/**
 * <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.util.HashMap;
import java.util.Iterator;

import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;

import at.gv.egiz.pdfas.exceptions.ErrorCode;
import at.gv.egiz.pdfas.framework.signator.SignatorInformation;
import at.gv.egiz.pdfas.utils.OgnlUtil;
import at.knowcenter.wag.egov.egiz.cfg.SettingsReader;
import at.knowcenter.wag.egov.egiz.exceptions.PresentableException;
import at.knowcenter.wag.egov.egiz.exceptions.SettingsException;
import at.knowcenter.wag.egov.egiz.sig.SignatureObject;

import com.lowagie.text.Rectangle;
import com.lowagie.text.pdf.AcroFields;
import com.lowagie.text.pdf.PdfDictionary;
import com.lowagie.text.pdf.PdfFormField;
import com.lowagie.text.pdf.PdfName;
import com.lowagie.text.pdf.PdfNumber;
import com.lowagie.text.pdf.PdfObject;
import com.lowagie.text.pdf.PdfSignature;
import com.lowagie.text.pdf.PdfSignatureAppearance;
import com.lowagie.text.pdf.PdfStamper;
import com.lowagie.text.pdf.PdfString;

/**
 * Helper class for creating adobe signature attributes.
 * 
 * @author dferbas
 *
 */
public class AdobeSignatureHelper {
   private static final String ADOBE_SIGN_FIELDNAME_KEY = "adobeSignFieldValue";
   
   private static final String ADOBE_SIGN_REASONNAME_KEY = "adobeSignReasonValue";

   private static final String ADOBE_SIG_ENABLED_KEY = "adobeSignEnabled";

   private static Logger logger = Logger.getLogger(AdobeSignatureHelper.class);
   
   public static final String ADOBE_SIG_FILTER = "Adobe.PDF-AS";
   
   public static final String ADOBE_SIG_TEXT_KEY = "adobeSignText";

   private static final String ADOBE_VERIFY_URL_KEY = "verifyURL";

   /**
    * Writes Adobe-pdf signature entry with itext
    * 
    * @param stamper
    * @param si
    * @param so
    * @param atp
    * @throws PresentableException
    */
   public static void createAdobeSignatureField(PdfStamper stamper, SignatorInformation si,
         SignatureObject so, ActualTablePos atp, StructContentHelper structHelper) throws PresentableException {

      try {
         logger.debug("Creating adobe signature field.");
         PdfSignatureAppearance sap = stamper.getSignatureAppearance();                  

         String profileId = so.getSignatureTypeDefinition().getType();
         String fieldName = getAdobeFieldName(profileId);
         // find field num
         /*
         int nexSigNum = 1;
         String finalFieldName = fieldName + " #" + nexSigNum;
         
         while (stamper.getAcroFields().getField(finalFieldName) != null) {
            nexSigNum++;
            finalFieldName = fieldName + " #" + nexSigNum;
         }
         */
         
         AcroFields af = stamper.getAcroFields();
         Iterator signatureNamesIt = af.getSignatureNames().iterator();
         PdfName referenceFilterName = new PdfName(ADOBE_SIG_FILTER);
         int nextSigNum = 1;
         while (signatureNamesIt.hasNext()) {
            PdfDictionary dictionary = (PdfDictionary) af.getSignatureDictionary((String) signatureNamesIt.next());
            PdfObject filterName = dictionary.get(PdfName.FILTER);
            if (filterName != null && filterName.isName()) {
               PdfName name = (PdfName) filterName;
               if (referenceFilterName.equals(name)) {
                  nextSigNum++;
               }
            }
         }
         String finalFieldName = fieldName + " #" + nextSigNum;

         sap.setCrypto(null, null, null, null);
         // supress overlay text for visible signatures
         sap.setLayer2Text("");
         sap.setLayer4Text("");

         // the following line marks the sig block as adobe sig
         // sap.setVisibleSignature(createRectangleFromTablePos(iui.actualTablePos),
         // iui.actualTablePos.page, "PDF-AS-Signatur");
         sap.setVisibleSignature(new Rectangle(0, 0, 0, 0), atp.page, finalFieldName);
         String subfilter = "unknown";
         if (so != null && so.getKZ() != null) {
            subfilter = so.getKZ().toString();
         } else if (si != null) {
            subfilter = si.getSignSignatureObject().kz;
         }         
         PdfSignature sig = new PdfSignature(new PdfName(ADOBE_SIG_FILTER), new PdfName(subfilter));
         // the following fields are not shown by the reader, because its is no
         // Standard filter
         // sig.setLocation("location is not visible");
         // sig.setReason("reason is not visible");
         
         // contact field is used to embed signature verification url for adobe handler
         String verifyURL = getVerifyUrl(profileId);
         if (!StringUtils.isEmpty(verifyURL)) {
            sig.setContact(getVerifyUrl(profileId));
         } else {
            logger.debug("No verify URL set -> verify URL is not embedded.");
         }
         // sig.setDate(new PdfDate());
         
