/**
 * <copyright> Copyright 2006 by Know-Center, Graz, Austria </copyright>
 * PDF-AS has been contracted by the E-Government Innovation Center EGIZ, a
 * joint initiative of the Federal Chancellery Austria and Graz University of
 * Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */
package at.knowcenter.wag.egov.egiz.pdf;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.apache.log4j.Logger;

import at.gv.egiz.pdfas.exceptions.ErrorCode;
import at.knowcenter.wag.egov.egiz.exceptions.PresentableException;
import at.knowcenter.wag.egov.egiz.sig.SignatureObject;

import com.lowagie.text.Rectangle;
import com.lowagie.text.pdf.PdfArray;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfDictionary;
import com.lowagie.text.pdf.PdfFormField;
import com.lowagie.text.pdf.PdfIndirectReference;
import com.lowagie.text.pdf.PdfName;
import com.lowagie.text.pdf.PdfNumber;
import com.lowagie.text.pdf.PdfObject;
import com.lowagie.text.pdf.PdfStamper;
import com.lowagie.text.pdf.PdfStamperImp;
import com.lowagie.text.pdf.PdfString;
import com.lowagie.text.pdf.PdfTemplate;
import com.lowagie.text.pdfas.StructContentWriter;
import com.lowagie.text.pdfas.StructContentWriterHolder;
import com.lowagie.text.pdfas.UrlInTextFinder;

/**
 * Helper class for writing the structure hierarchy of the signature elements.
 * Everything is written with the PdfObject low level API because there is no better support.
 * The structured content is only written for structured (==tagged) input documents. The methods have to be called in the
 * defined order. The object cannot be reused for several signatures.<br>
 * See pdf spec "Logical Structure" for details.<br>
 * The struct writing could be a little more abstracted, but this would include quite some itext extension work. And like this it
 * fits better to PDF-AS / wprinz coding style :-(
 * @author exthex
 *
 */
public class StructContentHelper implements StructContentWriter {
   private static final Logger logger = Logger.getLogger(StructContentHelper.class);

   private static final String SIGBLOCK_STRUCT_TYPE = "P";
   private static final PdfName PARENTTREENEXTKEY = new PdfName("ParentTreeNextKey");
   private static final String ALT_TEXT_DEFAULT = "Signaturbildmarke";
   private final static String ALT_TEXT_CONF_KEY = "sigLogoAltText";


   private int nextMcid = 0;
   /**
    * MCID value used for the sigblock marked contend identifier
    */
   private int sigBlockMcid =-1;
   /**
    * MCID value for "Bildmarke" marked content sequence
    */
   private int figureMcid = -1;
   /**
    * MCID value for verify link marked content sequence
    */
   private int linkMcid = -1;
   private String linkUrlString = null;
   private boolean isTagged = false;
   private Map linkPosMap = new HashMap();
   private Map tmpMap = new HashMap();

   private PdfStamper stamper;
   private PdfStamperImp stamperImp;
   private PdfContentByte content;
   private PdfDictionary page;
   private PdfNumber parentTreeNextKey = null;
   private PdfNumber annotationParentTreeKey = null;

   /**
    * Temporary save a pos
    */
   private Rectangle tempMarkedPos = null;
   /**
    * Cell position of the signature verify link overlay
    */
   private Rectangle verifyLinkCellPos = null;

   /**
    * Kids array (K) of the <code>StructTreeRoot</code>
    */
   private PdfArray structTreeRootKids = null;

   /**
    * Entry in the ParentTree.Nums array used for sigtable structs
    */
   private PdfArray mainParentTreeNumEntry;

   /**
    * Create new helper for one signature, and bind it to {@link StructContentWriterHolder}
    * for thread local access from itext.
    *
    * @param stamper
    * @param content
    * @param pageNr
    */
   StructContentHelper(PdfStamper stamper, PdfContentByte content, int pageNr) {
      this.stamper = stamper;
      this.content = content;
      stamperImp = ((PdfStamperImp) stamper.getWriter());
      page = stamper.getReader().getPageN(pageNr);
      StructContentWriterHolder.setThreadLocalWriter(this);
   }

   /**
    * Remove thread local helper
    */
   public void removeCurrent() {
      StructContentWriterHolder.removeThreadLocalWriter();
   }

