/**
    * Copyright 2005-2011 The Kuali Foundation
    *
    * Licensed under the Educational Community License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.opensource.org/licenses/ecl2.php
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.kuali.rice.ksb.security;
  
  import java.io.BufferedOutputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.security.GeneralSecurityException;
  
  import javax.servlet.ServletOutputStream;
  
  /**
   * An OutputStream which decorates another OutputStream with a wrapper that digitally
   * signs the data when the OutputStream is closed.  Since this class does not know where
   * the resulting digital signature will reside, a DigitalSigner will be invoked to
   * execute the actual signing of the message (i.e. put it in a header).
   * 
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class SignatureSigningOutputStream extends ServletOutputStream {
  
  	private boolean delayWrite;
  	private DigitalSigner signer;
  	private BufferedOutputStream bufferedDataHoldingStream;
  	private ByteArrayOutputStream dataHoldingStream;
  	private OutputStream wrappedOutputStream;
  	
  	/**
  	 * Constructs a SignatureSigningOutputStream with the given DigitalSigner and underlying OutputStream.
  	 * If true, the delayWrite boolean indicates that the stream should store all data internally until the
  	 * stream is closed, at which point it should forward all data to the wrapped OutputStream.  If delayWrite
  	 * is false, then the data will be forwarded immediately.
  	 */
  	public SignatureSigningOutputStream(DigitalSigner signer, OutputStream wrappedOutputStream, boolean delayWrite) {
  		super();
  		this.delayWrite = delayWrite;
  		if (delayWrite) {
  		    this.dataHoldingStream = new ByteArrayOutputStream();
  		    this.bufferedDataHoldingStream = new BufferedOutputStream(this.dataHoldingStream);
  		}
  		this.wrappedOutputStream = wrappedOutputStream;
  		this.signer = signer;
  	}
  
  	public void write(int data) throws IOException {
  		if (this.delayWrite) {
  		    this.bufferedDataHoldingStream.write(data);
  		} else {
  		    this.wrappedOutputStream.write(data);
  		}
  		try {
  		    this.signer.getSignature().update((byte)data);	
  		} catch (GeneralSecurityException e) {
  			IOException exception = new IOException("Error updating signature.");
  			exception.initCause(e);
  			throw exception;
  		}
  	}
  	
  	@Override
  	public void close() throws IOException {
  		// before we close, sign the message
  		try {
  		    this.signer.sign();
  			if (this.delayWrite) {
  			    this.bufferedDataHoldingStream.close();
  				byte[] data = this.dataHoldingStream.toByteArray();
  				for (int index = 0; index < data.length; index++) {
  				    this.wrappedOutputStream.write(data[index]);
  				}
  			}
  			this.wrappedOutputStream.close();
  		} catch (Exception e) {
  			IOException exception = new IOException("Error attaching digital signature to outbound response.");
  			exception.initCause(e);
  			throw exception;
  		} finally {
  			super.close();
  		}
  	}
  
  }