// $Header: /home/cvs/jakarta-jmeter/src/protocol/http/org/apache/jmeter/protocol/http/modifier/UserSequence.java,v 1.6 2004/02/12 00:29:49 sebb Exp $
/*
 * Copyright 2001-2004 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.
 * 
*/

package org.apache.jmeter.protocol.http.modifier;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.jorphan.logging.LoggingManager;
import org.apache.log.Logger;

/**
 * This module controls the Sequence in which user details are returned.  This
 * module uses round robin allocation of users.
 * 
 * @author     Mark Walsh
 * @version    $Revision: 1.6 $
 */
public class UserSequence implements Serializable
{
    transient private static Logger log = LoggingManager.getLoggerForClass();

    //-------------------------------------------
    // Constants and Data Members
    //-------------------------------------------
    private List allUsers;
    private Iterator indexOfUsers;

    //-------------------------------------------
    // Constructors
    //-------------------------------------------

    public UserSequence()
    {
    }

    /**
     * Load all user and parameter data into the sequence module.
     * 

     * ie a Set of Mapped "parameter names and parameter values" for each user
     * to be loaded into the sequencer.
     */
    public UserSequence(List allUsers)
    {
        this.allUsers = allUsers;

        // initalise pointer to first user
        indexOfUsers = allUsers.iterator();
    }

    //-------------------------------------------
    // Methods
    //-------------------------------------------
    
    /**
     * Returns the parameter data for the next user in the sequence
     * @return a Map object of parameter names and matching parameter
     *         values for the next user
     */
    public synchronized Map getNextUserMods()
    {
        // Use round robin allocation of user details
        if (!indexOfUsers.hasNext())
        {
            indexOfUsers = allUsers.iterator();
        }

        Map user;
        if (indexOfUsers.hasNext())
        {
            user = (Map) indexOfUsers.next();
            log.debug(
                "UserSequence.getNextuserMods(): current parameters will be "
                    + "changed to: "
                    + user);
        }
        else
        {
            // no entries in all users, therefore create an empty Map object
            user = new HashMap();
        }

        return user;
    }
}