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;

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

  /**
   * Builds the VPK from given parameters. 
   * @param identificationValue "ZMR-Zahl"
   * @param dateOfBirth "Geburtsdatum"
   * @param target "Verfahrensname"; will be transformed to lower case
   * @return VPK in a BASE64 encoding
   * @throws BuildException while building the VPK
   */
  public String buildVPK(String identificationValue, String dateOfBirth, String target) 
    throws BuildException {
    
    if (identificationValue == null || identificationValue.length() == 0 
      || dateOfBirth == null || dateOfBirth.length() == 0
      || target == null || target.length() == 0)
      throw new BuildException(
        "builder.00", 
        new Object[] {"VPK", 
          "Unvollständige Parameterangaben: identificationValue=" + identificationValue + 
          ",dateOfBirth=" + dateOfBirth + ",target=" + target});
    String basisbegriff = identificationValue + "+" + dateOfBirth + "+" + target.toLowerCase();
    try {
      MessageDigest md = MessageDigest.getInstance("SHA-1");
      byte[] hash = md.digest(basisbegriff.getBytes());
      String hashBase64 = Base64Utils.encode(hash);
      return hashBase64;
    }
    catch (Exception ex) {
      throw new BuildException(
        "builder.00", 
        new Object[] {"VPK", ex.toString()}, 
        ex);
    }
  }

}