source: src/main/java/weka/gui/SimpleCLIPanel.java @ 5

/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 * SimpleCLIPanel.java
 * Copyright (C) 2009 University of Waikato, Hamilton, New Zealand
 */

package weka.gui;

import weka.core.Capabilities;
import weka.core.CapabilitiesHandler;
import weka.core.ClassDiscovery;
import weka.core.OptionHandler;
import weka.core.Trie;
import weka.core.Utils;
import weka.gui.scripting.ScriptingPanel;

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Cursor;
import java.awt.Font;
import java.awt.Frame;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowEvent;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashSet;
import java.util.Properties;
import java.util.Vector;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JMenuBar;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JTextPane;

/**
 * Creates a very simple command line for invoking the main method of
 * classes. System.out and System.err are redirected to an output area.
 * Features a simple command history -- use up and down arrows to move
 * through previous commmands. This gui uses only AWT (i.e. no Swing).
 *
 * @author Len Trigg (trigg@cs.waikato.ac.nz)
 * @author FracPete (fracpete at waikato dot ac dot nz)
 */
public class SimpleCLIPanel
  extends ScriptingPanel
  implements ActionListener {
  
  /** for serialization. */
  private static final long serialVersionUID = 1089039734615114942L;

  /** The filename of the properties file. */
  protected static String FILENAME = "SimpleCLI.props";
  
  /** The default location of the properties file. */
  protected static String PROPERTY_FILE = "weka/gui/" + FILENAME;
  
  /** Contains the SimpleCLI properties. */
  protected static Properties PROPERTIES;

  static {
    // Allow a properties file in the current directory to override
    try {
      PROPERTIES = Utils.readProperties(PROPERTY_FILE);
      java.util.Enumeration keys = 
        (java.util.Enumeration) PROPERTIES.propertyNames();
      if (!keys.hasMoreElements()) {
        throw new Exception(
            "Failed to read a property file for the SimpleCLI");
      }
    }
    catch (Exception ex) {
      JOptionPane.showMessageDialog(
          null,
          "Could not read a configuration file for the SimpleCLI.\n"
          + "An example file is included with the Weka distribution.\n"
          + "This file should be named \"" + PROPERTY_FILE + "\" and\n"
          + "should be placed either in your user home (which is set\n"
          + "to \"" + System.getProperties().getProperty("user.home") + "\")\n"
          + "or the directory that java was started from\n",
          "SimpleCLI",
          JOptionPane.ERROR_MESSAGE);
    }
  }
  
  /** The output area canvas added to the frame. */
  protected JTextPane m_OutputArea;

  /** The command input area. */
  protected JTextField m_Input;

  /** The history of commands entered interactively. */
  protected Vector m_CommandHistory;

  /** The current position in the command history. */
  protected int m_HistoryPos;

  /** The thread currently running a class main method. */
  protected Thread m_RunThread;

  /** The commandline completion. */
  protected CommandlineCompletion m_Completion;

  /**
   * A class that handles running the main method of the class
   * in a separate thread.
   * 
   * @author Len Trigg (trigg@cs.waikato.ac.nz)
   * @version $Revision: 5855 $
   */
  class ClassRunner extends Thread {

    /** Stores the main method to call. */
    protected Method m_MainMethod;

    /** Stores the command line arguments to pass to the main method. */
    String[] m_CommandArgs;
    
    /**
     * Sets up the class runner thread.
     *
     * @param theClass the Class to call the main method of
     * @param commandArgs an array of Strings to use as command line args
     * @throws Exception if an error occurs
     */
    public ClassRunner(Class theClass, String [] commandArgs)
      throws Exception {
      
      setDaemon(true);
      Class[] argTemplate = {String[].class};
      m_CommandArgs = commandArgs;
      m_MainMethod = theClass.getMethod("main", argTemplate);
      if (((m_MainMethod.getModifiers() & Modifier.STATIC) == 0)
          || (m_MainMethod.getModifiers() & Modifier.PUBLIC) == 0) {
        throw new NoSuchMethodException("main(String[]) method of " +
                                        theClass.getName() +
                                        " is not public and static.");
      }
    }

    /**
     * Starts running the main method.
     */
    public void run() {
      PrintStream outOld = null;
      PrintStream outNew = null;
      String outFilename = null;
      
