/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you 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.

  */

 package org.apache.shiro.authc.pam;

 import org.apache.shiro.authc.AuthenticationException;

 import org.apache.shiro.authc.AuthenticationInfo;

 import org.apache.shiro.authc.AuthenticationToken;

 import org.apache.shiro.realm.Realm;

 import java.util.Collection;

 /**

  * A {@code AuthenticationStrategy} implementation assists the {@link ModularRealmAuthenticator} during the

  * log-in process in a pluggable realm (PAM) environment.

  *

  * <p>The {@code ModularRealmAuthenticator} will consult implementations of this interface on what to do during each

  * interaction with the configured Realms.  This allows a pluggable strategy of whether or not an authentication

  * attempt must be successful for all realms, only 1 or more realms, no realms, etc.

  *

  * @see AllSuccessfulStrategy

  * @see AtLeastOneSuccessfulStrategy

  * @see FirstSuccessfulStrategy

  * @since 0.2

  */

 public interface AuthenticationStrategy {

     /**

      * Method invoked by the ModularAuthenticator signifying that the authentication process is about to begin for the

      * specified {@code token} - called before any {@code Realm} is actually invoked.

      *

      * <p>The {@code AuthenticationInfo} object returned from this method is essentially an empty place holder for

      * aggregating account data across multiple realms.  It should be populated by the strategy implementation over the

      * course of authentication attempts across the multiple realms.  It will be passed into the

      * {@link #beforeAttempt} calls, allowing inspection of the aggregated account data up to that point in the

      * multi-realm authentication, allowing any logic to be executed accordingly.

      *

      * @param realms the Realms that will be consulted during the authentication process for the specified token.

      * @param token  the Principal/Credential representation to be used during authentication for a corresponding subject.

      * @return an empty AuthenticationInfo object that will populated with data from multiple realms.

      * @throws AuthenticationException if the strategy implementation does not wish the Authentication attempt to execute.

      */

     AuthenticationInfo beforeAllAttempts(Collection<? extends Realm> realms, AuthenticationToken token) throws AuthenticationException;

     /**

      * Method invoked by the ModularAuthenticator just prior to the realm being consulted for account data,

      * allowing pre-authentication-attempt logic for that realm only.

      *

      * <p>This method returns an {@code AuthenticationInfo} object that will be used for further interaction with realms.  Most

      * implementations will merely return the {@code aggregate} method argument if they don't have a need to

      * manipulate it.

      *

      * @param realm     the realm that will be consulted for {@code AuthenticationInfo} for the specified {@code token}.

      * @param token     the {@code AuthenticationToken} submitted for the subject attempting system log-in.

      * @param aggregate the aggregated AuthenticationInfo object being used across the multi-realm authentication attempt

      * @return the AuthenticationInfo object that will be presented to further realms in the authentication process - returning

      *         the {@code aggregate} method argument is the normal case if no special action needs to be taken.

      * @throws org.apache.shiro.authc.AuthenticationException

      *          an exception thrown by the Strategy implementation if it wishes the login

      *          process for the associated subject (user) to stop immediately.

      */

     AuthenticationInfo beforeAttempt(Realm realm, AuthenticationToken token, AuthenticationInfo aggregate) throws AuthenticationException;

     /**

      * Method invoked by the ModularAuthenticator just after the given realm has been consulted for authentication,

      * allowing post-authentication-attempt logic for that realm only.

      *

      * <p>This method returns an {@code AuthenticationInfo} object that will be used for further interaction with realms.  Most

      * implementations will merge the {@code singleRealmInfo} into the {@code aggregateInfo} and

      * just return the {@code aggregateInfo} for continued use throughout the authentication process.</p>

      *

      * @param realm           the realm that was just consulted for {@code AuthenticationInfo} for the given {@code token}.

      * @param token           the {@code AuthenticationToken} submitted for the subject attempting system log-in.

      * @param singleRealmInfo the info returned from a single realm.

      * @param aggregateInfo   the aggregate info representing all realms in a multi-realm environment.

      * @param t               the Throwable thrown by the Realm during the attempt, or {@code null} if the method returned normally.

      * @return the AuthenticationInfo object that will be presented to further realms in the authentication process - returning

      *         the {@code aggregateAccount} method argument is the normal case if no special action needs to be taken.

      * @throws AuthenticationException an exception thrown by the Strategy implementation if it wishes the login process

      *                                 for the associated subject (user) to stop immediately.

      */

     AuthenticationInfo afterAttempt(Realm realm, AuthenticationToken token, AuthenticationInfo singleRealmInfo, AuthenticationInfo aggregateInfo, Throwable t)

             throws AuthenticationException;

     /**

      * Method invoked by the ModularAuthenticator signifying that all of its configured Realms have been consulted

      * for account data, allowing post-proccessing after all realms have completed.

      *

      * <p>Returns the final AuthenticationInfo object that will be returned from the Authenticator to the authenticate() caller.

      * This is most likely the aggregate AuthenticationInfo object that has been populated by many realms, but the actual return value is

      * always up to the implementation.

      *

      * @param token     the {@code AuthenticationToken} submitted for the subject attempting system log-in.

      * @param aggregate the aggregate {@code AuthenticationInfo} instance populated by all realms during the log-in attempt.

      * @return the final {@code AuthenticationInfo} object to return to the Authenticator.authenticate() caller.

      * @throws AuthenticationException if the Strategy implementation wishes to fail the authentication attempt.

      */

     AuthenticationInfo afterAllAttempts(AuthenticationToken token, AuthenticationInfo aggregate) throws AuthenticationException;

 }