   /**
    * Prepare structured content for signature block. This method initializes the whole StructTreeRoot stuff.
    * @param sigBlockObj
    * @throws PresentableException
    */
   void prepareStructData(PdfTemplate sigBlockObj) throws PresentableException {

      try {
         checkTagging();
         if (!isTagged) {
            return;
         }

         doAnnoTabOrder();

         PdfDictionary structTreeRoot = getStructTreeRoot();
         stamperImp.markUsed(structTreeRoot);

         PdfArray parentTreeNums = getParentTreeNums();

         PdfNumber structParentsNr = page.getAsNumber(PdfName.STRUCTPARENTS);  // read StructParents entry from current page

         mainParentTreeNumEntry = obtainParentTreeEntry(structTreeRoot, parentTreeNums, structParentsNr, sigBlockObj);

         nextMcid = mainParentTreeNumEntry.size();
         sigBlockMcid = nextMcid;
         nextMcid++;

         this.structTreeRootKids = obtainStructTreeRootKids(structTreeRoot);

         if(this.structTreeRootKids == null)
         {
        	 this.structTreeRootKids = this.createStructTreeRootKids(structTreeRoot);
         }

      } catch (Exception ex) {
         logger.error("error", ex);
         throw new PresentableException(ErrorCode.CANNOT_WRITE_PDF,
               "error writing structured signature content", ex);
      }
   }

   PdfArray createStructTreeRootKids(PdfDictionary structTreeRoot) {
	   PdfArray tmp = new PdfArray();
	   structTreeRoot.put(PdfName.K, tmp);
	   return tmp;
   }

   /**
    * Create struct data for main signature block
    * @throws PresentableException
    */
   void buildSigBlockStructData() throws PresentableException {
      if (!isTagged) return;
      try {
         PdfIndirectReference newStructRef = createStructElem(SIGBLOCK_STRUCT_TYPE, new PdfNumber(
               sigBlockMcid), getStructTreeRoot().getIndRef());

         // ADD everything at the end because nothing can be written afterwards
         structTreeRootKids.add(newStructRef);
         mainParentTreeNumEntry.add(newStructRef);

         stamperImp.markUsed(mainParentTreeNumEntry);

      } catch (Exception ex) {
         logger.error("error", ex);
         throw new PresentableException(ErrorCode.CANNOT_WRITE_PDF,
               "error writing structured signature content", ex);
      }
   }


   /**
    * Finish struct data for signblock and it's elements (NOT for the external link and annot!)
    * @throws PresentableException
    */
   void finishMainStructData() throws PresentableException {
      try {
         if (isTagged && mainParentTreeNumEntry.getIndRef() == null) {
            getParentTreeNums().add(
                  stamper.getWriter().addToBody(mainParentTreeNumEntry).getIndirectReference());
            stamperImp.markUsed(getParentTreeNums());
            stamperImp.markUsed(getStructTreeRoot().getAsDict(PdfName.PARENTTREE));
         }
      } catch (Exception ex) {
         logger.error("error", ex);
         throw new PresentableException(ErrorCode.CANNOT_WRITE_PDF,
               "error writing structured signature content", ex);
      }
   }

   /**
    * Build the structured content for the signature logo (bildmarke). {@link #beginFigureContent(PdfContentByte)} and
    * {@link #endFigureContent(PdfContentByte)} have to be called before this method to mark the logo in the stream. This
    * is done implicitly in the modified itext source (see {@link StructContentWriterHolder}).
    * @param so
    * @param sigBlockObj
    * @throws PresentableException
    */
   void buildFigureStructData(SignatureObject so, PdfTemplate sigBlockObj) throws PresentableException {
      try {
         if (isTagged && isFigureMarked()) {

            PdfDictionary structTreeRoot = getStructTreeRoot();
            PdfIndirectReference mcrRef = createMcrStructElem(this.figureMcid, sigBlockObj.getIndirectReference());
            PdfIndirectReference figureRef = createStructElem("Figure", mcrRef,
                  getAltText(so.getSignatureTypeDefinition().getType()), structTreeRoot.getIndRef());

            structTreeRootKids.add(figureRef);
            mainParentTreeNumEntry.add(figureRef);

            stamperImp.markUsed(structTreeRootKids);
            stamperImp.markUsed(structTreeRoot);
            stamperImp.markUsed(mainParentTreeNumEntry);

         }

      } catch (Exception ex) {
         logger.error("error", ex);
         throw new PresentableException(ErrorCode.CANNOT_WRITE_PDF,
               "error writing structured signature content", ex);
      }