      // is the output redirected?
      if (m_CommandArgs.length > 2) {
        String action = m_CommandArgs[m_CommandArgs.length - 2];
        if (action.equals(">")) {
          outOld = System.out;
          try {
            outFilename = m_CommandArgs[m_CommandArgs.length - 1];
            // since file may not yet exist, command-line completion doesn't
            // work, hence replace "~" manually with home directory
            if (outFilename.startsWith("~"))
              outFilename = outFilename.replaceFirst("~", System.getProperty("user.home"));
            outNew = new PrintStream(new File(outFilename));
            System.setOut(outNew);
            m_CommandArgs[m_CommandArgs.length - 2] = "";
            m_CommandArgs[m_CommandArgs.length - 1] = "";
            // some main methods check the length of the "args" array
            // -> removed the two empty elements at the end
            String[] newArgs = new String[m_CommandArgs.length - 2];
            System.arraycopy(m_CommandArgs, 0, newArgs, 0, m_CommandArgs.length - 2);
            m_CommandArgs = newArgs;
          }
          catch (Exception e) {
            System.setOut(outOld);
            outOld = null;
          }
        }
      }
      
      try {
        Object[] args = {m_CommandArgs};
        m_MainMethod.invoke(null, args);
        if (isInterrupted()) {
          System.err.println("[...Interrupted]");
        }
      } catch (Exception ex) {
        if (ex.getMessage() == null) {
          System.err.println("[...Killed]");
        } else {
          System.err.println("[Run exception] " + ex.getMessage());
        }
      } finally {
        m_RunThread = null;
      }
      
      // restore old System.out stream
      if (outOld != null) {
        outNew.flush();
        outNew.close();
        System.setOut(outOld);
        System.out.println("Finished redirecting output to '" + outFilename + "'.");
      }
    }
  }

  /**
   * A class for commandline completion of classnames.
   * 
   * @author  FracPete (fracpete at waikato dot ac dot nz)
   * @version $Revision: 5855 $
   */
  public static class CommandlineCompletion {
    
    /** all the available packages. */
    protected static Vector<String> m_Packages;

    /** a trie for storing the packages. */
    protected static Trie m_Trie;
    
    /** debug mode on/off. */
    protected boolean m_Debug = false;
    
    /**
     * default constructor.
     */
    public CommandlineCompletion() {
      super();
      
      // build incremental list of packages
      if (m_Packages == null) {
        // get all packages
        Vector list = ClassDiscovery.findPackages();
        
        // create incremental list
        HashSet<String> set = new HashSet<String>();
        for (int i = 0; i < list.size(); i++) {
          String[] parts = ((String) list.get(i)).split("\\.");
          for (int n = 1; n < parts.length; n++) {
            String pkg = "";
            for (int m = 0; m <= n; m++) {
              if (m > 0)
                pkg += ".";
              pkg += parts[m];
            }
            set.add(pkg);
          }
        }
        
        // init packages
        m_Packages = new Vector<String>();
        m_Packages.addAll(set);
        Collections.sort(m_Packages);
        
        m_Trie = new Trie();
        m_Trie.addAll(m_Packages);
      }
    }
    
    /**
     * returns whether debug mode is on.
     * 
     * @return          true if debug is on
     */
    public boolean getDebug() {
      return m_Debug;
    }
    
    /**
     * sets debug mode on/off.
     * 
     * @param value     if true then debug mode is on
     */
    public void setDebug(boolean value) {
      m_Debug = value;
    }
    
    /**
     * tests whether the given partial string is the name of a class with
     * classpath - it basically tests, whether the string consists only
     * of alphanumeric literals, underscores and dots.
     * 
     * @param partial   the string to test
     * @return          true if it looks like a classname
     */
    public boolean isClassname(String partial) {
      return (partial.replaceAll("[a-zA-Z0-9\\-\\.]*", "").length() == 0);
    }
    
    /**
     * returns the packages part of the partial classname.
     * 
     * @param partial   the partial classname
     * @return          the package part of the partial classname
     */
    public String getPackage(String partial) {
      String    result;
      int       i;
      boolean   wasDot;
      char      c;
      
      result = "";
      wasDot = false;
      for (i = 0; i < partial.length(); i++) {
        c = partial.charAt(i);
        
