// joi/10/juno/CdCommand.java                         
//                                                            
//                                                            
// Copyright 2003, Bill Campbell and Ethan Bolker                         
                                                            
import java.util.*;

/**
 * The Juno shell command to change directory.
 * Usage:
 * <pre>
 *     cd [directory]
 * </pre>
 * for moving to the named directory.
 *
 * @version 10
 */

class CdCommand extends ShellCommand 
{
    CdCommand()
    {
        super( "change current directory", "[ directory ]" );
    }
    
    /**
     * Move to the named directory
     *
     * @param args the remainder of the command line.
     * @param sh   the current shell
     *
     * @exception JunoException for reporting errors
     */

    public void doIt( StringTokenizer args, Shell sh )
         throws JunoException 
    {
        String dirname = "";
        Directory d = sh.getUser().getHome(); // default
        if ( args.hasMoreTokens() ) {
            dirname = args.nextToken();
            if (dirname.equals("..")) {
                if (sh.getDot().isRoot()) 
                    d = sh.getDot(); // no change
                else 
                    d = sh.getDot().getParent();
            }
            else if (dirname.equals(".")) {
                d = sh.getDot(); // no change
            }
            else {
                d = (Directory)(sh.getDot().retrieveJFile(dirname));
            }
        }
        sh.setDot( d );
    }
}