   }

   /**
    * Build the link annotation for the signature verification link and the structured content accordingly.<br>
    * The tagging does NOT work if the link is placed in a binary signature replace cell (phlengh for this cell)!!
    * @param sigBlockObj
    * @param atp
    * @throws PresentableException
    */
   void buildVerifyLinkStructData(PdfTemplate sigBlockObj, ActualTablePos atp) throws PresentableException {
      if (!this.isTagged || !this.isLinkMarked() || !isLinkFound()) return;

      try {
         PdfNumber parentTreeKey = getNewParentTreeKey();

         PdfArray annots = obrainAnnotsFromPage();

         PdfIndirectReference linkAnnotRef = createLinkAnnot(parentTreeKey, atp);
         annots.add(linkAnnotRef);

         PdfIndirectReference objr = createObjrStructElem(linkAnnotRef);
         PdfIndirectReference mcr = createMcrStructElem(this.linkMcid, sigBlockObj.getIndirectReference());

         PdfDictionary structTreeRoot = getStructTreeRoot();

         PdfArray linkKids = new PdfArray();
         PdfIndirectReference linkKidsRef = stamper.getWriter().getPdfIndirectReference();

         PdfIndirectReference linkRef = createStructElem("Link", linkKidsRef, structTreeRoot.getIndRef());
         linkKids.add(objr);

         PdfIndirectReference span = createStructElem("Span", mcr, linkRef);
         linkKids.add(span);

         stamper.getWriter().addToBody(linkKids, linkKidsRef);
         structTreeRootKids.add(linkRef);

         // create new entry in ParentTree
         PdfArray parentTreeNums = getParentTreeNums();
         parentTreeNums.add(parentTreeKey);
         parentTreeNums.add(linkRef);

         stamperImp.markUsed(parentTreeNums);
         stamperImp.markUsed(structTreeRoot.getAsDict(PdfName.PARENTTREE));
         stamperImp.markUsed(structTreeRootKids);
         stamperImp.markUsed(linkKids);

         stamperImp.markUsed(structTreeRoot);

      } catch (IOException e) {
         logger.error("error", e);
         throw new PresentableException(ErrorCode.CANNOT_WRITE_PDF,
               "error writing structured signature content", e);
      }
   }

   private boolean isLinkFound() {
      return this.linkUrlString != null && this.verifyLinkCellPos != null && this.linkPosMap.size() > 0 && this.linkMcid >= 0;
   }

   /**
    * Build new StructParent entry for signature annotation.
    * @return
    */
   PdfNumber buildAdobeSigStructParent() {
      if (this.isTagged) {
         this.annotationParentTreeKey = getNewParentTreeKey();
         return annotationParentTreeKey;
      } else {
         return null;
      }
   }

   /**
    * Build and write structured content for adobe signature annotation
    *
    * @param sigFormField
    * @param title
    * @throws PresentableException
    */
   void buildAdobeSigStruct(PdfFormField sigFormField, String title) throws PresentableException {
      if (!isTagged)
         return;
      try {

         PdfDictionary root = getStructTreeRoot();

         PdfIndirectReference objrRef = createObjrStructElem(sigFormField.getIndirectReference());

         PdfIndirectReference adobeSigStructRef = createStructElem("Link", objrRef, root.getIndRef());

         PdfArray parentTreeNums = getParentTreeNums();
         // create new entry in ParentTree
         parentTreeNums.add(annotationParentTreeKey);
         parentTreeNums.add(adobeSigStructRef);

         structTreeRootKids.add(adobeSigStructRef);
         stamperImp.markUsed(structTreeRootKids);

         stamperImp.markUsed(parentTreeNums);
         stamperImp.markUsed(root.getAsDict(PdfName.PARENTTREE));

      } catch (Exception ex) {
         logger.error("error", ex);
         throw new PresentableException(ErrorCode.CANNOT_WRITE_PDF,
               "error writing structured signature content", ex);
      }

   }

   /**
    * Start tag for signature block content stream. Place this before the signature block is written to a content stream.
    * Call {@link #endSigBlockContent()} afterwards
    */
   void beginSigBlockContent() {
      if (isTagged) {
         content.getInternalBuffer().append(new PdfName(SIGBLOCK_STRUCT_TYPE).getBytes()).append(" <</MCID ")
               .append(sigBlockMcid).append(">> BDC").append('\n');
      }
   }