         String reason = getAdobeReasonName(profileId);
         if (!StringUtils.isEmpty(reason)) {
            sig.setReason(reason);
         }

         
         /* disabled in order to align adobe signature appearance for textual signatures with binary signatures
         if (si != null) {
            XMLGregorianCalendar c = DatatypeFactory.newInstance().newXMLGregorianCalendar(
                  si.getSignSignatureObject().date);
            sig.setDate(new PdfDate(c.toGregorianCalendar()));
         }
         */
         
         sig.setName(getAdobeSignText(profileId, si));
         sap.setCryptoDictionary(sig);
         sap.setCertificationLevel(PdfSignatureAppearance.NOT_CERTIFIED);

         // content element is mandatory but empty
         HashMap exc = new HashMap();
         exc.put(PdfName.CONTENTS, new Integer(2));
         
         PdfNumber parentNum = structHelper.buildAdobeSigStructParent();
         if (parentNum != null) {         
            PdfFormField sigField = PdfFormField.createSignature(stamper.getWriter());       
            sap.setSigFormField(sigField);
            sigField.put(PdfName.STRUCTPARENT, parentNum);                                         
            structHelper.buildAdobeSigStruct(sigField, finalFieldName);
         }
         sap.preClose(exc); // *2+2

         PdfDictionary dic = new PdfDictionary();
         dic.put(PdfName.CONTENTS, new PdfString((String) null).setHexWriting(true));
         sap.close(dic);
      } catch (Exception ex) {
         logger.error("error", ex);
         throw new PresentableException(ErrorCode.CANNOT_WRITE_PDF,
               "Error creating adobe signature attribute", ex);
      }
   }
   

   /**
    * Returns if adobe signature is enabled for the passed signature profile.
    * Config key: {@value #ADOBE_SIG_ENABLED_KEY}
    * @param sigProfile
    * @return
    */
   public static boolean isAdobeSignatureFieldEnabled(String sigProfile) {
      return "true".equalsIgnoreCase(
            getDefaultableConfigProperty(sigProfile, ADOBE_SIG_ENABLED_KEY, "false"));
   }

   protected static Rectangle createRectangleFromTablePos(ActualTablePos pos) {
      return new Rectangle(pos.x, pos.y, pos.x + pos.width, pos.y - pos.height);
   }
   
   private static String getAdobeFieldName(String sigProfile) {
      return getDefaultableConfigProperty(sigProfile, ADOBE_SIGN_FIELDNAME_KEY, "PDF-AS Signatur");
   }
   
   private static String getAdobeReasonName(String sigProfile) {
      return getDefaultableConfigProperty(sigProfile, ADOBE_SIGN_REASONNAME_KEY, "Informationen zur Prüfung finden Sie unter http://www.signaturpruefung.gv.at");
   }
   
   private static String getVerifyUrl(String sigProfile) {
      return getDefaultableConfigProperty(sigProfile, ADOBE_VERIFY_URL_KEY, "http://www.signaturpruefung.gv.at");
   }
   
   public static String getDefaultableConfigProperty(String sigProfile, String propName, String defaultValue) {      
      String confVal;
      try {
         confVal = SettingsReader.getInstance().getSetting(
               "sig_obj." + sigProfile + "." + propName,
               "default." + propName,
               defaultValue);
      } catch (SettingsException e) {
         logger.warn("error reading " + propName  + " from config. Using default: " + defaultValue, e);
         return defaultValue;
      }
      return confVal;            
   }

   /**
    * Evaluate name for adobe signature field. Get from config. Evaluate ognl if
    * ok.
    * 
    * @param sigProfile
    * @param si
    * @return
    */
   private static String getAdobeSignText(String sigProfile, SignatorInformation si) {
      String defaultName = "PDF-AS";
      try {
         logger.debug("reading adobe sig name for profile: " + sigProfile);
         String propKey = ADOBE_SIG_TEXT_KEY + ".textual";
         if (si == null) {
            propKey = propKey.replaceAll("textual", "binary");
         }
         String adobeStr = getDefaultableConfigProperty(sigProfile, propKey, defaultName);
       
         HashMap ognlCtx = new HashMap();
         OgnlUtil ognl = new OgnlUtil(ognlCtx);
         if (ognl.containsExpression(adobeStr)) {
            if (si == null) {
               logger
                     .error(ADOBE_SIG_TEXT_KEY
                           + " ognl expressions not allowed for binary signatures (SignatorInformation not available)");
               return defaultName;
            }
            ognlCtx.put("si", si);
            ognlCtx.put("sso", si.getSignSignatureObject());
            String res = ognl.compileMessage(adobeStr);
            return res;
         } else {
            return adobeStr;
         }

      } catch (Exception ex) {
         logger.warn("error creating adobe sign text, using default '" + defaultName + "'", ex);
         return defaultName;
      }
   }

}