package at.gv.egovernment.moa.id.auth.builder;

import java.security.MessageDigest;

import at.gv.egovernment.moa.id.BuildException;
import at.gv.egovernment.moa.util.Base64Utils;
import at.gv.egovernment.moa.util.Constants;

/**
 * Builder for the bPK, as defined in
 * <code>&quot;Ableitung f&uml;r die bereichsspezifische Personenkennzeichnung&quot;</code>
 * version <code>1.0.1</code> from <code>&quot;reference.e-government.gv.at&quot;</code>.
 *  
 * @author Paul Schamberger
 * @version $Id$
 */
public class BPKBuilder {

  /**
   * Builds the bPK from the given parameters. 
   * @param identificationValue Base64 encoded "Stammzahl" 
   * @param target "Bereich lt. Verordnung des BKA"
   * @return bPK in a BASE64 encoding
   * @throws BuildException if an error occurs on building the bPK
   */
  public String buildBPK(String identificationValue, String target) 
    throws BuildException {
    
    if ((identificationValue == null || 
         identificationValue.length() == 0 ||
    		 target == null || 
         target.length() == 0)) 
    {
      throw new BuildException("builder.00", 
      		                     new Object[] {"BPK", "Unvollständige Parameterangaben: identificationValue=" + 
                                             identificationValue + ",target=" + target});
    }
    String basisbegriff = identificationValue + "+" + Constants.URN_PREFIX_CDID + "+" + target;
    try {
      MessageDigest md = MessageDigest.getInstance("SHA-1");
      byte[] hash = md.digest(basisbegriff.getBytes("ISO-8859-1"));
      String hashBase64 = Base64Utils.encode(hash);
      return hashBase64;
    } catch (Exception ex) {
      throw new BuildException("builder.00", new Object[] {"BPK", ex.toString()}, ex);
    }
  }

}