/*
 * $Header: /home/cvs/jakarta-commons/httpclient/src/java/org/apache/commons/httpclient/auth/AuthScheme.java,v 1.4.2.2 2004/02/22 18:21:14 olegk Exp $
 * $Revision: 1.4.2.2 $
 * $Date: 2004/02/22 18:21:14 $
 *
 * ====================================================================
 *
 *  Copyright 2002-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 *
 * [Additional notices, if required by prior licensing conditions]
 *
 */

package org.apache.commons.httpclient.auth;

import org.apache.commons.httpclient.Credentials;

/**
 * 

 * This interface represents an abstract authentication scheme.
 * 
 * 

 * An authentication scheme should be able to support the following
 * functions:
 * 

 *   
Provide its textual designation
 *   
Provide its parameters, if available
 *   
Provide the realm this authentication scheme is applicable to,
 *       if available
 *   
Generate authorization string for the given set of credentials,
 *       request method and URI as specificed in the HTTP request line
 * 
 * 

 * 

 * Authentication schemes may ignore method name and URI parameters
 * if they are not relevant for the given authentication mechanism
 * 
 * 
 * @author Oleg Kalnichevski
 * @author Adrian Sutton
 *
 * @since 2.0beta1
 */

public interface AuthScheme {
    
    /**
     * Returns textual designation of the given authentication scheme.
     * 
     * @return the name of the given authentication scheme
     */
    String getSchemeName();

    /**
     * Returns authentication parameter with the given name, if available.
     * 
     * @param name The name of the parameter to be returned
     * 
     * @return the parameter with the given name
     */
    String getParameter(final String name);

    /**
     * Returns authentication realm. If the concept of an authentication
     * realm is not applicable to the given authentication scheme, returns
     * null.
     * 
     * @return the authentication realm
     */
    String getRealm();
    
    /**
     * Returns a String identifying the authentication challenge.  This is
     * used, in combination with the host and port to determine if
     * authorization has already been attempted or not.  Schemes which
     * require multiple requests to complete the authentication should
     * return a different value for each stage in the request.
     * 
     * 
Additionally, the ID should take into account any changes to the
     * authentication challenge and return a different value when appropriate.
     * For example when the realm changes in basic authentication it should be
     * considered a different authentication attempt and a different value should
     * be returned.
     * 
     * @return String a String identifying the authentication challenge.  The
     * returned value may be null.
     */
    String getID();
    
    /**
     * Produces an authorization string for the given set of {@link Credentials},
     * method name and URI using the given authentication scheme.
     * 
     * @param credentials The set of credentials to be used for athentication
     * @param method The name of the method that requires authorization. 
     *   This parameter may be ignored, if it is irrelevant 
     *   or not applicable to the given authentication scheme
     * @param uri The URI for which authorization is needed. 
     *   This parameter may be ignored, if it is irrelevant or not 
     *   applicable to the given authentication scheme
     * @throws AuthenticationException if authorization string cannot 
     *   be generated due to an authentication failure
     * 
     * @return the authorization string
     * 
     * @see org.apache.commons.httpclient.HttpMethod#getName()
     * @see org.apache.commons.httpclient.HttpMethod#getPath()
     */
    String authenticate(Credentials credentials, String method, String uri) 
      throws AuthenticationException;
       
}