historyqueue.java

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/*
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 *
 * $Id: HistoryQueue.java,v 1.2 2004/06/02 20:03:28 bondolo Exp $
 */

package net.jxta.impl.shell.bin.history;

import java.util.List;
import java.util.ArrayList;

/**
 *  A class that implements a history queue. It is a singelton class
 * that holds the history queus for all currently running ShellConsole objects.
 *
 * <br>The different queues are stored in a hashtable, where the key is
 **/
public class HistoryQueue {
    /** The maximum number of commands */
    protected static final int MAX_HISTORY = 100;
    
    /** The vector that holds the commands, which are strings */
    private List queue;
    
    /** The index at for the next commend to retrieve */
    private int nextCommand = -1;
    
    /** Array containing the commands that are not added to the command list */
    private final String exclude[];
    
    /**
     *  Create a new history queue
     */
    public HistoryQueue(){
        this( new String[0] );
    }
    
    /**
     *  Create a new history queue
     * @param exclude the commands to not add to the queue (that are the
     *                 usually Cursor up and down events )
     */
    public HistoryQueue(String exclude[]){
        queue = new ArrayList(MAX_HISTORY);
        nextCommand = -1;
        this.exclude = exclude;
    }
    
    public String toString(){
        return "History queue of " + queue.size();
    }
    
    /**
     * Adds a new command to the queue.
     *
     * <p/>If the queue has already reached  MAX_HISTORY, the element at
     * index 0 is discarded.
     *
     * @param cmd the command to add
     */
    public synchronized void addCommand(String cmd) {
        cmd = cmd.trim();
        
        // no empty commands
        if( 0 == cmd.length() )
            return;
        
        // none of the excludes
        for(int i = 0; i < exclude.length; i++){
            if( exclude[i].equals(cmd))
                return;
        }
        
        // remove extra commands
        while( queue.size() >= MAX_HISTORY) {
            queue.remove(0);
        }
        
        String last = null;
        if( queue.size() > 0 ) {
            last = (String) queue.get(queue.size() -1);
        }
        
        // add if not the same as the last command.
        if( !cmd.equals( last ) ) {
            queue.add(cmd);
        }
        
        nextCommand = queue.size();
    }
    
    /**
     * Removes the last command added to the queue
     */
    public synchronized void removeLastCommand(){
        if( queue.size() > 0) {
            queue.remove(queue.size() -1);
            nextCommand = queue.size();
        }
    }
    
    /**
     *  Returns the command immediately preceeding the previous command
     */
    public String getNextCommand(){
        nextCommand--;
        if( nextCommand < 0) nextCommand = -1;
        return getCommand(nextCommand);
    }
    
    /**
     *  Returns the command immediately succedding the previous command
     * THIS needs help !!
     */
    public String getPreviousCommand(){
        nextCommand++;
        if( nextCommand > queue.size() ) nextCommand = queue.size();
        return getCommand(nextCommand);
    }
    
    /**
     * Gets the command at index, if there is an element at index.
     * Otherwise, an empty string is returned
     *
     * @return the command at index, if there is an element at index
     *        or an empty string, if index is out of range
     */
    public String getCommand(int index){
        return ( index < 0 || index >= queue.size()) ? "" : (String) queue.get(index);
    }
    
    /** Prints the available commands to a String.
     * If no commands are available, we return and empty string
     */
    public String printHistory(){
        StringBuffer buffer = new StringBuffer();
        int k,i,max = queue.size();
        int length = String.valueOf(MAX_HISTORY).length();
        String number;
        
        for(i = 0; i < max; i++){
            number = String.valueOf(i);
            k = 0;
            while( (k++ + number.length()) != length) buffer.append(" ");
            buffer.append(number).append(" ");
            buffer.append(queue.get(i));
            buffer.append("\n");
        }
        return buffer.toString();
    }
}