/*
 * $Id: PDFOutput.java,v 1.3 2007/09/22 12:48:16 gil1 Exp $
 *
 * $Date: 2007/09/22 12:48:16 $
 *
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 */
package gnu.jpdf;

import java.io.*;
import java.util.*;

/**
 * This class is used to write a PDF document. It acts as a wrapper
 * to a real OutputStream, but is necessary for certain internal PDF
 * structures to be built correctly.
 *
 * @author Peter T. Mount
 * @author Eric Z. Beard, ericzbeard@hotmail.com
 * @version $Revision: 1.3 $, $Date: 2007/09/22 12:48:16 $
 */
public class PDFOutput
{
  /**
   * This is the actual OutputStream used to write to.
   */
  protected OutputStream os;
  
  /**
   * This is the OutputStream used to write each object to.
   *
   * <p>We use a separate stream, because we need to keep track of how
   * many bytes have been written for each object for the xref table to
   * work correctly.
   */
  protected ByteArrayOutputStream baos;
  
  /**
   * This is the current position within the stream
   */
  protected int offset;
  
  /**
   * This vector contains offsets of each object
   */
  protected Vector<PDFXref> offsets;
  
  /**
   * This is used to track the /Root object (catalog)
   */
  protected PDFObject rootID;
  
  /**
   * This is used to track the /Info object (info)
   */
  protected PDFObject infoID;
  
  /**
   * This creates a PDF OutputStream
   *
   * @param os The output stream to write the PDF file to.
   * @throws IOException if there is an I/O error.
   */
  public PDFOutput(OutputStream os) throws IOException
  {
    this.os = os;
    offset = 0;
    offsets = new Vector<PDFXref>();
    baos = new ByteArrayOutputStream();
    
    // Now write the PDF header
    //
    // Note: As the encoding is fixed here, we use getBytes().
    //
    baos.write("%PDF-1.2\n".getBytes());
    
    // This second comment is advised in the PDF Reference manual
    // page 61
    baos.write("%\342\343\317\323\n".getBytes());
    
    offset = baos.size();
    baos.writeTo(os);
  }
  
  /**
   * This method writes a PDFObject to the stream.
   *
   * @param ob PDFObject Obeject to write
   * @exception IOException on error
   */
  protected void write(PDFObject ob) throws IOException
  {
    // Check the object to see if it's one that is needed in the trailer
    // object
    if(ob instanceof PDFCatalog)   rootID=ob;
    if(ob instanceof PDFInfo)              infoID=ob;
    
    offsets.addElement(new PDFXref(ob.getSerialID(),offset));
    baos.reset();
    ob.write(baos);
    offset+=baos.size();
    baos.writeTo(os);
  }
  
  /**
   * This closes the Stream, writing the xref table
   */
  protected void close() throws IOException
  {
    // Make sure everything is written
    os.flush();
    
    // we use baos to speed things up a little.
    // Also, offset is preserved, and marks the begining of this block.
    // This is required by PDF at the end of the PDF file.
    baos.reset();
    baos.write("xref\n".getBytes());
    
    // Now a single subsection for object 0
    //baos.write("0 1\n0000000000 65535 f \n".getBytes());
    
    // Now scan through the offsets list. The should be in sequence,
    // but just in case:
    int firstid = 0;                    // First id in block
    int lastid = -1;                    // The last id used
    Vector<PDFXref> block = new Vector<PDFXref>();        // xrefs in this block
    
    // We need block 0 to exist
    block.addElement(new PDFXref(0,0,65535));
    
    for(PDFXref x : offsets) {
      
      if(firstid==-1) firstid=x.id;
      
      // check to see if block is in range (-1 means empty)
      if(lastid>-1 && x.id != (lastid+1)) {
        // no, so write this block, and reset
        writeblock(firstid,block);
        block.removeAllElements();
        firstid=-1;
      }
      
      // now add to block
      block.addElement(x);
      lastid = x.id;
    }
    
    // now write the last block
    if(firstid>-1)
      writeblock(firstid,block);
    
    // now the trailer object
    baos.write("trailer\n<<\n".getBytes());
    
    // the number of entries (REQUIRED)
    baos.write("/Size ".getBytes());
    baos.write(Integer.toString(offsets.size()+1).getBytes());
    baos.write("\n".getBytes());
    
    // the /Root catalog indirect reference (REQUIRED)
    if(rootID != null) {
      baos.write("/Root ".getBytes());
      baos.write(rootID.toString().getBytes());
      baos.write("\n".getBytes());
    } else
      throw new IOException("Root object is not present in document");
    
    // the /Info reference (OPTIONAL)
    if(infoID != null) {
      baos.write("/Info ".getBytes());
      baos.write(infoID.toString().getBytes());
      baos.write("\n".getBytes());
    }
    
    // end the trailer object
    baos.write(">>\nstartxref\n".getBytes());
    baos.write(Integer.toString(offset).getBytes());
    baos.write("\n%%EOF\n".getBytes());
    
    // now flush the stream
    baos.writeTo(os);
    os.flush();
  }
  
  /**
   * Writes a block of references to the PDF file
   * @param firstid ID of the first reference in this block
   * @param block Vector containing the references in this block
   * @exception IOException on write error
   */
  protected void writeblock(int firstid,Vector<PDFXref> block) throws IOException
  {
    baos.write(Integer.toString(firstid).getBytes());
    baos.write(" ".getBytes());
    baos.write(Integer.toString(block.size()).getBytes());
    baos.write("\n".getBytes());
    //baos.write("\n0000000000 65535 f\n".getBytes());
    
    for(PDFXref x : block) {
      baos.write(x.toString().getBytes());
      baos.write("\n".getBytes());
    }
  }
} // end class PDFOutput
