/*
 * Copyright (c) 2003,2009 Declarative Engineering LLC.
 * All rights reserved.  This program and the accompanying materials
 * are made available under the terms of the Declarative Engineering LLC
 * verson 1 which accompanies this distribution, and is available at
 * http://declarativeengineering.com/legal/DE_Developer_License_v1.txt
 */
package com.common.io;

import java.io.OutputStream;
import java.io.IOException;
import com.common.security.*;

/*
 * This class allows an asymmetric stream to be plugged into an output stream so that written bytes are encrypted using the public key.
 */
public abstract class CryptoOutputStream extends OutputStream implements IOutputStream {
	protected OutputStream stream = null;
	protected int encryptionCount;
	protected byte[] encryptedBuffer = null;
	protected byte[] decryptedBuffer = null;
	protected int decryptedBufferOffset = 0;
/**
 * CryptoOutputStream constructor.
 */
public CryptoOutputStream(OutputStream stream, IAlgorithm algorithm) {
	super();

	if(stream == null) {
		throw new IllegalArgumentException("Must provide a valid output stream.");
	}//if//
	else if(algorithm == null) {
		throw new IllegalArgumentException("Must provide a valid algorithm.");
	}//if//

	this.stream = stream;
}//CryptoOutputStream()//
/* (non-Javadoc)
 * @see com.common.io.IOutputStream#canEncrypt()
 */
public boolean canEncrypt() {
	return true;
}//canEncrypt()//
/* (non-Javadoc)
 * @see java.io.OutputStream#close()
 */
public void close() throws IOException {
	while(isEncrypting()) {
		encrypt(false);
	}//while//
	
	super.close();
	stream.close();
}//close()//
/**
 * Empties the buffer containing to-be encrypted data.
 */
protected void emptyBuffer() throws IOException {
	if(decryptedBufferOffset > 0) {
		int size = encrypt(decryptedBuffer, 0, decryptedBufferOffset, encryptedBuffer, 0);

		//Write the block header.//
		stream.write(0xFF);
		//Write the encrypted size.//
		StreamSupport.writeInt(size, stream);
		//Write the block data.//
		stream.write(encryptedBuffer, 0, size);
		//Reset the block indexes.//
		decryptedBufferOffset = 0;
	}//if//
}//emptyBuffer()//
/**
 * Encrypts or signs the data.
 * @param data The buffer containing unencrypted data.
 * @param dataOffset The index of the first unencrypted byte.
 * @param dataLength The number of unencrypted data bytes.
 * @param output A buffer to contain the encrypted data.
 * @param outputOffset The location of the first encrypted byte in the output buffer.
 * @return The number of encrypted bytes (includes formatting and padding).
 */
protected abstract int encrypt(byte[] data, int dataOffset, int dataLength, byte[] output, int outputOffset);
/* (non-Javadoc)
 * @see com.common.io.IOutputStream#encrypt(boolean)
 */
public void encrypt(boolean encrypt) throws IOException {
	if(encrypt) {
		//Flush any unencrypted data before beginning an encrypted segment.//
		if(encryptionCount == 0) {
//TODO: Should flush data from all wrappering streams.  This isn't possible with the current "pipe" design pattern for streams.//
		}//if//
		
		encryptionCount++;
	}//if//
	else {
		encryptionCount--;
		
		if(encryptionCount == 0) {
//TODO: Should flush data from all wrappering streams.  This isn't possible with the current "pipe" design pattern for streams.//
			//Empty the buffer and end the encrypted segment.//
			emptyBuffer();
			stream.write(0xF0);
		}//if//
	}//else//
}//encrypt()//
/* (non-Javadoc)
 * @see java.io.OutputStream#flush()
 */
public void flush() throws IOException {
	/* This could cause a lot of unnecessary padding.
	if(encryptionCount > 0) {
		emptyBuffer();
	}//if//
	*/
	stream.flush();
}//flush()//
/* (non-Javadoc)
 * @see com.common.io.IOutputStream#isEncrypting()
 */
public boolean isEncrypting() {
	return encryptionCount > 0;
}//isEncrypting()//
/* (non-Javadoc)
 * @see java.io.OutputStream#write(byte[], int, int)
 */
public void write(byte[] buffer, int offset, int length) throws IOException {
	if(encryptionCount > 0) {
		int count = 0;
		
		while(count != length) {
			int size = 0;
			
			if(decryptedBufferOffset == decryptedBuffer.length) {
				emptyBuffer();
			}//if//

			size = decryptedBuffer.length - decryptedBufferOffset;

			if(size > length - count) {
				size = length - count;
			}//if//

			System.arraycopy(buffer, offset + count, decryptedBuffer, decryptedBufferOffset, size);
			count += size;
			decryptedBufferOffset += size;
		}//while//
	}//if//
	else {
		stream.write(buffer, offset, length);
	}//else//
}//write()//
/* (non-Javadoc)
 * @see java.io.OutputStream#write(int)
 */
public void write(int b) throws IOException {
	if(encryptionCount > 0) {
		if(decryptedBufferOffset == decryptedBuffer.length) {
			emptyBuffer();
		}//if//

		decryptedBuffer[decryptedBufferOffset++] = (byte) b;
	}//if//
	else {
		stream.write(b);
	}//else//
}//write()//
}//CryptoOutputStream//