/**
 * <copyright> Copyright (c) 2006 by Know-Center, Graz, Austria </copyright>
 * 
 * This software is the confidential and proprietary information of Know-Center,
 * Graz, Austria. You shall not disclose such Confidential Information and shall
 * use it only in accordance with the terms of the license agreement you entered
 * into with Know-Center.
 * 
 * KNOW-CENTER MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
 * NON-INFRINGEMENT. KNOW-CENTER SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY
 * LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES.
 * 
 * $Id: TextualSignature.java,v 1.4 2006/10/31 08:12:45 wprinz Exp $
 */
package at.knowcenter.wag.egov.egiz.pdf;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;

import org.pdfbox.pdfparser.PDFParser;
import org.pdfbox.pdmodel.PDDocument;
import org.pdfbox.util.PDFTextStripper;

import at.knowcenter.wag.egov.egiz.cfg.SettingsReader;
import at.knowcenter.wag.egov.egiz.exceptions.PresentableException;

import com.lowagie.text.Document;
import com.lowagie.text.DocumentException;
import com.lowagie.text.Rectangle;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfImportedPage;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfWriter;

/**
 * Contains helper function for textual signatures.
 * 
 * @author wprinz
 */
public class TextualSignature
{

  /**
   * Extracts the document text from a given pdf.
   * 
   * @param pdf_stream
   *          The pdf_input stream.
   * @return Returns the extracted document text.
   * @throws PresentableException
   *           Forwarded exception.
   */
  public static String extractTextTextual(InputStream pdf_stream) throws PresentableException
  {
    try
    {
      // logger_.debug("====================================================");
      // logger_.debug("extractText:");

      // For text extraction, create a temporary object with iText just as the
      // one
      // created
      // when being signed, but of course without adding content.


      byte[] bytes = normalizePDF(pdf_stream);

      ByteArrayInputStream bais = new ByteArrayInputStream(bytes);

      PDFParser parser = new PDFParser(bais);
      File temporary_dir = SettingsReader.getTemporaryDirectory();
      parser.setTempDirectory(temporary_dir);
      parser.parse();

      PDDocument doc = parser.getPDDocument();

      PDFTextStripper stripper = new PDFTextStripper();
      stripper.setSortByPosition(false);
      // stripper.setStartPage(4);
      // stripper.setEndPage(4);
      String text = stripper.getText(doc);

      doc.close();

      // logger_.debug("text.length = " + text.length());
      // logger_.debug("====================================================");

      return text;

    }
    catch (Exception e)
    {
      throw new PresentableException(e);
    }
  }

  /**
   * Normalizes a given binary PDF to a version PDFbox can handle correctly.
   * 
   * <p>
   * PDFbox has serious problems with documents that use incremental updates or
   * XObject forms. Therefor use this to remove incremental updates and create a
   * streamlined document.
   * </p>
   * 
   * <p>
   * Note that this has nothing to do with text normalization. It just unifies
   * the PDF documents that are fed into PDFbox for text extraction and page
   * length determination.
   * </p>
   * 
   * @param input_pdf
   *          The input pdf to be normalized.
   * @return Returns the normalized pdf.
   * @throws IOException
   * @throws DocumentException
   */
  public static byte[] normalizePDF(InputStream input_pdf) throws IOException, DocumentException
  {
    PdfReader reader = new PdfReader(input_pdf);

    ByteArrayOutputStream baos = new ByteArrayOutputStream();

    // For some reason the Reader -> ImportPage -> Writer mechanism produces
    // problems en mass.
    // The text extractor may not be able to extract proper text from
    // documents
    // created with
    // this method (although it works when a Table is appended)... very
    // fragile.

    Document document = new Document();

    PdfWriter writer = PdfWriter.getInstance(document, baos);
    document.open();

    PdfContentByte cb = writer.getDirectContent();
    for (int page_num = 1; page_num <= reader.getNumberOfPages(); page_num++)
    {
      Rectangle new_size = reader.getPageSize(page_num);
      document.setPageSize(new_size);
      document.newPage();

      PdfImportedPage page = writer.getImportedPage(reader, page_num);

      // note that this will add an xobject form to the doc.
      // the xobject form contains the content of the page.
      cb.addTemplate(page, 0, 0);

      // wprinz: debugging
      // cb.beginText();
      // cb.setFontAndSize(BaseFont.createFont(BaseFont.HELVETICA,
      // BaseFont.CP1252, BaseFont.NOT_EMBEDDED), 14);
      // cb.showText("page " + page_num);
      // cb.endText();
      // wprinz: end debugging
    }

    document.close();

    // for (int i = 1; i <= reader.getNumberOfPages(); i++)
    // {
    // Rectangle rect = reader.getBoxSize(i, "bleed");
    // logger_.debug("rect[" + i + "] = " + rect);
    // }

    baos.close();
    byte[] normalizedPDF = baos.toByteArray();

    return normalizedPDF;
  }
}