        // start of classname?
        if (wasDot && ((c >= 'A') && (c <= 'Z'))) {
          break;
        }
        // package/class separator
        else if (c == '.') {
          wasDot = true;
          result += "" + c;
        }
        // regular char
        else {
          wasDot = false;
          result += "" + c;
        }
      }

      // remove trailing "."
      if (result.endsWith("."))
        result = result.substring(0, result.length() - 1);
      
      return result;
    }
    
    /**
     * returns the classname part of the partial classname.
     * 
     * @param partial   the partial classname
     * @return          the class part of the classname
     */
    public String getClassname(String partial) {
      String    result;
      String    pkg;
      
      pkg = getPackage(partial);
      if (pkg.length() + 1 < partial.length())
        result = partial.substring(pkg.length() + 1);
      else
        result = "";
      
      return result;
    }
    
    /**
     * returns all the file/dir matches with the partial search string.
     * 
     * @param partial   the partial search string
     * @return          all the matches
     */
    public Vector<String> getFileMatches(String partial) {
      Vector<String>    result;
      File              file;
      File              dir;
      File[]            files;
      int               i;
      String            prefix;
      boolean           caseSensitive;
      String            name;
      boolean           match;
      
      result = new Vector<String>();

      // is the OS case-sensitive?
      caseSensitive = (File.separatorChar != '\\');
      if (m_Debug)
        System.out.println("case-sensitive=" + caseSensitive);
      
      // is "~" used for home directory? -> replace with actual home directory
      if (partial.startsWith("~"))
        partial = System.getProperty("user.home") + partial.substring(1);
      
      // determine dir and possible prefix
      file   = new File(partial);
      dir    = null;
      prefix = null;
      if (file.exists()) {
        // determine dir to read
        if (file.isDirectory()) {
          dir    = file;
          prefix = null;  // retrieve all
        }
        else {
          dir    = file.getParentFile();
          prefix = file.getName();
        }
      }
      else {
        dir    = file.getParentFile();
        prefix = file.getName();
      }

      if (m_Debug)
        System.out.println("search in dir=" + dir + ", prefix=" + prefix);
      
      // list all files in dir
      if (dir != null) {
        files = dir.listFiles();
        if (files != null) {
          for (i = 0; i < files.length; i++) {
            name = files[i].getName();

            // does the name match?
            if ((prefix != null) && caseSensitive)
              match = name.startsWith(prefix);
            else if ((prefix != null) && !caseSensitive)
              match = name.toLowerCase().startsWith(prefix.toLowerCase());
            else
              match = true;

            if (match) {
              if (prefix != null) {
                result.add(partial.substring(0, partial.length() - prefix.length()) + name);
              }
              else {
                if (partial.endsWith("\\") || partial.endsWith("/"))
                  result.add(partial + name);
                else
                  result.add(partial + File.separator + name);
              }
            }
          }
        }
        else {
          System.err.println("Invalid path: " + partial);
        }
      }
      
      // sort the result
      if (result.size() > 1)
        Collections.sort(result);
      
      // print results
      if (m_Debug) {
        System.out.println("file matches:");
        for (i = 0; i < result.size(); i++)
          System.out.println(result.get(i));
      }
      
      return result;
    }
    
    /**
     * returns all the class/package matches with the partial search string.
     * 
     * @param partial   the partial search string
     * @return          all the matches
     */
    public Vector<String> getClassMatches(String partial) {
      String            pkg;
      String            cls;
      Vector<String>    result;
      Vector<String>    list;
      int               i;
      int               index;
      Trie              tmpTrie;
      HashSet           set;
      String            tmpStr;
      
      pkg = getPackage(partial);
      cls = getClassname(partial);
      
      if (getDebug())
        System.out.println(
            "\nsearch for: '" + partial + "' => package=" + pkg + ", class=" + cls);

      result = new Vector<String>();

      // find all packages that start with that string
      if (cls.length() == 0) {
        list = m_Trie.getWithPrefix(pkg);
        set  = new HashSet();
        for (i = 0; i < list.size(); i++) {
          tmpStr = list.get(i);
          if (tmpStr.length() < partial.length())
            continue;
          if (tmpStr.equals(partial))
            continue;
          
          index  = tmpStr.indexOf('.', partial.length() + 1);
          if (index > -1)
            set.add(tmpStr.substring(0, index));
          else
            set.add(tmpStr);
        }

        result.addAll(set);
        if (result.size() > 1)
          Collections.sort(result);
      }

