package gnu.crypto.sasl;

// ----------------------------------------------------------------------------
// $Id: AuthInfo.java,v 1.3 2005/10/06 04:24:17 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING.  If not, write to the
//
//    Free Software Foundation Inc.,
//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module.  An independent module is a module which is
// not derived from or based on this library.  If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so.  If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.StringTokenizer;

/**
 * A static class for creating {@link IAuthInfoProvider} providers. It
 * transparently locates and uses any provider instances, based on the value
 * assigned to the System property with the key
 * <code>gnu.crypto.sasl.auth.info.provider.pkgs</code>. If more than one is
 * specified they SHOULD be separated with a vertical bar character. Please note
 * that the GNU provider is always added last to the list, disregarding whether
 * it was mentioned or not in the value of that property, or if it that property
 * was not defined.
 *
 * @version $Revision: 1.3 $
 */
public class AuthInfo {

   // Constants and variables
   // -------------------------------------------------------------------------

   private static final ArrayList factories = new ArrayList();
   static {
      IAuthInfoProviderFactory ours = new AuthInfoProviderFactory();
      // if SASL_AUTH_INFO_PROVIDER_PKGS is defined then parse it
      String clazz;
      String pkgs = System.getProperty(Registry.SASL_AUTH_INFO_PROVIDER_PKGS, null);
      if (pkgs != null) {
         for (StringTokenizer st = new StringTokenizer(pkgs, "|"); st.hasMoreTokens(); ) {
            clazz = st.nextToken();
            if (!"gnu.crypto.sasl".equals(clazz)) {
               clazz += ".AuthInfoProviderFactory";
               try {
                  IAuthInfoProviderFactory factory = (IAuthInfoProviderFactory)
                        Class.forName(clazz).newInstance();
                  factories.add(factory);
               } catch (ClassCastException ignored) {
               } catch (ClassNotFoundException ignored) {
               } catch (InstantiationException ignored) {
               } catch (IllegalAccessException ignored) {
               }
            }
         }
      }
      // always add ours last; unless it's already there
      if (!factories.contains(ours)) {
         factories.add(ours);
      }
   }

   // Constructor(s)
   // -------------------------------------------------------------------------

   /** Trivial constructor to enforce Singleton pattern. */
   private AuthInfo() {
      super();
   }

   // Class methods
   // -------------------------------------------------------------------------

   /**
    * A convenience method to return the authentication information provider
    * for a designated SASL mechnanism. It goes through all the installed
    * provider factories, one at a time, and attempts to return a new instance
    * of the provider for the designated mechanism. It stops at the first
    * factory returning a non-null provider.
    *
    * @param mechanism the name of a SASL mechanism.
    * @return an implementation that provides {@link IAuthInfoProvider} for that
    * mechanism; or <code>null</code> if none found.
    */
   public static IAuthInfoProvider getProvider(String mechanism) {
      for (Iterator it = factories.iterator(); it.hasNext(); ) {
         IAuthInfoProviderFactory factory = (IAuthInfoProviderFactory) it.next();
         IAuthInfoProvider result = factory.getInstance(mechanism);
         if (result != null) {
            return result;
         }
      }
      return null;
   }
}
