/*
 * Copyright 2005-2010 the original author or authors.
 * 
 * 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.
 */
package org.wamblee.security.authentication;

import java.util.Set;

/**
 * Represents a set of users. Typical implementations would be an implementation
 * based on a static configuration file or an implementation backed by a
 * database.
 * 
 * @author Erik Brakkee
 */
public interface UserSet {
    /**
     * Creates a user.
     * 
     * @param aUsername
     *            User name.
     * @param aPassword
     *            Password.
     * 
     * @return New user.
     * 
     * @throws UserMgtException
     *             In case the user cannot be created.
     */
    User createUser(String aUsername, String aPassword) throws UserMgtException;

    /**
     * Must be called whenever a user object has been modified to notify the
     * user set.
     * 
     * @param aUser
     *            Modified user.
     */
    void userModified(User aUser);

    /**
     * Finds user.
     * 
     * @param aName
     *            Username.
     * 
     * @return User or null if not found.
     */
    User find(String aName);

    /**
     * Checks if a user exists.
     * 
     * @param aUser
     *            User.
     * 
     * @return True iff the user exists.
     */
    boolean contains(User aUser);

    /**
     * Adds a user. If the user already exists, the user details are updated
     * with that of the specified user object.
     * 
     * @param aUser
     *            User to add.
     * 
     */
    boolean add(User aUser);

    /**
     * Removes a user.
     * 
     * @param aUser
     *            User to remove
     * @return True iff user was removed.
     * 
     */
    boolean remove(User aUser);

    /**
     * Lists the current users.
     * 
     * @return Users.
     */
    Set<User> list();

    /**
     * Lists the users belonging to a particular group.
     * 
     * @param aGroup
     *            Group.
     * @return Groups.
     */
    Set<User> list(Group aGroup);

    /**
     * 
     * @return The number of users.
     */
    int size();

    /**
     * Clears the user cache.
     */
    void clearCache();
}