      // find all classes that start with that string
      list = ClassDiscovery.find(Object.class, pkg);
      tmpTrie = new Trie();
      tmpTrie.addAll(list);
      list = tmpTrie.getWithPrefix(partial);
      result.addAll(list);
      
      // sort the result
      if (result.size() > 1)
        Collections.sort(result);

      // print results
      if (m_Debug) {
        System.out.println("class/package matches:");
        for (i = 0; i < result.size(); i++)
          System.out.println(result.get(i));
      }
      
      return result;
    }
    
    /**
     * returns all the matches with the partial search string, files or
     * classes.
     * 
     * @param partial   the partial search string
     * @return          all the matches
     */
    public Vector<String> getMatches(String partial) {
      if (isClassname(partial))
        return getClassMatches(partial);
      else
        return getFileMatches(partial);
    }
    
    /**
     * returns the common prefix for all the items in the list.
     * 
     * @param list      the list to return the common prefix for
     * @return          the common prefix of all the items
     */
    public String getCommonPrefix(Vector<String> list) {
      String    result;
      Trie      trie;
      
      trie = new Trie();
      trie.addAll(list);
      result = trie.getCommonPrefix();
      
      if (m_Debug)
        System.out.println(list + "\n  --> common prefix: '" + result + "'");
      
      return result;
    }
  }
  
  /**
   * For initializing member variables.
   */
  protected void initialize() {
    super.initialize();

    m_CommandHistory = new Vector();
    m_HistoryPos     = 0;
    m_Completion     = new CommandlineCompletion();
  }
  
  /**
   * Sets up the GUI after initializing the members.
   */
  protected void initGUI() {
    super.initGUI();

    setLayout(new BorderLayout());

    m_OutputArea = new JTextPane();
    m_OutputArea.setEditable(false);
    m_OutputArea.setFont(new Font("Monospaced", Font.PLAIN, 12));
    add(new JScrollPane(m_OutputArea), "Center");

    m_Input = new JTextField();
    m_Input.setFont(new Font("Monospaced", Font.PLAIN, 12));
    m_Input.addActionListener(this);
    m_Input.setFocusTraversalKeysEnabled(false);
    m_Input.addKeyListener(new KeyAdapter() {
      public void keyPressed(KeyEvent e) {
        doHistory(e);
        doCommandlineCompletion(e);
      }
    });
    add(m_Input, "South");
  }
  
  /**
   * Finishes up after initializing members and setting up the GUI.
   */
  protected void initFinish() {
    super.initFinish();

    System.out.println(
          "\nWelcome to the WEKA SimpleCLI\n\n"
        + "Enter commands in the textfield at the bottom of \n"
        + "the window. Use the up and down arrows to move \n"
        + "through previous commands.\n"
        + "Command completion for classnames and files is \n"
        + "initiated with <Tab>. In order to distinguish \n"
        + "between files and classnames, file names must \n"
        + "be either absolute or start with '." + File.separator + "' or '~/'\n"
        + "(the latter is a shortcut for the home directory).\n"
        + "<Alt+BackSpace> is used for deleting the text\n"
        + "in the commandline in chunks.\n");
    try {
      runCommand("help");
    }
    catch (Exception e) {
      // ignored
    }
    
    loadHistory();
  }

  /**
   * Returns an icon to be used in a frame.
   * 
   * @return            the icon
   */
  public ImageIcon getIcon() {
    return ComponentHelper.getImageIcon("weka_icon.gif");
  }

  /**
   * Returns the current title for the frame/dialog.
   * 
   * @return            the title
   */
  public String getTitle() {
    return "SimpleCLI";
  }

  /**
   * Returns the text area that is used for displaying output on stdout
   * and stderr.
   * 
   * @return            the JTextArea
   */
  public JTextPane getOutput() {
    return m_OutputArea;
  }

  /**
   * Not supported.
   * 
   * @return            always null
   */
  public JMenuBar getMenuBar() {
    return null;
  }

  /**
   * Executes a simple cli command.
   *
   * @param commands the command string
   * @throws Exception if an error occurs
   */
  public void runCommand(String commands) throws Exception {

