/*

  * $Source$

  * $Revision$

  *

  * Copyright (C) 2000 William Chesters

  *

  * Part of Melati (http://melati.org), a framework for the rapid

  * development of clean, maintainable web applications.

  *

  * Melati is free software; Permission is granted to copy, distribute

  * and/or modify this software under the terms either:

  *

  * a) 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,

  *

  *    or

  *

  * b) any version of the Melati Software License, as published

  *    at http://melati.org

  *

  * You should have received a copy of the GNU General Public License and

  * the Melati Software License along with this program;

  * if not, write to the Free Software Foundation, Inc.,

  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the

  * GNU General Public License and visit http://melati.org to obtain the

  * Melati Software License.

  *

  * Feel free to contact the Developers of Melati (http://melati.org),

  * if you would like to work out a different arrangement than the options

  * outlined here.  It is our intention to allow Melati to be used by as

  * wide an audience as possible.

  *

  * This program 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.

  *

  * Contact details for copyright holder:

  *

  *     William Chesters <williamc At paneris.org>

  *     http://paneris.org/~williamc

  *     Obrechtstraat 114, 2517VX Den Haag, The Netherlands

  */

 package org.melati.login;

 import java.io.IOException;

 import javax.servlet.http.HttpServletResponse;

 import org.melati.poem.AccessPoemException;

 import org.melati.poem.PoemThread;

 import org.melati.poem.User;

 import org.melati.Melati;

 import org.melati.util.UnexpectedExceptionException;

 /**

  * An {@link AccessHandler} which uses the HTTP Basic Authentication scheme to

  * elicit and maintain the user's login and password.

  *

  * This implementation doesn't use the servlet session at all,

  * so it doesn't try to send cookies or

  * do URL rewriting.

  *

  */

 public class HttpBasicAuthenticationAccessHandler implements AccessHandler {

   private static final String className =

           new HttpBasicAuthenticationAccessHandler().getClass().getName();

   final String REALM = className + ".realm";

   final String USER = className + ".user";

   /**

    * Change here to use session, if that makes sense.

    * @return false

    */

   protected boolean useSession() {

     return false;

   }

   /**

    * Force a login by sending a 401 error back to the browser.

    * 

    * HACK Apache/Netscape appear not to do anything with message, which is

    * why it's just left as a String.

    */

   protected void forceLogin(HttpServletResponse resp,

                             String realm, String message) {

     String desc = realm == null ? "<unknown>"

                                 : realm.replace('"', ' ');

     resp.setHeader("WWW-Authenticate", "Basic realm=\"" + desc + "\"");

     // I don't believe there is a lot we can do about an IO exception here

     try {

       resp.sendError(HttpServletResponse.SC_UNAUTHORIZED, message);

     } catch (IOException e) {

       throw new UnexpectedExceptionException(e);

     }

   }

  /**

   * Called when an AccessPoemException is trapped.

   *

   * @param melati the Melati

   * @param accessException the particular access exception to handle

   * @see org.melati.login.AccessHandler#handleAccessException

   */

   public void handleAccessException(Melati melati,

                                     AccessPoemException accessException)

       throws Exception {

     String capName = "melati";

     if (useSession())

       melati.getSession().setAttribute(REALM, capName);

     forceLogin(melati.getResponse(), capName, accessException.getMessage());

   }

   @Override

   public Melati establishUser(Melati melati) {

     HttpAuthorization auth = HttpAuthorization.from(melati.getRequest());

     if (auth == null) {

       // No attempt to log in: become `guest'

       PoemThread.setAccessToken(melati.getDatabase().guestAccessToken());

       return melati;

     }

     else {

       // They are trying to log in

       // If allowed, we store the User in the session to avoid repeating the

       // SELECTion implied by firstWhereEq for every hit

       User sessionUser =

           useSession() ? (User)melati.getSession().getAttribute(USER) : null;

       User user = null;

       if (sessionUser == null ||

           !sessionUser.getLogin().equals(auth.username))

         user = (User)melati.getDatabase().getUserTable().getLoginColumn().

                    firstWhereEq(auth.username);

       else

         user = sessionUser;

       if (user == null || !user.getPassword_unsafe().equals(auth.password)) {

         // Login/password authentication failed; we must trigger another

         // attempt.  But do we know the "realm" (= POEM capability name) for

         // which they were originally found not to be authorized?

         String storedRealm;

         if (useSession() &&

             (storedRealm = (String)melati.getSession().getAttribute(REALM))

                  != null) {

           // The "realm" is stored in the session

           forceLogin(melati.getResponse(), storedRealm,

                      "Login/password not recognised");

           return null;

         }

         else {

           // We don't know the "realm", so we just let the user try again as

           // `guest' and hopefully trigger the same problem and get the same

           // message all over again.  Not very satisfactory but the alternative

           // is providing a default realm like "<unknown>".

           PoemThread.setAccessToken(melati.getDatabase().guestAccessToken());

           return melati;

         }

       }

       else {

         // Login/password authentication succeeded

         PoemThread.setAccessToken(user);

         if (useSession() && user != sessionUser)

           melati.getSession().setAttribute(USER, user);

         return melati;

       }

     }

   }

   @Override

   public void buildRequest(Melati melati)

       throws IOException {

   }

 }