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 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 Ivancsics
 * @version $Id$
 */
public class BPKBuilder {

  /**
   * Builds the BPK from given parameters. 
   * @param identificationValue Base64 encoded "Stammzahl" 
   * @param target "Verfahrensname"; will be transformed to lower case
   * @return PBK in a BASE64 encoding
   * @throws BuildException while 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 + "+" + 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);
    }
  }

}