    System.out.println("> " + commands + '\n');
    System.out.flush();
    String [] commandArgs = Utils.splitOptions(commands);
    if (commandArgs.length == 0) {
      return;
    }
    if (commandArgs[0].equals("java")) {
      // Execute the main method of a class
      commandArgs[0] = "";
      try {
        if (commandArgs.length == 1) {
          throw new Exception("No class name given");
        }
        String className = commandArgs[1];
        commandArgs[1] = "";
        if (m_RunThread != null) {
          throw new Exception("An object is already running, use \"break\""
                              + " to interrupt it.");
        }
        Class theClass = Class.forName(className);

        // some classes expect a fixed order of the args, i.e., they don't
        // use Utils.getOption(...) => create new array without first two
        // empty strings (former "java" and "<classname>")
        Vector argv = new Vector();
        for (int i = 2; i < commandArgs.length; i++)
          argv.add(commandArgs[i]);
  
        m_RunThread = new ClassRunner(theClass, (String[]) argv.toArray(new String[argv.size()]));
        m_RunThread.setPriority(Thread.MIN_PRIORITY); // UI has most priority
        m_RunThread.start();    
      } catch (Exception ex) {
        System.err.println(ex.getMessage());
      }

    } else if (commandArgs[0].equals("capabilities")) {
      try {
        Object obj = Class.forName(commandArgs[1]).newInstance();
        if (obj instanceof CapabilitiesHandler) {
          if (obj instanceof OptionHandler) {
            Vector<String> args = new Vector<String>();
            for (int i = 2; i < commandArgs.length; i++)
              args.add(commandArgs[i]);
            ((OptionHandler) obj).setOptions(args.toArray(new String[args.size()]));
          }
          Capabilities caps = ((CapabilitiesHandler) obj).getCapabilities();
          System.out.println(caps.toString().replace("[", "\n").replace("]", "\n"));
        }
        else {
          System.out.println("'" + commandArgs[1] + "' is not a " + CapabilitiesHandler.class.getName() + "!");
        }
      }
      catch (Exception e) {
        System.err.println(e.getMessage());
      }
    } else if (commandArgs[0].equals("cls")) {
      // Clear the text area
      m_OutputArea.setText("");
    } else if (commandArgs[0].equals("history")) {
      System.out.println("Command history:");
      for (int i = 0; i < m_CommandHistory.size(); i++)
        System.out.println(m_CommandHistory.get(i));
      System.out.println();
    } else if (commandArgs[0].equals("break")) {
      if (m_RunThread == null) {
        System.err.println("Nothing is currently running.");
      } else {
        System.out.println("[Interrupt...]");
        m_RunThread.interrupt();
      }
    } else if (commandArgs[0].equals("kill")) {
      if (m_RunThread == null) {
        System.err.println("Nothing is currently running.");
      } else {
        System.out.println("[Kill...]");
        m_RunThread.stop();
        m_RunThread = null;
      }
    } else if (commandArgs[0].equals("exit")) {
      // Shut down
      // determine parent
      Container parent = getParent();
      Container frame = null;
      boolean finished = false;
      while (!finished) {
        if (    (parent instanceof JFrame) 
             || (parent instanceof Frame) 
             || (parent instanceof JInternalFrame) ) {
          frame = parent;
          finished = true;
        }
        
        if (!finished) {
          parent = parent.getParent();
          finished = (parent == null);
        }
      }
      // fire the frame close event
      if (frame != null) {
        if (frame instanceof JInternalFrame)
          ((JInternalFrame) frame).doDefaultCloseAction();
        else
          ((Window) frame).dispatchEvent(
              new WindowEvent(
                  (Window) frame, WindowEvent.WINDOW_CLOSING));
      }
      
