/*
 * Copyright 2005 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.usermgt;

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.
     * @param aGroup Group.
     *
     * @return New user.
     *
     * @throws UserMgtException In case the user cannot be created.
     */
    User createUser(String aUsername, String aPassword, Group aGroup)
        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.
     *
     * @return DOCUMENT ME!
     */
    boolean add(User aUser);

    /**
     * Removes a user. If the user does not exist, nothing happens.
     *
     * @param aUser
     *
     * @return DOCUMENT ME!
     */
    boolean remove(User aUser);

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

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

    /**
     * DOCUMENT ME!
     *
     * @return The number of users.
     */
    int size();
}