   /**
    * End tag for signature block content stream. Place this after the signature block is written to a content stream
    */
   void endSigBlockContent() {
      if (isTagged) {
         content.endMarkedContentSequence();
      }
   }

   /**
    * Writes start tag for signature logo marked content sequence.
    */
   public void beginFigureContent(PdfContentByte localContent) {
      if (isTagged) {
         if (!isFigureMarked()) {
            this.figureMcid = this.nextMcid++;
            localContent.getInternalBuffer().append("/Figure <</MCID ").append(this.figureMcid).append(">> BDC\n");
         } else {
            logger.warn("cannot tag multiple figures (bildmarken)");
         }
      }
   }

   /**
    * Writes end tag for signature logo marked content sequence.
    */
   public void endFigureContent(PdfContentByte localContent) {
      if (isTagged && isFigureMarked()) {
         localContent.endMarkedContentSequence();
      }
   }

   /**
    * Writes start tag for verify link marked content sequence.
    */
   public void beginLinkContent(PdfContentByte localContent, String urlString) {
      // it's called from here com.lowagie.text.pdf.PdfContentByte.showText(String)

      if (isTagged) {
         if (!isLinkMarked()) {
            this.linkUrlString = urlString;
            this.linkMcid = this.nextMcid++;
            localContent.getInternalBuffer().append("/Span <</MCID ").append(this.linkMcid).append(">> BDC\n");
         } else {
            logger.warn("cannot tag multiple verify links");
         }
      }
   }

   /**
    * Writes end tag for verify link marked content sequence.
    */
   public void endLinkContent(PdfContentByte localContent) {
      if (isTagged && isLinkMarked()) {
         localContent.endMarkedContentSequence();
      }
   }

   /**
    * Implements {@link StructContentWriter#markPos(Rectangle)}
    */
   public void markPos(Rectangle pos) {
      this.tempMarkedPos = pos;
   }

   /**
    * Implements {@link StructContentWriter#storeCurrentPosAsLink()}
    */
   public void storeCurrentPosAsLink() {
      this.verifyLinkCellPos = new Rectangle(this.tempMarkedPos);
   }

   public void putVal(String key, Object val) {
      tmpMap.put(key, val);
   }

   public void storeVals() {
      linkPosMap = new HashMap(tmpMap);
   }

   /**
    * set explicit annotation tab order if missing
    */
   private void doAnnoTabOrder() {
      if (page.getAsName(new PdfName("Tabs")) == null) {
         page.put(new PdfName("Tabs"), PdfName.S);  // set explicit annotation TAB order
         stamperImp.markUsed(page);
      }
   }

   private void checkTagging() {
      PdfDictionary markDict = stamper.getReader().getCatalog().getAsDict(PdfName.MARKINFO);
      if (markDict != null) {
         isTagged = markDict.getAsBoolean(PdfName.MARKED).booleanValue();
      }
      if (!isTagged) {
         logger.debug("input document is not tagged. no structure/wai information is written");
      }
      logger.debug("Input is tagged. Writing structure/WAI data.");
   }



   private PdfIndirectReference createLinkAnnot(PdfNumber structParentNr, ActualTablePos atp) throws IOException {
      PdfDictionary linkAnnot = new PdfDictionary();

      PdfDictionary a = new PdfDictionary();
      a.put(PdfName.S, new PdfName("URI"));
      a.put(PdfName.TYPE, PdfName.ACTION);
      a.put(PdfName.URI, new PdfString(this.linkUrlString));
      linkAnnot.put(PdfName.A, a);

      PdfDictionary bs = new PdfDictionary();
      bs.put(PdfName.W, new PdfNumber(0));
      linkAnnot.put(PdfName.BS, bs);
      linkAnnot.put(PdfName.F, new PdfNumber(4));

      // iText "converts" 0.0f to an integer, therefore we cannot use 0, not nice...
      //linkAnnot.put(PdfName.RECT, new PdfArray(new float[] {0.01f, 0.01f, 0.01f, 0.01f}));
      // take cell pos as link pos
      linkAnnot.put(PdfName.RECT, new PdfArray(calcLinkPos(atp)));

      linkAnnot.put(PdfName.STRUCTPARENT, structParentNr);
      linkAnnot.put(PdfName.SUBTYPE, PdfName.LINK);

      return stamper.getWriter().addToBody(linkAnnot).getIndirectReference();
   }


   private PdfArray calcLinkPos(ActualTablePos atp) {
      PdfArray res = new PdfArray();

      float downY = atp.y - atp.height;

      float startX = atp.x + this.verifyLinkCellPos.getLeft();
      float yLine = getPosMapVal("yLine");
      float lineHigh = getPosMapVal("maxSize");
      float lineWidth = getPosMapVal("lineWidth");
      UrlInTextFinder finder = (UrlInTextFinder) this.linkPosMap.get("urlFinder");