    } else {
      boolean help = ((commandArgs.length > 1)
                      && commandArgs[0].equals("help"));
      if (help && commandArgs[1].equals("java")) {
        System.out.println(
            "java <classname> <args>\n\n"
            + "Starts the main method of <classname> with "
            + "the supplied command line arguments (if any).\n"
            + "The command is started in a separate thread, "
            + "and may be interrupted with the \"break\"\n"
            + "command (friendly), or killed with the \"kill\" "
            + "command (unfriendly).\n"
            + "Redirecting can be done with '>' followed by the "
            + "file to write to, e.g.:\n"
            + "  java some.Class > ." + File.separator + "some.txt");
      } else if (help && commandArgs[1].equals("break")) {
        System.out.println(
            "break\n\n"
            + "Attempts to nicely interrupt the running job, "
            + "if any. If this doesn't respond in an\n"
            + "acceptable time, use \"kill\".\n");
      } else if (help && commandArgs[1].equals("kill")) {
        System.out.println(
            "kill\n\n"
            + "Kills the running job, if any. You should only "
            + "use this if the job doesn't respond to\n"
            + "\"break\".\n");
      } else if (help && commandArgs[1].equals("capabilities")) {
        System.out.println(
            "capabilities <classname> <args>\n\n"
            + "Lists the capabilities of the specified class.\n"
            + "If the class is a " + OptionHandler.class.getName() + " then\n"
            + "trailing options after the classname will be\n"
            + "set as well.\n");
      } else if (help && commandArgs[1].equals("cls")) {
        System.out.println(
            "cls\n\n"
            + "Clears the output area.\n");
      } else if (help && commandArgs[1].equals("history")) {
        System.out.println(
            "history\n\n"
            + "Prints all issued commands.\n");
      } else if (help && commandArgs[1].equals("exit")) {
        System.out.println(
            "exit\n\n"
            + "Exits the SimpleCLI program.\n");
      } else {
        // Print a help message
        System.out.println(
            "Command must be one of:\n"
            + "\tjava <classname> <args> [ > file]\n"
            + "\tbreak\n"
            + "\tkill\n"
            + "\tcapabilities <classname> <args>\n"
            + "\tcls\n"
            + "\thistory\n"
            + "\texit\n"
            + "\thelp <command>\n");
      }
    }
  }

  /**
   * Changes the currently displayed command line when certain keys
   * are pressed. The up arrow moves back through history entries
   * and the down arrow moves forward through history entries.
   *
   * @param e a value of type 'KeyEvent'
   */
  public void doHistory(KeyEvent e) {
    
    if (e.getSource() == m_Input) {
      switch (e.getKeyCode()) {
      case KeyEvent.VK_UP:
        if (m_HistoryPos > 0) {
          m_HistoryPos--;
          String command = (String) m_CommandHistory.elementAt(m_HistoryPos);
          m_Input.setText(command);
        }
        break;
      case KeyEvent.VK_DOWN:
        if (m_HistoryPos < m_CommandHistory.size()) {
          m_HistoryPos++;
          String command = "";
          if (m_HistoryPos < m_CommandHistory.size()) {
            command = (String) m_CommandHistory.elementAt(m_HistoryPos);
          }
          m_Input.setText(command);
        }
        break;
      default:
        break;
      }
    }
  }

  /**
   * performs commandline completion on packages and classnames.
   * 
   * @param e a value of type 'KeyEvent'
   */
  public void doCommandlineCompletion(KeyEvent e) {
    if (e.getSource() == m_Input) {
      switch (e.getKeyCode()) {
        // completion
        case KeyEvent.VK_TAB:
          if (e.getModifiers() == 0) {
            // it might take a while before we determined all of the possible
            // matches (Java doesn't have an application wide cursor handling??)
            m_Input.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
            m_OutputArea.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));

            try {
              String txt = m_Input.getText();

              // java call?
              if (txt.trim().startsWith("java ")) {
                int pos = m_Input.getCaretPosition();
                int nonNameCharPos = -1;
                // find first character not part of a name, back from current position
                // i.e., " or blank
                for (int i = pos - 1; i >= 0; i--) {
                  if (    (txt.charAt(i) == '"') 
                      || (txt.charAt(i) == ' ') ) {
                    nonNameCharPos = i;
                    break;
                  }
                }

                if (nonNameCharPos > -1) {
                  String search = txt.substring(nonNameCharPos + 1, pos);

                  // find matches and common prefix
                  Vector<String> list = m_Completion.getMatches(search);
                  String common = m_Completion.getCommonPrefix(list);

                  // just extending by separator is not a real extension
                  if ((search.toLowerCase() + File.separator).equals(common.toLowerCase()))
                    common = search;

