *
     * @param message uncompressed message.
     *
     * @return compressed message.
     * @throws IOException
     */
    protected byte[] compress( byte[] message ) throws IOException
        {
        // O P E N
        // will grow if needed.
        ByteArrayOutputStream baos =
                new ByteArrayOutputStream( message.length );
        GZIPOutputStream gzos =
                new GZIPOutputStream( baos, 4 * 1024 );
        // W R I T E
        gzos
                .write( message, 0
                        /* offset */, message.length
                        /* bytes to write */ );
        gzos.finish();
        gzos.flush();
        byte[] compressedMessage = baos.toByteArray();
        // C L O S E
        gzos.close();
        return compressedMessage;
        }

    /**
     * Serialise an object for sending
     *
     * @param o Object to serialize
     *
     * @return Pickled object as a byte array.
     * @throws IOException if cannot serialise the object
     */
    protected byte[] serialize( Object o ) throws IOException
        {
        // O P E N
        // will grow if needed.
        ByteArrayOutputStream baos =
                new ByteArrayOutputStream( Tools.TYPICAL_MESSAGE_SIZE );
        ObjectOutputStream oos = new ObjectOutputStream( baos );
        // W R I T E
        oos.writeObject( o );
        oos.flush();
        byte[] pickled = baos.toByteArray();
        // C L O S E
        oos.close();
        return pickled;
        }

    /**
     * Wraps object for sending via CGI Post, serialised, compressed, and base64u encoded. Does not build parm=value.
     *
     * @param o Object to wrap for sending.
     *
     * @return base64u-encoded string to send.
     * @throws IOException if cannot wrate the serialisable object.
     */
    public String wrap( Serializable o ) throws IOException
        {
        return armour( compress( serialize( o ) ) );
        }
    }