/*
 * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
 * Please refer to the LICENSE.txt for licensing details.
 */
package ch.ethz.ssh2.crypto.cipher;

import java.io.IOException;
import java.io.OutputStream;

/**
 * CipherOutputStream.
 *
 * @author Christian Plattner
 * @version $Id: CipherOutputStream.java 85 2014-04-07 14:05:09Z dkocher@sudo.ch $
 */
public class CipherOutputStream {
    BlockCipher currentCipher;
    OutputStream bo;
    byte[] buffer;
    byte[] enc;
    int blockSize;
    int pos;

    /*
     * We cannot use java.io.BufferedOutputStream, since that is not available
     * in J2ME. Everything could be improved here alot.
     */

    private static final int BUFF_SIZE = 8192;
    byte[] out_buffer = new byte[BUFF_SIZE];
    int out_buffer_pos = 0;

    public CipherOutputStream(BlockCipher tc, OutputStream bo) {
        this.bo = bo;
        changeCipher(tc);
    }

    private void internal_write(byte[] src, int off, int len) throws IOException {
        while (len > 0) {
            int space = BUFF_SIZE - out_buffer_pos;
            int copy = (len > space) ? space : len;
            System.arraycopy(src, off, out_buffer, out_buffer_pos, copy);
            off += copy;
            out_buffer_pos += copy;
            len -= copy;

            if (out_buffer_pos >= BUFF_SIZE) {
                bo.write(out_buffer, 0, BUFF_SIZE);
                out_buffer_pos = 0;
            }
        }
    }

    private void internal_write(int b) throws IOException {
        out_buffer[out_buffer_pos++] = (byte) b;

        if (out_buffer_pos >= BUFF_SIZE) {
            bo.write(out_buffer, 0, BUFF_SIZE);
            out_buffer_pos = 0;
        }
    }

    public void flush() throws IOException {
        if (pos != 0) {
            throw new IOException("FATAL: cannot flush since crypto buffer is not aligned.");
        }

        if (out_buffer_pos > 0) {
            bo.write(out_buffer, 0, out_buffer_pos);
            out_buffer_pos = 0;
        }

        bo.flush();
    }

    public void changeCipher(BlockCipher bc) {
        this.currentCipher = bc;
        blockSize = bc.getBlockSize();
        buffer = new byte[blockSize];
        enc = new byte[blockSize];
        pos = 0;
    }

    private void writeBlock() throws IOException {
        try {
            currentCipher.transformBlock(buffer, 0, enc, 0);
        }
        catch (Exception e) {
            throw new IOException("Error while decrypting block.", e);
        }

        internal_write(enc, 0, blockSize);
        pos = 0;
    }

    public void write(byte[] src, int off, int len) throws IOException {
        while (len > 0) {
            int avail = blockSize - pos;
            int copy = Math.min(avail, len);
            System.arraycopy(src, off, buffer, pos, copy);
            pos += copy;
            off += copy;
            len -= copy;

            if (pos >= blockSize) {
                writeBlock();
            }
        }
    }

    public void write(int b) throws IOException {
        buffer[pos++] = (byte) b;

        if (pos >= blockSize) {
            writeBlock();
        }
    }

    public void writePlain(int b) throws IOException {
        if (pos != 0) {
            throw new IOException("Cannot write plain since crypto buffer is not aligned.");
        }

        internal_write(b);
    }

    public void writePlain(byte[] b, int off, int len) throws IOException {
        if (pos != 0) {
            throw new IOException("Cannot write plain since crypto buffer is not aligned.");
        }

        internal_write(b, off, len);
    }
}