      // maybe one could calc the link pos even more exactly with char width counting
      // but this should be close enough (see BidiLine.processLine and chunk.getcharwith)
      float lineCorr = -2;
      float xCorr = 5;
      res.add(new PdfNumber(1 + startX + finder.calcLinkPosXStart(lineWidth)));
      res.add(new PdfNumber(downY + yLine + lineHigh + lineCorr));
      res.add(new PdfNumber(xCorr + startX + finder.calcLinkPosXEnd(lineWidth)));
      res.add(new PdfNumber(downY + yLine + lineCorr));

      return res;
   }

   private float getPosMapVal(String key) {
      return ((Float) this.linkPosMap.get(key)).floatValue();
   }

   protected static PdfArray createPdfArrayFromTablePos(ActualTablePos pos) {
      return new PdfArray( new float[] {pos.x, pos.y, pos.x + pos.width, pos.y - pos.height});
   }

   private PdfArray obrainAnnotsFromPage() throws IOException {
      PdfArray annots = this.page.getAsArray(PdfName.ANNOTS);
      if (annots == null) {
         annots = new PdfArray();
         page.put(PdfName.ANNOTS, annots);
         stamperImp.markUsed(this.page);
         stamper.getWriter().addToBody(annots);
      }
      return annots;
   }

   private PdfArray obtainStructTreeRootKids(PdfDictionary structTreeRoot) {
      PdfArray rk = null;
      PdfObject root_k = structTreeRoot.getDirectObject(PdfName.K);
      stamperImp.markUsed(root_k);
      if (root_k instanceof PdfDictionary) {
         rk = new PdfArray();
         stamperImp.markUsed(structTreeRootKids);
         rk.add(root_k.getIndRef());
         structTreeRoot.put(PdfName.K, structTreeRootKids);

      } else if(root_k != null) { // has to be array
         rk = (PdfArray) root_k;
      }
      return rk;
   }

   private PdfArray obtainParentTreeEntry(PdfDictionary structTreeRoot, PdfArray parentTreeNums,
         PdfNumber structParentsNr, PdfTemplate sigBlockObj) {
      int numsIdx = -1;
      PdfArray parentTreeEntry = null;

      if (structParentsNr == null) { // no StructParents entry yet, make new one and add new parenttree entry
         PdfNumber parentTreeKey = null;
         parentTreeNextKey = structTreeRoot.getAsNumber(PARENTTREENEXTKEY); // read next proposed key
         if (parentTreeNextKey == null) { // this can be null if a non-perfect pdf creator was at work
            // find the next key by counting
            int nextI = ((int) parentTreeNums.size() / 2);  // know the "Number Trees" data structure from pdf-ref
            this.parentTreeNextKey = new PdfNumber(nextI);
            structTreeRoot.put(PARENTTREENEXTKEY, this.parentTreeNextKey); // write ParentTreeNextKey entry
         }

         parentTreeKey = new PdfNumber(parentTreeNextKey.intValue());
         parentTreeNextKey.increment();
         page.put(PdfName.STRUCTPARENTS, parentTreeKey); // write /StructParents entry to page
         structParentsNr = parentTreeKey;

         stamperImp.markUsed(page);
         // create new entry in ParentTree
         parentTreeNums.add(parentTreeKey);
         parentTreeEntry = new PdfArray();
         numsIdx = parentTreeNums.size() - 1;

      } else { // structparents entry already available, find parenttree entry
         //parentTreeKey = structParentsNr;
         parentTreeNextKey = structTreeRoot.getAsNumber(PARENTTREENEXTKEY); // read next proposed key
         if (parentTreeNextKey == null) { // this can be null if a non-perfact pdf creator was at work
            // find the next key by counting
            int nextI = 0;
            if (parentTreeNums != null) {
               nextI = ((int) parentTreeNums.size() / 2);
            }
            this.parentTreeNextKey = new PdfNumber(nextI);
            structTreeRoot.put(PARENTTREENEXTKEY, this.parentTreeNextKey);
         }
      }

