/**
 * <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.sig.signaturelayout;

import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Vector;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import at.gv.egiz.pdfas.exceptions.ErrorCode;
import at.knowcenter.wag.egov.egiz.cfg.SettingsReader;
import at.knowcenter.wag.egov.egiz.exceptions.ConnectorException;
import at.knowcenter.wag.egov.egiz.exceptions.SettingNotFoundException;
import at.knowcenter.wag.egov.egiz.exceptions.SettingsException;

/**
 * Returns instances of signature layout handlers based on given bku
 * identifiers.
 * 
 * @author tknall
 */
public class SignatureLayoutHandlerFactory {

   /**
    * Prefix of configuration keys defining bku identifiers for a signature layout.
    */
   private final static String SIGNATURE_LAYOUT_CONFIG_KEY_PATTERN = "signaturelayout.pattern";
   
   /**
    * Prefix of configuration keys defining implementations of signature layout handlers.
    * @see SignatureLayoutHandler
    */
   private final static String SIGNATURE_LAYOUT_CONFIG_KEY_IMPL = "signaturelayout.implementation";
   
   /**
    * A map holding instantiated signature layout implementations (for performance reasons).
    */
   private final static Map instances = Collections.synchronizedMap(new HashMap());

   /**
    * The log.
    */
   private static Log log = LogFactory.getLog(SignatureLayoutHandlerFactory.class);
   
   /**
    * Returns an instance of a signature layout handler based on the given bku identifier.
    * @param bkuIdentifier The bku identifier (e.g. <code>citizen-card-environment/1.2 MOCCA/1.1.1</code>).
    * @return An implementation of a signature layout handler.
    * @throws ConnectorException Thrown in case of an error finding a match within the configuration with the given bku identifier.
    * @throws SettingsException Thrown in case of an error within the configuration.
    */
   public static SignatureLayoutHandler getSignatureLayoutHandlerInstance(String bkuIdentifier) throws ConnectorException, SettingsException {
      if (bkuIdentifier == null) {
         throw new SettingsException(ErrorCode.MISSING_HEADER_SERVER_USER_AGENT, "Unable to determine type of citizen card environment. Response header \"Server\" resp. \"user-agent\" is missing. Refer to security layer specification 1.2.2, section 3.3.2.");
      }
      
      log.debug("Trying to get SignatureLayoutHandler for \"" + bkuIdentifier + "\".");
      
      SignatureLayoutHandler signatureLayoutHandler = (SignatureLayoutHandler) instances.get(bkuIdentifier);
      
      if (signatureLayoutHandler == null) {
         SettingsReader sr = SettingsReader.getInstance();

         Vector v = sr.getSettingKeys(SIGNATURE_LAYOUT_CONFIG_KEY_PATTERN);
         String implValue = null;

         Iterator it = v.iterator();
         try {
            while (it.hasNext()) {
               String subKey = (String) it.next();
               String key = SIGNATURE_LAYOUT_CONFIG_KEY_PATTERN + "." + subKey;
               String value = sr.getSetting(key);
               Pattern p = Pattern.compile(value);
               if (p.matcher(bkuIdentifier).matches()) {
                  String implKey = SIGNATURE_LAYOUT_CONFIG_KEY_IMPL + "." + subKey;
                  implValue = sr.getSetting(implKey);
               }
            }
         } catch (SettingNotFoundException e) {
            throw new SettingsException(ErrorCode.INVALID_SIGNATURE_LAYOUT_IMPL_CONFIGURED, e.getMessage());
         }

         if (implValue == null) {
            throw new ConnectorException(ErrorCode.BKU_NOT_SUPPORTED, "Unsupported BKU: " + bkuIdentifier);
         }
         
         log.debug("Trying to instantiate SignatureLayoutHandler \"" + implValue + "\".");

         try {
            Class clazz = Class.forName(implValue);
            Object obj = clazz.newInstance();
            if (!(obj instanceof SignatureLayoutHandler)) {
               throw new SettingsException(ErrorCode.INVALID_SIGNATURE_LAYOUT_IMPL_CONFIGURED, "Invalid signature layout implementation (\"" + implValue + "\") configured for bku identifier \"" + bkuIdentifier + "\".");
            }
            signatureLayoutHandler = (SignatureLayoutHandler) obj;
         } catch (InstantiationException e) {
            throw new SettingsException(ErrorCode.INVALID_SIGNATURE_LAYOUT_IMPL_CONFIGURED, "Error instantiating signature layout implementation (\"" + implValue + "\") configured for bku identifier \"" + bkuIdentifier + "\".");
         } catch (IllegalAccessException e) {
            throw new SettingsException(ErrorCode.INVALID_SIGNATURE_LAYOUT_IMPL_CONFIGURED, "Illegal access instantiating signature layout implementation (\"" + implValue + "\") configured for bku identifier \"" + bkuIdentifier + "\".");
         } catch (ClassNotFoundException e) {
            throw new SettingsException(ErrorCode.INVALID_SIGNATURE_LAYOUT_IMPL_CONFIGURED, "Unable to find signature layout implementation (\"" + implValue + "\") configured for bku identifier \"" + bkuIdentifier + "\".");
         }

         log.debug("SignatureLayoutHandler successfully instantiated.");
         instances.put(bkuIdentifier, signatureLayoutHandler);
      } else {
    	 log.debug("SignatureLayoutHandler has already been instantiated. Class: \"" + 
    			 signatureLayoutHandler.getClass().getName() + "\"");
         log.trace("SignatureLayoutHandler has already been instantiated. Returning old instance.");
      }
      
      return signatureLayoutHandler;

   }

   /**
    * Verifies that the bku is supported trying to match the given bku identifier.
    * @param bkuIdentifier The bku identifier (e.g. <code>citizen-card-environment/1.2 MOCCA/1.1.1</code>).
    * @throws ConnectorException Thrown in case of an error (e.g. bku not supported).
    * @throws SettingsException Thrown in case of an error within the configuration.
    */
   public static void verifyBKUSupport(String bkuIdentifier) throws ConnectorException, SettingsException {
      getSignatureLayoutHandlerInstance(bkuIdentifier);
   }

}