                  // can we complete the string?
                  if (common.length() > search.length()) {
                    try {
                      m_Input.getDocument().remove(nonNameCharPos + 1, search.length());
                      m_Input.getDocument().insertString(nonNameCharPos + 1, common, null);
                    }
                    catch (Exception ex) {
                      ex.printStackTrace();
                    }
                  }
                  // ambigiuous? -> print matches
                  else if (list.size() > 1) {
                    System.out.println("\nPossible matches:");
                    for (int i = 0; i < list.size(); i++)
                      System.out.println("  " + list.get(i));
                  }
                  else {
                    // nothing found, don't do anything
                  }
                }
              }
            }
            finally {
              // set cursor back to default
              m_Input.setCursor(null);
              m_OutputArea.setCursor(null);
            }
          }
          break;

        // delete last part up to next blank or dot
        case KeyEvent.VK_BACK_SPACE:
          if (e.getModifiers() == KeyEvent.ALT_MASK) {
            String txt = m_Input.getText();
            int pos    = m_Input.getCaretPosition();
            
            // skip whitespaces
            int start = pos;
            start--;
            while (start >= 0) {
              if (    (txt.charAt(start) == '.') 
                   || (txt.charAt(start) == ' ') 
                   || (txt.charAt(start) == '\\')
                   || (txt.charAt(start) == '/') )
                start--;
              else
                break;
            }
            
            // find first blank or dot back from position
            int newPos = -1;
            for (int i = start; i >= 0; i--) {
              if (    (txt.charAt(i) == '.') 
                   || (txt.charAt(i) == ' ')
                   || (txt.charAt(i) == '\\') 
                   || (txt.charAt(i) == '/') ) {
                newPos = i;
                break;
              }
            }

            // remove string
            try {
              m_Input.getDocument().remove(newPos + 1, pos - newPos - 1);
            }
            catch (Exception ex) {
              ex.printStackTrace();
            }
          }
          break;
      }
    }
  }
  
  /**
   * Only gets called when return is pressed in the input area, which
   * starts the command running.
   *
   * @param e a value of type 'ActionEvent'
   */
  public void actionPerformed(ActionEvent e) {

    try {
      if (e.getSource() == m_Input) {
        String command = m_Input.getText();
        int last = m_CommandHistory.size() - 1;
        if ((last < 0)
            || !command.equals((String)m_CommandHistory.elementAt(last))) {
          m_CommandHistory.addElement(command);
          saveHistory();
        }
        m_HistoryPos = m_CommandHistory.size();
        runCommand(command);
        
        m_Input.setText("");
      }
    } catch (Exception ex) {
      System.err.println(ex.getMessage());
    }
  }

  /**
   * loads the command history from the user's properties file.
   */
  protected void loadHistory() {
    int         size;
    int         i;
    String      cmd;
    
    size = Integer.parseInt(PROPERTIES.getProperty("HistorySize", "50"));

    m_CommandHistory.clear();
    for (i = 0; i < size; i++) {
      cmd = PROPERTIES.getProperty("Command" + i, "");
      if (cmd.length() != 0)
        m_CommandHistory.add(cmd);
      else 
        break;
    }
    
    m_HistoryPos = m_CommandHistory.size();
  }
  
  /**
   * saves the current command history in the user's home directory.
   */
  protected void saveHistory() {
    int                         size;
    int                         from;
    int                         i;
    String                      filename;
    BufferedOutputStream        stream;
    
    size = Integer.parseInt(PROPERTIES.getProperty("HistorySize", "50"));
    
    // determine first command to save
    from = m_CommandHistory.size() - size;
    if (from < 0)
      from = 0;

    // fill properties
    PROPERTIES.setProperty("HistorySize", "" + size);
    for (i = from; i < m_CommandHistory.size(); i++)
      PROPERTIES.setProperty("Command" + (i-from), (String) m_CommandHistory.get(i));
    
    try {
      filename = System.getProperties().getProperty("user.home") + File.separatorChar + FILENAME;
      stream = new BufferedOutputStream(new FileOutputStream(filename));
      PROPERTIES.store(stream, "SimpleCLI");
      stream.close();
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }
  
  /**
   * Displays the panel in a frame.
   * 
   * @param args        ignored
   */
  public static void main(String[] args) {
    showPanel(new SimpleCLIPanel(), args);
  }
}