/* AuthInfo.java -- 
   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath 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 of the License, or (at
your option) any later version.

GNU Classpath 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 GNU Classpath; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, 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
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independent module, the terms and conditions of the license of that
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package gnu.javax.crypto.sasl;

import gnu.java.security.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.
 */
public class AuthInfo
{
  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().trim();
              if (! "gnu.javax.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);
    }

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

  /**
   * 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;
  }
}