      // add Structparents entry to xobject content stream
      sigBlockObj.addAttribute(PdfName.STRUCTPARENTS, structParentsNr);

      // find my structParentEntry
      if (numsIdx < 0) {
         // it's a weird data structure: "number tree", see pdf reference if you really want to understand

         // if the array has no gaps it is easy:
         numsIdx = structParentsNr.intValue() * 2;
         if (parentTreeNums.getAsNumber(numsIdx).intValue() != structParentsNr.intValue()) { // there seem to be gaps
            for (numsIdx = 0; numsIdx < parentTreeNums.size(); numsIdx += 2) { // search manually
               if (parentTreeNums.getAsNumber(numsIdx).intValue() == structParentsNr.intValue()) {
                  break;
               }
            }
         }
         numsIdx += 1;
      }
      if (parentTreeEntry == null) {
         parentTreeEntry = parentTreeNums.getAsArray(numsIdx);
      }
      return parentTreeEntry;
   }

//   private PdfIndirectReference createStructElem(String structType, PdfObject kid) throws IOException {
//      return createStructElem(structType, kid, null);
//   }

   private PdfIndirectReference createStructElem(String structType, PdfObject kid, PdfIndirectReference parentRef) throws IOException {
      return createStructElem(structType, kid, null, parentRef);
   }

   private PdfIndirectReference createStructElem(String structType, PdfObject kid, String altText,
         PdfIndirectReference parentRef) throws IOException {

      PdfDictionary newStruct = new PdfDictionary();
      newStruct.put(PdfName.S, new PdfName(structType));
      //newStruct.put(PdfName.T, new PdfString("PDF-AS Signaturblock"));// eher nicht
      if (parentRef != null) {
         newStruct.put(PdfName.P, parentRef);
      }
      newStruct.put(PdfName.TYPE, new PdfName("StructElem"));

      newStruct.put(PdfName.PG, page.getIndRef());
      if (altText != null) {
         newStruct.put(PdfName.ALT, new PdfString(altText));
      }
      // newStruct.put(PdfName.ALT, new PdfString(getAltText(so.getSignatureTypeDefinition().getType())));
      //newStruct.put(PdfName.K, new PdfNumber(nextMcid));
      newStruct.put(PdfName.K, kid);

      return stamper.getWriter().addToBody(newStruct).getIndirectReference();
   }

   private boolean isFigureMarked() {
      return this.figureMcid > -1;
   }

   private boolean isLinkMarked() {
      return this.linkMcid > -1;
   }


   private PdfNumber getNewParentTreeKey() {
      // new parent tree entry
      if (parentTreeNextKey == null) {
         parentTreeNextKey = getStructTreeRoot().getAsNumber(PARENTTREENEXTKEY); // read next proposed key
      }
      PdfNumber res = new PdfNumber(parentTreeNextKey.intValue());
      parentTreeNextKey.increment();
      return res;
   }


   private PdfIndirectReference createObjrStructElem(PdfIndirectReference objRef) throws IOException {
      PdfDictionary objr = new PdfDictionary();
      objr.put(PdfName.TYPE, new PdfName("OBJR"));
      objr.put(PdfName.PG, page.getIndRef());
      objr.put(new PdfName("Obj"), objRef);

      return stamper.getWriter().addToBody(objr).getIndirectReference();
   }

   private PdfIndirectReference createMcrStructElem(int mcid, PdfIndirectReference streamRef) throws IOException {
      PdfDictionary objr = new PdfDictionary();
      objr.put(PdfName.TYPE, new PdfName("MCR"));
      objr.put(PdfName.PG, page.getIndRef());
      objr.put(PdfName.MCID, new PdfNumber(mcid));
      objr.put(new PdfName("Stm"), streamRef);

      return stamper.getWriter().addToBody(objr).getIndirectReference();
   }

   private PdfArray getParentTreeNums() {
      return getStructTreeRoot().getAsDict(PdfName.PARENTTREE).getAsArray(PdfName.NUMS);
   }

   private PdfDictionary getStructTreeRoot() {
      return stamper.getReader().getCatalog().getAsDict(PdfName.STRUCTTREEROOT);
   }

   private static String getAltText(String sigProfile) {
      return AdobeSignatureHelper.getDefaultableConfigProperty(sigProfile, ALT_TEXT_CONF_KEY, ALT_TEXT_DEFAULT);
   }

}